Fix: run plugin hooks on command failure, not just success

[derekmisler]

This PR is part of a trilogy:

1. docker/cli <-- you are here
2. docker/ai
3. docker/pinata

---

Closes https://github.com/docker/gordon/issues/125

- What I did

Enabled CLI plugin hooks to fire on command failure, not just success. Previously, when a plugin-delegated command like docker build (buildx) or docker compose up failed, the hooks system was skipped entirely. This meant plugins like ai, scout, and debug could never show "What's next:" hints for failed builds or compose errors, which is exactly when our users would benefit from a docker ai "fix my problem" command.

- How I did it

Two changes:

1. cli-plugins/manager/hooks.go: Added cmdErrorMessage string parameter to RunPluginHooks, forwarding it to runHooks instead of hardcoding "". This makes it symmetric with RunCLICommandHooks, which already accepts error messages.
2. cmd/docker/docker.go: Moved the plugin hooks invocation outside the if err == nil block so it fires regardless of plugin exit status. The error message is extracted the same way the native command path already does it.

- How to verify it

1. Register a plugin with hooks for a plugin-delegated command (e.g., buildx build):

# In ~/.docker/config.json, ensure:
# "features": { "hooks": "true" }
# "plugins": { "<plugin>": { "hooks": "buildx build" } }

2. Before this change — run a failing build, observe no "What's next:" hints:

echo "FROM nonexistent:image" > /tmp/Dockerfile
docker build /tmp
# No hints shown

3. After this change — same failing build now shows plugin hints:

docker build /tmp
# "What's next:" hints from registered plugins appear

4. Verify successful commands still show hints (no regression):

docker build -t test -f /dev/null .  # or any successful build
# Hooks fire with empty error message, same as before

5. Verify native commands are unaffected:

docker run nonexistent:image
# Hooks fire on failure (worked before, still works)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 25.00000% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cmd/docker/docker.go	0.00%	6 Missing ⚠️

📢 Thoughts on this report? Let us know!

[thaJeztah]

cc @vvoland @laurazard looks related to what was implemented in;

• hooks: pass command execution error to plugins #5033

[derekmisler]

cc @vvoland @laurazard looks related to what was implemented in;

• hooks: pass command execution error to plugins #5033

Yeah, that PR was helpful when working on this one. I saw we were hard-coding an empty "" in place of the error here: https://github.com/docker/cli/pull/5033/changes#diff-7e76b3d50db2ee696d1cdbaa3f1e429b179da962bb8f308960ef85bc0ba835a2R43

[derekmisler]

I'm not sure about that e2e test, @thaJeztah, it passes sometimes and fails others, and I can't figure out why.

[thaJeztah]

Yeah, that test is rather flaky; not an issue with this PR; I restarted CI.

Yeah, that PR was helpful when working on this one. I saw we were hard-coding an empty "" in place of the error here

Yup; I mostly pinged @vvoland and @laurazard to check if they recalled there was a specific reason; there was this line in the PR description;

This is only available for CLI command executions.

And I do recall there was some chatter at the the about some risks with hook being triggered recursively (with a growing number of plugins, there's also a growing amount of overhead).

[thaJeztah]

Just so I don't forget; this function is exported (and may be in use elsewhere), so we probably can't change the signature.

[derekmisler]

This was the only implementation site I could find: https://github.com/docker/cli/pull/6794/changes#diff-3dcd6325b70a5f5db393a3ecc08060b69007fcef371fb4dabf3164da95646fb6R488