LeetLLM
MediumEditing SystemsPython 3

Patch Conflict Detector

Apply optimistic multi-file patches atomically while rejecting stale or overlapping edits.

40m3 sample tests7 hidden tests

Implement apply_patches(files, patches), an atomic patch applier with optimistic conflict checks.

Requirements

  • files maps file path to text.
  • Each patch is (path, start, end, expected_old_text, replacement).
  • Validate all patches before mutating anything.
  • Raise ValueError for invalid ranges (start < 0, end < start, or end > len(text)), missing files, overlapping patches in the same file, and expected-text mismatches.
  • Adjacent ranges that only touch at an endpoint are allowed. Multiple empty inserts at the same offset are allowed; sort stably and apply right-to-left within each file.
  • Apply patches from the end of each file so offsets stay stable.
  • Return a new dictionary and leave input untouched.

Example

The first patch succeeds without changing files. The stale patch then fails against the same input, which remains untouched.

python
1files = {"app.py": "print('old')\n"} 2patches = [("app.py", 6, 11, "'old'", "'new'")] 3assert apply_patches(files, patches)["app.py"] == "print('new')\n" 4assert files["app.py"] == "print('old')\n" 5 6try: 7 apply_patches(files, [("app.py", 6, 11, "'stale'", "'new'")]) 8except ValueError: 9 pass 10else: 11 raise AssertionError("expected stale patch conflict") 12 13assert files["app.py"] == "print('old')\n"

Constraints

  • No diff parser is required.
  • Treat offsets as Python string indexes.

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