fix: preserve indentation when applying code edits to Python files

[mvanhorn]

Summary

• When the code edit tool uses fallback matching strategies (trimmedMatch, whitespaceIgnoredMatch) to find a match, the replacement string's indentation is now adjusted to match the actual indentation level in the file
• This fixes Python code edits where the LLM provides search/replace strings with different indentation than the target code, resulting in broken indentation after the edit

How it works

• adjustReplacementIndentation() detects the leading whitespace of the matched text in the file and the LLM-provided old_string
• If they differ (indicating a fuzzy match with different indentation), each line of new_string is re-indented: the old indent prefix is stripped and replaced with the matched indent
• Exact matches are passed through unchanged, preserving existing behavior

Test plan

• Verify Python files with indented code blocks are edited correctly when the LLM provides unindented search/replace strings
• Verify exact match replacements still work as before (no indentation adjustment)
• Verify replaceAll mode also applies indentation normalization

Fixes #11282

🤖 Generated with Claude Code

---

Summary by cubic

Preserves indentation when applying fuzzy-matched code edits so Python blocks remain valid. Re-indents the replacement text to match the file’s actual indent level.

• Bug Fixes
  • Detects leading indent of matched text and re-indents each line of newString when it differs from the oldString.
  • Applies to both single replacements and replaceAll.
  • Skips adjustment for exact/empty matches to keep current behavior.

^{Written for commit 70b6b17. Summary will update on new commits.}

[mvanhorn]

I have read the CLA Document and I hereby sign the CLA

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="core/edit/searchAndReplace/performReplace.ts">

<violation number="1" location="core/edit/searchAndReplace/performReplace.ts:58">
P2: First replacement line can remain unindented when `oldIndent` is non-empty, because fallback indentation adjustment only runs for `oldIndent === ""`.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

P2: First replacement line can remain unindented when oldIndent is non-empty, because fallback indentation adjustment only runs for oldIndent === "".

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At core/edit/searchAndReplace/performReplace.ts, line 58:

<comment>First replacement line can remain unindented when `oldIndent` is non-empty, because fallback indentation adjustment only runs for `oldIndent === ""`.</comment>

<file context>
@@ -1,6 +1,67 @@
+    // For lines that don't start with the old indent (e.g. first line
+    // might have no indent if old_string was trimmed), apply the
+    // matched indent directly
+    if (index === 0 && oldIndent === "" && matchedIndent !== "") {
+      return matchedIndent + line;
+    }
</file context>