fix(vitest-plugin-vis): show snapshot paths relative to the project root

[unional]

Closes #93.

The ask

use relative path to project root for failed snapshots — instead of abs path.

Two motivations, pointing the same way: terminals and editors linkify a project-relative path fine, and an absolute path leaks /home/<someone>/... into any failure output pasted into an issue.

The 2024 blocker is gone

The issue was parked on microsoft/vscode#237086 ("gitignored relative file link in Terminal not clickable"), with a note to fix it "once that is fixed and released". That issue closed verified in the November 2025 milestone and has long since shipped stable, so the premise holds and the reason to wait is gone.

The change

compare_image_snapshot.ts builds three failure messages — no baseline, matched-but-expected-to-fail, and mismatched. Every path in them was resolve(info.projectRoot, info.<baseline|result|diff>Path). info.*Path is already project-relative; the resolve() was what made it absolute.

Those Expected: / Actual: / Difference: lines now go through a new formatSnapshotPath helper in compare_image_snapshot.logic.ts:

Expected:   ./__vis__/local/HD/__baselines__/client/expect/to_match_image_snapshot.spec.tsx/case-1.png

Only the human-facing message strings changed. The ~20 other resolve(projectRoot, ...) call sites are filesystem I/O — writeSnapshot, tryReadFile, playwright's screenshot path, snapshot_path_limits.ts, the globs in vis_server_context.logic.ts — and all stay absolute. The three writeSnapshot calls in this same file still use resolve().

Judgment calls

• ./ prefix. Both bare and ./-prefixed paths linkify, but the prefix marks the path unambiguously as relative rather than a bare package-ish name, and it survives copy-paste into a shell.
• Outside the project root — reachable in a monorepo via a custom snapshotRootDir — falls back to absolute rather than emitting ../../../.. noise, which is neither shorter nor clearer.
• Filenames beginning with .. (e.g. ..vis/) are not mistaken for an escape; the check is === '..' or startsWith('../'), not a bare startsWith('..').

Tests

• Five unit tests for formatSnapshotPath in compare_image_snapshot.unit.ts: relative-within-root, absolute-within-root (the leak case), outside-root fallback, the root itself, and the ..-prefixed-filename edge case.
• to_match_image_snapshot.spec.tsx now asserts the actual Expected: / Actual: / Difference: lines are ./__vis__/…-relative, on both the mismatch and the matched-but-expected-to-fail message. These assertions were confirmed to be genuinely exercised (deliberately breaking one fails the suite), not silently skipped by the specs' hasImageSnapshot() early return.

storybook-addon-vis surfaces no paths of its own — it renders these same messages from vitest-plugin-vis — so it is untouched. Its suite passes unchanged.

Verification

• pnpm build — 7/7 tasks ✅
• vitest-plugin-vis: 182 passed | 4 skipped (playwright), 87 passed | 1 skipped (node), tsc --noEmit clean
• storybook-addon-vis: 83 passed
• biome check clean on all changed files

Changeset: patch for vitest-plugin-vis.

🤖 Generated with Claude Code

https://claude.ai/code/session_01J1RSK6XtmajN5fASgJHqVb

[changeset-bot]

🦋 Changeset detected

Latest commit: 5364614

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
vitest-plugin-vis	Patch
storybook-addon-vis	Patch

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