test: add validation tests for esbuild and eslint config

[gaurav0107]

Summary

Adds unit tests for esbuild.config.js and eslint.config.js covering the invariants called out in #16114: native-module externalization, WASM plugin resolution, and the security / license-header / node: protocol rules in the ESLint flat config.

This is a deliberately narrow, additive PR. It does not refactor esbuild.config.js into a helpers file, it does not touch unrelated subsystems, and it does not change runtime behavior of node esbuild.config.js.

Details

esbuild.config.js (4 line-touches)

Prepends export to four existing declarations so a test can reach them:

• external, baseConfig, commonAliases
• createWasmPlugins()

No other changes. The script's top-level Promise.allSettled([esbuild.build(cliConfig), esbuild.build(a2aServerConfig)]) trailer still runs on node esbuild.config.js. The test short-circuits it by mocking the esbuild module so esbuild.build() becomes a no-op that returns { metafile: { inputs: {}, outputs: {} } } — the module can be safely imported from a test without kicking off a real build.

scripts/tests/esbuild.config.test.ts (new, 13 tests)

Asserts:

• external contains node-pty, @lydell/node-pty (plus every platform-specific prebuild), @github/keytar, and @google/gemini-cli-devtools.
• baseConfig targets node, emits esm, has bundle: true, write: true, and routes .node through the file loader.
• baseConfig.external is the same reference as the exported external array (single source of truth).
• commonAliases.punycode === 'punycode/' — the trailing slash is load-bearing (without it, Node's built-in punycode module shadows the npm package).
• createWasmPlugins() returns two plugins: a named 'wasm-binary' plugin plus the esbuild-plugin-wasm loader.
• The wasm-binary plugin registers an onResolve handler with a \.wasm\?binary$ filter that correctly strips the ?binary suffix for absolute and relative paths and returns them in the wasm-embedded namespace.

scripts/tests/eslint-config.test.ts (new, 8 tests)

Imports the real eslint.config.js (it already export defaults a flat-config array) and asserts structural invariants:

• A global-ignores entry covers **/node_modules/**, bundle/**, dist/**, **/coverage/**.
• no-restricted-imports blocks node:os with importNames: ['homedir', 'tmpdir'], and separately blocks the bare os specifier for the same imports (defense in depth).
• no-debugger and no-console are enforced as errors.
• headers/header-format requires SPDX-License-Identifier: Apache-2.0.
• import/enforce-node-protocol-usage is set to ['error', 'always'].

No linter actually runs during the test — these are pure configuration-shape assertions.

Related Issues

Fixes #16114

How to Validate

npm ci
npm run lint
npm run test:scripts -- scripts/tests/esbuild.config.test.ts scripts/tests/eslint-config.test.ts

Expected: 21 tests pass (13 in esbuild.config.test.ts, 8 in eslint-config.test.ts).

Regression probe — prove the tests catch real breakage:

# Temporarily remove a platform prebuild from `external` in esbuild.config.js
# and rerun the tests. `marks node-pty and its platform-specific prebuilds as external`
# should fail.

# Temporarily lower 'no-debugger' to 'warn' in eslint.config.js and rerun.
# `enforces no-debugger as an error somewhere in the config` should fail.

Two pre-existing failures on main in scripts/tests/generate-settings-doc.test.ts and scripts/tests/generate-settings-schema.test.ts are unrelated to this change and reproduce on main prior to the diff.

Pre-Merge Checklist

• npm run lint passes on the full repository (exit 0, no warnings with --max-warnings 0).
• npm run test:scripts runs; the two new test files add 21 passing tests. Pre-existing failures in generate-settings-* are unrelated and reproduce on main.
• esbuild.config.js runtime behavior is unchanged — only export keywords added to four existing declarations; no reordering, no side-effect changes, no new imports.
• New test files include the Apache-2.0 license header and pass the repo's headers/header-format rule.
• No unrelated files touched — the diff is 3 files: 1 modified, 2 added.
• Context: the prior PR (test: add validation tests for esbuild and eslint config files #19866) attempting this was closed for branch-sync scope bleed (1,867 files, 1M+ deletions), not on technical merit. Reviewer feedback explicitly suggested splitting into a focused, tests-only PR; this PR follows that advice.
• CLA signed (flagged for the contributor to sign at https://cla.developers.google.com/).

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a suite of unit tests to validate the integrity of the project's build and linting configurations. By asserting structural and functional invariants, these tests help prevent regressions in esbuild settings and ESLint rules, ensuring that security, license compliance, and module resolution policies remain strictly enforced.

Highlights

• Configuration Validation: Added comprehensive unit tests for esbuild and ESLint configurations to ensure critical invariants are maintained.
• Test Coverage: Implemented 21 new tests covering native-module externalization, WASM plugin resolution, and ESLint security/license-header rules.
• Codebase Minimal Changes: Exported necessary constants and functions from esbuild.config.js to facilitate testing without altering runtime behavior.

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[gemini-code-assist]

Code Review

This pull request exports key configuration objects from esbuild.config.js and introduces comprehensive unit tests for both the esbuild and ESLint configurations. The new tests verify bundling settings, external module exclusions, path aliasing, and various linting rules including security restrictions, production safety, and license header requirements. I have no feedback to provide.

[sehoon38]

As we are re-prioritizing our works, we are going to close issues that are not high priority for now. Thanks for understanding!