Initial commit

hooks/post-tool-use/04-block-pre-existing-checks.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+"""
+PostToolUse hook to block git checkout when checking for pre-existing errors.
+
+When projects use pre-commit hooks that enforce passing tests, checking if
+errors are "pre-existing" is unnecessary and wastes time. All test failures
+and lint errors must be from current changes because pre-commit hooks prevent
+commits with failures.
+
+Blocked patterns:
+- git checkout <sha> (or git stash && git checkout)
+- Combined with test/lint commands (ruff, pytest, mypy, cargo test, npm test, etc.)
+"""
+
+import json
+import sys
+import re
+
+# Test and lint command patterns that might be run on previous commits
+VERIFICATION_COMMANDS = [
+    r'\bruff\b',
+    r'\bpytest\b',
+    r'\bmypy\b',
+    r'\bflake8\b',
+    r'\bblack\b',
+    r'\bisort\b',
+    r'\bcargo\s+test\b',
+    r'\bcargo\s+clippy\b',
+    r'\bnpm\s+test\b',
+    r'\bnpm\s+run\s+test\b',
+    r'\byarn\s+test\b',
+    r'\bgo\s+test\b',
+    r'\bmvn\s+test\b',
+    r'\bgradle\s+test\b',
+    r'\bpylint\b',
+    r'\beslint\b',
+    r'\btsc\b',  # TypeScript compiler
+    r'\bpre-commit\s+run\b',
+]
+
+def is_checking_previous_commit(command):
+    """
+    Detect if command is checking out previous commits to run tests/lints.
+
+    Patterns:
+    - git checkout <sha>
+    - git stash && git checkout
+    - git diff <sha>..<sha>
+    """
+    # Check for git checkout patterns
+    if re.search(r'git\s+checkout\s+[a-f0-9]{6,40}', command):
+        return True
+
+    if re.search(r'git\s+stash.*?&&.*?git\s+checkout', command):
+        return True
+
+    # Check if command contains verification commands
+    # (only flag if combined with git checkout)
+    has_verification = any(re.search(pattern, command) for pattern in VERIFICATION_COMMANDS)
+    has_git_checkout = re.search(r'git\s+checkout', command)
+
+    return has_verification and has_git_checkout
+
+def main():
+    # Read tool use event from stdin
+    try:
+        input_data = json.load(sys.stdin)
+    except json.JSONDecodeError:
+        # If we can't parse JSON, allow the operation
+        sys.exit(0)
+
+    tool_name = input_data.get("tool_name", "")
+    tool_input = input_data.get("tool_input", {})
+
+    # Only check Bash tool calls
+    if tool_name != "Bash":
+        sys.exit(0)
+
+    command = tool_input.get("command", "")
+
+    if not command:
+        sys.exit(0)
+
+    # Check if this looks like checking previous commits for errors
+    if is_checking_previous_commit(command):
+        # Block the command and provide helpful feedback
+        output = {
+            "hookSpecificOutput": {
+                "hookEventName": "PostToolUse",
+                "permissionDecision": "deny",
+                "permissionDecisionReason": (
+                    "⚠️  CHECKING FOR PRE-EXISTING ERRORS IS UNNECESSARY\n\n"
+                    "Your project uses pre-commit hooks that enforce all tests pass before commits.\n"
+                    "Therefore, ALL test failures and errors are from your current changes.\n\n"
+                    "Do not check if errors were pre-existing. Pre-commit hooks guarantee they weren't.\n\n"
+                    "What you should do instead:\n"
+                    "1. Read the error messages from the current test run\n"
+                    "2. Fix the errors directly\n"
+                    "3. Run tests again to verify the fix\n\n"
+                    "Checking git history for errors is wasting time when pre-commit hooks enforce quality.\n\n"
+                    "Blocked command:\n"
+                    f"{command[:200]}"  # Show first 200 chars of command
+                )
+            }
+        }
+        print(json.dumps(output))
+        sys.exit(0)
+
+    # Allow command if not checking for pre-existing errors
+    sys.exit(0)
+
+if __name__ == "__main__":
+    main()