# Week 7 Day 1 - Type-Safe Configuration Implementation
**Status:** Complete ✅
**Date:** 2025-10-29
**Focus:** Create `SessionPaths` dataclass with comprehensive testing
______________________________________________________________________
## Overview
Day 1 focused on creating the foundation for ACB DI refactoring by implementing a type-safe `SessionPaths` configuration class. This addresses the root cause of 4 failing DI infrastructure tests where string-based keys conflict with Bevy's type checking system.
## Accomplishments
### ✅ Created SessionPaths Dataclass
**File Created:** `session_buddy/di/config.py` (99 lines)
**Key Features:**
1. **Frozen Dataclass** - Immutable configuration prevents runtime modifications
1. **Factory Method** - `from_home()` class method for flexible instantiation
1. **Environment-Aware** - Uses `os.path.expanduser("~")` for test-friendly paths
1. **Directory Management** - `ensure_directories()` method for idempotent setup
**Architecture:**
```python
@dataclass(frozen=True)
class SessionPaths:
"""Type-safe path configuration for session management."""
claude_dir: Path
logs_dir: Path
commands_dir: Path
@classmethod
def from_home(cls, home: Path | None = None) -> SessionPaths:
"""Create SessionPaths from home directory."""
if home is None:
home = Path(os.path.expanduser("~"))
claude_dir = home / ".claude"
return cls(
claude_dir=claude_dir,
logs_dir=claude_dir / "logs",
commands_dir=claude_dir / "commands",
)
def ensure_directories(self) -> None:
"""Create all configured directories if they don't exist."""
self.claude_dir.mkdir(parents=True, exist_ok=True)
self.logs_dir.mkdir(parents=True, exist_ok=True)
self.commands_dir.mkdir(parents=True, exist_ok=True)
```
### ✅ Comprehensive Unit Tests
**File Created:** `tests/unit/test_di_config.py` (282 lines, 20 tests)
**Test Coverage:**
| Category | Tests | Focus |
|----------|-------|-------|
| **Creation** | 4 | Factory methods, explicit paths, environment variables |
| **Immutability** | 4 | Frozen dataclass enforcement, attribute protection |
| **Directory Creation** | 3 | Filesystem operations, idempotency, parent handling |
| **Equality & Hashing** | 3 | Dataclass equality, dict key usage |
| **String Representation** | 1 | Debugging output |
| **Type Annotations** | 2 | Type safety, frozen configuration |
| **Edge Cases** | 3 | Relative paths, symlinks, file conflicts |
**Test Results:**
- ✅ **20/20 tests passing** (100% pass rate)
- ⚡ **0.41s execution time** (fast, efficient)
- 🎯 **100% coverage** of SessionPaths class
______________________________________________________________________
## Technical Implementation Details
### Design Decision: Frozen Dataclass
**Why `frozen=True`?**
```text
@dataclass(frozen=True)
class SessionPaths:
# ...
```
**Benefits:**
1. **Immutability** - Prevents accidental modifications after creation
1. **Hashable** - Can be used as dict keys or in sets
1. **Thread-Safe** - No risk of concurrent modification
1. **Clear Intent** - Configuration should not change after initialization
**Test Verification:**
```text
def test_immutability_claude_dir(self) -> None:
"""Should raise FrozenInstanceError when attempting to modify."""
paths = SessionPaths.from_home()
with pytest.raises(FrozenInstanceError):
paths.claude_dir = Path("/tmp/hacked") # ❌ Raises error
```
### Design Decision: Factory Method Pattern
**Why `from_home()` class method?**
```text
@classmethod
def from_home(cls, home: Path | None = None) -> SessionPaths:
if home is None:
home = Path(os.path.expanduser("~"))
# ...
```
**Benefits:**
1. **Flexible Creation** - Supports both default and custom home paths
1. **Test-Friendly** - Easy to provide temp directories in tests
1. **Environment-Aware** - Respects HOME environment variable
1. **Clear Interface** - `SessionPaths.from_home()` vs complex constructor
**Test Verification:**
```python
def test_from_home_respects_home_env_var(
self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
) -> None:
"""Should respect HOME environment variable for test isolation."""
monkeypatch.setenv("HOME", str(tmp_path))
paths = SessionPaths.from_home() # No argument needed
# Uses monkeypatched HOME
assert paths.claude_dir == tmp_path / ".claude"
```
### Design Decision: Directory Management Method
**Why `ensure_directories()` method?**
```python
def ensure_directories(self) -> None:
"""Create all configured directories if they don't exist."""
self.claude_dir.mkdir(parents=True, exist_ok=True)
self.logs_dir.mkdir(parents=True, exist_ok=True)
self.commands_dir.mkdir(parents=True, exist_ok=True)
```
**Benefits:**
1. **Idempotent** - Safe to call multiple times
1. **Atomic Operation** - All directories created together
1. **Parent Creation** - `parents=True` handles missing parents
1. **Clear Responsibility** - Separates creation from configuration
**Test Verification:**
```python
def test_ensure_directories_is_idempotent(self, tmp_path: Path) -> None:
"""Should safely handle multiple calls without errors."""
paths = SessionPaths.from_home(tmp_path)
paths.ensure_directories()
paths.ensure_directories() # ✅ No error
assert paths.claude_dir.exists()
```
______________________________________________________________________
## Test Strategy
### 1. Creation Tests (4 tests)
**Coverage:**
- Explicit path construction
- Default home directory usage
- Custom home directory
- Environment variable respect
**Key Test:**
```text
def test_from_home_with_explicit_path(self, tmp_path: Path) -> None:
"""Should create paths from explicit home directory."""
paths = SessionPaths.from_home(tmp_path)
expected_claude_dir = tmp_path / ".claude"
assert paths.claude_dir == expected_claude_dir
assert paths.logs_dir == expected_claude_dir / "logs"
assert paths.commands_dir == expected_claude_dir / "commands"
```
### 2. Immutability Tests (4 tests)
**Coverage:**
- Individual field modification attempts
- New attribute addition prevention
- Frozen dataclass enforcement
**Key Test:**
```text
def test_immutability_prevents_new_attributes(self) -> None:
"""Should prevent adding new attributes (frozen dataclass behavior)."""
paths = SessionPaths.from_home()
with pytest.raises(FrozenInstanceError):
paths.new_attribute = "should fail"
```
### 3. Directory Creation Tests (3 tests)
**Coverage:**
- All paths created successfully
- Idempotent behavior (multiple calls)
- Parent directory creation
**Key Test:**
```python
def test_ensure_directories_handles_missing_parents(self, tmp_path: Path) -> None:
"""Should create parent directories when they don't exist."""
deep_home = tmp_path / "level1" / "level2" / "level3"
paths = SessionPaths.from_home(deep_home)
assert not deep_home.exists() # Parents don't exist
paths.ensure_directories() # ✅ Creates all parents
assert paths.claude_dir.exists()
assert paths.logs_dir.exists()
assert paths.commands_dir.exists()
```
### 4. Equality & Hashing Tests (3 tests)
**Coverage:**
- Same paths equality
- Different paths inequality
- Hashable for dict keys
**Key Test:**
```python
def test_hashable_for_dict_keys(self, tmp_path: Path) -> None:
"""Should be hashable and usable as dict keys (frozen dataclass)."""
paths = SessionPaths.from_home(tmp_path)
cache: dict[SessionPaths, str] = {paths: "cached_value"}
assert cache[paths] == "cached_value"
```
### 5. Edge Cases Tests (3 tests)
**Coverage:**
- Relative paths
- Symlinked home directories
- File conflicts (file exists where directory should be)
**Key Test:**
```python
def test_from_home_with_symlink(self, tmp_path: Path) -> None:
"""Should handle symlinked home directories."""
real_home = tmp_path / "real_home"
symlink_home = tmp_path / "symlink_home"
real_home.mkdir()
symlink_home.symlink_to(real_home)
paths = SessionPaths.from_home(symlink_home)
# Should use the symlink path as provided
assert paths.claude_dir == symlink_home / ".claude"
```
______________________________________________________________________
## Technical Challenges & Solutions
### Challenge 1: Type Annotation String vs Type
**Issue:** In Python 3.13+, dataclass field annotations are stored as strings in some contexts.
**Error:**
```python
AssertionError: Field claude_dir should be Path type
assert 'Path' == Path # String vs Type comparison
```
**Root Cause:** Python 3.13's deferred annotation evaluation means `field.type` can be a string `'Path'` instead of the `Path` type object.
**Solution:**
```python
def test_type_annotations_are_path(self) -> None:
"""Should have Path type annotations for all fields."""
from dataclasses import fields
path_fields = fields(SessionPaths)
for field in path_fields:
# Accept either 'Path' (string) or Path (type)
assert field.type in (Path, "Path"), (
f"Field {field.name} should be Path type, got {field.type}"
)
```
______________________________________________________________________
## Integration Readiness
The `SessionPaths` class is now ready for integration with the DI system:
### Next Steps (Day 2):
1. **Update `session_buddy/di/__init__.py`:**
```python
from session_buddy.di.config import SessionPaths
def configure(*, force: bool = False) -> None:
# Create type-safe paths
paths = SessionPaths.from_home()
paths.ensure_directories()
# Register with DI container
depends.set(SessionPaths, paths)
```
1. **Update `_register_*` functions** to use SessionPaths instead of string keys
1. **Verify DI container tests pass** with new type-safe keys
______________________________________________________________________
## Files Created
1. **`session_buddy/di/config.py`** (99 lines)
- SessionPaths frozen dataclass
- Factory method and directory management
- Comprehensive documentation
1. **`tests/unit/test_di_config.py`** (282 lines, 20 tests)
- Complete test coverage across 7 categories
- Edge cases and error conditions
- Performance validation
1. **`docs/WEEK7_DAY1_PROGRESS.md`** (this document)
- Implementation details and design decisions
- Test strategy and coverage analysis
- Integration readiness assessment
______________________________________________________________________
## Metrics
### Code Quality
- ✅ **20/20 tests passing** (100% pass rate)
- ✅ **0.41s test execution** (fast feedback)
- ✅ **99 lines production code** (concise implementation)
- ✅ **282 lines test code** (comprehensive coverage)
- ✅ **7 test categories** (thorough validation)
### Test Coverage by Category
- Creation: 4 tests ✅
- Immutability: 4 tests ✅
- Directory Creation: 3 tests ✅
- Equality & Hashing: 3 tests ✅
- String Representation: 1 test ✅
- Type Annotations: 2 tests ✅
- Edge Cases: 3 tests ✅
### Time Spent
- **Planning:** Completed in Week 7 Day 0
- **Implementation:** ~1.5 hours
- **Testing:** ~1 hour
- **Documentation:** ~0.5 hours
- **Total:** ~3 hours (within 2-3 hour estimate)
______________________________________________________________________
## Success Criteria Status
**Day 1 Goals:**
- ✅ Create `SessionPaths` dataclass with frozen immutability
- ✅ Add comprehensive unit tests (20 tests, 100% pass rate)
- ✅ Verify frozen dataclass immutability (4 tests)
- ✅ Test `from_home()` factory method with various inputs (4 tests)
**Risk Assessment:** ✅ **Low Risk Achieved**
- New code with no existing dependencies
- Complete test coverage
- No breaking changes to existing code
______________________________________________________________________
## Technical Insights
### Insight 1: Frozen Dataclass for Configuration
Frozen dataclasses are ideal for configuration objects because:
- **Immutability** prevents accidental modifications
- **Hashability** enables use as dict keys or in sets
- **Thread-Safety** eliminates race conditions
- **Clear Intent** signals that configuration should not change
### Insight 2: Factory Methods for Flexibility
The `from_home()` class method pattern provides:
- **Default Behavior** - Works without arguments for production
- **Test Flexibility** - Accepts custom paths for test isolation
- **Environment Awareness** - Respects HOME environment variable
- **Clear API** - Self-documenting interface
### Insight 3: Test-Friendly Path Resolution
Using `os.path.expanduser("~")` instead of `Path.home()`:
- **Environment Variables** - Respects monkeypatched HOME in tests
- **Test Isolation** - Enables temp directory usage
- **Consistent Behavior** - Same resolution strategy as Week 6 fixes
- **Cross-Platform** - Works correctly on all platforms
______________________________________________________________________
## Next Session Actions
**Day 2 Implementation:**
1. **Update DI Configuration** (`session_buddy/di/__init__.py`)
- Import SessionPaths
- Replace string keys with SessionPaths instances
- Register SessionPaths with DI container
- Update `_register_*` functions
1. **Update Tests** (`tests/unit/test_di_container.py`)
- Replace string key references with SessionPaths
- Verify singleton reset behavior
- Ensure proper test isolation
1. **Verify DI Tests** (Goal: 2/2 passing in test_di_container.py)
**Estimated Time:** 3-4 hours
______________________________________________________________________
**Created:** 2025-10-29
**Author:** Claude Code + Les
**Project:** session-buddy
**Phase:** Week 7 Day 1 - Type-Safe Configuration ✅ Complete
