Value that describes an error found by a given rule, that contains the name of the rule that raised the error, and a description of the error.

error : LintError
error =
    LintError "NoDebug" "Forbidden use of Debug"

When visiting the AST, nodes are visited twice:

• on Enter, before the children of the node will be visited

• on Exit, after the children of the node have been visited

  expressionFn : Context -> Direction Expression -> ( List LintError, Context ) expressionFn ctx node = case node of Enter (Variable names) -> ( [], markVariableAsUsed ctx names )

        -- Find variables declared in `let .. in ..` expression
        Enter (Let declarations body) ->
            ( [], registerVariables ctx declarations )
  
  
        -- When exiting the `let .. in ..` expression, report the variables that were not used.
        Exit (Let _ _) ->
            ( unusedVariables ctx |> List.map createError, ctx )

Shortcut to a lint rule

Severity associated to a rule.

• Critical: Transgressions reported by the rule will make the linting process fail.
• Warning: Transgressions reported by the rule will not make the linting process fail.
• Disabled: Rule will not be enforced.

A LintRuleImplementation is the implementation of a rule. It is a record that contains:

• initialContext: An initial context

• expressionFn: A LintImplementation for Expression nodes

• moduleEndFn: A function that takes a context and returns a list of error. Similar to a LintImplementation, but will be called after visiting the whole AST.

  rule : LintRule rule input = lint input implementation

  implementation : LintRuleImplementation Context implementation = { expressionFn = expressionFn , moduleEndFn = (\ctx -> ( [], ctx )) , initialContext = Context }

A LintImplementation is a function that takes a given Context object, as defined by each rule, a node (with a Direction) and returns a list of errors and an updated Context. Every rule should implement three LintImplementation functions, one for every Node type (Statement, Type and Expression). The Context is there to accumulate information about the source code as the AST is being visited and is shared by all the LintImplementation functions of your rule. It must return a list of errors which will be reported to the user, that are violations of the thing the rule wants to enforce.

rule : LintRule
rule input =
    lint input implementation


implementation : LintRuleImplementation Context
implementation =
    { statementFn = doNothing
    , typeFn = doNothing
    , expressionFn = expressionFn
    , moduleEndFn = \ctx -> ( [], ctx )
    , initialContext = Context
    }

Shorthand for a function that takes a rule's implementation, a context and returns ( List LintError, context ). A Visitor represents a node and calls the appropriate function for the given node type.

Note: this is internal API, and will be removed in a future version.

Shortcut to the result of a lint rule