Use formatWithCursor() API to preserve cursor position after formatting

[ntotten]

Problem

The extension currently uses Prettier's format() API, which causes the cursor to jump after formatting. This is a common user complaint and differs from the expected behavior of maintaining editing context.

Proposed Solution

Use Prettier's formatWithCursor() API instead of format(). This API accepts a cursorOffset option and returns both the formatted text and the adjusted cursor offset.

Current Implementation

// PrettierEditService.ts:format() (around line 622)
const formatted = await prettierInstance.format(text, options);

Proposed Implementation

const cursorOffset = document.offsetAt(editor.selection.active);
const result = await prettierInstance.formatWithCursor(text, { 
  ...options, 
  cursorOffset 
});
// Use result.formatted for the text
// Use result.cursorOffset to restore cursor position

Impact

• User Experience: Major improvement - cursor stays in place during format-on-save
• Effort: Medium - requires changes to how provideEdits() returns edits and potentially using VS Code's WorkspaceEdit with cursor positioning

Relevant Files

• src/PrettierEditService.ts - format() and provideEdits() methods
• src/types.ts - PrettierInstance interface may need formatWithCursor added

References

• Prettier API docs: https://prettier.io/docs/api#prettierformatwithcursorsource-options