Aider-AI/aider · error · DiffError

Empty patch section found.

Error message

Empty patch section found.

What it means

Raised by PatchCoder when an update-file section consumed zero body lines and no '*** End of File' marker was present (index == start_index and not is_eof). The parser expects at least one patch line, chunk, or the EOF marker between section headers.

Source

Thrown at aider/coders/patch_coder.py:189

    # Finalize any pending chunk at the end of the section
    if del_lines or ins_lines:
        chunks.append(
            Chunk(
                orig_index=len(context_lines) - len(del_lines),
                del_lines=del_lines,
                ins_lines=ins_lines,
            )
        )

    # Check for EOF marker
    is_eof = False
    if index < len(lines) and _norm(lines[index]) == "*** End of File":
        index += 1
        is_eof = True

    if index == start_index and not is_eof:  # Should not happen if patch is well-formed
        raise DiffError("Empty patch section found.")

    return context_lines, chunks, index, is_eof


def identify_files_needed(text: str) -> List[str]:
    """Extracts file paths from Update and Delete actions."""
    lines = text.splitlines()
    paths = set()
    for line in lines:
        norm_line = _norm(line)
        if norm_line.startswith("*** Update File: "):
            paths.add(norm_line[len("*** Update File: ") :].strip())
        elif norm_line.startswith("*** Delete File: "):
            paths.add(norm_line[len("*** Delete File: ") :].strip())
    return list(paths)


# --------------------------------------------------------------------------- #

View on GitHub (pinned to 5dc9490bb3)

Solutions

1. Provide at least one context/added/deleted line after every '*** Update File:' header, or drop the empty section entirely.
2. Check for truncation if the patch ends abruptly — increase output limits.
3. Retry the model with the error message so it re-emits complete sections.
4. If the intent was a no-op update, remove the header rather than leaving an empty section.

Example fix

# before
*** Update File: foo.py
*** End Patch

# after
*** Update File: foo.py
@@
 context line
-old line
+new line
*** End Patch

def empty_update_sections(patch_text: str) -> list[str]:
    lines = patch_text.splitlines()
    empty, i = [], 0
    while i < len(lines):
        if lines[i].strip().startswith("*** Update File:"):
            j, body = i + 1, 0
            while j < len(lines) and not lines[j].strip().startswith("***"):
                if lines[j].strip():
                    body += 1
                j += 1
            if body == 0:
                empty.append(lines[i])
            i = j
        else:
            i += 1
    return empty  # non-empty → drop these sections before parsing

try:
    coder.get_edits(patch_text)
except ValueError as e:
    if "Empty patch section" in str(e):
        patch_text = drop_or_fill_empty_sections(patch_text)
        coder.get_edits(patch_text)
    else:
        raise

When it happens

Trigger: A '*** Update File: path' header immediately followed by another header or '*** End Patch' with no +/-/space lines in between; or two consecutive section markers with an empty body.

Common situations: Model emits an update header then forgets the hunk; degenerate/m truncated patches; placeholders like '*** Update File: foo.py' with the body accidentally stripped.

Related errors

• Invalid patch line found in update section: {line}
• Invalid line prefix in update section: {line}
• Error parsing patch content: {e}
• Unexpected error parsing patch: {e}
• Update File action missing path.

AI-assisted analysis of Aider-AI/aider@5dc9490bb3 (2026-08-15). Data as JSON: /api/errors/b51cafdb2426dc88. Report an issue: GitHub.