RENDER_NUNJUCKS not available within 3 seconds

[twschiller]

Describe the bug

• RENDER_NUNJUCKS not available within 3 seconds

To Reproduce

The error is intermittent. What @brittanyjoiner15 is seeing is most likely that either: 1) a selection watch trigger is failing, or 2) a page load trigger (e.g., to fetch announcements) is failing on some pages

Likely steps to reproduce:

• Add a page load trigger with no debounce
• Configure the trigger to show an error on failure
• Add a brick that uses a nunjucks template. E.g., the identity brick with {{ @input.url }}
• Browse the web and wait for the error to pop up

Actual behavior

• A mod fails with error "RENDER_NUNJUCKS not available within 3 seconds"
• Behavior depends on what the triggers error handler is set to (i.e., whether or not an error toast will be shown)

Discussion

• RENDER_NUNJUCKS is handled by the sandbox injected into the page: https://github.com/pixiebrix/pixiebrix-extension/blob/6e2f02e1d6f2c6fa8bf8f96be25278bc4586bbe5/src/sandbox/messenger/api.ts#L62-L62
• In MV3, all nunjucks evaluation is run via the Sandbox. (In MV2, you have to toggle it on. Javascript brick is always run in the sandbox though)
• To diagnose the error, you need to figure out whether that error would be thrown if:
  • Is the sandbox not getting added to the page properly? Or,
  • Is the sandbox added, but then getting removed?
  • Is the sandbox on the page, but it's not responding in time (e.g., b/c it's processing another message)?

Potential Solution

• Add automatic retries when renderNunjucks fails
• Advice users to refresh the page if renderNunjucks fails 4 times
• Similar to: https://github.com/pixiebrix/pixiebrix-extension/pull/8474