Commit 4b0d1225 authored by Will Fancher's avatar Will Fancher
Browse files

lib/asserts: Factor out NixOS's toplevel assertion / warning logic.

parent cad590f3

lib/asserts.nix

+68 −0
Original line number Diff line number Diff line 
{ lib }:



let

  inherit (lib.strings)

    concatStringsSep

    ;

  inherit (lib.lists)

    filter

    ;

  inherit (lib.trivial)

    showWarnings

    ;

in

rec {



  /**
@@ -131,4 +142,61 @@ rec { 
      "each element in ${name} must be one of ${lib.generators.toPretty { } xs}, but is: ${

        lib.generators.toPretty { } vals

      }";



  /**

    Wrap a value with logic that throws an error when assertions

    fail and emits any warnings.



    # Inputs



    `assertions`



    : A list of assertions. If any of their `assertion` attrs is `false`, their `message` attrs will be emitted in a `throw`.



    `warnings`



    : A list of strings to emit as warnings. This function does no filtering on this list.



    `val`



    : A value to return, wrapped in `warn`, if a `throw` is not necessary.



    # Type



    ```

    checkAssertWarn :: [ { assertion :: Bool; message :: String } ] -> [ String ] -> Any -> Any

    ```



    # Examples

    :::{.example}

    ## `lib.asserts.checkAssertWarn` usage example

    ```nix

    checkAssertWarn

      [ { assertion = false; message = "Will fail"; } ]

      [ ]

      null

    stderr>        error:

    stderr>        Failed assertions:

    stderr>        - Will fail



    checkAssertWarn

      [ { assertion = true; message = "Will not fail"; } ]

      [ "Will warn" ]

      null

    stderr> evaluation warning: Will warn

    null

    ```



    :::

  */

  checkAssertWarn =

    assertions: warnings: val:

    let

      failedAssertions = map (x: x.message) (filter (x: !x.assertion) assertions);

    in

    if failedAssertions != [ ] then

      throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failedAssertions)}"

    else

      showWarnings warnings val;



}

nixos/modules/system/activation/top-level.nix

+1 −8
Original line number Diff line number Diff line
@@ -77,14 +77,7 @@ let 
  );



  # Handle assertions and warnings



  failedAssertions = map (x: x.message) (filter (x: !x.assertion) config.assertions);



  baseSystemAssertWarn =

    if failedAssertions != [ ] then

      throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failedAssertions)}"

    else

      showWarnings config.warnings baseSystem;

  baseSystemAssertWarn = lib.asserts.checkAssertWarn config.assertions config.warnings baseSystem;



  # Replace runtime dependencies

  system =