Safe Haskell	None
Language	Haskell98

Language.Haskell.HLint3

Contents

Idea data type
Settings
Hints
Scopes
Haskell-src-exts

Description

WARNING: This module represents the evolving second version of the HLint API. It will be renamed to drop the "3" in the next major version.

This module provides a way to apply HLint hints. As an example of approximating the hlint experience:

(flags, classify, hint) <- autoSettings
Right m <- parseModuleEx flags "MyFile.hs" Nothing
print $ applyHints classify hint [m]

Synopsis

Documentation

applyHints :: [Classify] -> Hint -> [(Module SrcSpanInfo, [Comment])] -> [Idea] Source

Given a way of classifying results, and a Hint, apply to a set of modules generating a list of Ideas. The Idea values will be ordered within a file.

Idea data type

data Idea Source

An idea suggest by a Hint.

Constructors

Idea

Fields

ideaModule :: String: The module the idea applies to, may be "" if the module cannot be determined or is a result of cross-module hints.
ideaDecl :: String: The declaration the idea applies to, typically the function name, but may be a type name.
ideaSeverity :: Severity: The severity of the idea, e.g. Warning.
ideaHint :: String: The name of the hint that generated the idea, e.g. "Use reverse".
ideaSpan :: SrcSpan: The source code the idea relates to.
ideaFrom :: String: The contents of the source code the idea relates to.
ideaTo :: Maybe String: The suggested replacement, or Nothing for no replacement (e.g. on parse errors).
ideaNote :: [Note]: Notes about the effect of applying the replacement.

Instances

Eq Idea
Ord Idea
Show Idea

data Severity Source

How severe an issue is.

Constructors

Ignore	The issue has been explicitly ignored and will usually be hidden (pass `--show` on the command line to see ignored ideas).
Warning	Warnings are things that some people may consider improvements, but some may not.
Error	Errors are suggestions that are nearly always a good idea to apply.

Instances

Bounded Severity
Enum Severity
Eq Severity
Ord Severity
Read Severity
Show Severity

data Note Source

A note describing the impact of the replacement.

Constructors

IncreasesLaziness	The replacement is increases laziness, for example replacing `reverse (reverse x)` with `x` makes the code lazier.
DecreasesLaziness	The replacement is decreases laziness, for example replacing `(fst x, snd x)` with `x` makes the code stricter.
RemovesError String	The replacement removes errors, for example replacing `foldr1 (+)` with `sum` removes an error on `[]`, and might contain the text `"on []"`.
ValidInstance String String	The replacement assumes standard type class lemmas, a hint with the note `ValidInstance "Eq" "x"` might only be valid if the `x` variable has a reflexive `Eq` instance.
Note String	An arbitrary note.

Instances

Eq Note
Ord Note
Show Note

Settings

data Classify Source

How to classify an Idea. If any matching field is "" then it matches everything.

Constructors

Classify
Fields classifySeverity :: Severity Severity to set the `Idea` to. classifyHint :: String Match on `Idea` field `ideaHint`. classifyModule :: String Match on `Idea` field `ideaModule`. classifyDecl :: String Match on `Idea` field `ideaDecl`.

Instances

Show Classify

getHLintDataDir :: IO FilePath Source

Get the Cabal configured data directory of HLint.

autoSettings :: IO (ParseFlags, [Classify], Hint) Source

The function produces a tuple containg ParseFlags (for parseModuleEx), and Classify and Hint for applyHints. It approximates the normal HLint configuration steps, roughly:

Use findSettings with readSettingsFile to find and load the HLint settings files.
Use parseFlagsAddFixities and resolveHints to transform the outputs of findSettings.

If you want to do anything custom (e.g. using a different data directory, storing intermediate outputs, loading hints from a database) you are expected to copy and paste this function, then change it to your needs.

findSettings :: (String -> IO (FilePath, Maybe String)) -> Maybe String -> IO ([Fixity], [Classify], [Either HintBuiltin HintRule]) Source

Given a function to load a module (typically readSettingsFile), and a module to start from (defaults to HLint.HLint) find the information from all settings files.

readSettingsFile :: Maybe FilePath -> String -> IO (FilePath, Maybe String) Source

Given a directory (or Nothing to imply getHLintDataDir), and a mdoule name (e.g. HLint.Default), find the settings file associated with it, returning the name of the file, and (optionally) the contents.

This function looks for all settings files starting with HLint. in the directory argument, and all other files relative to the current directory.

Hints

data HintBuiltin Source

A list of the builtin hints wired into HLint. This list is likely to grow over time.

Constructors

HintList
HintListRec
HintMonad
HintLambda
HintBracket
HintNaming
HintStructure
HintImport
HintPragma
HintExtensions
HintUnsafe
HintDuplicate
HintComment

Instances

Bounded HintBuiltin
Enum HintBuiltin
Eq HintBuiltin
Ord HintBuiltin
Show HintBuiltin

data HintRule Source

A LHS ==> RHS style hint rule.

Constructors

HintRule

Fields

hintRuleSeverity :: Severity: Default severity for the hint.
hintRuleName :: String: Name for the hint.
hintRuleScope :: Scope: Module scope in which the hint operates.
hintRuleLHS :: Exp SrcSpanInfo: LHS
hintRuleRHS :: Exp SrcSpanInfo: RHS
hintRuleSide :: Maybe (Exp SrcSpanInfo): Side condition, typically specified with where _ = ....
hintRuleNotes :: [Note]: Notes about application of the hint.

Instances

Show HintRule

data Hint Source

Functions to generate hints, combined using the Monoid instance.

Constructors

Hint

Fields

hintModules :: [(Scope, Module SrcSpanInfo)] -> [Idea]: Given a list of modules (and their scope information) generate some Ideas.
hintModule :: Scope -> Module SrcSpanInfo -> [Idea]: Given a single module and its scope information generate some Ideas.
hintDecl :: Scope -> Module SrcSpanInfo -> Decl SrcSpanInfo -> [Idea]: Given a declaration (with a module and scope) generate some Ideas. This function will be partially applied with one module/scope, then used on multiple Decl values.
hintComment :: Comment -> [Idea]: Given a comment generate some Ideas.

Instances

Monoid Hint

resolveHints :: [Either HintBuiltin HintRule] -> Hint Source

Transform a list of HintRule into a Hint.

Scopes

data Scope Source

Data type representing the modules in scope within a module. Created with scopeCreate and queried with scopeMatch and scopeMove. Note that the mempty Scope is not equivalent to scopeCreate on an empty module, due to the implicit import of Prelude.

Instances

Show Scope
Monoid Scope

scopeCreate :: Module SrcSpanInfo -> Scope Source

Create a Scope value from a module, based on the modules imports.

scopeMatch :: (Scope, QName SrcSpanInfo) -> (Scope, QName SrcSpanInfo) -> Bool Source

Given a two names in scopes, could they possibly refer to the same thing. This property is reflexive.

scopeMove :: (Scope, QName SrcSpanInfo) -> Scope -> QName SrcSpanInfo Source

Given a name in a scope, and a new scope, create a name for the new scope that will refer to the same thing. If the resulting name is ambiguous, it picks a plausible candidate.

Haskell-src-exts

parseModuleEx :: ParseFlags -> FilePath -> Maybe String -> IO (Either ParseError (Module SrcSpanInfo, [Comment])) Source

Parse a Haskell module. Applies the C pre processor, and uses best-guess fixity resolution if there are ambiguities. The filename - is treated as stdin. Requires some flags (often defaultParseFlags), the filename, and optionally the contents of that file.

defaultParseFlags :: ParseFlags Source

Default value for ParseFlags.

parseFlagsAddFixities :: [Fixity] -> ParseFlags -> ParseFlags Source

data ParseError Source

A parse error from parseModuleEx.

Constructors

ParseError
Fields parseErrorLocation :: SrcLoc Location of the error. parseErrorMessage :: String Message about the cause of the error. parseErrorContents :: String Snippet of several lines (typically 5) including a `>` character pointing at the faulty line.

data ParseFlags Source

Created with defaultParseFlags, used by parseModuleEx.

Constructors

ParseFlags
Fields encoding :: TextEncoding How the file is read in (defaults to `utf8`). cppFlags :: CppFlags How the file is preprocessed (defaults to `NoCpp`). hseFlags :: ParseMode How the file is parsed (defaults to all fixities in the `base` package and most non-conflicting extensions).

data CppFlags Source

What C pre processor should be used.

Constructors

NoCpp	No pre processing is done.
CppSimple	Lines prefixed with `#` are stripped.
Cpphs CpphsOptions	The `cpphs` library is used.