fix(diffstats): Fix diff stats to correctly capture the edits (#7446)

Co-authored-by: Shnatu <snatu@google.com>
Co-authored-by: Gaurav <39389231+gsquared94@users.noreply.github.com>

packages/core/src/tools/edit.ts

@@ -86,9 +86,9 @@ export interface EditToolParams {
   modified_by_user?: boolean;
 
   /**
-   * Initially proposed string.
+   * Initially proposed content.
    */
-  ai_proposed_string?: string;
+  ai_proposed_content?: string;
 }
 
 interface CalculatedEdit {
@@ -365,12 +365,12 @@ class EditToolInvocation implements ToolInvocation<EditToolParams, ToolResult> {
       let displayResult: ToolResultDisplay;
       const fileName = path.basename(this.params.file_path);
       const originallyProposedContent =
-        this.params.ai_proposed_string || this.params.new_string;
+        this.params.ai_proposed_content || editData.newContent;
       const diffStat = getDiffStat(
         fileName,
         editData.currentContent ?? '',
         originallyProposedContent,
-        this.params.new_string,
+        editData.newContent,
       );
 
       if (editData.isNewFile) {
@@ -572,16 +572,13 @@ Expectation for required parameters:
         oldContent: string,
         modifiedProposedContent: string,
         originalParams: EditToolParams,
-      ): EditToolParams => {
-        const content = originalParams.new_string;
-        return {
-          ...originalParams,
-          ai_proposed_string: content,
-          old_string: oldContent,
-          new_string: modifiedProposedContent,
-          modified_by_user: true,
-        };
-      },
+      ): EditToolParams => ({
+        ...originalParams,
+        ai_proposed_content: oldContent,
+        old_string: oldContent,
+        new_string: modifiedProposedContent,
+        modified_by_user: true,
+      }),
     };
   }
 }