# Entity Flattening Implementation - Reconnaissance Summary

**Date**: 2025-12-04
**Status**: ✅ COMPLETE - Ready for implementation

---

## Executive Summary

Reconnaissance completed for entity flattening implementation plan. All critical information gathered:

1. ✅ **Only ONE caller** of `execute_mutation_rust` found (simplified Task 5)
2. ✅ **Test infrastructure ready** (`mutation_result_v2` type already exists)
3. ✅ **Success type patterns validated** (can use `__annotations__` for introspection)
4. ✅ **Test workaround identified** (lines 77-81 in cascade test need reversion)

**Plan Status**: 100% ready for delegation. No gaps remain.

---

## Key Findings

### Finding 1: Single Caller Simplifies Implementation
**Impact**: MAJOR - Reduces Task 5 from "unknown number of files" to "one file change"

```
Location: src/fraiseql/mutations/mutation_decorator.py:189
Context: MutationResolver.__call__() method
Available: self.success_type (the Python class, not just string name)
```

**Before reconnaissance**: Plan said "Find all callers, update each one"
**After reconnaissance**: Plan now says "Update single caller at line 189"

### Finding 2: Test Infrastructure Complete
**Impact**: HIGH - Can start implementation immediately, no fixture setup needed

```
mutation_result_v2 type: tests/fixtures/cascade/conftest.py:85-88
Test function: create_post() returns mutation_result_v2
Test tables: posts, users already created in fixture
```

**Before reconnaissance**: Unknown if test fixtures were ready
**After reconnaissance**: Confirmed all test infrastructure exists

### Finding 3: Success Type Patterns Validated
**Impact**: MEDIUM - Confirms `should_flatten_entity()` logic is correct

```
Patterns found:
- Minimal: Only message field
- Explicit: post, message, cascade fields
- Entity-based: user/post field matching entity

All have __annotations__ attribute (can introspect)
```

**Before reconnaissance**: Assumed patterns, not verified
**After reconnaissance**: Confirmed patterns match plan assumptions

### Finding 4: Test Workaround Identified
**Impact**: MEDIUM - Know exactly which lines to change in Task 6

```
File: tests/integration/test_graphql_cascade.py
Lines to fix:
- Line 77: data["data"]["createPost"]["entity"]["entityId"]
- Line 78: data["data"]["createPost"]["entity"]["message"]
- Line 81: cascade = data["data"]["createPost"]["entity"]["cascade"]

Change to:
- Line 77: data["data"]["createPost"]["id"] (or entityId directly)
- Line 78: data["data"]["createPost"]["message"]
- Line 81: cascade = data["data"]["createPost"]["cascade"]
```

**Before reconnaissance**: Knew test had workaround, didn't know exact lines
**After reconnaissance**: Exact lines and structure documented

---

## Updated Plan Sections

The following sections in `entity-flattening-implementation-plan.md` have been updated:

### Section Added: Pre-Implementation Reconnaissance (lines 110-165)
- Documents all reconnaissance results
- Shows commands run and findings
- Explains impact on each task

### Section Updated: Task 5 (lines 668-751)
- Replaced vague "find callers" with concrete findings
- Shows exact location and code
- Provides exact change needed (one-line addition)
- Notes that tests don't need updates

---

## Files That Will Be Modified

### New Files (3)
1. `src/fraiseql/mutations/entity_flattener.py` - Flattening logic
2. `tests/unit/mutations/test_entity_flattener.py` - Unit tests
3. `tests/integration/test_entity_flattening.py` - Integration tests

### Modified Files (3)
1. `src/fraiseql/mutations/rust_executor.py` - Add parameter and call flattener
2. `src/fraiseql/mutations/mutation_decorator.py` - Pass success_type_class parameter
3. `tests/integration/test_graphql_cascade.py` - Revert workaround (lines 77-81)

---

## Confidence Assessment

**Overall Confidence**: 95% (Very High)

| Aspect | Confidence | Rationale |
|--------|-----------|-----------|
| Single caller | 100% | Grep confirmed, no ambiguity |
| Caller has access to class | 100% | `self.success_type` visible at line 162 |
| Test infrastructure ready | 100% | Found existing fixtures with mutation_result_v2 |
| Success type patterns | 95% | Saw multiple examples, patterns consistent |
| Cascade handling | 90% | Logic sound, but edge case: what if entity HAS cascade field? |

**Remaining Risk**:
- Edge case: If PostgreSQL function returns `entity` JSONB with its own `cascade` field
- Mitigation: Plan already handles this (lines 227-234) - top-level cascade takes priority

---

## Pre-Implementation Checklist

Before delegating to opencode:

- [x] Find all callers of `execute_mutation_rust`
- [x] Verify caller has access to Success type class
- [x] Verify test infrastructure exists (`mutation_result_v2`)
- [x] Survey Success type patterns in codebase
- [x] Identify test workarounds to revert
- [x] Update plan with reconnaissance findings
- [x] Document exact line numbers and changes needed

---

## Next Steps

1. **Delegate Task 1-7** to opencode with updated plan
2. **Verification after each task** (run tests, check files)
3. **Commit after successful verification**
4. **Move to next task**

**Estimated Time**:
- Implementation: ~3 hours (tasks automated with opencode)
- Verification & Testing: ~1 hour
- Total: ~4 hours

---

## Notes for Implementation

### Critical: Cascade Field Priority

The flattening logic MUST respect this priority:

```python
# If Success type has 'cascade' field:
if field_name == "cascade":
    # NEVER extract from entity
    # Cascade comes from top-level mutation_result_v2 ONLY
    continue

# For all other fields:
if field_name in entity:
    flattened[field_name] = entity[field_name]
```

**Why**: Cascade is a `mutation_result_v2` field (structural), not entity data (domain).

### Error Handling Gap (Noted in Review)

Plan doesn't handle:
- What if `entity` is a string instead of dict? → Current code: `isinstance(entity, dict)` check (line 208)
- What if `entity` is None? → Current code: "entity" not in mutation_result check (line 201)

**Status**: Adequate error handling already in plan. No changes needed.

---

## Conclusion

✅ **Plan is 100% ready for implementation**

All reconnaissance tasks completed. No gaps or unknowns remain. The plan has been updated with:
- Exact caller location and code
- Concrete line numbers for all changes
- Test fixture confirmation
- Pattern validation

**Recommendation**: Proceed with delegation to opencode.
