| Copyright | © 2015–present Megaparsec contributors |
|---|---|
| License | FreeBSD |
| Maintainer | Mark Karpov <markkarpov92@gmail.com> |
| Stability | experimental |
| Portability | portable |
| Safe Haskell | Safe |
| Language | Haskell2010 |
Text.Megaparsec.Error
Contents
Description
Parse errors. The current version of Megaparsec supports typed errors
instead of String-based ones. This gives a lot of flexibility in
describing what exactly went wrong as well as a way to return arbitrary
data in case of failure.
You probably do not want to import this module directly because Text.Megaparsec re-exports it anyway.
Synopsis
- data ErrorItem t
- data ErrorFancy e
- data ParseError s e
- = TrivialError Int (Maybe (ErrorItem (Token s))) (Set (ErrorItem (Token s)))
- | FancyError Int (Set (ErrorFancy e))
- mapParseError :: Ord e' => (e -> e') -> ParseError s e -> ParseError s e'
- errorOffset :: ParseError s e -> Int
- setErrorOffset :: Int -> ParseError s e -> ParseError s e
- data ParseErrorBundle s e = ParseErrorBundle {
- bundleErrors :: NonEmpty (ParseError s e)
- bundlePosState :: PosState s
- attachSourcePos :: (Traversable t, TraversableStream s) => (a -> Int) -> t a -> PosState s -> (t (a, SourcePos), PosState s)
- class Ord a => ShowErrorComponent a where
- showErrorComponent :: a -> String
- errorComponentLen :: a -> Int
- errorBundlePretty :: forall s e. (VisualStream s, TraversableStream s, ShowErrorComponent e) => ParseErrorBundle s e -> String
- parseErrorPretty :: (VisualStream s, ShowErrorComponent e) => ParseError s e -> String
- parseErrorTextPretty :: forall s e. (VisualStream s, ShowErrorComponent e) => ParseError s e -> String
- showErrorItem :: VisualStream s => Proxy s -> ErrorItem (Token s) -> String
Parse error type
A data type that is used to represent “unexpected/expected” items in
ParseError. It is parametrized over the token type t.
Since: 5.0.0
Constructors
| Tokens (NonEmpty t) | Non-empty stream of tokens |
| Label (NonEmpty Char) | Label (cannot be empty) |
| EndOfInput | End of input |
Instances
| Functor ErrorItem Source # | |
| Data t => Data (ErrorItem t) Source # | |
Defined in Text.Megaparsec.Error Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> ErrorItem t -> c (ErrorItem t) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (ErrorItem t) # toConstr :: ErrorItem t -> Constr # dataTypeOf :: ErrorItem t -> DataType # dataCast1 :: Typeable t0 => (forall d. Data d => c (t0 d)) -> Maybe (c (ErrorItem t)) # dataCast2 :: Typeable t0 => (forall d e. (Data d, Data e) => c (t0 d e)) -> Maybe (c (ErrorItem t)) # gmapT :: (forall b. Data b => b -> b) -> ErrorItem t -> ErrorItem t # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ErrorItem t -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ErrorItem t -> r # gmapQ :: (forall d. Data d => d -> u) -> ErrorItem t -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> ErrorItem t -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> ErrorItem t -> m (ErrorItem t) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> ErrorItem t -> m (ErrorItem t) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> ErrorItem t -> m (ErrorItem t) # | |
| Generic (ErrorItem t) Source # | |
| Read t => Read (ErrorItem t) Source # | |
| Show t => Show (ErrorItem t) Source # | |
| NFData t => NFData (ErrorItem t) Source # | |
Defined in Text.Megaparsec.Error | |
| Eq t => Eq (ErrorItem t) Source # | |
| Ord t => Ord (ErrorItem t) Source # | |
Defined in Text.Megaparsec.Error | |
| type Rep (ErrorItem t) Source # | |
Defined in Text.Megaparsec.Error type Rep (ErrorItem t) = D1 ('MetaData "ErrorItem" "Text.Megaparsec.Error" "megaparsec-9.4.1-19lkSzk18352CXPok8aqBO" 'False) (C1 ('MetaCons "Tokens" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (NonEmpty t))) :+: (C1 ('MetaCons "Label" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (NonEmpty Char))) :+: C1 ('MetaCons "EndOfInput" 'PrefixI 'False) (U1 :: Type -> Type))) | |
data ErrorFancy e Source #
Additional error data, extendable by user. When no custom data is
necessary, the type is typically indexed by Void to “cancel” the
ErrorCustom constructor.
Since: 6.0.0
Constructors
| ErrorFail String |
|
| ErrorIndentation Ordering Pos Pos | Incorrect indentation error: desired ordering between reference level and actual level, reference indentation level, actual indentation level |
| ErrorCustom e | Custom error data |
Instances
data ParseError s e Source #
ParseError s es and the custom data e.
Semigroup and Monoid instances of the data type allow us to merge
parse errors from different branches of parsing. When merging two
ParseErrors, the longest match is preferred; if positions are the same,
custom data sets and collections of message items are combined. Note that
fancy errors take precedence over trivial errors in merging.
Since: 7.0.0
Constructors
| TrivialError Int (Maybe (ErrorItem (Token s))) (Set (ErrorItem (Token s))) | Trivial errors, generated by the Megaparsec's machinery. The data constructor includes the offset of error, unexpected token (if any), and expected tokens. Type of the first argument was changed in the version 7.0.0. |
| FancyError Int (Set (ErrorFancy e)) | Fancy, custom errors. Type of the first argument was changed in the version 7.0.0. |
Instances
mapParseError :: Ord e' => (e -> e') -> ParseError s e -> ParseError s e' Source #
errorOffset :: ParseError s e -> Int Source #
Get the offset of a ParseError.
Since: 7.0.0
setErrorOffset :: Int -> ParseError s e -> ParseError s e Source #
Set the offset of a ParseError.
Since: 8.0.0
data ParseErrorBundle s e Source #
A non-empty collection of ParseErrors equipped with PosState that
allows us to pretty-print the errors efficiently and correctly.
Since: 7.0.0
Constructors
| ParseErrorBundle | |
Fields
| |
Instances
Arguments
| :: (Traversable t, TraversableStream s) | |
| => (a -> Int) | How to project offset from an item (e.g. |
| -> t a | The collection of items |
| -> PosState s | Initial |
| -> (t (a, SourcePos), PosState s) | The collection with |
Attach SourcePoses to items in a Traversable container given that
there is a projection allowing us to get an offset per item.
Items must be in ascending order with respect to their offsets.
Since: 7.0.0
Pretty-printing
class Ord a => ShowErrorComponent a where Source #
The type class defines how to print a custom component of ParseError.
Since: 5.0.0
Minimal complete definition
Methods
showErrorComponent :: a -> String Source #
Pretty-print a component of ParseError.
errorComponentLen :: a -> Int Source #
Length of the error component in characters, used for highlighting of parse errors in input string.
Since: 7.0.0
Instances
| ShowErrorComponent Void Source # | |
Defined in Text.Megaparsec.Error | |
Arguments
| :: forall s e. (VisualStream s, TraversableStream s, ShowErrorComponent e) | |
| => ParseErrorBundle s e | Parse error bundle to display |
| -> String | Textual rendition of the bundle |
Pretty-print a ParseErrorBundle. All ParseErrors in the bundle will
be pretty-printed in order together with the corresponding offending
lines by doing a single pass over the input stream. The rendered String
always ends with a newline.
Since: 7.0.0
Arguments
| :: (VisualStream s, ShowErrorComponent e) | |
| => ParseError s e | Parse error to render |
| -> String | Result of rendering |
Pretty-print a ParseError. The rendered String always ends with a
newline.
Since: 5.0.0
Arguments
| :: forall s e. (VisualStream s, ShowErrorComponent e) | |
| => ParseError s e | Parse error to render |
| -> String | Result of rendering |
Pretty-print a textual part of a ParseError, that is, everything
except for its position. The rendered String always ends with a
newline.
Since: 5.1.0
showErrorItem :: VisualStream s => Proxy s -> ErrorItem (Token s) -> String Source #
Pretty-print an ErrorItem.
Since: 9.4.0