chore(serde_v8): throw error when string buffer exceeds v8 max length

[GJZwiers]

When using TextDecoder on very large data (> 512MB) Rust will panic, because the buffer passed to v8::String::new_from_two_byte exceeds v8::String::max_length. This PR adds a more descriptive error message in case this happens.

Related to #13648

before:

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', serde_v8\magic\u16string.rs:16:10

after:

error: Uncaught (in promise) TypeError: Error serializing return: Cannot allocate String from UTF-16: buffer exceeds maximum length.

[lucacasonato]

Ideally this doesn't panic at all, but gracefully errors. @AaronO WDYT?

[bartlomieju]

Ideally this doesn't panic at all, but gracefully errors. @AaronO WDYT?

I agree, it should be an error

[GJZwiers]

I've updated the code to throw an Err instead

[cjihrig]

Can you add a test please.

[cjihrig]

It's probably worth including a comment here stating that new_from_two_byte() only fails if the buffer length is greater than kMaxLength.

[GJZwiers]

Done!

[AaronO]

Ideally this doesn't panic at all, but gracefully errors. @AaronO WDYT?

Yeah, I'll do a pass soon™️ removing all of serde_v8's unwraps (besides tests/benches/examples) either passing through errors or adding .expect() panic messages.

[bartlomieju]

Thanks @GJZwiers!