feat(ci): diagram-scoped e2e test selection

[pbrolin47]

Summary

Resolves #7593

• Adds scripts/e2e-diagram-scope.mjs — a pure Node.js ESM detection engine that reads changed file paths and emits only the matching Cypress --spec pattern (or an empty string to trigger the full suite)
• Adds scripts/run-e2e-scoped.ts — local dev runner that diffs HEAD vs a base ref and spawns Cypress with the scoped spec list
• Adds scripts/e2e-diagram-scope.spec.ts — 14 unit tests covering all classification paths (single diagram, shared code, unknown diagram, multi-diagram, cross-cutting specs)
• Adds 4 new pnpm scripts: e2e:scope, e2e:scope:harness, e2e:scope:run, e2e:scope:detect
• Adds a detect-scope CI job that runs in parallel with cache (no critical-path penalty), uses a dynamic matrix ([1] when scoped, [1,2,3,4,5] for the full suite), and passes the spec: filter to cypress-io/github-action
• Diagram-specific rendering tests are moved into subfolders

Classification

• Change type: CI/tooling
• Breaking change: No — feature flag (E2E_SCOPE_BY_DIAGRAM) defaults to false; existing behavior is fully preserved until the flag is enabled
• Shared code touched: No diagram source code changed

How to enable

Set a repository variable in GitHub → Settings → Secrets and variables → Actions → Variables:

E2E_SCOPE_BY_DIAGRAM = true

When enabled, a PR that only touches (e.g.) packages/mermaid/src/diagrams/flowchart/ will run only cypress/integration/rendering/flowchart/flowchart*.spec.* in a single container instead of the full 5-container suite.

Any change to shared code (rendering-util/, themes/, config, diagram-api/, parser/, etc.) falls back automatically to the full suite.

Verification

• Unit tests added (scripts/e2e-diagram-scope.spec.ts) — run with vitest run scripts/e2e-diagram-scope
• comp-review-changes: passed (0 blockers)
• Breaking change: No — opt-in only, full suite is the default
• Lint: run pnpm lint locally
• Full e2e: N/A for CI-only change; existing suite validates once merged to develop

Note for testing locally:
In your local repo, do changes locally. Then you can issue command
git status --short | awk '{print $2}' | node scripts/e2e-diagram-scope.mjs

If an empty string is will result in the full e2e-suite will be run in CI, otherwise specific diagram folders will be returned

For testing locally together with cypress, you can use the steps below:

# For hardcoded local testing, use echo with newlines
SPEC=$(echo "packages/mermaid/src/diagrams/state/stateDiagram.ts" | node scripts/e2e-diagram-scope.mjs)

# Multiple files
SPEC=$(printf "packages/mermaid/src/diagrams/state/foo.ts\npackages/mermaid/src/diagrams/flowchart/bar.ts" | node scripts/e2e-diagram-scope.mjs)

echo "Running spec: ${SPEC:-'(full suite)'}"
pnpm cypress --spec "$SPEC"

🤖 Generated with Claude Code

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commit: ab1ce31

[codecov]

Codecov Report

❌ Patch coverage is 0.53476% with 186 lines in your changes missing coverage. Please review.
✅ Project coverage is 3.31%. Comparing base (530124c) to head (ab1ce31).
⚠️ Report is 21 commits behind head on develop.

Files with missing lines	Patch %	Lines
scripts/e2e-diagram-scope.mjs	0.00%	166 Missing ⚠️
scripts/run-e2e-scoped.ts	4.76%	20 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #7619      +/-   ##
==========================================
- Coverage     3.32%   3.31%   -0.01%     
==========================================
  Files          537     540       +3     
  Lines        56477   56675     +198     
  Branches       822     824       +2     
==========================================
+ Hits          1879    1880       +1     
- Misses       54598   54795     +197     

Flag	Coverage Δ
unit	3.31% <0.53%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
scripts/run-e2e-scoped.ts	4.76% <4.76%> (ø)
scripts/e2e-diagram-scope.mjs	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes

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Build	Status	Details	Updated (UTC)
default (Inspect)	👍 Changes approved	1 changed	Apr 21, 2026, 8:17 AM

[knsv]

One change we should think about. We could do that in a separate PR but that one should not wait too long.

[knsv]

Also check the linting

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