refactor(transformer/react-refresh): calculate signature key once

[Dunqing]

I can't remember why I wrote such code. This change reduced big allocation.

[Dunqing]

• refactor(transformer/react-refresh): calculate signature key once #7970 👈 (View in Graphite)
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging #7970 will not alter performance

_{Comparing 12-18-refactor_transformer_react-refresh_calculate_signature_key_once (4ea90d4) with main (d59bbae)}

Summary

✅ 29 untouched benchmarks

[overlookmotel]

Nice. Avoids allocating lots of Atoms into arena which never end up in the AST.

[overlookmotel]

Merge activity

• Dec 17, 12:11 PM EST: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Dec 17, 12:11 PM EST: A user added this pull request to the Graphite merge queue.
• Dec 17, 12:15 PM EST: A user merged this pull request with the Graphite merge queue.

[overlookmotel]

I think there's one further thing you could do if you wanted.

If I understand right (which maybe I don't), the values of self.hook_calls always end up being inserted into AST.

So instead of building a Vec<CompactString>, you could build a single oxc_allocator::String and push new keys onto the end of it. Then when you come to use it, convert to an Atom with Atom::from(arena_string.into_bump_str()).

That remove all heap allocations, as the string is built entirely in the arena.

[overlookmotel]

Or, after #7973, can just do Atom::from(arena_string). Not sure why we didn't have that method already.

[Dunqing]

I think there's one further thing you could do if you wanted.

If I understand right (which maybe I don't), the values of self.hook_calls always end up being inserted into AST.

So instead of building a Vec<CompactString>, you could build a single oxc_allocator::String and push new keys onto the end of it. Then when you come to use it, convert to an Atom with Atom::from(arena_string.into_bump_str()).

That remove all heap allocations, as the string is built entirely in the arena.

By default, we also need to hash the key by sha1, so we can't call arena_string.into_bump_str() directly

oxc/crates/oxc_transformer/src/jsx/refresh.rs

Lines 521 to 530 in 67d255c

	if !self.emit_full_signatures {
	// Prefer to hash when we can (e.g. outside of ASTExplorer).
	// This makes it deterministically compact, even if there's
	// e.g. a useState initializer with some code inside.
	// We also need it for www that has transforms like cx()
	// that don't understand if something is part of a string.
	let mut hasher = Sha1::new();
	hasher.update(key);
	key = BASE64_STANDARD.encode(hasher.finalize());
	}

[overlookmotel]

Ah I missed that. Doh!

Still, I think you could probably make a gain by replacing the Vec<CompactString> with a single String (std's String, not ArenaString) which you push to each time a hook is found. That'd be 1 allocation rather than many, and no need for the join call at the end.