There's a separate effort by nxia@ to make the plugin display actual builds, rather than removing it entirely, but I've lost track of the progress of that effort. Ningning, what's the status?

Due to some constraints, we decided to develop our own plugin go/chromeos-cl-status-viewer, so we're not using the buildbucket-plugin to show the tryjobs for ChromeOS CLs. It shows "No tryjobs" because we aren't using it and all Pre-CQs don't have the buildset tag attached. 

pass agable@ to comment

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/gerrit-plugins/buildbucket/+/7bfb67a2be9c4ece89145fa77a218fcf68d96197

commit 7bfb67a2be9c4ece89145fa77a218fcf68d96197
Author: Aaron Gable <agable@chromium.org>
Date: Wed Jan 03 20:24:29 2018

Don't display at all if no buckets are configured

If no buckets are configured, the user can't trigger any tryjobs,
so there shouldn't be any jobs to display. As such, don't bother
querying for jobs, and don't mark the plugin as loaded, so it
won't display at all.

R=qyearsley

Bug:  777937 
Change-Id: I05b7025f798164dc68bd4a6e9eb6bfcf20398297
Reviewed-on: https://chromium-review.googlesource.com/849253
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>

[modify] https://crrev.com/7bfb67a2be9c4ece89145fa77a218fcf68d96197/src/main/resources/static/cr-buildbucket-view.js

https://chromium-review.googlesource.com/c/infra/gerrit-plugins/buildbucket/+/849253 has been submitted and imported internally (cl/180703447); this will be fixed with the next gerrit deployment.

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/gerrit-plugins/buildbucket/+/8cb90e76824afa2e08c3e8fb4c074aacb856da4d

commit 8cb90e76824afa2e08c3e8fb4c074aacb856da4d
Author: Quinten Yearsley <qyearsley@chromium.org>
Date: Thu Jan 04 21:52:26 2018

Buildbucket plugin: Fix checking for config and add test

This is a follow-up to https://crrev.com/c/849253, made after noticing that on
https://canary-chromium-review.googlesource.com/ try jobs are no longer
displayed as of today.

Bug:  777937 
Change-Id: I668901b53c38b96303373d34f75dc9bdb81b79b1
Reviewed-on: https://chromium-review.googlesource.com/850847
Reviewed-by: Aaron Gable <agable@chromium.org>

[modify] https://crrev.com/8cb90e76824afa2e08c3e8fb4c074aacb856da4d/test/cr-buildbucket-view_test.html
[modify] https://crrev.com/8cb90e76824afa2e08c3e8fb4c074aacb856da4d/src/main/resources/static/cr-buildbucket-view.js

this is about to be unfixed by https://chromium-review.googlesource.com/c/infra/gerrit-plugins/buildbucket/+/854767

So, the buildbucket plugin is enabled on a dozen different hosts (e.g. chromium, fuchsia, dart, skia, webrtc, pdfium). Each host has lots of projects; for some projects on some hosts, there are try jobs; for some projects there are try bots that can be triggered (determined by buckets list).

There are several different ways that we can handle this:

 (A) The original way is that the buildbucket UI is always displayed, and if there are no try jobs to display, a message is always shown that says "No tryjobs". (Disadvantage: this shows unnecessary UI for some projects like chromiumos)

 (B) We could require non-empty buckets in config, whenever we want to display try jobs. Note, the buckets to list will vary by host and project, and the bucket lists have to be maintained and updated.

 (C) We could hide the buildbucket UI whenever there are no try jobs, i.e. never show a block that says "No tryjobs", and instead just hide it completely. (Possible disadvantage: This is different that current behavior and some chromium developers might think that the buildbucket plugin is disabled or missing if they don't see it.)

 (C) We could override config for specific subprojects where we don't want to show buildbucket UI at all. This might involve adding another field to buildbucket config (e.g. "disable") or adding an empty buildbucket.config for some projects. (Disadvantage: This might not be a very obvious way to disable the buildbucket plugin for subprojects.)

The last paragraph was meant to be labeled (D).

Another proposal (E): If there are buckets configured, we always want to display some UI so that the user can trigger try jobs. If there are no buckets AND no try jobs, then the UI could be hidden.

Draft CL for (E): https://chromium-review.googlesource.com/#/c/infra/gerrit-plugins/buildbucket/+/854790

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/gerrit-plugins/buildbucket/+/2f34895bdb36f433c8f1deb97042fcdc57004085

commit 2f34895bdb36f433c8f1deb97042fcdc57004085
Author: Quinten Yearsley <qyearsley@chromium.org>
Date: Tue Jan 09 17:43:35 2018

Hide buildbucket plugin UI when there are no builds or buckets.

This change would make it so that in most cases where "No tryjobs"
is currently displayed, the UI would instead be entirely hidden.

For chromium and other projects where users can trigger try jobs,
"No tryjobs" would still be shown, and the tryjob picker should
also be shown.

Bug:  777937 , 799922
Change-Id: I20ed6750209cbf52563be5fb391686c367f7aa1e
Reviewed-on: https://chromium-review.googlesource.com/854790
Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Reviewed-by: jrn <jrn@google.com>

[modify] https://crrev.com/2f34895bdb36f433c8f1deb97042fcdc57004085/test/cr-buildbucket-view_test.html
[modify] https://crrev.com/2f34895bdb36f433c8f1deb97042fcdc57004085/src/main/resources/static/cr-buildbucket-view.html
[modify] https://crrev.com/2f34895bdb36f433c8f1deb97042fcdc57004085/src/main/resources/static/cr-buildbucket-view.js

Thank you for landing the change for (E) while I was out. I believe this has been deployed.