Changes between Version 28 and Version 29 of Commentary/GSoCMultipleInstances

Timestamp:

06/19/12 07:00:14 (12 months ago)

Author:

kosmikus

Comment:

--

Commentary/GSoCMultipleInstances

@@ -5 +5 @@
 
  * Cabal should install packages to a location that does not just depend on name and version,
- * `ghc-pkg` should always add instances to the PackageDB and never overwrite them,
+ * `ghc-pkg` should always add instances to the `PackageDB` and never overwrite them,
  * `ghc --make`, `ghci`, and the configure phase of Cabal should select suitable instances according to some rule of thumb (similar to the current resolution technique),
  * we want to be able to make more fine-grained distinctions between package instances than currently possible, for example by distinguishing different build flavours or "ways" (profiling, etc.)
- * `cabal-install` should still find an InstallPlan, and still avoid unnecessarily rebuilding packages whenever it makes sense
+ * `cabal-install` should still find an `InstallPlan`, and still avoid unnecessarily rebuilding packages whenever it makes sense
  * some form of garbage collection should be offered to have a chance to reduce the amount of installed packages
 
@@ -156 +156 @@
 What is ComponentLocalBuildInfo for?
 
+== Currently open design decisions ==
+
+=== `InstalledPackageId` and install path ===
+
+Options for uniquely identifying `InstalledPackageId`:
+
+   * Cabal hash only
+   * Cabal + ABI hash (truly unique)
+   * random number
+
+Options for identifying install path:
+
+   * Cabal hash
+   * random number
+
+ABI hash cannot be in install path because it's only available after build.
+
+=== Build flavours ===
+
+To what degree should we distinguish package instances?
+
+   * Only package versions transitively
+   * Ways and Cabal flags
+   * Everything Haskell-specific info that we can query
+   * Even non-Haskell-specific inputs such as OS dependencies
+
+=== `InstalledPackageInfo` and solver algorithm ===
+
+Options for `InstalledPackageInfo`:
+
+   * Only add Cabal hash.
+   * Add (nearly) all information, but in an extensible format.
+   * Add all information in a way that `ghc-pkg` itself can use it.
+
+[These aren't necessarily mutually exclusive.]
+
+Options for the solver:
+
+   * Direct (see above): requires a certain amount of info in the `InstalledPackageInfo`.
+
+   * Agnostic (except for builtin packages): could be done with only the Cabal hash in `InstalledPackageInfo`.