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111 lines
2.3 KiB
Elm
111 lines
2.3 KiB
Elm
module NoExtraBooleanComparison exposing (rule)
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{-| Forbid the use of boolean comparisons that can be simplified.
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# Rule
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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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{-| Forbid the use of boolean comparisons that can be simplified.
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config =
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[ NoExtraBooleanComparison.rule
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]
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## Fail
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if someBooleanValue == True then
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a
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else
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b
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if someBooleanValue == False then
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a
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else
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b
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## Success
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if someBooleanValue then
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a
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else
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b
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if not someBooleanValue then
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a
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else
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b
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# When not to use this rule
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You should not use this rule if you
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- prefer the explicitness of expressions like `value == True`
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- dislike the use of the `not` function
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- do not see the value in simplifying boolean comparisons
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-}
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rule : Rule
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rule =
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Rule.newModuleRuleSchema "NoExtraBooleanComparison" ()
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|> Rule.withSimpleExpressionVisitor expressionVisitor
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|> Rule.fromModuleRuleSchema
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error : Node a -> String -> String -> Error {}
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error node operator comparedValue =
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Rule.error
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{ message = "Unnecessary comparison with `" ++ comparedValue ++ "`"
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, details = [ "You can simplify this expression by removing the `" ++ operator ++ "` operator and the value `" ++ comparedValue ++ "`." ]
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}
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(Node.range node)
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expressionVisitor : Node Expression -> List (Error {})
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expressionVisitor node =
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case Node.value node of
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Expression.OperatorApplication operator _ left right ->
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if isEqualityOperator operator then
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List.filterMap isTrueOrFalse [ left, right ]
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|> List.map (error node operator)
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else
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[]
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_ ->
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[]
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isEqualityOperator : String -> Bool
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isEqualityOperator operator =
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operator == "==" || operator == "/="
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isTrueOrFalse : Node Expression -> Maybe String
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isTrueOrFalse node =
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case Node.value node of
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FunctionOrValue [] functionOrValue ->
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if functionOrValue == "True" || functionOrValue == "False" then
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Just functionOrValue
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else
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Nothing
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_ ->
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Nothing
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