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108 lines
2.6 KiB
Elm
108 lines
2.6 KiB
Elm
module NoMissingTypeAnnotationInLetIn exposing (rule)
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{-|
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@docs rule
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-}
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import Elm.Syntax.Expression as Expression exposing (Expression)
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import Elm.Syntax.Node as Node exposing (Node)
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import Review.Rule as Rule exposing (Error, Rule)
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{-| Reports `let in` declarations that do not have a type annotation.
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Type annotations help you understand what happens in the code, and it will help the compiler give better error messages.
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config =
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[ NoMissingTypeAnnotationInLetIn.rule
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]
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This rule does not report top-level declarations without a type annotation inside a `let in`.
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For that, enable [`NoMissingTypeAnnotation`](./NoMissingTypeAnnotation).
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## Fail
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a : number
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a =
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let
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-- Missing annotation
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b =
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2
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in
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b
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## Success
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-- Top-level annotation is not necessary, but good to have!
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a : number
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a =
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let
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b : number
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b =
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2
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in
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b
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## Try it out
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You can try this rule out by running the following command:
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```bash
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elm-review --template jfmengels/elm-review-common/example --rules NoMissingTypeAnnotationInLetIn
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```
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-}
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rule : Rule
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rule =
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Rule.newModuleRuleSchema "NoMissingTypeAnnotationInLetIn" ()
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|> Rule.withSimpleExpressionVisitor expressionVisitor
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|> Rule.fromModuleRuleSchema
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expressionVisitor : Node Expression -> List (Error {})
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expressionVisitor expression =
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case Node.value expression of
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Expression.LetExpression { declarations } ->
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List.filterMap
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(\declaration ->
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case Node.value declaration of
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Expression.LetFunction function ->
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reportFunctionWithoutSignature function
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_ ->
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Nothing
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)
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declarations
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_ ->
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[]
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reportFunctionWithoutSignature : Expression.Function -> Maybe (Error {})
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reportFunctionWithoutSignature function =
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case function.signature of
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Just _ ->
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Nothing
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Nothing ->
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let
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name : Node String
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name =
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function.declaration
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|> Node.value
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|> .name
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in
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Rule.error
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{ message = "Missing type annotation for `" ++ Node.value name ++ "`"
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, details =
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[ "Type annotations help you understand what happens in the code, and it will help the compiler give better error messages."
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]
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}
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(Node.range name)
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|> Just
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