perf(plugin): Avoid data copy when transformation finished

[CPunisher]

Description:

When the transformation is done, we can make sure that the transformed_result won't be used by wasm imports. So it's safe to fetch the data from it without cloning the bytes.

[changeset-bot]

🦋 Changeset detected

Latest commit: 992ac65

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[Copilot]

Pull Request Overview

This PR refactors the PluginTransformState::run method to take ownership of self instead of a mutable reference, enabling the extraction of transform_result from Arc<Mutex<T>> without cloning. The cleanup operations are also moved earlier in the execution flow.

• Changed method signature from &mut self to mut self for ownership transfer
• Moved instance cleanup and memory deallocation before extracting transform results
• Eliminated cloning by using Arc::try_unwrap to extract the final result

Comments suppressed due to low confidence (1)

crates/swc_plugin_runner/src/transform_executor.rs:1

• Explicitly dropping self.instance before calling Arc::try_unwrap suggests there may be a shared reference issue. However, since the method now consumes self (line 41), all fields will be dropped at the end of the function anyway. This explicit drop only makes sense if instance holds a reference to transform_result, but this relationship is not clear from the code. Consider adding a comment explaining why this explicit drop is necessary for Arc::try_unwrap to succeed.

use std::{env, sync::Arc}; 

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[codspeed-hq]

CodSpeed Performance Report

Merging #11223 will not alter performance

_{Comparing CPunisher:11-03-perf/plugin-ast-copy (992ac65) with main (b9aeaa3)}

Summary

✅ 138 untouched

[Copilot]

Pull Request Overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

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[Copilot]

The Arc::try_unwrap may fail even after dropping self.instance because the instance's import object closures hold cloned references to transform_env, which in turn holds a clone of the transform_result Arc. The instance's Drop implementation and the cleanup() method (which has a default no-op implementation) don't guarantee that these closures are released. Consider keeping the original .lock().clone() approach, or ensure the runtime implementation properly releases all import object closures during cleanup/drop.

Suggested change

	let transformed_result = Arc::try_unwrap(self.transform_result)
	.map_err(|_| {
	anyhow!("Failed to unwrap Arc: other references to transform_result exist")
	})?
	.into_inner();
	// Instead of trying to unwrap the Arc, clone the inner value.
	let transformed_result = self.transform_result.lock().clone();

[github-actions]

Binary Sizes

File	Size
swc.linux-x64-gnu.node	31M (31933576 bytes)

Commit: 5d3877d