Prep Verification Build

This skill modifies workspace files to ensure LUCI builders run, isolates target test suites in builder Starlark files for speed, and uploads a Work-In-Progress (WIP) Gerrit CL. It is used to prepare both experimental branches with fixes and clean baseline branches.

When to Use This Skill

After making potential configuration fixes and needing to run a verification build.
To create a "Baseline" CL on a clean branch, with only the necessary modifications to trigger and speed up the build.

Inputs (Read from scratch/triage_state.json)

This skill reads its primary inputs directly from scratch/triage_state.json. The only dynamic selector passed in the subagent prompt is role ("Control" vs. "Fix"):

target_files: A list of file paths that need a dummy comment to ensure they are included in the build's affected files.
builders_of_concern: A list of target builder names (e.g. ["linux-rel"]). To locate the .star Starlark configuration file for each builder, reference builder_star_map.json.
test_suites: The test suite names to isolate in the builder configurations.
bug_id: The issue ID for context in the CL description.
control_branch_name / fix_branch_name: The git branch to check out. If role is "Control" (or "control"), check out control_branch_name. If role is "Fix" (or "fix"), check out fix_branch_name.

Workflow

Checkout Branch:

Read scratch/triage_state.json and check out control_branch_name (if role is "Control") or fix_branch_name (if role is "Fix").
bash
```
git checkout {{selected_branch_name}}
```
Add Dummy Comments:
- Iterate through each file in target_files (from scratch/triage_state.json).
- Append a unique dummy comment to each file (e.g., // Verification run for b/{{bug_id}}).
bash
```
# Example for one file
echo "// Verification run for b/{{bug_id}} $(date)" >> {{file_path}}
```
Optimize Builder Configurations:
- For each builder in builders_of_concern and its .star file:
  - Locate the builder definition.
  - Modify the test suite declarations to only include the target suites from test_suites (from scratch/triage_state.json).
  - Example Modification: Change existing test bundles to:
    python
```
# Example for a builder's test targets
targets = targets.bundle(targets = {{test_suites}})
```
  - After modifying the .star file(s), regenerate configuration artifacts directly from the repository root:
    bash
```
lucicfg generate infra/config/main.star
```
    This updates the underlying JSON build specifications.

Commit Changes:

Stage all modified tracked files in the workspace using git add -u. This stages the dummy comments and updated builder configurations while safely ignoring any untracked scratch files or local skills.

bash

git add -u

Create a commit using the structured naming format. Note that the commit title must explicitly state (Control) or (Fix) based on role. If test_suites contains multiple test suites, join their names or list them.

Commit Message:

text

Verify Code Coverage Change for {{test_suites}} ({{role}})

This was generated by the Code Coverage Debugging Agent.

Role: {{role}} Verification
Target Files: {{ target_files }}

{{ summary of applied GN/Starlark/recipe fixes or trimming }}

Bug: {{bug_id}}

bash

git commit \
  -m "Verify Code Coverage Change for {{test_suites}} ({{role}})" \
  -m "This was generated by the Code Coverage Debugging Agent." \
  -m "Role: {{role}} Verification" \
  -m "Target Files: {{ target_files }}" \
  -m "{{ summary of applied GN/Starlark/recipe fixes or trimming }}" \
  -m "Bug: {{bug_id}}"

Upload to Gerrit:
- Upload the CL as a Work-In-Progress (WIP).
- Do NOT pass --cq-dry-run to the upload command.
bash
```
git cl upload -f --bypass-hooks -o wip
```
Update State File:
- Update scratch/triage_state.json: write the uploaded CL URL into control_cl (if role is "Control") or fix_cl (if role is "Fix").

Output

The URL of the uploaded Gerrit CL.
Confirmation that scratch/triage_state.json (control_cl or fix_cl) has been updated.

References

lucicfg Reference Manual