Use BufferSource in TextDecoder API

[jdm]

Now that #20267 has merged, we can uncomment the decode method in TextDecoder.webidl that accepts BufferSource and remove the one that fakes it by accepting an option value. This will require similar cleanup as #20342.

Code: components/script/dom/webidls/TextDecoder.webidl, components/script/dom/textdecoder.rs
Tests: ./mach test-wpt tests/wpt/web-platform-tests/encoding/textdecoder*

[christianpoveda]

@highfive assign me

[highfive]

Hey @christianpoveda! Thanks for your interest in working on this issue. It's now assigned to you!

[christianpoveda]

Just started working on it. I have a first working version here. Nevertheless a bunch of tests are failing. They are failing because fatal is set to true and in cases where the decoding is supposed to fail Decode does not throw anything. For example:

 FAIL [expected PASS] Fatal flag: utf-16le - truncated code unit
  │   → assert_throws: function "function () {
            new TextDecoder(t.encoding, {fatal: true}).decode(new Uint8Array(t.input))
        }" did not throw

However reading the spec, {fatal: true} should be passed as a second parameter to decode (which is the options parameter in the rust code) not to TextDecoder's constructor.

Should I modify the tests? or should I keep using self.fatal instead of options.fatal?

PD: when using self.fatal all the tests pass.

[jdm]

We should update our implementation to match the specification: https://encoding.spec.whatwg.org/#interface-textdecoder

[christianpoveda]

Ohh sorry I was confused, I did not realized TextDecodeOptions exists and is not just a typo. Nevertheless what should I do with TextDecodeOptions and stream?

Also, the specification says Decode does not throw exceptions, but https://encoding.spec.whatwg.org/#dom-textdecoder-decode says it could throw an TypeError exception

[jdm]

Let's accept a TextDecodeOptions as the second argument but ignore the stream member for the purposes of this issue. We can file another issue to implement the steps in https://encoding.spec.whatwg.org/#dom-textdecoder-decode that it affects.

[jdm]

Actually, we shouldn't need to add TextDecodeOptions for this issue at all. I'll file the issue for updating the implementation to match the spec.

[jdm]

Ah, that's #13234.

[christianpoveda]

hehe, Ok i'll let the TextDecodeOptions in the webidl file but will not use it in the body of Decode. What about the exceptions?

[jdm]

What do you mean by "the specification says Decode does not throw exceptions"? If you mean that the spec webIDL doesn't include [Throws], that's because that's an implementation-specific extension that we use.

[christianpoveda]

oh ok got it