fix(editor): log why an edit was rejected before the editor drops it (#1569)

When the backend rejects an edit for any reason other than a stale version, the editor replaces its unsaved text with the file's content, but the reason was only printed to the webview console. The backend now logs the rejected edit with its path, and the editor writes the sync error and the discarded edits to the log file, so reports of edits that roll back (#1530, #1522) can be diagnosed from the log.

crates/ide-workspace/src/documents.rs

@@ -537,9 +537,15 @@ impl Documents {
     pub fn edit(&self, doc: DocId, base_version: u32, changes: ChangeSet) -> IdeResult<u32> {
         self.with_doc(doc, |st| {
             if st.read_only {
+                tracing::warn!("edit rejected: {} is read-only", st.path.display());
                 return Err(read_only_error(&st.path));
             }
-            let (applied, edits) = st.doc.apply_detailed(base_version, &changes)?;
+            let (applied, edits) = st.doc.apply_detailed(base_version, &changes).inspect_err(|e| {
+                // A stale version is routine (the UI rebases); anything else makes the editor drop the edit.
+                if e.kind != ErrorKind::OutOfSync {
+                    tracing::warn!("edit of {} rejected: {e}", st.path.display());
+                }
+            })?;
             self.set_dirty(doc, st, true);
             self.notify_changed(doc, st, &applied, &edits);
             Ok(st.doc.version())

src/editor/core/model/document.ts

@@ -62,6 +62,7 @@ import {
 import { setMethodLines, softWrapActive } from "../cm/prefs";
 import type { EditorSlot } from "./slot";
 import { tx } from "@/platform/i18n";
+import { logError } from "@/platform/errorLog";
 import { WorkspaceHistory } from "./workspaceHistory";
 
 export type Banner = "binary" | "tooLarge" | "readOnly" | "library" | null;
@@ -263,13 +264,15 @@ export class DocModel {
       },
       {
         applyRemote: (cs, grouped) => this.applyRemote(cs, grouped),
-        onDiscarded: () =>
+        onDiscarded: (reason) => {
+          logError(`document ${this.path}: unsaved edits replaced by the file's content`, reason);
           manager.notify({
             level: "warning",
             title: "Editor resynchronised",
             body: tx`Some unsaved edits to ${this.path} could not be applied and were replaced by the file's current content.`,
-          }),
-        onError: (e) => console.warn(`document ${this.path}: sync error`, e),
+          });
+        },
+        onError: (e) => logError(`document ${this.path}: sync error`, e),
       },
       manager.scheduler,
     );

src/editor/core/sync/DocSync.test.ts

@@ -226,7 +226,8 @@ describe("DocSync", () => {
     await server.processAll();
     await flushMicrotasks();
     expect(view.text.toString()).toBe("abc");
-    expect(host.onDiscarded).toHaveBeenCalled();
+    // The rejection reaches the host, which writes it to the log file.
+    expect(host.onDiscarded).toHaveBeenCalledWith(expect.objectContaining({ kind: "permissionDenied" }));
     expect(sync.idle).toBe(true);
   });