"run a classic script" returns completion records and throws

[Ms2ger]

What is the issue with the HTML Standard?

run a classic script has both of these steps:

• Throw a "NetworkError" DOMException.
• Return Completion { [[Type]]: throw, [[Value]]: a new "QuotaExceededError" DOMException, [[Target]]: empty }.

It's not clear to me whether these are supposed to have the same effect. If yes, they should probably be phrased the same way; if no, the calling convention could be clarified.

[domenic]

This algorithm is suffering from the problem of trying to bridge the JS and web conventions. We can definitely do better.

But stepping back, there's a bit of a mess in general. "run a classic script" has the following callers:

• execute the script element: ignores the return value, and is not prepared to deal with throws
• evaluate a javascript: URL: checks the return value to see if it's a normal completion with a string. Doesn't seem equipped to deal with throws
• timer initialization steps: ignores the return value, and is not prepared to deal with throws
• run a worker: ignores the return value; doesn't seem equipped to deal with throws
• import scripts into worker global scope: ignores the return value, but explicitly wants errors to be rethrown.

My proposal:

• "run a classic script" should behave entirely according to web conventions. I.e., it should return or throw, and should never return completion records (in either success or failure cases).

• "run a classic script" should only throw if rethrow errors is set.

I think this would work better with what callers expect.

Concretely, I think the changes are then:

• Step 7.3.3. should return null instead of evaluationStatus.
• Step 9 should return evaluationStatus.[[Value]] instead of evaluationStatus.
• Step 10 should return null.
• "evaluate a javascript: URL" should be updated to use web conventions instead of getting a completion record.

If this makes sense to you, a PR implementing it would be welcome.