.. highlight:: console Quickstart ========== Suppose that you are in a directory containing a single Cabal package which you wish to build. You can configure and build it using Nix-style local builds with this command (configuring is not necessary): :: $ cabal new-build To open a GHCi shell with this package, use this command: :: $ cabal new-repl Developing multiple packages ---------------------------- Many Cabal projects involve multiple packages which need to be built together. To build multiple Cabal packages, you need to first create a ``cabal.project`` file which declares where all the local package directories live. For example, in the Cabal repository, there is a root directory with a folder per package, e.g., the folders ``Cabal`` and ``cabal-install``. The ``cabal.project`` file specifies each folder as part of the project: .. code-block:: cabal packages: Cabal/ cabal-install/ The expectation is that a ``cabal.project`` is checked into your source control, to be used by all developers of a project. If you need to make local changes, they can be placed in ``cabal.project.local`` (which should not be checked in.) Then, to build every component of every package, from the top-level directory, run the command: (Warning: cabal-install-1.24 does NOT have this behavior; you will need to upgrade to HEAD.) :: $ cabal new-build To build a specific package, you can either run ``new-build`` from the directory of the package in question: :: $ cd cabal-install $ cabal new-build or you can pass the name of the package as an argument to ``cabal new-build`` (this works in any subdirectory of the project): :: $ cabal new-build cabal-install You can also specify a specific component of the package to build. For example, to build a test suite named ``package-tests``, use the command: :: $ cabal new-build package-tests Targets can be qualified with package names. So to request ``package-tests`` *from* the ``Cabal`` package, use ``Cabal:package-tests``. Unlike sandboxes, there is no need to setup a sandbox or ``add-source`` projects; just check in ``cabal.project`` to your repository and ``new-build`` will just work. Cookbook ======== How can I profile my library/application? ----------------------------------------- First, make sure you have HEAD; 1.24 is affected by :issue:`3790`, which means that if any project which transitively depends on a package which has a Custom setup built against Cabal 1.22 or earlier will silently not work. Create or edit your ``cabal.project.local``, adding the following line:: profiling: True Now, ``cabal new-build`` will automatically build all libraries and executables with profiling. You can fine-tune the profiling settings for each package using :cfg-field:`profiling-detail`:: package p profiling-detail: toplevel-functions Alternately, you can call ``cabal new-build --enable-profiling`` to temporarily build with profiling. How it works ============ Local versus external packages ------------------------------ One of the primary innovations of Nix-style local builds is the distinction between local packages, which users edit and recompile and must be built per-project, versus external packages, which can be cached across projects. To be more precise: 1. A **local package** is one that is listed explicitly in the ``packages``, ``optional-packages`` or ``extra-packages`` field of a project. Usually, these refer to packages whose source code lives directly in a folder in your project (although, you can list an arbitrary Hackage package in ``extra-packages`` to force it to be treated as local). Local packages, as well as the external packages (below) which depend on them, are built **inplace**, meaning that they are always built specifically for the project and are not installed globally. Inplace packages are not cached and not given unique hashes, which makes them suitable for packages which you want to edit and recompile. 2. An **external package** is any package which is not listed in the ``packages`` field. The source code for external packages is usually retrieved from Hackage. When an external package does not depend on an inplace package, it can be built and installed to a **global** store, which can be shared across projects. These build products are identified by a hash that over all of the inputs which would influence the compilation of a package (flags, dependency selection, etc.). Just as in Nix, these hashes uniquely identify the result of a build; if we compute this identifier and we find that we already have this ID built, we can just use the already built version. The global package store is ``~/.cabal/store``; if you need to clear your store for whatever reason (e.g., to reclaim disk space or because the global store is corrupted), deleting this directory is safe (``new-build`` will just rebuild everything it needs on its next invocation). This split motivates some of the UI choices for Nix-style local build commands. For example, flags passed to ``cabal new-build`` are only applied to *local* packages, so that adding a flag to ``cabal new-build`` doesn't necessitate a rebuild of *every* transitive dependency in the global package store. In cabal-install HEAD, Nix-style local builds also take advantage of a new Cabal library feature, `per-component builds `__, where each component of a package is configured and built separately. This can massively speed up rebuilds of packages with lots of components (e.g., a package that defines multiple executables), as only one executable needs to be rebuilt. Packages that use Custom setup scripts are not currently built on a per-component basis. Where are my build products? ---------------------------- A major deficiency in the current implementation of new-build is that there is no programmatic way to access the location of build products. The location of the build products is intended to be an internal implementation detail of new-build, but we also understand that many unimplemented features (e.g., ``new-test``) can only be reasonably worked around by accessing build products directly. The location where build products can be found varies depending on the version of cabal-install: - In cabal-install-1.24, the dist directory for a package ``p-0.1`` is stored in ``dist-newstyle/build/p-0.1``. For example, if you built an executable or test suite named ``pexe``, it would be located at ``dist-newstyle/build/p-0.1/build/pexe/pexe``. - In cabal-install HEAD, the dist directory for a package ``p-0.1`` defining a library built with GHC 8.0.1 on 64-bit Linux is ``dist-newstyle/build/x86_64-linux/ghc-8.0.1/p-0.1``. When per-component builds are enabled (any non-Custom package), a subcomponent like an executable or test suite named ``pexe`` will be stored at ``dist-newstyle/build/x86_64-linux/ghc-8.0.1/p-0.1/c/pexe``; thus, the full path of the executable is ``dist-newstyle/build/x86_64-linux/ghc-8.0.1/p-0.1/c/pexe/build/pexe/pexe`` (you can see why we want this to be an implementation detail!) The paths are a bit longer in HEAD but the benefit is that you can transparently have multiple builds with different versions of GHC. We plan to add the ability to create aliases for certain build configurations, and more convenient paths to access particularly useful build products like executables. Caching ------- Nix-style local builds sport a robust caching system which help reduce the time it takes to execute a rebuild cycle. While the details of how ``cabal-install`` does caching are an implementation detail and may change in the future, knowing what gets cached is helpful for understanding the performance characteristics of invocations to ``new-build``. The cached intermediate results are stored in ``dist-newstyle/cache``; this folder can be safely deleted to clear the cache. The following intermediate results are cached in the following files in this folder (the most important two are first): ``solver-plan`` (binary) The result of calling the dependency solver, assuming that the Hackage index, local ``cabal.project`` file, and local ``cabal`` files are unmodified. (Notably, we do NOT have to dependency solve again if new build products are stored in the global store; the invocation of the dependency solver is independent of what is already available in the store.) ``source-hashes`` (binary) The hashes of all local source files. When all local source files of a local package are unchanged, ``cabal new-build`` will skip invoking ``setup build`` entirely (saving us from a possibly expensive call to ``ghc --make``). The full list of source files participating in compilation are determined using ``setup sdist --list-sources`` (thus, if you do not list all your source files in a Cabal file, you may fail to recompile when you edit them.) ``config`` (same format as ``cabal.project``) The full project configuration, merged from ``cabal.project`` (and friends) as well as the command line arguments. ``compiler`` (binary) The configuration of the compiler being used to build the project. ``improved-plan`` (binary) Like ``solver-plan``, but with all non-inplace packages improved into pre-existing copies from the store. Note that every package also has a local cache managed by the Cabal build system, e.g., in ``$distdir/cache``. There is another useful file in ``dist-newstyle/cache``, ``plan.json``, which is a JSON serialization of the computed install plan. (TODO: docs) Commands ======== We now give an in-depth description of all the commands, describing the arguments and flags they accept. cabal new-configure ------------------- ``cabal new-configure`` takes a set of arguments and writes a ``cabal.project.local`` file based on the flags passed to this command. ``cabal new-configure FLAGS; cabal new-build`` is roughly equivalent to ``cabal new-build FLAGS``, except that with ``new-configure`` the flags are persisted to all subsequent calls to ``new-build``. ``cabal new-configure`` is intended to be a convenient way to write out a ``cabal.project.local`` for simple configurations; e.g., ``cabal new-configure -w ghc-7.8`` would ensure that all subsequent builds with ``cabal new-build`` are performed with the compiler ``ghc-7.8``. For more complex configuration, we recommend writing the ``cabal.project.local`` file directly (or placing it in ``cabal.project``!) ``cabal new-configure`` inherits options from ``Cabal``. semantics: - Any flag accepted by ``./Setup configure``. - Any flag accepted by ``cabal configure`` beyond ``./Setup configure``, namely ``--cabal-lib-version``, ``--constraint``, ``--preference`` and ``--solver.`` - Any flag accepted by ``cabal install`` beyond ``./Setup configure``. - Any flag accepted by ``./Setup haddock``. The options of all of these flags apply only to *local* packages in a project; this behavior is different than that of ``cabal install``, which applies flags to every package that would be built. The motivation for this is to avoid an innocuous addition to the flags of a package resulting in a rebuild of every package in the store (which might need to happen if a flag actually applied to every transitive dependency). To apply options to an external package, use a ``package`` stanza in a ``cabal.project`` file. cabal new-build --------------- ``cabal new-build`` takes a set of targets and builds them. It automatically handles building and installing any dependencies of these targets. A target can take any of the following forms: - A package target: ``package``, which specifies that all enabled components of a package to be built. By default, test suites and benchmarks are *not* enabled, unless they are explicitly requested (e.g., via ``--enable-tests``.) - A component target: ``[package:][ctype:]component``, which specifies a specific component (e.g., a library, executable, test suite or benchmark) to be built. - All packages: ``all``, which specifies all packages within the project. - Components of a particular type: ``ctype``, ``package:ctype``, ``all:ctype``: which specifies all components of the given type. In component targets, ``package:`` and ``ctype:`` (valid component types are ``lib``, ``exe``, ``test`` and ``bench``) can be used to disambiguate when multiple packages define the same component, or the same component name is used in a package (e.g., a package ``foo`` defines both an executable and library named ``foo``). We always prefer interpreting a target as a package name rather than as a component name. Some example targets: :: $ cabal new-build lib:foo-pkg # build the library named foo-pkg $ cabal new-build foo-pkg:foo-tests # build foo-tests in foo-pkg (There is also syntax for specifying module and file targets, but it doesn't currently do anything.) Beyond a list of targets, ``cabal new-build`` accepts all the flags that ``cabal new-configure`` takes. Most of these flags are only taken into consideration when building local packages; however, some flags may cause extra store packages to be built (for example, ``--enable-profiling`` will automatically make sure profiling libraries for all transitive dependencies are built and installed.) cabal new-repl -------------- ``cabal new-repl TARGET`` loads all of the modules of the target into GHCi as interpreted bytecode. It takes the same flags as ``cabal new-build``. Currently, it is not supported to pass multiple targets to ``new-repl`` (``new-repl`` will just successively open a separate GHCi session for each target.) cabal new-freeze ---------------- ``cabal new-freeze`` writes out a ``cabal.project.freeze`` file which records all of the versions and flags which that are picked by the solver under the current index and flags. A ``cabal.project.freeze`` file has the same syntax as ``cabal.project`` and looks something like this: .. highlight:: cabal :: constraints: HTTP ==4000.3.3, HTTP +warp-tests -warn-as-error -network23 +network-uri -mtl1 -conduit10, QuickCheck ==2.9.1, QuickCheck +templatehaskell, -- etc... For end-user executables, it is recommended that you distribute the ``cabal.project.freeze`` file in your source repository so that all users see a consistent set of dependencies. For libraries, this is not recommended: users often need to build against different versions of libraries than what you developed against. Unsupported commands -------------------- The following commands are not currently supported: ``cabal new-test`` (:issue:`3638`) Workaround: run the test executable directly (see `Where are my build products <#where-are-my-build-products>`__?) ``cabal new-bench`` (:issue:`3638`) Workaround: run the benchmark executable directly (see `Where are my build products <#where-are-my-build-products>`__?) ``cabal new-run`` (:issue:`3638`) Workaround: run the executable directly (see `Where are my build products <#where-are-my-build-products>`__?) ``cabal new-exec`` Workaround: if you wanted to execute GHCi, consider using ``cabal new-repl`` instead. Otherwise, use ``-v`` to find the list of flags GHC is being invoked with and pass it manually. ``cabal new-haddock`` (:issue:`3535`) Workaround: run ``cabal act-as-setup -- haddock --builddir=dist-newstyle/build/pkg-0.1`` (or execute the Custom setup script directly). ``cabal new-install`` (:issue:`3737`) Workaround: no good workaround at the moment. (But note that you no longer need to install libraries before building!) Configuring builds with cabal.project ===================================== ``cabal.project`` files support a variety of options which configure the details of your build. The general syntax of a ``cabal.project`` file is similar to that of a Cabal file: there are a number of fields, some of which live inside stanzas: :: packages: */*.cabal with-compiler: /opt/ghc/8.0.1/bin/ghc package cryptohash optimization: False In general, the accepted field names coincide with the accepted command line flags that ``cabal install`` and other commands take. For example, ``cabal new-configure --enable-profiling`` will write out a project file with ``profiling: True``. The full configuration of a project is determined by combining the following sources (later entries override earlier ones): 1. ``~/.cabal/config`` (the user-wide global configuration) 2. ``cabal.project`` (the project configuratoin) 3. ``cabal.project.freeze`` (the output of ``cabal new-freeze``) 4. ``cabal.project.local`` (the output of ``cabal new-configure``) Specifying the local packages ----------------------------- The following top-level options specify what the local packages of a project are: .. cfg-field:: packages: package location list (space or comma separated) :synopsis: Project packages. :default: ``./*.cabal`` Specifies the list of package locations which contain the local packages to be built by this project. Package locations can take the following forms: 1. They can specify a Cabal file, or a directory containing a Cabal file, e.g., ``packages: Cabal cabal-install/cabal-install.cabal``. 2. They can specify a glob-style wildcards, which must match one or more (a) directories containing a (single) Cabal file, (b) Cabal files (extension ``.cabal``), or (c) [STRIKEOUT:tarballs which contain Cabal packages (extension ``.tar.gz``)] (not implemented yet). For example, to match all Cabal files in all subdirectories, as well as the Cabal projects in the parent directories ``foo`` and ``bar``, use ``packages: */*.cabal ../{foo,bar}/`` 3. [STRIKEOUT:They can specify an ``http``, ``https`` or ``file`` URL, representing the path to a remote tarball to be downloaded and built.] (not implemented yet) There is no command line variant of this field; see :issue:`3585`. .. cfg-field:: optional-packages: package location list (space or comma-separated) :synopsis: Optional project packages. :default: ``./*/*.cabal`` Like :cfg-field:`packages`, specifies a list of package locations containing local packages to be built. Unlike :cfg-field:`packages`, if we glob for a package, it is permissible for the glob to match against zero packages. The intended use-case for :cfg-field:`optional-packages` is to make it so that vendored packages can be automatically picked up if they are placed in a subdirectory, but not error if there aren't any. There is no command line variant of this field. .. cfg-field:: extra-packages: package list with version bounds (comma separated) :synopsis: Adds external pacakges as local [STRIKEOUT:Specifies a list of external packages from Hackage which should be considered local packages.] (Not implemented) There is no command line variant of this field. [STRIKEOUT:There is also a stanza ``source-repository-package`` for specifying packages from an external version control.] (Not implemented.) All local packages are *vendored*, in the sense that if other packages (including external ones from Hackage) depend on a package with the name of a local package, the local package is preferentially used. This motivates the default settings:: packages: ./*.cabal optional-packages: ./*/*.cabal ...any package can be vendored simply by making a checkout in the top-level project directory, as might be seen in this hypothetical directory layout:: foo.cabal foo-helper/ # local package unix/ # vendored external package All of these options support globs. ``cabal new-build`` has its own glob format: - Anywhere in a path, as many times as you like, you can specify an asterisk ``*`` wildcard. E.g., ``*/*.cabal`` matches all ``.cabal`` files in all immediate subdirectories. Like in glob(7), asterisks do not match hidden files unless there is an explicit period, e.g., ``.*/foo.cabal`` will match ``.private/foo.cabal`` (but ``*/foo.cabal`` will not). - You can use braces to specify specific directories; e.g., ``{vendor,pkgs}/*.cabal`` matches all Cabal files in the ``vendor`` and ``pkgs`` subdirectories. Formally, the format described by the following BNF: .. code-block:: abnf FilePathGlob ::= FilePathRoot FilePathGlobRel FilePathRoot ::= {- empty -} # relative to cabal.project | "/" # Unix root | [a-zA-Z] ":" [/\\] # Windows root | "~" # home directory FilePathGlobRel ::= Glob "/" FilePathGlobRel # Unix directory | Glob "\\" FilePathGlobRel # Windows directory | Glob # file | {- empty -} # trailing slash Glob ::= GlobPiece * GlobPiece ::= "*" # wildcard | [^*{},/\\] * # literal string | "\\" [*{},] # escaped reserved character | "{" Glob "," ... "," Glob "}" # union (match any of these) Global configuration options ---------------------------- The following top-level configuration options are not specific to any package, and thus apply globally: .. cfg-field:: verbose: nat --verbose=n, -vn :synopsis: Build verbosity level. :default: 1 Control the verbosity of ``cabal`` commands, valid values are from 0 to 3. The command line variant of this field is ``--verbose=2``; a short form ``-v2`` is also supported. .. cfg-field:: jobs: nat or $ncpus --jobs=n, -jn, --jobs=$ncpus :synopsis: Number of builds running in parallel. :default: 1 Run *nat* jobs simultaneously when building. If ``$ncpus`` is specified, run the number of jobs equal to the number of CPUs. Package building is often quite parallel, so turning on parallelism can speed up build times quite a bit! The command line variant of this field is ``--jobs=2``; a short form ``-j2`` is also supported; a bare ``--jobs`` or ``-j`` is equivalent to ``--jobs=$ncpus``. .. cfg-field:: keep-going: boolean --keep-going :synopsis: Try to continue building on failure. :default: False If true, after a build failure, continue to build other unaffected packages. The command line variant of this field is ``--keep-going``. .. option:: --builddir=DIR Specifies the name of the directory where build products for build will be stored; defaults to ``dist-newstyle``. If a relative name is specified, this directory is resolved relative to the root of the project (i.e., where the ``cabal.project`` file lives.) This option cannot be specified via a ``cabal.project`` file. .. option:: --project-file=FILE Specifies the name of the project file used to specify the rest of the top-level configuration; defaults to ``cabal.project``. This name not only specifies the name of the main project file, but also the auxiliary project files ``cabal.project.freeze`` and ``cabal.project.local``; for example, if you specify ``--project-file=my.project``, then the other files that will be probed are ``my.project.freeze`` and ``my.project.local``. If the specified project file is a relative path, we will look for the file relative to the current working directory, and then for the parent directory, until the project file is found or we have hit the top of the user's home directory. This option cannot be specified via a ``cabal.project`` file. Solver configuration options ---------------------------- The following settings control the behavior of the dependency solver: .. cfg-field:: constraints: constraints list (comma separated) --constraint="pkg >= 2.0" :synopsis: Extra dependencies constraints. Add extra constraints to the version bounds, flag settings, and other properties a solver can pick for a package. For example: :: constraints: bar == 2.1 A package can be specified multiple times in ``constraints``, in which case the specified constraints are intersected. This is useful, since the syntax does not allow you to specify multiple constraints at once. For example, to specify both version bounds and flag assignments, you would write: :: constraints: bar == 2.1, bar +foo -baz Valid constraints take the same form as for the `constraint command line option `__. .. cfg-field:: preferences: preference (comma separated) --preference="pkg >= 2.0" :synopsis: Prefered dependency versions. Like :cfg-field:`constraints`, but the solver will attempt to satisfy these preferences on a best-effort basis. The resulting install is locally optimal with respect to preferences; specifically, no single package could be replaced with a more preferred version that still satisfies the hard constraints. Operationally, preferences can cause the solver to attempt certain version choices of a package before others, which can improve dependency solver runtime. One way to use :cfg-field:`preferences` is to take a known working set of constraints (e.g., via ``cabal new-freeze``) and record them as preferences. In this case, the solver will first attempt to use this configuration, and if this violates hard constraints, it will try to find the minimal number of upgrades to satisfy the hard constraints again. The command line variant of this field is ``--preference="pkg >= 2.0"``; to specify multiple preferences, pass the flag multiple times. .. cfg-field:: allow-newer: none, all or list of scoped package names (space or comma separated) --allow-newer, --allow-newer=[none,all,pkg] :synopsis: Lift dependencies upper bound constaints. :default: ``none`` Allow the solver to pick an newer version of some packages than would normally be permitted by than the :pkg-field:`build-depends` bounds of packages in the install plan. This option may be useful if the dependency solver cannot otherwise find a valid install plan. For example, to relax ``pkg``\ s :pkg-field:`build-depends` upper bound on ``dep-pkg``, write a scoped package name of the form: :: allow-newer: pkg:dep-pkg This syntax is recommended, as it is often only a single package whose upper bound is misbehaving. In this case, the upper bounds of other packages should still be respected; indeed, relaxing the bound can break some packages which test the selected version of packages. However, in some situations (e.g., when attempting to build packages on a new version of GHC), it is useful to disregard *all* upper-bounds, with respect to a package or all packages. This can be done by specifying just a package name, or using the keyword ``all`` to specify all packages: :: -- Disregard upper bounds involving the dependencies on -- packages bar, baz and quux allow-newer: bar, baz, quux -- Disregard all upper bounds when dependency solving allow-newer: all :cfg-field:`allow-newer` is often used in conjunction with a constraint (in the cfg-field:`constraints` field) forcing the usage of a specific, newer version of a package. The command line variant of this field is ``--allow-newer=bar``. A bare ``--allow-newer`` is equivalent to ``--allow-newer=all``. .. cfg-field:: allow-older: none, all, list of scoped package names (space or comma separated) --allow-older, --allow-older=[none,all,pkg] :synopsis: Lift dependency lower bound constaints. :default: ``none`` Like :cfg-field:`allow-newer`, but applied to lower bounds rather than upper bounds. The command line variant of this field is ``--allow-older=all``. A bare ``--allow-older`` is equivalent to ``--allow-older=all``. .. cfg-field:: index-state: HEAD, unix-timestamp, ISO8601 UTC timestamp. :synopsis: Use source package index state as it existed at a previous time. :since: 2.0 :default: ``HEAD`` This allows to change the source package index state the solver uses to compute install-plans. This is particularly useful in combination with freeze-files in order to also freeze the state the package index was in at the time the install-plan was frozen. :: -- UNIX timestamp format example index-state: @1474739268 -- ISO8601 UTC timestamp format example -- This format is used by 'cabal new-configure' -- for storing `--index-state` values. index-state: 2016-09-24T17:47:48Z Package configuration options ----------------------------- Package options affect the building of specific packages. There are two ways a package option can be specified: - They can be specified at the top-level, in which case they apply only to **local package**, or - They can be specified inside a ``package`` stanza, in which case they apply to the build of the package, whether or not it is local or external. For example, the following options specify that :cfg-field:`optimization` should be turned off for all local packages, and that ``bytestring`` (possibly an external dependency) should be built with ``-fno-state-hack``:: optimization: False package bytestring ghc-options: -fno-state-hack ``ghc-options`` is not specifically described in this documentation, but is one of many fields for configuring programs. They take the form ``progname-options`` and ``progname-location``, and can only be set inside package stanzas. (TODO: They are not supported at top-level, see :issue:`3579`.) At the moment, there is no way to specify an option to apply to all external packages or all inplace packages. Additionally, it is only possible to specify these options on the command line for all local packages (there is no per-package command line interface.) Some flags were added by more recent versions of the Cabal library. This means that they are NOT supported by packages which use Custom setup scripts that require a version of the Cabal library older than when the feature was added. .. cfg-field:: flags: list of +flagname or -flagname (space separated) --flags="+foo -bar", -ffoo, -f-bar :synopsis: Enable or disable package flags. Force all flags specified as ``+flagname`` to be true, and all flags specified as ``-flagname`` to be false. For example, to enable the flag ``foo`` and disable ``bar``, set: :: flags: +foo -bar If there is no leading punctuation, it is assumed that the flag should be enabled; e.g., this is equivalent: :: flags: foo -bar Flags are *per-package*, so it doesn't make much sense to specify flags at the top-level, unless you happen to know that *all* of your local packages support the same named flags. If a flag is not supported by a package, it is ignored. See also the solver configuration field :cfg-field:`constraints`. The command line variant of this flag is ``--flags``. There is also a shortened form ``-ffoo -f-bar``. A common mistake is to say ``cabal new-build -fhans``, where ``hans`` is a flag for a transitive dependency that is not in the local package; in this case, the flag will be silently ignored. If ``haskell-tor`` is the package you want this flag to apply to, try ``--constraint="haskell-tor +hans"`` instead. .. cfg-field:: with-compiler: executable --with-compiler=executable :synopsis: Path to compiler executable. Specify the path to a particular compiler to be used. If not an absolute path, it will be resolved according to the :envvar:`PATH` environment. The type of the compiler (GHC, GHCJS, etc) must be consistent with the setting of the :cfg-field:`compiler` field. The most common use of this option is to specify a different version of your compiler to be used; e.g., if you have ``ghc-7.8`` in your path, you can specify ``with-compiler: ghc-7.8`` to use it. This flag also sets the default value of :cfg-field:`with-hc-pkg`, using the heuristic that it is named ``ghc-pkg-7.8`` (if your executable name is suffixed with a version number), or is the executable named ``ghc-pkg`` in the same directory as the ``ghc`` directory. If this heuristic does not work, set :cfg-field:`with-hc-pkg` explicitly. For inplace packages, ``cabal new-build`` maintains a separate build directory for each version of GHC, so you can maintain multiple build trees for different versions of GHC without clobbering each other. At the moment, it's not possible to set :cfg-field:`with-compiler` on a per-package basis, but eventually we plan on relaxing this restriction. If this is something you need, give us a shout. The command line variant of this flag is ``--with-compiler=ghc-7.8``; there is also a short version ``-w ghc-7.8``. .. cfg-field:: with-hc-pkg: executable --with-hc-pkg=executable :synopsis: Specifies package tool. Specify the path to the package tool, e.g., ``ghc-pkg``. This package tool must be compatible with the compiler specified by :cfg-field:`with-compiler` (generally speaking, it should be precisely the tool that was distributed with the compiler). If this option is omitted, the default value is determined from :cfg-field:`with-compiler`. The command line variant of this flag is ``--with-hc-pkg=ghc-pkg-7.8``. .. cfg-field:: optimization: nat --enable-optimization --disable-optimization :synopsis: Build with optimization. :default: ``1`` Build with optimization. This is appropriate for production use, taking more time to build faster libraries and programs. The optional *nat* value is the optimisation level. Some compilers support multiple optimisation levels. The range is 0 to 2. Level 0 disables optimization, level 1 is the default. Level 2 is higher optimisation if the compiler supports it. Level 2 is likely to lead to longer compile times and bigger generated code. If you are not planning to run code, turning off optimization will lead to better build times and less code to be rebuilt when a module changes. We also accept ``True`` (equivalent to 1) and ``False`` (equivalent to 0). Note that as of GHC 8.0, GHC does not recompile when optimization levels change (see :ghc-ticket:`10923`), so if you change the optimization level for a local package you may need to blow away your old build products in order to rebuild with the new optimization level. The command line variant of this flag is ``-O2`` (with ``-O1`` equivalent to ``-O``). There are also long-form variants ``--enable-optimization`` and ``--disable-optimization``. .. cfg-field:: configure-options: args (space separated) --configure-option=arg :synopsis: Options to pass to configure script. A list of extra arguments to pass to the external ``./configure`` script, if one is used. This is only useful for packages which have the ``Configure`` build type. See also the section on `system-dependent parameters `__. The command line variant of this flag is ``--configure-option=arg``, which can be specified multiple times to pass multiple options. .. cfg-field:: compiler: ghc, ghcjs, jhc, lhc, uhc or haskell-suite --compiler=compiler :synopsis: Compiler to build with. :default: ``ghc`` Specify which compiler toolchain to be used. This is independent of ``with-compiler``, because the choice of toolchain affects Cabal's build logic. The command line variant of this flag is ``--compiler=ghc``. .. cfg-field:: tests: boolean --enable-tests --disable-tests :synopsis: Build tests. :default: ``False`` Force test suites to be enabled. For most users this should not be needed, as we always attempt to solve for test suite dependencies, even when this value is ``False``; furthermore, test suites are automatically enabled if they are requested as a built target. The command line variant of this flag is ``--enable-tests`` and ``--disable-tests``. .. cfg-field:: benchmarks: boolean --enable-benchmarks --disable-benchmarks :synopsis: Build benchmarks. :default: ``False`` Force benchmarks to be enabled. For most users this should not be needed, as we always attempt to solve for benchmark dependencies, even when this value is ``False``; furthermore, benchmarks are automatically enabled if they are requested as a built target. The command line variant of this flag is ``--enable-benchmarks`` and ``--disable-benchmarks``. .. cfg-field:: extra-prog-path: paths (newline or comma separated) --extra-prog-path=PATH :synopsis: Add directories to program search path. :since: 1.18 A list of directories to search for extra required programs. Most users should not need this, as programs like ``happy`` and ``alex`` will automatically be installed and added to the path. This can be useful if a ``Custom`` setup script relies on an exotic extra program. The command line variant of this flag is ``--extra-prog-path=PATH``, which can be specified multiple times. .. cfg-field:: run-tests: boolean --run-tests :synopsis: Run package test suite upon installation. :default: ``False`` Run the package test suite upon installation. This is useful for saying "When this package is installed, check that the test suite passes, terminating the rest of the build if it is broken." .. warning:: One deficiency: the :cfg-field:`run-tests` setting of a package is NOT recorded as part of the hash, so if you install something without :cfg-field:`run-tests` and then turn on ``run-tests``, we won't subsequently test the package. If this is causing you problems, give us a shout. The command line variant of this flag is ``--run-tests``. Object code options ^^^^^^^^^^^^^^^^^^^ .. cfg-field:: debug-info: boolean --enable-debug-info --disable-debug-info :synopsis: Build with debug info enabled. :since: 1.22 :default: False If the compiler (e.g., GHC 7.10 and later) supports outputing OS native debug info (e.g., DWARF), setting ``debug-info: True`` will instruct it to do so. See the GHC wiki page on :ghc-wiki:`DWARF` for more information about this feature. (This field also accepts numeric syntax, but as of GHC 8.0 this doesn't do anything.) The command line variant of this flag is ``--enable-debug-info`` and ``--disable-debug-info``. .. cfg-field:: split-objs: boolean --enable-split-objs --disable-split-objs :synopsis: Use GHC split objects feature. :default: False Use the GHC ``-split-objs`` feature when building the library. This reduces the final size of the executables that use the library by allowing them to link with only the bits that they use rather than the entire library. The downside is that building the library takes longer and uses considerably more memory. The command line variant of this flag is ``--enable-split-objs`` and ``--disable-split-objs``. .. cfg-field:: executable-stripping: boolean --enable-executable-stripping --disable-executable-stripping :synopsis: Strip installed programs. :default: True When installing binary executable programs, run the ``strip`` program on the binary. This can considerably reduce the size of the executable binary file. It does this by removing debugging information and symbols. Not all Haskell implementations generate native binaries. For such implementations this option has no effect. (TODO: Check what happens if you combine this with ``debug-info``.) The command line variant of this flag is ``--enable-executable-stripping`` and ``--disable-executable-stripping``. .. cfg-field:: library-stripping: boolean --enable-library-stripping --disable-library-stripping :synopsis: Strip installed libraries. :since: 1.19 When installing binary libraries, run the ``strip`` program on the binary, saving space on the file system. See also ``executable-stripping``. The command line variant of this flag is ``--enable-library-stripping`` and ``--disable-library-stripping``. Executable options ^^^^^^^^^^^^^^^^^^ .. cfg-field:: program-prefix: prefix --program-prefix=prefix :synopsis: Prepend prefix to program names. [STRIKEOUT:Prepend *prefix* to installed program names.] (Currently implemented in a silly and not useful way. If you need this to work give us a shout.) *prefix* may contain the following path variables: ``$pkgid``, ``$pkg``, ``$version``, ``$compiler``, ``$os``, ``$arch``, ``$abi``, ``$abitag`` The command line variant of this flag is ``--program-prefix=foo-``. .. cfg-field:: program-suffix: suffix --program-suffix=suffix :synopsis: Append refix to program names. [STRIKEOUT:Append *suffix* to installed program names.] (Currently implemented in a silly and not useful way. If you need this to work give us a shout.) The most obvious use for this is to append the program's version number to make it possible to install several versions of a program at once: ``program-suffix: $version``. *suffix* may contain the following path variables: ``$pkgid``, ``$pkg``, ``$version``, ``$compiler``, ``$os``, ``$arch``, ``$abi``, ``$abitag`` The command line variant of this flag is ``--program-suffix='$version'``. Dynamic linking options ^^^^^^^^^^^^^^^^^^^^^^^ .. cfg-field:: shared: boolean --enable-shared --disable-shared :synopsis: Build shared library. :default: False Build shared library. This implies a separate compiler run to generate position independent code as required on most platforms. The command line variant of this flag is ``--enable-shared`` and ``--disable-shared``. .. cfg-field:: executable-dynamic: boolean --enable-executable-dynamic --disable-executable-dynamic :synopsis: Link executables dynamically. :default: False Link executables dynamically. The executable's library dependencies should be built as shared objects. This implies ``shared: True`` unless ``shared: False`` is explicitly specified. The command line variant of this flag is ``--enable-executable-dynamic`` and ``--disable-executable-dynamic``. .. cfg-field:: library-for-ghci: boolean --enable-library-for-ghci --disable-library-for-ghci :synopsis: Build libraries suitable for use with GHCi. :default: True Build libraries suitable for use with GHCi. This involves an extra linking step after the build. Not all platforms support GHCi and indeed on some platforms, trying to build GHCi libs fails. In such cases, consider setting ``library-for-ghci: False``. The command line variant of this flag is ``--enable-library-for-ghci`` and ``--disable-library-for-ghci``. .. cfg-field:: relocatable: --relocatable :synopsis: Build relocatable package. :since: 1.21 :default: False [STRIKEOUT:Build a package which is relocatable.] (TODO: It is not clear what this actually does, or if it works at all.) The command line variant of this flag is ``--relocatable``. Foreign function interface options ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ .. cfg-field:: extra-include-dirs: directories (comma or newline separated list) --extra-include-dirs=DIR :synopsis: Adds C header search path. An extra directory to search for C header files. You can use this flag multiple times to get a list of directories. You might need to use this flag if you have standard system header files in a non-standard location that is not mentioned in the package's ``.cabal`` file. Using this option has the same affect as appending the directory *dir* to the :pkg-field:`include-dirs` field in each library and executable in the package's ``.cabal`` file. The advantage of course is that you do not have to modify the package at all. These extra directories will be used while building the package and for libraries it is also saved in the package registration information and used when compiling modules that use the library. The command line variant of this flag is ``--extra-include-dirs=DIR``, which can be specified multiple times. .. cfg-field:: extra-lib-dirs: directories (comma or newline separated list) --extra-lib-dirs=DIR :synopsis: Adds library search directory. An extra directory to search for system libraries files. The command line variant of this flag is ``--extra-lib-dirs=DIR``, which can be specified multiple times. .. cfg-field:: extra-framework-dirs: directories (comma or newline separated list) --extra-framework-dirs=DIR :synopsis: Adds framework search directory (OS X only). An extra directory to search for frameworks (OS X only). You might need to use this flag if you have standard system libraries in a non-standard location that is not mentioned in the package's ``.cabal`` file. Using this option has the same affect as appending the directory *dir* to the :cfg-field:`extra-lib-dirs` field in each library and executable in the package's ``.cabal`` file. The advantage of course is that you do not have to modify the package at all. These extra directories will be used while building the package and for libraries it is also saved in the package registration information and used when compiling modules that use the library. The command line variant of this flag is ``--extra-framework-dirs=DIR``, which can be specified multiple times. Profiling options ^^^^^^^^^^^^^^^^^ .. cfg-field:: profiling: boolean --enable-profiling --disable-profiling :synopsis: Enable profiling builds. :since: 1.21 :default: False Build libraries and executables with profiling enabled (for compilers that support profiling as a separate mode). It is only necessary to specify :cfg-field:`profiling` for the specific package you want to profile; ``cabal new-build`` will ensure that all of its transitive dependencies are built with profiling enabled. To enable profiling for only libraries or executables, see :cfg-field:`library-profiling` and :cfg-field:`executable-profiling`. For useful profiling, it can be important to control precisely what cost centers are allocated; see :cfg-field:`profiling-detail`. The command line variant of this flag is ``--enable-profiling`` and ``--disable-profiling``. .. cfg-field:: profiling-detail: level --profiling-detail=level :synopsis: Profiling detail level. :since: 1.23 Some compilers that support profiling, notably GHC, can allocate costs to different parts of the program and there are different levels of granularity or detail with which this can be done. In particular for GHC this concept is called "cost centers", and GHC can automatically add cost centers, and can do so in different ways. This flag covers both libraries and executables, but can be overridden by the ``library-profiling-detail`` field. Currently this setting is ignored for compilers other than GHC. The levels that cabal currently supports are: default For GHC this uses ``exported-functions`` for libraries and ``toplevel-functions`` for executables. none No costs will be assigned to any code within this component. exported-functions Costs will be assigned at the granularity of all top level functions exported from each module. In GHC, this is for non-inline functions. Corresponds to ``-fprof-auto-exported``. toplevel-functions Costs will be assigned at the granularity of all top level functions in each module, whether they are exported from the module or not. In GHC specifically, this is for non-inline functions. Corresponds to ``-fprof-auto-top``. all-functions Costs will be assigned at the granularity of all functions in each module, whether top level or local. In GHC specifically, this is for non-inline toplevel or where-bound functions or values. Corresponds to ``-fprof-auto``. The command line variant of this flag is ``--profiling-detail=none``. .. cfg-field:: library-profiling-detail: level --library-profiling-detail=level :synopsis: Libraries profiling detail level. :since: 1.23 Like :cfg-field:`profiling-detail`, but applied only to libraries The command line variant of this flag is ``--library-profiling-detail=none``. .. cfg-field:: library-vanilla: boolean --enable-library-vanilla --disable-library-vanilla :synopsis: Build libraries without profiling. :default: True Build ordinary libraries (as opposed to profiling libraries). Mostly, you can set this to False to avoid building ordinary libraries when you are profiling. The command line variant of this flag is ``--enable-library-vanilla`` and ``--disable-library-vanilla``. .. cfg-field:: library-profiling: boolean --enable-library-profiling --disable-library-profiling :synopsis: Build libraries with profiling enabled. :since: 1.21 :default: False Build libraries with profiling enabled. You probably want to use :cfg-field:`profiling` instead. The command line variant of this flag is ``--enable-library-profiling`` and ``--disable-library-profiling``. .. cfg-field:: executable-profiling: boolean --enable-executable-profiling --disable-executable-profiling :synopsis: Build executables with profiling enabled. :since: 1.21 :default: False Build executables with profiling enabled. You probably want to use :cfg-field:`profiling` instead. The command line variant of this flag is ``--enable-executable-profiling`` and ``--disable-executable-profiling``. Coverage options ^^^^^^^^^^^^^^^^ .. cfg-field:: coverage: boolean --enable-coverage --disable-coverage :synopsis: Build with coverage enabled. :since: 1.21 :default: False Build libraries and executables (including test suites) with Haskell Program Coverage enabled. Running the test suites will automatically generate coverage reports with HPC. The command line variant of this flag is ``--enable-coverage`` and ``--disable-coverage``. .. cfg-field:: library-coverage: boolean --enable-library-coverage --disable-library-coverage :since: 1.21 :deprecated: :default: False Deprecated, use :cfg-field:`coverage`. The command line variant of this flag is ``--enable-library-coverage`` and ``--disable-library-coverage``. Haddock options ^^^^^^^^^^^^^^^ Documentation building support is fairly sparse at the moment. Let us know if it's a priority for you! .. cfg-field:: documentation: boolean --enable-documentation --disable-documentation :synopsis: Enable building of documentation. :default: False Enables building of Haddock documentation The command line variant of this flag is ``--enable-documentation`` and ``--disable-documentation``. .. cfg-field:: doc-index-file: templated path --doc-index-file=TEMPLATE :synopsis: Path to haddock templates. A central index of Haddock API documentation (template cannot use ``$pkgid``), which should be updated as documentation is built. The command line variant of this flag is ``--doc-index-file=TEMPLATE`` The following commands are equivalent to ones that would be passed when running ``setup haddock``. (TODO: Where does the documentation get put.) .. cfg-field:: haddock-hoogle: boolean :synopsis: Generate Hoogle file. :default: False Generate a text file which can be converted by Hoogle_ into a database for searching. This is equivalent to running ``haddock`` with the ``--hoogle`` flag. The command line variant of this flag is ``--hoogle`` (for the ``haddock`` command). .. cfg-field:: haddock-html: boolean :synopsis: Build HTML documentation. :default: True Build HTML documentation. The command line variant of this flag is ``--html`` (for the ``haddock`` command). .. cfg-field:: haddock-html-location: templated path :synopsis: Haddock HTML templates location. Specify a template for the location of HTML documentation for prerequisite packages. The substitutions are applied to the template to obtain a location for each package, which will be used by hyperlinks in the generated documentation. For example, the following command generates links pointing at [Hackage] pages: :: html-location: 'http://hackage.haskell.org/packages/archive/$pkg/latest/doc/html' Here the argument is quoted to prevent substitution by the shell. If this option is omitted, the location for each package is obtained using the package tool (e.g. ``ghc-pkg``). The command line variant of this flag is ``--html-location`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-executables: boolean :synopsis: Generate documentation for executables. :default: False Run haddock on all executable programs. The command line variant of this flag is ``--executables`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-tests: boolean :synopsis: Generate documentation for tests. :default: False Run haddock on all test suites. The command line variant of this flag is ``--tests`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-benchmarks: boolean :synopsis: Generate documentation for benchmarks. :default: False Run haddock on all benchmarks. The command line variant of this flag is ``--benchmarks`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-all: boolean :synopsis: Generate documentation for everything :default: False Run haddock on all components. The command line variant of this flag is ``--all`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-internal: boolean :synopsis: Generate documentation for internal modules :default: False Build haddock documentation which includes unexposed modules and symbols. The command line variant of this flag is ``--internal`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-css: path :synopsis: Location of Haddoc CSS file. The CSS file that should be used to style the generated documentation (overriding haddock's default.) The command line variant of this flag is ``--css`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-hyperlink-source: boolean :synopsis: Generate hyperlinked source code for documentation :default: False Generated hyperlinked source code using `HsColour`_, and have Haddock documentation link to it. The command line variant of this flag is ``--hyperlink-source`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-hscolour-css: path :synopsis: Location of CSS file for HsColour The CSS file that should be used to style the generated hyperlinked source code (from `HsColour`_). The command line variant of this flag is ``--hscolour-css`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-contents-location: URL :synopsis: URL for contents page. A baked-in URL to be used as the location for the contents page. The command line variant of this flag is ``--contents-location`` (for the ``haddock`` subcommand). .. cfg-field:: haddock-keep-temp-files: boolean :synopsis: Keep temporary Haddock files. Keep temporary files. The command line variant of this flag is ``--keep-temp-files`` (for the ``haddock`` subcommand). Advanced global configuration options ------------------------------------- .. cfg-field:: http-transport: curl, wget, powershell, or plain-http --http-transport=transport :synopsis: Transport to use with http(s) requests. :default: ``curl`` Set a transport to be used when making http(s) requests. The command line variant of this field is ``--http-transport=curl``. .. cfg-field:: ignore-expiry: boolean --ignore-expiry :synopsis: Ignore Hackage expiration dates. :default: False If ``True``, we will ignore expiry dates on metadata from Hackage. In general, you should not set this to ``True`` as it will leave you vulnerable to stale cache attacks. However, it may be temporarily useful if the main Hackage server is down, and we need to rely on mirrors which have not been updated for longer than the expiry period on the timestamp. The command line variant of this field is ``--ignore-expiry``. .. cfg-field:: remote-repo-cache: directory --remote-repo-cache=DIR :synopsis: Location of packages cache. :default: ``~/.cabal/packages`` [STRIKEOUT:The location where packages downloaded from remote repositories will be cached.] Not implemented yet. The command line variant of this flag is ``--remote-repo-cache=DIR``. .. cfg-field:: logs-dir: directory --logs-dir=DIR :synopsis: Directory to store build logs. :default: ``~/.cabal/logs`` [STRIKEOUT:The location where build logs for packages are stored.] Not implemented yet. The command line variant of this flag is ``--logs-dir=DIR``. .. cfg-field:: build-summary: template filepath --build-summary=TEMPLATE :synopsis: Build summaries location. :default: ``~/.cabal/logs/build.log`` [STRIKEOUT:The file to save build summaries. Valid variables which can be used in the path are ``$pkgid``, ``$compiler``, ``$os`` and ``$arch``.] Not implemented yet. The command line variant of this flag is ``--build-summary=TEMPLATE``. .. cfg-field:: local-repo: directory --local-repo=DIR :deprecated: [STRIKEOUT:The location of a local repository.] Deprecated. See "Legacy repositories." The command line variant of this flag is ``--local-repo=DIR``. .. cfg-field:: world-file: path --world-file=FILE :deprecated: [STRIKEOUT:The location of the world file.] Deprecated. The command line variant of this flag is ``--world-file=FILE``. Undocumented fields: ``root-cmd``, ``symlink-bindir``, ``build-log``, ``remote-build-reporting``, ``report-planned-failure``, ``one-shot``, ``offline``. Advanced solver options ^^^^^^^^^^^^^^^^^^^^^^^ Most users generally won't need these. .. cfg-field:: solver: modular --solver=modular :synopsis: Which solver to use. This field is reserved to allow the specification of alternative dependency solvers. At the moment, the only accepted option is ``modular``. The command line variant of this field is ``--solver=modular``. .. cfg-field:: max-backjumps: nat --max-backjumps=N :synopsis: Maximum number of solver backjumps. :default: 2000 Maximum number of backjumps (backtracking multiple steps) allowed while solving. Set -1 to allow unlimited backtracking, and 0 to disable backtracking completely. The command line variant of this field is ``--max-backjumps=2000``. .. cfg-field:: reorder-goals: boolean --reorder-goals --no-reorder-goals :synopsis: Allow solver to reorder goals. :default: False When enabled, the solver will reorder goals according to certain heuristics. Slows things down on average, but may make backtracking faster for some packages. It's unlikely to help for small projects, but for big install plans it may help you find a plan when otherwise this is not possible. See :issue:`1780` for more commentary. The command line variant of this field is ``--(no-)reorder-goals``. .. cfg-field:: count-conflicts: boolean --count-conflicts --no-count-conflicts :synopsis: Solver prefers versions with less conflicts. :default: True Try to speed up solving by preferring goals that are involved in a lot of conflicts. The command line variant of this field is ``--(no-)count-conflicts``. .. cfg-field:: strong-flags: boolean --strong-flags --no-strong-flags :synopsis: Do not defer flag choices when solving. :default: False Do not defer flag choices. (TODO: Better documentation.) The command line variant of this field is ``--(no-)strong-flags``. .. cfg-field:: allow-boot-library-installs: boolean --allow-boot-library-installs --no-allow-boot-library-installs :synopsis: Allow cabal to install or upgrade any package. :default: False By default, the dependency solver doesn't allow ``base``, ``ghc-prim``, ``integer-simple``, ``integer-gmp``, and ``template-haskell`` to be installed or upgraded. This flag removes the restriction. The command line variant of this field is ``--(no-)allow-boot-library-installs``. .. cfg-field:: cabal-lib-version: version --cabal-lib-version=version :synopsis: Version of Cabal library used to build package. This field selects the version of the Cabal library which should be used to build packages. This option is intended primarily for internal development use (e.g., forcing a package to build with a newer version of Cabal, to test a new version of Cabal.) (TODO: Specify its semantics more clearly.) The command line variant of this field is ``--cabal-lib-version=1.24.0.1``. .. include:: references.inc