ci(alt_text): add alt text linter

Author: amyheather

.github/workflows/lint_alt_text.yml

@@ -0,0 +1,24 @@
+name: Check Alt Text
+run-name: Check Alt Text
+
+on:
+  push:
+    paths:
+      - '**.qmd'
+      - 'lint_alt_text.py'
+      - '.github/workflows/lint_alt_text.yml'
+  pull_request:
+    paths:
+      - '**.qmd'
+      - 'lint_alt_text.py'
+      - '.github/workflows/lint_alt_text.yml'
+  workflow_dispatch:
+
+jobs:
+  check-alt-text:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Check images for alt text
+        run: python lint_alt_text.py

lint_alt_text.py

@@ -0,0 +1,56 @@
+import re
+import sys
+from pathlib import Path
+
+
+def find_images_without_alt(file_path):
+    """Find images in qmd files missing alt text (both markdown and HTML)"""
+    with open(file_path, "r", encoding="utf-8") as f:
+        content = f.read()
+
+    issues = []
+
+    # Remove fenced code blocks ```...``` (including ```{.md} etc.)
+    code_fence_pattern = r"```[\s\S]*?```"
+    content_no_code = re.sub(code_fence_pattern, "", content)
+
+    # Remove inline code `...`
+    inline_code_pattern = r"`[^`]*`"
+    content_no_code = re.sub(inline_code_pattern, "", content_no_code)
+
+    # Pattern 1: ![...](...)  - markdown images without fig-alt
+    # Only flag images whose alt text is empty or whitespace
+    # Negative lookahead: (?!.*\{[^}]*fig-alt=) - ensures no fig-alt follows
+    md_pattern = r"(?<!\[)!\[(?:\s*)\]\([^)]+\)(?!.*?\{[^}]*fig-alt=)"
+
+    for match in re.finditer(md_pattern, content_no_code):
+        line_num = content[:match.start()].count("\n") + 1
+        issues.append(("markdown", line_num, match.group(0)))
+
+    # Pattern 2: <img> tags without alt attribute
+    # Matches <img...> that doesn't contain alt=
+    img_pattern = r"<img\s+(?![^>]*\balt=)[^>]*>"
+
+    for match in re.finditer(img_pattern, content, re.IGNORECASE):
+        line_num = content[:match.start()].count("\n") + 1
+        issues.append(("html", line_num, match.group(0)))
+
+    return issues
+
+
+# Check all qmd files
+qmd_files = Path(".").rglob("*.qmd")
+found_issues = False
+
+for file in qmd_files:
+    issues = find_images_without_alt(file)
+    if issues:
+        found_issues = True
+        print(f"\n{file}:")
+        for img_type, line_num, img in issues:
+            print(f"  Line {line_num} [{img_type}]: {img}")
+
+if not found_issues:
+    print("✓ All images have alt text!")
+else:
+    sys.exit(1)  # Non-zero exit for CI/CD