assertNoUnits and assertUnit return null instead of the number called on when it passes the assertion

[roydukkey]

I've been trying to work with the JS API, but can seem to figure out why documented methods doesn't seem to be available. I've even tried some of the examples, but they don't seem to be working either.

https://github.com/sass/sass/blob/12cee2dab996a5424160e644ff56f040a42bc0e3/js-api-doc/options.d.ts#L37-L48

Tested using Dart Sass 1.51.0

NoSuchMethodError: method not found: 'assertNumber' on null
       ╷
    14 │         $assert: sum(1, 5)
       │                  ^^^^^^^^^
       ╵
      node_modules/@sass-fairy/math/test/_sum.sass 14:12  @content
      node_modules/sass-true/sass/test/_test.scss 50:5          @content
      node_modules/sass-true/sass/test/_test.scss 24:3          test()
      node_modules/sass-true/sass/test/_test.scss 49:3          it()
      node_modules/@sass-fairy/math/test/_sum.sass 13:2   @content
      node_modules/sass-true/sass/module/_modules.scss 68:5     @content
      node_modules/sass-true/sass/module/_modules.scss 36:3     test-module()
      node_modules/sass-true/sass/module/_modules.scss 67:3     describe()
      node_modules/@sass-fairy/math/test/_sum.sass 9:1    @use
      node_modules/@sass-fairy/math/test/index.sass 16:1      @use
      test/index.sass 24:1                                      root stylesheet

      18 |      functions: {
      19 |              "sum($arg1, $arg2)": (args) => {
    > 20 |                      const value1 = args[0].assertNumber('arg1').value;
         |                                             ^
      21 |                      const value2 = args[1].assertNumber('arg2').convertValueToMatch(arg1, 'arg2', 'arg1');
      22 |                      return new sass.SassNumber(value1 + value2).coerceToMatch(arg1);
      23 |              }

      at Object.sum($arg1, $arg2) (test/index.test.js:20:27)
      at LegacyJavaScriptObject.apply$2 (node_modules/sass/sass.dart.js:24984:23)
      at Object.apply$2$x (node_modules/sass/sass.dart.js:24521:43)
      at _parseFunctions__closure0.call$1 (node_modules/sass/sass.dart.js:85427:30)
      at _EvaluateVisitor1._evaluate0$_runBuiltInCallable$3 (node_modules/sass/sass.dart.js:80667:27)
      at _EvaluateVisitor1._evaluate0$_runFunctionCallable$3 (node_modules/sass/sass.dart.js:80605:55)
      at _EvaluateVisitor_visitFunctionExpression_closure4.call$0 (node_modules/sass/sass.dart.js:82365:25)
      at _EvaluateVisitor1._evaluate0$_addErrorSpan$1$2 (node_modules/sass/sass.dart.js:81186:23)
      at _EvaluateVisitor1._evaluate0$_addErrorSpan$2 (node_modules/sass/sass.dart.js:81204:19)
      at _EvaluateVisitor1.visitFunctionExpression$1 (node_modules/sass/sass.dart.js:80571:22)

[roydukkey]

Here a runkit of the same issue as above. https://runkit.com/embed/kz2azdg8nhpz

[jathak]

The provided runkit doesn't actually report an error calling assertNumber on null, but it does reveal a bug in assertNoUnits where it's not returning the number in question. Re-targeting this issue for that bug.