fix: typecheck write file args

[RomneyDa]

Description

Fixes #8382

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Summary by cubic

Adds strict arg validation to the writeFile tool to prevent crashes when filepath or content are not strings. Safely generates diffs and previews, fixing #8382.

• Bug Fixes
  • Validate filepath is a string; throw clear error if not.
  • Validate content is a string; default to "" when missing.
  • Use sanitized values for fs checks, diff creation, and preview.
  • Return normalized args (filepath, content) from preprocess.

^{Written for commit 01bef16. Summary will update automatically on new commits.}

[github-actions]

✅ Review Complete

Code Review Summary

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[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (all 1 issues)

Understand the root cause of the following 1 issues and fix them.


<file name="extensions/cli/src/tools/writeFile.ts">

<violation number="1" location="extensions/cli/src/tools/writeFile.ts:113">
The normalized `filepath`/`content` values are only returned in the new-file path, but when the file already exists this branch still returns the original `args`, so `run` receives `content` as `undefined` and `fs.writeFileSync` throws. Please return the sanitized args in both branches.</violation>
</file>

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[cubic-dev-ai]

The normalized filepath/content values are only returned in the new-file path, but when the file already exists this branch still returns the original args, so run receives content as undefined and fs.writeFileSync throws. Please return the sanitized args in both branches.

Prompt for AI agents

Address the following comment on extensions/cli/src/tools/writeFile.ts at line 113:

<comment>The normalized `filepath`/`content` values are only returned in the new-file path, but when the file already exists this branch still returns the original `args`, so `run` receives `content` as `undefined` and `fs.writeFileSync` throws. Please return the sanitized args in both branches.</comment>

<file context>
@@ -103,7 +110,10 @@ export const writeFileTool: Tool = {
 
     return {
-      args,
+      args: {
+        filepath,
+        content,
</file context>