fix(swcLoader): should correctly generate the default value of env_na… #11906

Zeahan · 2025-10-17T08:45:53Z

…me in swc options (#11903)

Summary

In the previous implementation, the remaining fields of the Options struct (swc_core::base::config::Options) were initialized using ..Default::default(). However, this approach can result in some fields having default values that do not match the expected behavior. The root cause is that the fields in Options are defined with serde macros, and custom logic is used to generate default values during deserialization.

pub(crate) fn default_env_name() -> String {
    if let Ok(v) = env::var("SWC_ENV") {
        return v;
    }

    match env::var("NODE_ENV") {
        Ok(v) => v,
        Err(_) => "development".into(),
    }
}

pub struct Options {
    #[serde(default = "default_env_name")]
    pub env_name: String,

    #[serde(default = "default_swcrc")]
    pub swcrc: bool,

    #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"))))]
    #[serde(default = "default_cwd")]
    pub cwd: PathBuf,
    // ...
}

When initializing Options with ..Default::default(), this custom logic is bypassed, leading to discrepancies between the generated fields and the original behavior in swc-loader. This inconsistency may cause certain swc plugins (such as @swc/plugin-emotion) to behave unexpectedly.

To address this issue and ensure consistency with the original swc implementation, the initialization of the remaining fields in Options has been changed to use deserialization from an empty JSON object via serde_json (which is the approach used in the swc source code). This ensures that the configuration is generated in a manner consistent with the original swc behavior.

Checklist

Tests updated (or not required).
Documentation updated (or not required).

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CLAassistant · 2025-10-17T08:45:59Z

All committers have signed the CLA.

CPunisher · 2025-10-17T08:54:33Z

Could you please add a test case?

Zeahan · 2025-10-17T09:14:15Z

Could you please add a test case?

Thanks for your reply, a test case will be provided later.

Zeahan · 2025-10-17T12:30:24Z

Could you please add a test case?

@CPunisher rust test cases have been provided.
Since the complete rspack build process requires an additional custom SWC plugin for testing, Node.js test cases are not implemented, sorry for that.

codspeed-hq · 2025-10-17T13:17:02Z

CodSpeed Performance Report

Merging #11906 will not alter performance

_{Comparing Zeahan:fix-swc-env-name (cbe85dc) with main (a457128)}

Summary

✅ 17 untouched

…me in swc options (web-infra-dev#11903)

Zeahan · 2025-10-21T10:21:46Z

@CPunisher Hi, I’ve tried running CI multiple times in my forked repo after syncing my PR branch with the main repo, but I noticed that the test Serial.test.js always fails.

Then, I tried running CI based on the latest version of the main branch (a457128) and encountered similar test errors.

I realized that these errors might be caused by another PR rather than mine, so I rolled back the base of my PR branch to 0f38cf19, and the CI finally passed in my forked repo.

I’ve now force-pushed the updated PR branch. Would you mind approving the CI workflows again?

CPunisher · 2025-10-22T03:06:06Z

ild process requires an additional custom SWC plugin for testing, Node.js test cases are not implemented, sorry for that.

😂 Sorry, recently our ci is not stable.

github-actions · 2025-10-22T03:15:57Z

📝 Benchmark detail: Open

Name	Base (2025-10-22 0eb1382)	Current	Change
10000_big_production-mode_disable-minimize + exec	56.9 s ± 1.21 s	27.9 s ± 1.14 s	-51.03 %
10000_development-mode + exec	1.32 s ± 26 ms	1.61 s ± 32 ms	+21.59 %
10000_development-mode_hmr + exec	650 ms ± 5 ms	649 ms ± 16 ms	-0.13 %
10000_development-mode_noop-loader + exec	2.28 s ± 108 ms	2.56 s ± 64 ms	+12.32 %
10000_production-mode + exec	30.2 s ± 699 ms	1.6 s ± 53 ms	-94.70 %
10000_production-mode_persistent-cold + exec	30.4 s ± 659 ms	1.8 s ± 17 ms	-94.09 %
10000_production-mode_persistent-hot + exec	30.2 s ± 608 ms	1.34 s ± 41 ms	-95.57 %
arco-pro_development-mode + exec	1.6 s ± 78 ms	1.67 s ± 184 ms	+4.32 %
arco-pro_development-mode_hmr + exec	359 ms ± 1.3 ms	367 ms ± 1.4 ms	+2.10 %
arco-pro_production-mode + exec	3.05 s ± 72 ms	3.04 s ± 143 ms	-0.37 %
arco-pro_production-mode_generate-package-json-webpack-plugin + exec	3.11 s ± 87 ms	3.06 s ± 209 ms	-1.88 %
arco-pro_production-mode_persistent-cold + exec	3.13 s ± 108 ms	3.12 s ± 57 ms	-0.46 %
arco-pro_production-mode_persistent-hot + exec	1.77 s ± 62 ms	1.82 s ± 143 ms	+2.36 %
arco-pro_production-mode_traverse-chunk-modules + exec	3.08 s ± 108 ms	3.03 s ± 111 ms	-1.67 %
large-dyn-imports_development-mode + exec	1.59 s ± 49 ms	1.9 s ± 57 ms	+19.92 %
large-dyn-imports_production-mode + exec	5.74 s ± 56 ms	1.86 s ± 106 ms	-67.68 %
threejs_development-mode_10x + exec	1.32 s ± 13 ms	1.43 s ± 24 ms	+8.41 %
threejs_development-mode_10x_hmr + exec	908 ms ± 21 ms	904 ms ± 23 ms	-0.42 %
threejs_production-mode_10x + exec	4.07 s ± 19 ms	4.23 s ± 235 ms	+4.16 %
threejs_production-mode_10x_persistent-cold + exec	4.2 s ± 28 ms	4.32 s ± 50 ms	+2.73 %
threejs_production-mode_10x_persistent-hot + exec	3.74 s ± 203 ms	3.84 s ± 199 ms	+2.45 %
10000_big_production-mode_disable-minimize + rss memory	8740 MiB ± 376 MiB	8479 MiB ± 250 MiB	-2.99 %
10000_development-mode + rss memory	646 MiB ± 15.5 MiB	762 MiB ± 26.2 MiB	+17.98 %
10000_development-mode_hmr + rss memory	815 MiB ± 19.3 MiB	930 MiB ± 49.2 MiB	+14.17 %
10000_development-mode_noop-loader + rss memory	963 MiB ± 22.8 MiB	1068 MiB ± 27.2 MiB	+10.93 %
10000_production-mode + rss memory	658 MiB ± 19.9 MiB	697 MiB ± 42.2 MiB	+5.92 %
10000_production-mode_persistent-cold + rss memory	759 MiB ± 52 MiB	866 MiB ± 27.9 MiB	+14.09 %
10000_production-mode_persistent-hot + rss memory	750 MiB ± 42.1 MiB	867 MiB ± 40.9 MiB	+15.61 %
arco-pro_development-mode + rss memory	555 MiB ± 42.9 MiB	576 MiB ± 56.7 MiB	+3.84 %
arco-pro_development-mode_hmr + rss memory	433 MiB ± 17.1 MiB	475 MiB ± 14.1 MiB	+9.64 %
arco-pro_production-mode + rss memory	669 MiB ± 17.9 MiB	671 MiB ± 92.3 MiB	+0.42 %
arco-pro_production-mode_generate-package-json-webpack-plugin + rss memory	659 MiB ± 81.5 MiB	675 MiB ± 32.1 MiB	+2.45 %
arco-pro_production-mode_persistent-cold + rss memory	735 MiB ± 35.4 MiB	780 MiB ± 25.6 MiB	+6.07 %
arco-pro_production-mode_persistent-hot + rss memory	583 MiB ± 77 MiB	598 MiB ± 70.6 MiB	+2.58 %
arco-pro_production-mode_traverse-chunk-modules + rss memory	669 MiB ± 79.4 MiB	690 MiB ± 37.6 MiB	+3.15 %
large-dyn-imports_development-mode + rss memory	695 MiB ± 14.1 MiB	788 MiB ± 17.4 MiB	+13.30 %
large-dyn-imports_production-mode + rss memory	632 MiB ± 3.37 MiB	627 MiB ± 5.47 MiB	-0.72 %
threejs_development-mode_10x + rss memory	566 MiB ± 20.9 MiB	597 MiB ± 8.49 MiB	+5.51 %
threejs_development-mode_10x_hmr + rss memory	804 MiB ± 9.92 MiB	859 MiB ± 28.5 MiB	+6.88 %
threejs_production-mode_10x + rss memory	778 MiB ± 223 MiB	792 MiB ± 178 MiB	+1.80 %
threejs_production-mode_10x_persistent-cold + rss memory	839 MiB ± 43.3 MiB	832 MiB ± 39 MiB	-0.88 %
threejs_production-mode_10x_persistent-hot + rss memory	699 MiB ± 24.4 MiB	732 MiB ± 25.5 MiB	+4.78 %

Threshold exceeded: ["10000_development-mode + exec","10000_development-mode_noop-loader + exec","large-dyn-imports_development-mode + exec","threejs_development-mode_10x + exec"]

Zeahan · 2025-10-22T04:48:42Z

@CPunisher Adding default_env_name is enough to solve this issue—that was my first thought as well. However, with this approach, some default field values(such as cwd and swcrc) would still be different from the original SWC behavior.

So in the end, I decided to copy this part of the code directly from the SWC repo 😂(https://github.com/swc-project/swc/blob/4848301edca71ed84d147e90baccae217b0a8938/bindings/binding_core_node/src/bundle.rs#L208), hoping to offer a more complete solution rather than just fixing the env_name problem. But of course, I’m happy to go with whichever approach your team prefers! 😁

CPunisher · 2025-10-22T06:01:09Z

Yes, I have realized your consideration. I will merge this pr after we stablize CI.

Thanks for your contribution!

github-actions bot added the release: bug fix release: bug related release(mr only) label Oct 17, 2025

CPunisher self-requested a review October 17, 2025 08:54

Zeahan force-pushed the fix-swc-env-name branch from 3ba840b to 003f1c1 Compare October 17, 2025 09:26

Zeahan force-pushed the fix-swc-env-name branch 3 times, most recently from a8307e9 to cf1a735 Compare October 17, 2025 14:48

fix(swcLoader): should correctly generate the default value of env_na…

cbe85dc

…me in swc options (web-infra-dev#11903)

Zeahan force-pushed the fix-swc-env-name branch from cf1a735 to cbe85dc Compare October 21, 2025 10:21

CPunisher approved these changes Oct 22, 2025

View reviewed changes

CPunisher merged commit 3cb5cfc into web-infra-dev:main Oct 22, 2025
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fix(swcLoader): should correctly generate the default value of env_na… #11906

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Zeahan commented Oct 17, 2025

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