40 lines
1.7 KiB
Markdown
40 lines
1.7 KiB
Markdown
# Jinja2 Template Inheritance Debugging
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## Silent Block Omission
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**Symptom**: Child template's `{% block X %}` content is completely absent from rendered page. No error, no warning.
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**Root cause**: Parent template (base.html) does NOT define `{% block X %}{% endblock %}`. Jinja2 silently ignores child blocks that don't have a corresponding parent block definition.
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**Detection**:
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```bash
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# Check if parent template defines the block
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grep -n "block_name" templates/base.html
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# Check rendered output for the expected content
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curl -s https://site/page | grep -o "expected_js_variable"
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```
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**Example from ephron.ren**:
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- `blog/templates/admin/collection_edit.html` defined `{% block extra_scripts %}` with critical JavaScript
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- `blog/templates/base.html` had `{% block extra_styles %}` and `{% block content %}` but NO `{% block extra_scripts %}`
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- Result: All JavaScript for article selection was silently omitted from the page
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- Other services (prompt, auth, canvas, home) all had `extra_scripts` defined in their base templates
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**Fix**: Add the missing block definition to the parent template:
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```html
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<!-- Before </body> -->
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{% block extra_scripts %}{% endblock %}
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```
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**Prevention**: When creating child templates, verify the parent template defines all blocks you intend to override. Use `grep` to check.
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**Cross-service consistency check**: When debugging template issues in multi-service sites, compare the base templates across all services to find missing block definitions:
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```bash
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for svc in blog auth canvas prompt home; do
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echo "=== $svc ==="
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grep -n "block.*endblock\|{% block" $svc/templates/base.html 2>/dev/null || \
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grep -n "block.*endblock\|{% block" $svc/templates/_design_system/page_shell.html 2>/dev/null
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done
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```
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