Safe Haskell	None
Language	Haskell98

Language.Haskell.HLint2

Contents

Idea data type
Settings
Hints
Scopes
Haskell-src-exts
File encodings

Description

WARNING: This module represents the evolving second version of the HLint API. It will be deleted in favour of Language.Haskell.HLint3 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 to find and load the HLint settings files.
Use readSettings to interpret the settings files, producing HintRule values (LHS ==> RHS replacements) and Classify values to assign Severity ratings to hints.
Use builtinHints and hintRules to generate a Hint value.
Take all fixities from the findSettings modules and put them in the ParseFlags.

autoSettings' :: FilePath -> IO (ParseFlags, [Classify], Hint) Source

findSettings :: FilePath -> FilePath -> Maybe String -> IO ([String], [Module SrcSpanInfo]) Source

Given the data directory (where the hlint data files reside, see getHLintDataDir), and a filename to read, and optionally that file's contents, produce a pair containing:

Builtin hints to use, e.g. List, which should be resolved using builtinHints.
A list of modules containing hints, suitable for processing with readSettings.

Any parse failures will result in an exception.

readSettings :: Module SrcSpanInfo -> ([Classify], [HintRule]) Source

Given a module containing HLint settings information return the Classify rules and the HintRule expressions. Any fixity declarations will be discarded, but any other unrecognised elements will result in an exception.

Hints

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

builtinHints :: [(String, Hint)] Source

A list of builtin hints, currently including entries such as "List" and "Bracket".

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

hintRules :: [HintRule] -> Hint Source

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.

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.

File encodings

type Encoding = TextEncoding Source

An Encoding represents how characters are stored in a file. Created with defaultEncoding or readEncoding and used with useEncoding.

defaultEncoding :: Encoding Source

The system default encoding.

readEncoding :: String -> IO Encoding Source

Create an encoding from a string, or throw an error if the encoding is not known. Accepts many encodings including locale, utf-8 and all those supported by the GHC mkTextEncoding function.

useEncoding :: Handle -> Encoding -> IO () Source

Apply an encoding to a Handle.