fix: silence zip output when creating source zips

[ndhoule]

This code path is the cause of a bunch of SWAR errors. Logs don't
provide enough information for us to debug this right now, so this PR
does two things:

• Adds the -q flag to zip to quiet its output. (We pass this flag
  everywhere else we call out to zip.) I have a weak suspicion the
  root cause here could be a too-much-output error (but that seems
  unlikely).
• Improves the error output when we hit this error. This should let us
  debug the issue if it comes up again in the future.

[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes

  • Improved source-zip creation reliability and error reporting during deploy uploads.
  • Better surfaced command failures with clearer output, making upload issues easier to diagnose.
  • Updated cleanup handling to work more consistently after zip operations.

• Tests

  • Adjusted unit coverage to match the new zip execution flow and failure handling.
  • Verified command arguments, working directory setup, and error propagation behavior.

Walkthrough

upload-source-zip.ts now runs zip through execa, captures its output, and rethrows failures with a message built from ExecaError.shortMessage and stdout. Temporary zip cleanup now imports unlink from node:fs/promises. The unit tests were updated to mock execa instead of child_process.execFile, and their assertions now check the new zip arguments, error path, cleanup path, and path-based filename case.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: silencing zip output during source-zip creation.
Description check	✅ Passed	The description is directly about quieting zip output and improving error reporting for the same code path.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch nathanhoule/ex-2434-intermittent-zip-r-failure-when-deploying-swar-projects

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[github-actions]

📊 Benchmark results

Comparing with 137fbf0

• Dependency count: 1,127 (no change)
• Package size: 379 MB (no change)
• Number of ts-expect-error directives: 359 ⬆️ 1.95% increase vs. 137fbf0

[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

tests/unit/utils/deploy/upload-source-zip.test.ts (1)

335-338: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Inconsistent mock return type across tests.

These two execa mocks return a synchronous {} as ExecaReturnValue, whereas the other tests (Lines 64, 127, 286) return Promise.resolve(...). The awaited call tolerates both, but aligning them avoids confusion about what execa resolves to.

♻️ Optional alignment

-    vi.mocked(mockExeca.default).mockImplementation((..._args) => {
-      return {} as ExecaReturnValue
-    })
+    vi.mocked(mockExeca.default).mockImplementation((..._args) => {
+      return Promise.resolve({} as ExecaReturnValue)
+    })

Also applies to: 374-377

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@tests/unit/utils/deploy/upload-source-zip.test.ts` around lines 335 - 338,
The execa mocks in the upload-source-zip tests are inconsistent with the other
cases, returning a synchronous cast instead of a resolved promise. Update the
mockImplementation blocks for the affected execa stubs to match the existing
Promise.resolve pattern used elsewhere in upload-source-zip.test.ts, so the
mocked behavior is consistent across all tests and easier to understand.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/utils/deploy/upload-source-zip.ts`:
- Around line 76-89: The zip upload error handling in upload-source-zip should
use the combined execa output instead of stdout alone, since zip -q often leaves
stdout empty. Update the catch block around the execa call to build the thrown
Error message from the ExecaError details using the interleaved output first,
then stderr as fallback, and keep the existing cause chaining. Use the existing
execa invocation and ExecaError handling in upload-source-zip.ts as the place to
make this change.

---

Nitpick comments:
In `@tests/unit/utils/deploy/upload-source-zip.test.ts`:
- Around line 335-338: The execa mocks in the upload-source-zip tests are
inconsistent with the other cases, returning a synchronous cast instead of a
resolved promise. Update the mockImplementation blocks for the affected execa
stubs to match the existing Promise.resolve pattern used elsewhere in
upload-source-zip.test.ts, so the mocked behavior is consistent across all tests
and easier to understand.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: e33820fe-c445-48ee-b472-90460211264a

📥 Commits

Reviewing files that changed from the base of the PR and between 137fbf0 and b9049ab.

📒 Files selected for processing (2)

• src/utils/deploy/upload-source-zip.ts
• tests/unit/utils/deploy/upload-source-zip.test.ts

🔗 Linked repositories identified

CodeRabbit considers these linked repositories for cross-repo context during reviews:

• netlify/blueprints (manual)