[DOC] Update template error documentation with final solution

docs/FIX_TEMPLATE_ERROR_SUMMARY.md

@@ -1,7 +1,8 @@
 # Fix Template Error Summary - website_sale_aplicoop
 
 **Date**: 2026-02-16
-**Status**: ✅ RESOLVED
+**Final Status**: ✅ PERMANENTLY RESOLVED
+**Solution Commit**: 5721687
 **Version**: 18.0.1.1.1
 
 ---
@@ -10,45 +11,120 @@
 
 The `eskaera_shop_products` QWeb template was throwing a `TypeError: 'NoneType' object is not callable` error when loading the store page.
 
-### Root Cause
+### Root Cause - QWeb Parsing Limitations
 
-QWeb templates don't handle the `or` operator reliably when used directly in `t-attf-*` (attribute) expressions, especially when values can be `None`.
+QWeb has strict limitations on what expressions it can parse:
 
-**Original problematic code**:
-```xml
-<form ...
-    t-attf-data-product-price="{{ display_price or product.list_price or 0 }}"
-    t-attf-data-uom-category="{{ product.uom_id.category_id.name if product.uom_id.category_id else '' }}"
->
-```
+1. **Complex nested conditionals in t-set fail**
+   ```xml
+   ❌ <t t-set="x" t-value="a if a else (b if b else c)"/>
+   ```
 
-When `display_price` was `None`, QWeb would try to evaluate the `or` operator incorrectly, causing the error.
+2. **Direct 'or' in attributes unreliable**
+   ```xml
+   ❌ <div t-attf-val="{{ price or fallback }}"/>
+   ```
+
+3. **Deep object chains with conditionals fail**
+   ```xml
+   ❌ t-set="uom" t-value="product.uom_id.category_id.name if product.uom_id.category_id else ''"
+   ```
 
 ---
 
 ## Solution
 
-### Pattern: Intermediate Variable + Simple Fallback
+### Architecture: Move Logic to Controller
 
-The key insight is that complex conditional expressions in `t-set` can fail. Instead,
-use Python's native `or` operator with intermediate variables to handle None values safely.
+**Final insight**: Don't fight QWeb's limitations. Move ALL complex logic to the Python controller where it belongs.
 
-**Fixed code**:
-```xml
-<!-- Step 1: Extract the price value from price_info -->
-<t t-set="display_price_value"
-   t-value="price_info.get('price')"/>
+#### The Pattern
 
-<!-- Step 2: Use Python's 'or' operator for safe fallback -->
-<t t-set="display_price"
-   t-value="display_price_value or product.list_price or 0.0"/>
-
-<!-- Step 3: Reference the computed variable in attributes -->
-<form ...
-    t-attf-data-product-price="{{ display_price }}"
-    t-attf-data-uom-category="{{ safe_uom_category }}"
->
 ```
+CONTROLLER (Python)
+   ↓ (process data, handle None)
+product_display_info = {
+    product.id: {
+        'display_price': 10.99,      # Always a float, never None
+        'safe_uom_category': 'Weight' # Always a string, never None
+    }
+}
+   ↓ (pass clean data to template)
+TEMPLATE (QWeb)
+   ↓ (simple dict.get() calls, no logic)
+<form t-attf-data-price="{{ product_display_info.get(product.id, {}).get('display_price', 0.0) }}"/>
+```
+
+#### Implementation
+
+**In Controller** - Added `_prepare_product_display_info()` method:
+
+```python
+def _prepare_product_display_info(self, product, product_price_info):
+    """Pre-process all display values for QWeb safety.
+
+    All logic happens HERE in Python, not in template.
+    Returns dict with safe values ready for display.
+    """
+    # Get price - handle None safely
+    price_data = product_price_info.get(product.id, {})
+    price = price_data.get("price", product.list_price) if price_data else product.list_price
+    price_safe = float(price) if price else 0.0
+
+    # Get UoM category - handle None/nested attributes safely
+    uom_category_name = ""
+    if product.uom_id:
+        if product.uom_id.category_id:
+            uom_category_name = product.uom_id.category_id.name or ""
+
+    return {
+        "display_price": price_safe,        # Never None
+        "safe_uom_category": uom_category_name,  # Never None
+    }
+```
+
+**In Template** - Simple dict.get() calls:
+
+```xml
+<!-- Just retrieve pre-processed values -->
+<t t-set="display_price"
+   t-value="product_display_info.get(product.id, {}).get('display_price', 0.0)"/>
+
+<t t-set="safe_uom_category"
+   t-value="product_display_info.get(product.id, {}).get('safe_uom_category', '')"/>
+
+<!-- Use simple variable references -->
+<form t-attf-data-product-price="{{ display_price }}"
+      t-attf-data-uom-category="{{ safe_uom_category }}"/>
+```
+
+---
+
+## What Changed
+
+### Files Modified
+
+1. **website_sale_aplicoop/controllers/website_sale.py**
+   - Added `_prepare_product_display_info()` method (lines 390-417)
+   - Generate `product_display_info` dict in `eskaera_shop()` (lines 1062-1065)
+   - Generate `product_display_info` dict in `load_eskaera_page()` (lines 1260-1263)
+   - Pass to template renders
+
+2. **website_sale_aplicoop/views/website_templates.xml**
+   - Removed complex conditional expressions from template
+   - Replaced with simple `dict.get()` calls
+   - No business logic remains in template
+
+### Iteration History
+
+| Commit | Approach | Result |
+|--------|----------|--------|
+| df57233 | Add `or` operators in attributes | ❌ Error persisted |
+| 0a0cf5a | Complex nested conditionals in t-set | ❌ Error persisted |
+| 8e5a4a3 | Three-step pattern with `or` chains | ⚠️ Error persisted |
+| 5721687 | Move logic to controller | ✅ SOLVED |
+
+
 
 ### Why This Works