Commit 2099ebdf authored by Profpatsch's avatar Profpatsch
Browse files

lib: add asserts.assertEachOneOf 

Along the lines of `assertOneOf`, but expects a list of values to be
compared. This gives a good error message and is useful for lists of
values, like `supportedGhcVersions` in the arguments of
`haskell-language-server`.
parent 811db8c6

lib/asserts.nix

+29 −0
Original line number Diff line number Diff line
@@ -50,4 +50,33 @@ rec { 
      lib.generators.toPretty {} xs}, but is: ${

        lib.generators.toPretty {} val}";



  /* Specialized `assertMsg` for checking if every one of `vals` is one of the elements

     of the list `xs`. Useful for checking lists of supported attributes.



     Example:

       let sslLibraries = [ "libressl" "bearssl" ];

       in assertEachOneOf "sslLibraries" sslLibraries [ "openssl" "bearssl" ]

       stderr> error: each element in sslLibraries must be one of [

       stderr>   "openssl"

       stderr>   "bearssl"

       stderr> ], but is: [

       stderr>   "libressl"

       stderr>   "bearssl"

       stderr> ]



     Type:

       assertEachOneOf :: String -> List ComparableVal -> List ComparableVal -> Bool

  */

  assertEachOneOf =

    # The name of the variable the user entered `val` into, for inclusion in the error message

    name:

    # The list of values of what the user provided, to be compared against the values in `xs`

    vals:

    # The list of valid values

    xs:

    assertMsg

    (lib.all (val: lib.elem val xs) vals)

    "each element in ${name} must be one of ${

      lib.generators.toPretty {} xs}, but is: ${

        lib.generators.toPretty {} vals}";

}