feat: pdf export visual snapshot testing (#29)

Author: peter-gy

.github/workflows/export-notebooks.yml

@@ -43,13 +43,31 @@ jobs:
       - name: 📄 Install system dependencies (LaTeX and Pandoc)
         run: |
           sudo apt-get update
-          sudo apt-get install -y texlive-xetex texlive-fonts-recommended texlive-plain-generic pandoc
+          sudo apt-get install -y texlive-xetex texlive-fonts-recommended texlive-plain-generic pandoc poppler-utils
         continue-on-error: true
 
       - name: 📦 Install Python dependencies
         run: |
           uv sync --extra pdf
 
+      - name: 🎭 Install Chromium (for WebPDF)
+        run: |
+          uv run python -m playwright install --with-deps chromium
+
+      - name: 🖼️ PDF visual snapshot test
+        id: pdf_snapshot
+        run: |
+          uv run scripts/test_pdf_visual_snapshots.py
+
+      - name: 📦 Upload PDF snapshot artifacts (on failure)
+        if: failure() && steps.pdf_snapshot.outcome == 'failure'
+        uses: actions/upload-artifact@v6
+        with:
+          name: pdf-visual-snapshot-artifacts
+          path: snapshot_artifacts/
+          if-no-files-found: ignore
+          retention-days: 7
+
       - name: 📂 Setup examples
         run: |
           uv run scripts/setup_examples.py

.gitignore

@@ -1,6 +1,9 @@
 # marimo
 /examples
 
+# Snapshot artifacts (generated locally / uploaded in CI on failure)
+/snapshot_artifacts/
+
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]

notebooks/pdf_snapshot_smoke.py

@@ -0,0 +1,45 @@
+# /// script
+# requires-python = ">=3.12"
+# dependencies = [
+#     "marimo",
+#     "matplotlib",
+# ]
+# ///
+
+import marimo
+
+__generated_with = "0.19.7"
+app = marimo.App(width="medium")
+
+with app.setup:
+    import marimo as mo
+
+
+@app.cell(hide_code=True)
+def _():
+    import matplotlib as mpl
+    mpl.use("Agg")
+
+    import matplotlib.pyplot as plt
+
+    plt.rcParams.update(
+        {
+            # Keeping this small so that the PDF fits on a single page.
+            "figure.figsize": (2.6, 1.4),
+            "figure.dpi": 150,
+        }
+    )
+
+    x = [1, 2, 3]
+    y = [1, 4, 9]
+
+    fig, ax = plt.subplots()
+    ax.plot(x, y, marker="o")
+    ax.set_title("y=x^2")
+    fig.tight_layout()
+    fig
+    return
+
+
+if __name__ == "__main__":
+    app.run()

pyproject.toml

@@ -13,6 +13,7 @@ dependencies = [
     "matplotlib",
     "pandas",
     "nbconvert",
+    "pillow",
 ]
 
 [project.optional-dependencies]