fix(prerender): ensure failed prerenders are retried

[wildlyinaccurate]

Right now if a page fails to prerender, it is not retried. I see things like this in my logs:

[prerender] Crawling: /site/klg75hzo
[prerender] Encountered error, retrying: /site/klg75hzo in 10000ms

but that URL /site/klg75hzo is never retried.

Summary by CodeRabbit

• Bug Fixes
  • Improved prerendering retry behavior so page requests are retried until a successful response is received or the configured retry limit is reached.
  • Collected asynchronous queue task failures and surfaced the first relevant error after prerender completes.
  • Maintained existing error-handling semantics, including failOnError: false stopping retries without throwing.
• Tests
  • Added Vitest coverage for retry success, retry-limit stop behavior, and promise rejection/throwing based on failOnError.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 5df01d2a-b28f-4f4e-9776-a0361f3206a6

📥 Commits

Reviewing files that changed from the base of the PR and between 8bcd97e and e87c462.

📒 Files selected for processing (2)

• packages/start-plugin-core/src/prerender.ts
• packages/start-plugin-core/tests/prerender-retry.test.ts

🚧 Files skipped from review as they are similar to previous changes (2)

• packages/start-plugin-core/tests/prerender-retry.test.ts
• packages/start-plugin-core/src/prerender.ts

---

📝 Walkthrough

Walkthrough

prerenderPages now uses a named renderPage task for initial rendering and retries, captures queue failures, and rethrows them after settlement. Tests verify eventual success and configured retry exhaustion behavior.

Changes

Prerender retry scheduling

Layer / File(s)	Summary
Render and retry flow packages/start-plugin-core/src/prerender.ts	Extracts page rendering into renderPage, preserves output generation and link crawling, directly queues retries, and rethrows collected queue errors after completion.
Retry behavior validation packages/start-plugin-core/tests/prerender-retry.test.ts	Mocks filesystem and logging operations and verifies successful retries, non-throwing exhaustion, and rejection after retries are exhausted.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant prerenderPages
  participant Queue
  participant renderPage
  participant handler.request
  prerenderPages->>Queue: schedule renderPage(page)
  Queue->>renderPage: execute page task
  renderPage->>handler.request: request page with redirects
  renderPage->>Queue: requeue renderPage(page) when retries remain
  Queue-->>prerenderPages: report task error
  prerenderPages->>Queue: await queue settlement
  prerenderPages-->>prerenderPages: rethrow first collected error

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: fixing prerender retries for failed pages.
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.

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (2)

packages/start-plugin-core/tests/prerender-retry.test.ts (2)

4-22: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

any usage and as any casts weaken type safety.

vi.importActual<any>(...) and the as any cast on makeStartConfig's return bypass type checking entirely for startConfig. As per coding guidelines, **/*.{ts,tsx} should use TypeScript strict mode with extensive type safety. This is a common/pragmatic tradeoff for test mocks, so treat as optional.

Also applies to: 38-62

🤖 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 `@packages/start-plugin-core/tests/prerender-retry.test.ts` around lines 4 -
22, Replace the `vi.importActual<any>` usages in the `utils` and `node:fs` mocks
with appropriately typed imports or inferred types, and remove the `as any` cast
from `makeStartConfig` while preserving the mocked APIs and test behavior. Keep
the changes limited to improving type safety in these test mocks.

Source: Coding guidelines

---

64-107: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Missing coverage for the failOnError: true (default) exhaustion path.

Both tests avoid the scenario where retries are exhausted with failOnError at its default (true). Given the propagation concerns raised in prerender.ts (whether prerender() actually rejects/throws when a page permanently fails), a test asserting await expect(prerender(...)).rejects.toThrow() for that case would directly validate (or expose) that behavior.

🤖 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 `@packages/start-plugin-core/tests/prerender-retry.test.ts` around lines 64 -
107, The prerender retry tests lack coverage for exhausted retries with the
default failOnError behavior. Add a test alongside the existing cases using a
permanently failing request, retryCount: 2, and retryDelay: 0 without setting
failOnError: false; assert that prerender rejects with an error and that the
request mock is called three times.

🤖 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 `@packages/start-plugin-core/src/prerender.ts`:
- Around line 217-230: Collect task failures in the prerender flow around
queue.add and queue.start instead of relying on the current throw inside
renderPage. Capture queue errors via queue.onError/onSettled or handled
queue.add promises, await queue.start(), then rethrow the collected error when
failOnError is enabled, while preserving retry scheduling and preventing
unhandled rejections.

---

Nitpick comments:
In `@packages/start-plugin-core/tests/prerender-retry.test.ts`:
- Around line 4-22: Replace the `vi.importActual<any>` usages in the `utils` and
`node:fs` mocks with appropriately typed imports or inferred types, and remove
the `as any` cast from `makeStartConfig` while preserving the mocked APIs and
test behavior. Keep the changes limited to improving type safety in these test
mocks.
- Around line 64-107: The prerender retry tests lack coverage for exhausted
retries with the default failOnError behavior. Add a test alongside the existing
cases using a permanently failing request, retryCount: 2, and retryDelay: 0
without setting failOnError: false; assert that prerender rejects with an error
and that the request mock is called three times.

🪄 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: defaults

Review profile: CHILL

Plan: Pro

Run ID: 317def34-292c-457b-8027-d20ce61ff9d2

📥 Commits

Reviewing files that changed from the base of the PR and between 41f7bf3 and 8dcd787.

📒 Files selected for processing (2)

• packages/start-plugin-core/src/prerender.ts
• packages/start-plugin-core/tests/prerender-retry.test.ts

[wildlyinaccurate]

Fixes from CodeRabbit's first review have been applied and squashed.