Fix the deep review issues #143-#180, and the SSR rendering gap

.github/workflows/test.yml

@@ -6,21 +6,44 @@ on:
   pull_request:
     branches: [main]
 
+env:
+  # The Observable Plot commit whose committed snapshots are the parity oracle
+  # (v0.6.17-41-g1c6b239d). Bumping it means refreshing parity-allow.json in the
+  # same commit: yarn parity --allow parity-allow.json --update.
+  UPSTREAM_COMMIT: 1c6b239d1e42eb5c0d8c5b09f51b0c6ce51bea69
+
 jobs:
   test:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # The Node LTS lines that are still maintained.
+        node-version: [22, 24]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 22
+          node-version: ${{ matrix.node-version }}
           cache: yarn
       - run: yarn --frozen-lockfile
+      # The snapshot oracle is byte comparison against committed files, and one
+      # plot is not byte-stable across V8 lines: projectionDomainRatioNC renders
+      # the same polygon starting from a different vertex on Node 24 than on 22,
+      # because d3-geo's clipping is sensitive to floating-point differences in
+      # the V8 the tests run on. The baselines are therefore generated and
+      # checked on the primary line only, and the other lines run everything
+      # except the snapshot harness, so a Node-specific breakage in the library
+      # still shows up here.
       - run: yarn test:mocha
+        if: matrix.node-version == 22
+      - run: yarn test:units
+        if: matrix.node-version != 22
       - run: yarn test:tsc
       - run: yarn test:lint
       - run: yarn test:prettier
       - run: yarn prepublishOnly
+      - run: yarn test:smoke
       - run: yarn test:publint
       - run: yarn test:attw
       - run: yarn docs:build
@@ -29,3 +52,29 @@ jobs:
         with:
           name: test-output-changes
           path: test/output/*-changed.*
+
+  # A green test job says Replot's snapshots have not changed; it does not say
+  # they match Observable Plot's. This job compares the committed snapshots
+  # with upstream's at the pinned commit, and fails on any plot that differs in
+  # a way parity-allow.json does not already record.
+  parity:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: yarn
+      - run: yarn --frozen-lockfile
+      # Upstream's snapshots are the whole oracle, so fetch its test/output at
+      # that one commit: shallow, blobless (no file contents until the checkout
+      # asks for them) and sparse.
+      - name: Fetch the pinned Observable Plot snapshots
+        run: |
+          git init ../observablehq-plot
+          git -C ../observablehq-plot remote add origin https://github.com/observablehq/plot.git
+          git -C ../observablehq-plot config core.sparseCheckout true
+          echo 'test/output/*' > ../observablehq-plot/.git/info/sparse-checkout
+          git -C ../observablehq-plot fetch --depth 1 --filter=blob:none origin "$UPSTREAM_COMMIT"
+          git -C ../observablehq-plot checkout FETCH_HEAD
+      - run: yarn -s parity --upstream ../observablehq-plot --allow parity-allow.json --fail

.gitignore

@@ -1,8 +1,9 @@
 .DS_Store
+.claude/settings.local.json
+.claude/worktrees/
+.playwright-cli/
 coverage/
 dist/
-docs/.vitepress/cache
-docs/.vitepress/dist
 node_modules/
 test/output/*-changed.svg
 test/output/*-changed.html