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128 lines
3.9 KiB
Elm
128 lines
3.9 KiB
Elm
module NoSimpleLetBody 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 (Rule)
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{-| Reports when a let expression's body is a simple reference to a value declared in the let expression.
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config =
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[ NoSimpleLetBody.rule
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]
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The reasoning behind this rule is that it is not necessary to assign a name (and type annotation) to the result of a let expression,
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since they are redundant with the value or function containing the expression.
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If it feels necessary to give a name anyway because it helps clarify the context, then it might be a sign that the computation of that value should be extracted to a function.
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## Fail
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a =
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let
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b =
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1
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c =
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b + 1
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in
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c
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## Success
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Anything that is not simply a reference to a value declared in the let expression is okay.
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a =
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let
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b =
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1
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in
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b + 1
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The rule will not report when the referenced value was destructured in the let expression.
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first tuple =
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let
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( value, _ ) =
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tuple
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in
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value
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## When (not) to enable this rule
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This rule resolves a minor style issue, and may not be worth enforcing depending on how strongly you feel about this issue.
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I recommend having your full team's buy-in before enabling this rule to reduce the amount of frustration it will trigger when
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it causes the tests or even the CI pipeline to fail. This rule does not (currently) provide an automatic fix which may increase
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your team's frustration if they disagree with or don't care about this rule.
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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-code-style/example --rules NoSimpleLetBody
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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 "NoSimpleLetBody" ()
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|> Rule.withSimpleExpressionVisitor expressionVisitor
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|> Rule.fromModuleRuleSchema
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expressionVisitor : Node Expression -> List (Rule.Error {})
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expressionVisitor node =
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case Node.value node of
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Expression.LetExpression { declarations, expression } ->
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case Node.value expression of
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Expression.FunctionOrValue [] name ->
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let
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declared : List String
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declared =
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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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function.declaration
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|> Node.value
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|> .name
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|> Node.value
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|> Just
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Expression.LetDestructuring _ _ ->
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Nothing
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)
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declarations
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in
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if List.member name declared then
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[ Rule.error
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{ message = "The referenced value should be inlined."
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, details =
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[ "The name of the value is redundant with the surrounding expression."
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, "If you believe that the expression needs a name because it is too complex, consider splitting the expression up more or extracting it to a new function."
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]
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}
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(Node.range expression)
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]
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else
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[]
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_ ->
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[]
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_ ->
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[]
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