docs: add submodule update step before test runs

[kdy1]

Summary

• add a testing instruction in AGENTS.md
• require running git submodule update --init --recursive before any test execution

Testing

• not run (documentation-only change)

[changeset-bot]

⚠️ No Changeset found

Latest commit: ec4c8fc

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[claude]

PR Review: docs: add submodule update step before test runs

Summary: This is a documentation-only change that adds a single line to AGENTS.md instructing AI agents to run git submodule update --init --recursive before running tests.

Assessment

LGTM. This is a sensible and well-placed addition. The repo has three git submodules (test262-parser-tests, html5lib-tests, decorator-tests) that are used by test fixtures in swc_ecma_parser, swc_html_parser, and swc_ecma_transforms_proposal. Without initializing these submodules, test runs in those crates will fail or produce misleading results.

Minor observations

1. Placement: The instruction is well-placed in the Testing section, right after the general testing guidelines and before the UPDATE=1 hint. This ensures agents see it early in the testing workflow.

2. Potential improvement (non-blocking): The instruction could also be mentioned in the Verification section, since that section describes the full pre-completion checklist. However, it's reasonable to assume agents will read the Testing section before reaching Verification, so the current placement should be sufficient.

3. Idempotency: git submodule update --init --recursive is safe to run repeatedly, so there's no risk of agents running it unnecessarily — good choice of command.

No issues with code quality, security, or correctness. Straightforward documentation improvement.

[Copilot]

Pull request overview

This documentation-only PR adds a testing instruction to AGENTS.md that requires running git submodule update --init --recursive before executing tests. The repository contains three git submodules used for test fixtures (test262-parser-tests, html5lib-tests, and decorator-tests), making this instruction necessary for proper test execution.

Changes:

• Added instruction to run git submodule update --init --recursive before running tests in AGENTS.md

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[github-actions]

Binary Sizes

File	Size
swc.linux-x64-gnu.node	28M (28582344 bytes)

Commit: a5a4e06

[codspeed-hq]

Merging this PR will degrade performance by 2.02%

❌ 1 regressed benchmark
✅ 183 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	es/oxc/benches/assets/UserSettings.tsx/sourceMap=true/reactDev=true	1.4 ms	1.4 ms	-2.02%

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_{Comparing kdy1/update-agents-submodule-testing (ec4c8fc) with main (81b22c3)¹}

Footnotes

1. No successful run was found on main (5a02692) during the generation of this report, so 81b22c3 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩