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Lynx-ZhangLynx-Zhang
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Added DIY branch coverage tool
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‎BRANCH_COVERAGE_GUIDE.md‎

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## Add Branch Coverage
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### Step 1: Register in `mypy/branch_coverage.py`
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```python
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BRANCH_COVERAGE = {
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'check_return_stmt': set(),
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'your_function_name': set(), # Add your function
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}
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BRANCH_DESCRIPTIONS = {
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'your_function_name': {
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1: 'Function entry',
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2: 'if condition_x - TRUE',
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3: 'if condition_x - FALSE',
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4: 'elif condition_y - TRUE',
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5: 'else branch',
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}
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}
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```
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### Step 2: Instrument Your Function
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```python
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def your_function_name(self, param):
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from mypy.branch_coverage import record_branch
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record_branch('your_function_name', 1) # Function entry
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if condition_x:
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record_branch('your_function_name', 2) # TRUE
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# code...
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elif condition_y:
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record_branch('your_function_name', 3) # FALSE from if
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record_branch('your_function_name', 4) # TRUE for elif
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# code...
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else:
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record_branch('your_function_name', 3) # FALSE from if
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record_branch('your_function_name', 5) # else
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# code...
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```
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**Important:** Import `record_branch` inside the function to avoid circular imports.
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## Run Tests
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**CRITICAL**: Must use `-n0` to disable parallel execution, or coverage data will not be collected!
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```bash
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# Activate virtual environment first
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source venv/bin/activate
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# Run all tests
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pytest mypy/test/testcheck.py -n0
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# Run specific test file
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pytest mypy/test/testcheck.py::TypeCheckSuite::::check-basic.test::testInvalidReturn -n0
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```
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## View Reports
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Reports are automatically saved in the project root directory:`branch_coverage_report.txt`

‎mypy/branch_coverage.py‎

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"""Branch Coverage Tracking Module"""
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import json
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from pathlib import Path
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BRANCH_COVERAGE = {
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'check_return_stmt': set()
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}
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BRANCH_DESCRIPTIONS = {
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'check_return_stmt': {
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1: 'Function entry',
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2: 'defn is not None - TRUE',
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3: 'defn is not None - FALSE',
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4: 'defn.is_generator - TRUE',
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5: 'defn.is_generator - FALSE (else/elif)',
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6: 'defn.is_coroutine - TRUE',
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7: 'defn.is_coroutine - FALSE (else)',
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8: 'isinstance(return_type, UninhabitedType) - TRUE',
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9: 'isinstance(return_type, UninhabitedType) - FALSE',
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10: 'not is_lambda and not return_type.ambiguous - TRUE',
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11: 'not is_lambda and not return_type.ambiguous - FALSE',
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12: 's.expr - TRUE (has return value)',
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13: 's.expr - FALSE (empty return)',
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14: 'isinstance(s.expr, (CallExpr, ...)) or isinstance(s.expr, AwaitExpr) - TRUE',
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15: 'isinstance(s.expr, (CallExpr, ...)) or isinstance(s.expr, AwaitExpr) - FALSE',
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16: 'isinstance(typ, Instance) and typ.type.fullname in NOT_IMPLEMENTED - TRUE',
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17: 'isinstance(typ, Instance) and typ.type.fullname in NOT_IMPLEMENTED - FALSE',
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18: 'defn.is_async_generator - TRUE',
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19: 'defn.is_async_generator - FALSE',
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20: 'isinstance(typ, AnyType) - TRUE',
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21: 'isinstance(typ, AnyType) - FALSE',
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22: 'warn_return_any conditions - TRUE (all conditions met)',
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23: 'warn_return_any conditions - FALSE (at least one condition not met)',
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24: 'declared_none_return - TRUE',
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25: 'declared_none_return - FALSE',
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26: 'is_lambda or isinstance(typ, NoneType) - TRUE',
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27: 'is_lambda or isinstance(typ, NoneType) - FALSE',
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28: 'defn.is_generator and not defn.is_coroutine and isinstance(return_type, AnyType) - TRUE',
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29: 'defn.is_generator and not defn.is_coroutine and isinstance(return_type, AnyType) - FALSE',
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30: 'isinstance(return_type, (NoneType, AnyType)) - TRUE',
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31: 'isinstance(return_type, (NoneType, AnyType)) - FALSE',
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32: 'self.in_checked_function() - TRUE',
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33: 'self.in_checked_function() - FALSE',
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}
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}
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def record_branch(function_name, branch_id):
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if function_name in BRANCH_COVERAGE:
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BRANCH_COVERAGE[function_name].add(branch_id)
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def get_coverage_report():
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report = []
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report.append("=" * 80)
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report.append("BRANCH COVERAGE REPORT")
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report.append("=" * 80)
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for func_name, covered_branches in BRANCH_COVERAGE.items():
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report.append(f"\n{'=' * 80}")
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report.append(f"Function: {func_name}")
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report.append(f"{'=' * 80}")
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descriptions = BRANCH_DESCRIPTIONS.get(func_name, {})
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total_branches = len(descriptions)
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covered_count = len(covered_branches)
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report.append(f"Coverage: {covered_count}/{total_branches} branches ({covered_count/total_branches*100:.1f}%)")
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report.append("")
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for branch_id in sorted(descriptions.keys()):
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status = "COVERED" if branch_id in covered_branches else "NOT COVERED"
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desc = descriptions[branch_id]
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report.append(f" Branch {branch_id:2d}: {status:15s} | {desc}")
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uncovered = set(descriptions.keys()) - covered_branches
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if uncovered:
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report.append("\n" + "=" * 80)
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report.append("UNCOVERED BRANCHES:")
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report.append("=" * 80)
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for branch_id in sorted(uncovered):
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report.append(f" Branch {branch_id:2d}: {descriptions[branch_id]}")
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report.append("\n" + "=" * 80)
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return "\n".join(report)
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def save_coverage_report(filename="branch_coverage_report.txt"):
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report = get_coverage_report()
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output_path = Path.cwd() / filename
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with open(output_path, 'w', encoding='utf-8') as f:
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f.write(report)
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print(f"\nCoverage report saved to: {output_path}")
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‎mypy/test/conftest.py‎

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"""
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Pytest configuration for branch coverage collection
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"""
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import pytest
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def pytest_sessionfinish(session, exitstatus):
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"""
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Hook that runs after all tests complete
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"""
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try:
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from mypy.branch_coverage import (
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save_coverage_report,
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get_coverage_report,
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BRANCH_COVERAGE
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)
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total_covered = sum(len(branches) for branches in BRANCH_COVERAGE.values())
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if total_covered > 0:
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print("\n" + "=" * 80)
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print("BRANCH COVERAGE COLLECTION COMPLETED")
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print("=" * 80)
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print(f"Total branches covered: {total_covered}")
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save_coverage_report()
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print("\n" + get_coverage_report())
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print("\n" + "=" * 80)
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print("Coverage reports saved!")
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print("=" * 80)
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else:
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print("\nWarning: No branch coverage data collected")
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except ImportError:
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print("\nBranch coverage module not found - skipping coverage report")
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except Exception as e:
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print(f"\nError saving coverage report: {e}")
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import traceback
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traceback.print_exc()

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