WIP: Use Messenger with named target for sidebar panel rendering

[fregante]

Not ready for review

Second part to:

• Use Messenger for sidebar bricks #1642

Related/included:

• How can a content script target a frame? webext-messenger#41
• WIP: Add support for named targets (like the sidebar) webext-messenger#43

Questions:

• Are the nonces necessary? The current setup in the named targets PR probably does not allow them. Currently the context-matching mechanism is the "sidebar" target name:
  1. The sidebar registers itself as "sidebar" for the current tab with the background script
  2. The content script sends messages to "sidebar"

To do:

• Test
• Test
• Test
• Review
• Finalize WIP: Add support for named targets (like the sidebar) webext-messenger#43

[fregante]

(Having some trouble debugging this. The messages don't seem to arrive into the iframe even if the tabId and frameId are resolved correctly. Once every 10 times it works. 😰 )

[twschiller]

The messages don't seem to arrive into the iframe even if the tabId and frameId are resolved correctly

I can help take a look this afternoon. Is this an issue when opening/closing the sidebar, or while the sidebar is open?

Are the messages arriving but then getting discarded for being stale?

For the messaging, I was thinking about investing some time at some point in using a tool like https://bestchai.bitbucket.io/shiviz/ to visualize the communication trace between the components. We could probably instrument the messaging library to produce the format it needs

[fregante]

Is this an issue when opening/closing the sidebar, or while the sidebar is open?

I only tried the initial messages at first. It could be that the retries stop too early, but the "named target registered" message happens 3-4 seconds before the last retry.

Are the messages arriving but then getting discarded for being stale?

The raw onMessage handler in the sidebar isn't called, so they don't arrive at all. However, if I later message it manually the messages arrive.

investing some time at some point in using a tool like

That looks good! I can look into it. It might be complicated since there's no "global" communication watcher, so each step would have to probably report back to the background page (via messenger itself) and generate the viz there.

[fregante]

I might have found the issue, please don't attempt to debug 😅 it's in pixiebrix/webext-messenger#43

[fregante]

This last commit seems to have finally resolved the issue I was having. I will have to keep testing and then clean the PR. ✅ 🥳

Repro for future reference

1. Open editor
2. Open sidebar
3. Click "Save"
4. See editor error:

   Error fetching remote bricks: No handler for REGISTRY_SYNC was registered in the receiving end
   

if you close the sidebar, it works correctly:

[fregante]

Closing for now. I'll focus on making the messenger more debuggable first:

• Reorganize extension for clarity webext-messenger#49
• Provide way to correlate messages/responses in logs webext-messenger#50
• Provide way to see unified log of message events webext-messenger#48