Safe Haskell	None
Language	Haskell2010

Language.Haskell.HLint

Contents

Generate hints
Idea data type
Settings
Hints
Modules
Parse flags

Description

This module provides a way to apply HLint hints. If you want to just run hlint in-process and collect the results see hlint.

If you want to approximate the hlint experience with a more structured API try:

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

Synopsis

hlint :: [String] -> IO [Idea]
applyHints :: [Classify] -> Hint -> [ModuleEx] -> [Idea]
data Idea = Idea {
- ideaModule :: [String]
- ideaDecl :: [String]
- ideaSeverity :: Severity
- ideaHint :: String
- ideaSpan :: SrcSpan
- ideaFrom :: String
- ideaTo :: Maybe String
- ideaNote :: [Note]
- ideaRefactoring :: [Refactoring SrcSpan]
}
data Severity
- = Ignore
- | Suggestion
- | Warning
- | Error
data Note
- = IncreasesLaziness
- | DecreasesLaziness
- | RemovesError String
- | ValidInstance String String
- | RequiresExtension String
- | Note String
unpackSrcSpan :: SrcSpan -> Maybe (FilePath, (Int, Int), (Int, Int))
showIdeaANSI :: Idea -> String
data Classify = Classify {
- classifySeverity :: Severity
- classifyHint :: String
- classifyModule :: String
- classifyDecl :: String
}
getHLintDataDir :: IO FilePath
autoSettings :: IO (ParseFlags, [Classify], Hint)
argsSettings :: [String] -> IO (ParseFlags, [Classify], Hint)
findSettings :: (String -> IO (FilePath, Maybe String)) -> Maybe String -> IO ([FixityInfo], [Classify], Hint)
readSettingsFile :: Maybe FilePath -> String -> IO (FilePath, Maybe String)
data Hint
data ModuleEx
parseModuleEx :: ParseFlags -> FilePath -> Maybe String -> IO (Either ParseError ModuleEx)
createModuleEx :: ApiAnns -> Located (HsModule GhcPs) -> ModuleEx
data ParseError = ParseError {
- parseErrorLocation :: SrcSpan
- parseErrorMessage :: String
- parseErrorContents :: String
}
defaultParseFlags :: ParseFlags
data ParseFlags = ParseFlags {
- cppFlags :: CppFlags
- baseLanguage :: Maybe Language
- enabledExtensions :: [Extension]
- disabledExtensions :: [Extension]
- fixities :: [FixityInfo]
}
data CppFlags
- = NoCpp
- | CppSimple
- | Cpphs CpphsOptions
type FixityInfo = (String, Associativity, Int)
parseFlagsAddFixities :: [FixityInfo] -> ParseFlags -> ParseFlags

Generate hints

hlint :: [String] -> IO [Idea] Source #

This function takes a list of command line arguments, and returns the given hints. To see a list of arguments type hlint --help at the console. This function writes to the stdout/stderr streams, unless --quiet is specified.

As an example:

do hints <- hlint ["src", "--ignore=Use map","--quiet"]
   when (length hints > 3) $ error "Too many hints!"

Warning: The flags provided by HLint are relatively stable, but do not have the same API stability guarantees as the rest of the strongly-typed API. Do not run this function on your server with untrusted input.

applyHints :: [Classify] -> Hint -> [ModuleEx] -> [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.

Given a set of modules, it may be faster to pass each to applyHints in a singleton list. When given multiple modules at once this function attempts to find hints between modules, which is slower and often pointless (by default HLint passes modules singularly, using --cross to pass all modules together).

Idea data type

data Idea Source #

An idea suggest by a Hint.

Constructors

Idea

Fields

ideaModule :: [String]
The modules the idea is for, usually a singleton.
ideaDecl :: [String]
The declarations the idea is for, usually a singleton, 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.
ideaRefactoring :: [Refactoring SrcSpan]
How to perform this idea

Instances

Instances details

Eq Idea Source #
Instance details Defined in Idea Methods (==) :: Idea -> Idea -> Bool (/=) :: Idea -> Idea -> Bool
Ord Idea Source #
Instance details Defined in Idea Methods compare :: Idea -> Idea -> Ordering (<) :: Idea -> Idea -> Bool (<=) :: Idea -> Idea -> Bool (>) :: Idea -> Idea -> Bool (>=) :: Idea -> Idea -> Bool max :: Idea -> Idea -> Idea min :: Idea -> Idea -> Idea
Show Idea Source #
Instance details Defined in Idea Methods showsPrec :: Int -> Idea -> ShowS show :: Idea -> String showList :: [Idea] -> ShowS

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).
Suggestion	Suggestions are things that some people may consider improvements, but some may not.
Warning	Warnings are suggestions that are nearly always a good idea to apply.
Error	Available as a setting for the user. Only parse errors have this setting by default.

Instances

Instances details

Bounded Severity Source #
Instance details Defined in Config.Type Methods minBound :: Severity maxBound :: Severity
Enum Severity Source #
Instance details Defined in Config.Type Methods succ :: Severity -> Severity pred :: Severity -> Severity toEnum :: Int -> Severity fromEnum :: Severity -> Int enumFrom :: Severity -> [Severity] enumFromThen :: Severity -> Severity -> [Severity] enumFromTo :: Severity -> Severity -> [Severity] enumFromThenTo :: Severity -> Severity -> Severity -> [Severity]
Eq Severity Source #
Instance details Defined in Config.Type Methods (==) :: Severity -> Severity -> Bool (/=) :: Severity -> Severity -> Bool
Ord Severity Source #
Instance details Defined in Config.Type Methods compare :: Severity -> Severity -> Ordering (<) :: Severity -> Severity -> Bool (<=) :: Severity -> Severity -> Bool (>) :: Severity -> Severity -> Bool (>=) :: Severity -> Severity -> Bool max :: Severity -> Severity -> Severity min :: Severity -> Severity -> Severity
Read Severity Source #
Instance details Defined in Config.Type Methods readsPrec :: Int -> ReadS Severity readList :: ReadS [Severity] readPrec :: ReadPrec Severity readListPrec :: ReadPrec [Severity]
Show Severity Source #
Instance details Defined in Config.Type Methods showsPrec :: Int -> Severity -> ShowS show :: Severity -> String showList :: [Severity] -> ShowS

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.
RequiresExtension String	The replacement requires this extension to be available.
Note String	An arbitrary note.

Instances

Instances details

Eq Note Source #
Instance details Defined in Config.Type Methods (==) :: Note -> Note -> Bool (/=) :: Note -> Note -> Bool
Ord Note Source #
Instance details Defined in Config.Type Methods compare :: Note -> Note -> Ordering (<) :: Note -> Note -> Bool (<=) :: Note -> Note -> Bool (>) :: Note -> Note -> Bool (>=) :: Note -> Note -> Bool max :: Note -> Note -> Note min :: Note -> Note -> Note
Show Note Source #
Instance details Defined in Config.Type Methods showsPrec :: Int -> Note -> ShowS show :: Note -> String showList :: [Note] -> ShowS

unpackSrcSpan :: SrcSpan -> Maybe (FilePath, (Int, Int), (Int, Int)) Source #

Unpack a SrcSpan value. Useful to allow using the Idea information without adding a dependency on ghc or ghc-lib-parser. Unpacking gives:

(filename, (startLine, startCol), (endLine, endCol))

Following the GHC API, he end column is the column after the end of the error. Lines and columns are 1-based. Returns Nothing if there is no helpful location information.

showIdeaANSI :: Idea -> String Source #

Show an Idea with ANSI color codes to give syntax coloring to the Haskell code.

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

Instances details

Show Classify Source #
Instance details Defined in Config.Type Methods showsPrec :: Int -> Classify -> ShowS show :: Classify -> String showList :: [Classify] -> ShowS

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.

argsSettings :: [String] -> IO (ParseFlags, [Classify], Hint) Source #

A version of autoSettings which respects some of the arguments supported by HLint. If arguments unrecognised by HLint are used it will result in an error. Arguments which have no representation in the return type are silently ignored.

findSettings :: (String -> IO (FilePath, Maybe String)) -> Maybe String -> IO ([FixityInfo], [Classify], Hint) Source #

Given a function to load a module (typically readSettingsFile), and a module to start from (defaults to hlint.yaml) 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 module 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 Hint Source #

Functions to generate hints, combined using the Monoid instance.

Instances

Instances details

Semigroup Hint Source #
Instance details Defined in Hint.Type Methods (<>) :: Hint -> Hint -> Hint sconcat :: NonEmpty Hint -> Hint stimes :: Integral b => b -> Hint -> Hint
Monoid Hint Source #
Instance details Defined in Hint.Type Methods mempty :: Hint mappend :: Hint -> Hint -> Hint mconcat :: [Hint] -> Hint

Modules

data ModuleEx Source #

Result of parseModuleEx, representing a parsed module.

parseModuleEx :: ParseFlags -> FilePath -> Maybe String -> IO (Either ParseError ModuleEx) 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.

Note that certain programs, e.g. main = do successfully parse with GHC, but then fail with an error in the renamer. These programs will return a successful parse.

createModuleEx :: ApiAnns -> Located (HsModule GhcPs) -> ModuleEx Source #

Create a ModuleEx from GHC annotations and module tree. It is assumed the incoming parse module has not been adjusted to account for operator fixities (it uses the HLint default fixities).

data ParseError Source #

A parse error.

Constructors

ParseError
Fields parseErrorLocation :: SrcSpan 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.

Parse flags

defaultParseFlags :: ParseFlags Source #

Default value for ParseFlags.

data ParseFlags Source #

Created with defaultParseFlags, used by parseModuleEx.

Constructors

ParseFlags

Fields

cppFlags :: CppFlags
How the file is preprocessed (defaults to NoCpp).
baseLanguage :: Maybe Language
Base language (e.g. Haskell98, Haskell2010), defaults to Nothing.
enabledExtensions :: [Extension]
List of extensions enabled for parsing, defaults to many non-conflicting extensions.
disabledExtensions :: [Extension]
List of extensions disabled for parsing, usually empty.
fixities :: [FixityInfo]
List of fixities to be aware of, defaults to those defined in base.

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.

type FixityInfo = (String, Associativity, Int) Source #

A Fixity definition, comprising the name the fixity applies to, the direction and the precedence. As an example, a source file containing:

infixr 3 `foo`

would create ("foo", RightAssociative, 3).

parseFlagsAddFixities :: [FixityInfo] -> ParseFlags -> ParseFlags Source #

Given some fixities, add them to the existing fixities in ParseFlags.