add tests for first class mixins

[connorskees]

This is some initial work at adding the baseline tests for first class mixins.

Embedded node host PR: sass/embedded-host-node#253
Tracking issue: sass/sass#626
Protobuf changes: sass/sass#3674
dart-sass changes: sass/dart-sass#2073

[skip dart-sass]
[skip sass-embedded]

Closes #1927

[connorskees]

It seems like, from some comments I read, that these tests are typically auto-generated? Is there documentation somewhere on how to generate these?

[nex3]

The test cases are written by hand, but for error tests specifically the output can be auto-generated. Just write test cases with empty error output:

<===> test/input.scss
a {b: }

<===> test/error

then run npm run sass-spec --interactive. When it gets to one of these test cases, use O! to tell it to overwrite the output for all tests that have similar failures (in this case, "the error doesn't match the expected error output") to match the actual output generated by the test runner.

For bonus points, explicitly document this pattern in the README 🙂.

[nex3]

Use two spaces for indentation

[connorskees]

Resolved. It would be nice if lint-spec enforced this or if lint-spec --fix fixed this -- it was somewhat tedious to grep for to find all places with the wrong indentation.

[nex3]

Almost there!

[ntkme]

Can we add a js-api test can round-trip a mixin reference from Sass similar to this:

sass-spec/js-api-spec/value/function.test.ts

Lines 9 to 31 in dff3578

	it('can round-trip a function reference from Sass', () => {
	const fn = spy(args => {
	expect(args).toBeArrayOfSize(1);
	expect(args[0]).toBeInstanceOf(SassFunction);
	return args[0];
	});
	expect(
	compileString(
	`
	@use 'sass:meta';
	@function plusOne($n) {@return $n + 1}
	a {b: meta.call(foo(meta.get-function('plusOne')), 2)}
	`,
	{
	functions: {'foo($arg)': fn},
	}
	).css
	).toBe('a {\n b: 3;\n}');
	expect(fn).toHaveBeenCalled();
	});

[connorskees]

Do we have JS API tests today that read a value from Sass? The function tests (and all the tests I've looked at so far) seem to involve declaring a function/another value in JavaScript and sending it to Sass, which is not possible with mixins.

[ntkme]

Do we have JS API tests today that read a value from Sass? The function tests (and all the tests I've looked at so far) seem to involve declaring a function/another value in JavaScript and sending it to Sass, which is not possible with mixins.

The sass function test I linked above declares a sass function plusOne in sass code, pass it to the host via a host function foo and then the host function foo return the compiler function plusOne back to compiler, which then get invoked.

[ntkme]

You should add [skip sass-embedded] to this PR's description, and then trigger test from dart-sass or embedded-host-node repo if needed.

[ntkme]

Existing sass values has some test regarding assert like:

sass-spec/js-api-spec/value/argument-list.test.ts

Lines 98 to 107 in dff3578

	it("isn't any other type", () => {
	expect(() => list.assertBoolean()).toThrow();
	expect(() => list.assertCalculation()).toThrow();
	expect(() => list.assertColor()).toThrow();
	expect(() => list.assertFunction()).toThrow();
	expect(() => list.assertMap()).toThrow();
	expect(list.tryMap()).toBe(null);
	expect(() => list.assertNumber()).toThrow();
	expect(() => list.assertString()).toThrow();
	});

sass-spec/js-api-spec/value/boolean.test.ts

Lines 27 to 36 in dff3578

	it("isn't any other type", () => {
	expect(value.assertCalculation).toThrow();
	expect(value.assertColor).toThrow();
	expect(value.assertFunction).toThrow();
	expect(value.assertMap).toThrow();
	expect(value.tryMap()).toBe(null);
	expect(value.assertNumber).toThrow();
	expect(value.assertString).toThrow();
	});
	});

We should add assertMixin to these tests.

[nex3]

What was wrong with the assertion in 55fe148?

[connorskees]

I'm not sure -- I was somewhat hoping for a subsequent CI run to validate that the later checks are true to get a better idea.

This test failed in https://github.com/sass/dart-sass/actions/runs/6399530354/job/17372158557, only on the browser environment. I am expecting reproducing the run in the browser environment locally to be hard.

[connorskees]

It seems to pass with the assertion removed, so it does correctly execute assertMixin. It just isn't an instanceof SassMixin in the browser? I'm not familiar enough with the end-to-end process here to know what would be causing this and why it only fails in the browser environment. My assumption at least is that it's not a bug.

[nex3]

Every Sass value object is expected to be instanceof its type—this is part of the API contract we provide to the user, so if it's not passing somewhere that's a bug that needs to be fixed.

[nex3]

We use isInstanceOf() everywhere else, why wouldn't it work here?

[connorskees]

In this particular case, I changed the check from toBeInstanceOf to a bare instanceof check to get a better sense of the issue from the CI run. I would like for the check to eventually be toBeInstanceOf. I meant proper in the commit message in the sense of "instanceof proper".

I was hoping to be able to debug without having to download the chrome executable, but I suppose I will have to.