elm-review/tests/NoUnusedVariablesTest.elm

module NoUnusedVariablesTest exposing (all)

import Lint.Rule.NoUnusedVariables exposing (rule)
import Lint.Test exposing (LintResult)
import Test exposing (Test, describe, test)


testRule : String -> LintResult
testRule =
    Lint.Test.run rule


tests : List Test
tests =
    [ test "should not report exposed top-level variables" <|
        \() ->
            testRule """module A exposing (a)
a = 1"""
                |> Lint.Test.expectNoErrors
    , test "should not report used top-level variables" <|
        \() ->
            testRule """module A exposing (b)
a n = 1
b = a 1"""
                |> Lint.Test.expectNoErrors
    , test "should report unused top-level variables" <|
        \() ->
            testRule """module A exposing (b)
a = 1"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `a` is not used"
                        , under = "a"
                        }
                    ]
    , test "should report unused top-level variables even if they are annotated" <|
        \() ->
            testRule """module A exposing (b)
a: Int
a = 1"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `a` is not used"
                        , under = "a"
                        }
                        |> Lint.Test.atExactly { start = { row = 3, column = 1 }, end = { row = 3, column = 2 } }
                    ]
    , test "should not report unused top-level variables if everything is exposed" <|
        \() ->
            testRule """module A exposing (..)
a n = 1
b = a 1"""
                |> Lint.Test.expectNoErrors
    , test "should not report unused top-level variables that are exposed by name" <|
        \() ->
            testRule """module A exposing (a, b)
a = 1
b = 2"""
                |> Lint.Test.expectNoErrors
    , test "should not report unused top-level variables that are exposed by name, but report others" <|
        \() ->
            testRule """module A exposing (a, b)
a = 1
b = 2
c = 3"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `c` is not used"
                        , under = "c"
                        }
                    ]
    , test "should not report unused top-level variables if everything is exposed (port module)" <|
        \() ->
            testRule """port module A exposing (..)
a n = 1
b = a 1"""
                |> Lint.Test.expectNoErrors
    , test "should not report unused top-level variables that are exposed by name (port module)" <|
        \() ->
            testRule """port module A exposing (a, b)
a = 1
b = 2"""
                |> Lint.Test.expectNoErrors
    , test "should not report unused top-level variables that are exposed by name, but report others (port module)" <|
        \() ->
            testRule """port module A exposing (a, b)
a = 1
b = 2
c = 3"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `c` is not used"
                        , under = "c"
                        }
                    ]
    , test "should report unused variables from let declarations" <|
        \() ->
            testRule """module A exposing (a)
a = let b = 1
    in 2"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `b` is not used"
                        , under = "b"
                        }
                    ]
    , test "should report unused variables from let even if they are exposed by name" <|
        \() ->
            testRule """module A exposing (a, b)
a = let b = 1
    in 2"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `b` is not used"
                        , under = "b"
                        }
                        |> Lint.Test.atExactly { start = { row = 2, column = 9 }, end = { row = 2, column = 10 } }
                    ]
    , test "should report unused functions from let even if they are exposed by name" <|
        \() ->
            testRule """module A exposing (a)
a = let b param = 1
    in 2"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `b` is not used"
                        , under = "b"
                        }
                    ]
    , test "should report unused variables from let even if everything is exposed" <|
        \() ->
            testRule """module A exposing (..)
a = let b = 1
    in 2"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `b` is not used"
                        , under = "b"
                        }
                    ]
    , test "should not report top-level variables used inside a let expression" <|
        \() ->
            testRule """module A exposing (a)
b = 1
a = let c = 1
    in b + c"""
                |> Lint.Test.expectNoErrors
    , test "should not report top-level variables used inside let declarations" <|
        \() ->
            testRule """module A exposing (a)
b = 1
a = let c = b
    in c"""
                |> Lint.Test.expectNoErrors
    , test "should not report top-level variables used in nested lets" <|
        \() ->
            testRule """module A exposing (a)
b = 1
a = let
      c = b
      d = let
            e = 1
          in
            b + c + e
    in
      d"""
                |> Lint.Test.expectNoErrors
    , test "should not report variables used in a record update expression's value to be updated" <|
        \() ->
            testRule """module A exposing (a)
b = { c = 1 }
a = { b | c = 3 }"""
                |> Lint.Test.expectNoErrors
    , test "should not report variables used in a record update expression's updates" <|
        \() ->
            testRule """module A exposing (a)
b = { y = 1, z = 1 }
d = 3
e = 3
a = { b | y = d, z = e }"""
                |> Lint.Test.expectNoErrors
    , test "should report variables even if they appear as keys of a record update expression's updates" <|
        \() ->
            testRule """module A exposing (a)
b = { z = 1, c = 2 }
c = 1
a = { b | c = 3 }"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `c` is not used"
                        , under = "c"
                        }
                        |> Lint.Test.atExactly { start = { row = 3, column = 1 }, end = { row = 3, column = 2 } }
                    ]
    , test "should not report variables from let declarations that are used in the expression" <|
        \() ->
            testRule """module A exposing (a)
a = let c = 1
    in c"""
                |> Lint.Test.expectNoErrors
    , test "should not report unused function parameters" <|
        \() ->
            testRule """module A exposing (a)
a n = 1"""
                |> Lint.Test.expectNoErrors
    , test "should report unused imported functions" <|
        \() ->
            testRule """module A exposing (b)
import Foo exposing (a)"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Imported variable `a` is not used"
                        , under = "a"
                        }
                    ]
    , test "should report unused imported functions (multiple imports)" <|
        \() ->
            testRule """module A exposing (d)
import Foo exposing (C, a, b)"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Imported variable `b` is not used"
                        , under = "b"
                        }
                    , Lint.Test.error
                        { message = "Imported variable `a` is not used"
                        , under = "a"
                        }
                    , Lint.Test.error
                        { message = "Imported type `C` is not used"
                        , under = "C"
                        }
                    ]

    -- TODO Needs to be improved, every case should create a new scope stack
    -- Right now, every parameter is considered used, which is not great
    , test "should not report unused pattern matching parameters" <|
        \() ->
            testRule """module A exposing (a)
a = case thing of
    Foo b c -> []"""
                |> Lint.Test.expectNoErrors

    -- Should B and C be reported if they are not used? Probably.
    , test "should report unused custom type declarations" <|
        \() ->
            testRule """module A exposing (a)
type A = B | C"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Type `A` is not used"
                        , under = "A"
                        }
                        |> Lint.Test.atExactly { start = { row = 2, column = 6 }, end = { row = 2, column = 7 } }
                    ]
    , test "should report unused type aliases declarations" <|
        \() ->
            testRule """module A exposing (a)
type alias A = { a : B }"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Type `A` is not used"
                        , under = "A"
                        }
                        |> Lint.Test.atExactly { start = { row = 2, column = 12 }, end = { row = 2, column = 13 } }
                    ]
    , test "should not report type used in a signature" <|
        \() ->
            testRule """module A exposing (a)
type alias A = { a : B }
a : A
a = {a = 1}"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in a signature with multiple arguments" <|
        \() ->
            testRule """module A exposing (a)
type alias A = { a : B }
a : String -> A
a str = {a = str}"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in a signature with parameterized types (as generic type)" <|
        \() ->
            testRule """module A exposing (a)
type alias A = { a : B }
a : A B
a = []"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in a signature with parameterized types (as parameter)" <|
        \() ->
            testRule """module A exposing (a)
type alias A = { a : B }
a : List A
a = []"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in a signature with a record" <|
        \() ->
            testRule """module A exposing (a)
type alias A = { a : B }
a : { c: A }
a str = {c = str}"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in a signature with a generic record" <|
        \() ->
            testRule """module A exposing (a)
type alias A = { a : B }
a : { r | c: A }
a str = {c = str}"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in a custom type constructor definition" <|
        \() ->
            testRule """module A exposing (ExposedType)
type A = B

type ExposedType = Something A
"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in type signature inside a let-in" <|
        \() ->
            testRule """module A exposing (a)
type A = A

a = let
      b : A
      b = 1
    in
    b
"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in a type alias field" <|
        \() ->
            testRule """module A exposing (ExposedType)
type A = B | C

type alias ExposedType = { a : A }
"""
                |> Lint.Test.expectNoErrors
    , test "should not report type used in a type alias field's arguments " <|
        \() ->
            testRule """module A exposing (ExposedType)
type A = B | C

type alias ExposedType = { a : Maybe A }
"""
                |> Lint.Test.expectNoErrors
    , test "should not report type if it's exposed" <|
        \() ->
            testRule """module A exposing (A)
type A a = B a"""
                |> Lint.Test.expectNoErrors
    , test "should not report custom type if it's exposed with its sub-types" <|
        \() ->
            testRule """module A exposing (A(..))
type A = B | C | D"""
                |> Lint.Test.expectNoErrors
    , test "should report unused variable even if it's present in a generic type" <|
        \() ->
            testRule """module A exposing (A)
a = 1
type A a = B a"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `a` is not used"
                        , under = "a"
                        }
                        |> Lint.Test.atExactly { start = { row = 2, column = 1 }, end = { row = 2, column = 2 } }
                    ]
    , test "should report unused variable even if it's present in a generic record type" <|
        \() ->
            testRule """module A exposing (a)
r = 1
a : { r | c: A }
a str = {c = str}"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `r` is not used"
                        , under = "r"
                        }
                        |> Lint.Test.atExactly { start = { row = 2, column = 1 }, end = { row = 2, column = 2 } }
                    ]
    , test "should report unused operator import" <|
        \() ->
            testRule """module A exposing (a)
import Parser exposing ((</>))"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Imported operator `</>` is not used"
                        , under = "(</>)"
                        }
                    ]
    , test "should not report used operator (infix)" <|
        \() ->
            testRule """module A exposing (a)
import Parser exposing ((</>))
a = 1 </> 2"""
                |> Lint.Test.expectNoErrors
    , test "should not report used operator (prefix)" <|
        \() ->
            testRule """module A exposing (a)
import Parser exposing ((</>))
a = (</>) 2"""
                |> Lint.Test.expectNoErrors
    , test "should report unused opaque types" <|
        \() ->
            testRule """module A exposing (a)
type A = A Int"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Type `A` is not used"
                        , under = "A"
                        }
                        |> Lint.Test.atExactly { start = { row = 2, column = 6 }, end = { row = 2, column = 7 } }
                    ]
    , test "should not report used opaque types" <|
        \() ->
            testRule """module A exposing (a)
type A = A Int
a : A
a = 1"""
                |> Lint.Test.expectNoErrors
    , test "should report unused import" <|
        \() ->
            testRule """module A exposing (a)
import Html"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Imported module `Html` is not used"
                        , under = "Html"
                        }
                    ]
    , test "should report unused import (multiples segments)" <|
        \() ->
            testRule """module A exposing (a)
import Html.Styled.Attributes"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Imported module `Html.Styled.Attributes` is not used"
                        , under = "Html.Styled.Attributes"
                        }
                    ]
    , test "should not report import if it exposes all (should be improved by detecting if any exposed value is used)" <|
        \() ->
            testRule """module A exposing (a)
import Html.Styled.Attributes exposing (..)"""
                |> Lint.Test.expectNoErrors
    , test "should report unused variable even if a homonym from a module is used" <|
        \() ->
            testRule """module A exposing (a)
href = 1
a = Html.Styled.Attributes.href"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Variable `href` is not used"
                        , under = "href"
                        }
                        |> Lint.Test.atExactly { start = { row = 2, column = 1 }, end = { row = 2, column = 5 } }
                    ]
    , test "should not report used import (function access)" <|
        \() ->
            testRule """module A exposing (a)
import Html.Styled.Attributes
a = Html.Styled.Attributes.href"""
                |> Lint.Test.expectNoErrors
    , test "should not report unused import if it is aliased" <|
        \() ->
            testRule """module A exposing (a)
import Html.Styled.Attributes as Html
a = Html.href"""
                |> Lint.Test.expectNoErrors
    , test "should report unused import alias" <|
        \() ->
            testRule """module A exposing (a)
import Html.Styled.Attributes as Html"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Module alias `Html` is not used"
                        , under = "Html"
                        }
                        |> Lint.Test.atExactly { start = { row = 2, column = 34 }, end = { row = 2, column = 38 } }
                    ]
    , test "should not report import that exposes a used exposed type" <|
        \() ->
            testRule """module A exposing (a)
import B exposing (C(..))
a : C
a = 1"""
                |> Lint.Test.expectNoErrors
    , test "should not report import that exposes an unused exposed type (but whose subtype is potentially used)" <|
        \() ->
            testRule """module A exposing (a)
import B exposing (C(..))
a : D
a = 1"""
                |> Lint.Test.expectNoErrors
    , test "should not report types that are used in ports" <|
        \() ->
            testRule """module A exposing (output, input)
import Json.Decode
import Json.Encode
port output : Json.Encode.Value -> Cmd msg
port input : (Json.Decode.Value -> msg) -> Sub msg"""
                |> Lint.Test.expectNoErrors
    , test "should report unused ports (ingoing)" <|
        \() ->
            testRule """module A exposing (a)
import Json.Decode
port input : (Json.Decode.Value -> msg) -> Sub msg"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Port `input` is not used (Warning: Removing this port may break your application if it is used in the JS code)"
                        , under = "input"
                        }
                    ]
    , test "should report unused ports (outgoing)" <|
        \() ->
            testRule """module A exposing (a)
import Json.Encode
port output : Json.Encode.Value -> Cmd msg"""
                |> Lint.Test.expectErrors
                    [ Lint.Test.error
                        { message = "Port `output` is not used (Warning: Removing this port may break your application if it is used in the JS code)"
                        , under = "output"
                        }
                    ]
    ]


all : Test
all =
    describe "NoUnusedVariables" tests