fix(trail): warn on failed body fetch during update

Address PR review: resolveTrailUpdateBody swallowed detail-fetch errors,
so a failed fetch left the form's Body baseline blank and a subsequent
edit could overwrite a description the user never saw. Return the fetch
error and warn on stderr (mirroring runTrailShow) so the blank baseline
is never silent.

Also drop the redundant re-trim (fetchTrailDescription already trims) and
refresh the helper/inline comments, which still described an unconditional
"full-body wipe" that the change-detection logic already prevents.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Entire-Checkpoint: 01KY4W1R808FYPN32C0VKBGJCH

Author: gtrrz-victor

cmd/entire/cli/trail_cmd.go

@@ -1101,18 +1101,26 @@ func newTrailCreateRequest(title, body, branch, base, statusStr, typeStr, priori
 
 // resolveTrailUpdateBody returns the body text to seed the interactive update
 // form with. The list resource omits the description (it lives in
-// body_document, detail-endpoint only), so update must fetch the detail body
-// or it would seed an empty field and PATCH a full-body wipe. Best-effort:
-// a failed or empty detail fetch falls back to the list body, mirroring
-// runTrailShow.
-func resolveTrailUpdateBody(ctx context.Context, client *api.Client, forge, owner, repo string, found *api.TrailResource) string {
+// body_document, served only by the detail endpoint), so update must fetch the
+// detail body — otherwise the form prefills from the empty list body and a
+// user edit against that blank baseline can overwrite a description they never
+// saw. Best-effort: on a failed detail fetch it returns the list body plus the
+// error so the caller can warn (mirroring runTrailShow); an empty detail body
+// (older/partial server) falls back to the list body with no error.
+func resolveTrailUpdateBody(ctx context.Context, client *api.Client, forge, owner, repo string, found *api.TrailResource) (string, error) {
 	body := found.Body
 	if found.Number > 0 {
-		if bt, err := fetchTrailDescription(ctx, client, forge, owner, repo, found.Number); err == nil && strings.TrimSpace(bt) != "" {
+		bt, err := fetchTrailDescription(ctx, client, forge, owner, repo, found.Number)
+		if err != nil {
+			return body, err
+		}
+		// fetchTrailDescription already trims; a non-empty result supersedes
+		// the list body, an empty one (older/partial server) leaves it intact.
+		if bt != "" {
 			body = bt
 		}
 	}
-	return body
+	return body, nil
 }
 
 func newTrailUpdateCmd() *cobra.Command {
@@ -1238,9 +1246,14 @@ func runTrailUpdate(ctx context.Context, w, errW io.Writer, insecureHTTP bool, i
 			statusStr = string(metadata.Status)
 			title = metadata.Title
 			// The list resource omits the description; fetch the detail body so
-			// the form is prefilled with the current text instead of blank
-			// (blank + BodyChanged would PATCH a full-body wipe).
-			body = resolveTrailUpdateBody(ctx, client, forge, owner, repoName, found)
+			// the form prefills with the current text and change detection below
+			// compares against the real server value. Warn on a fetch failure so
+			// a blank baseline doesn't silently overwrite an unseen description.
+			seedBody, bodyErr := resolveTrailUpdateBody(ctx, client, forge, owner, repoName, found)
+			if bodyErr != nil {
+				fmt.Fprintf(errW, "Warning: could not load current trail body: %v\n", bodyErr)
+			}
+			body = seedBody
 			origStatus, origTitle, origBody := statusStr, title, body
 
 			form := NewAccessibleForm(

cmd/entire/cli/trail_cmd_test.go

@@ -604,7 +604,10 @@ func TestResolveTrailUpdateBody_PrefersDetailSnapshot(t *testing.T) {
 	// The list resource omits the description, so found.Body is empty. The
 	// seed must come from the detail endpoint, not the empty list body.
 	found := &api.TrailResource{Number: 42, Body: ""}
-	body := resolveTrailUpdateBody(t.Context(), client, "gh", "acme", "repo", found)
+	body, err := resolveTrailUpdateBody(t.Context(), client, "gh", "acme", "repo", found)
+	if err != nil {
+		t.Fatalf("resolveTrailUpdateBody: %v", err)
+	}
 	if body != "the real body" {
 		t.Fatalf("body = %q, want %q", body, "the real body")
 	}
@@ -623,12 +626,35 @@ func TestResolveTrailUpdateBody_FallsBackToListBody(t *testing.T) {
 
 	client := api.NewClientWithBaseURL("tok", srv.URL)
 	found := &api.TrailResource{Number: 42, Body: "list body"}
-	body := resolveTrailUpdateBody(t.Context(), client, "gh", "acme", "repo", found)
+	body, err := resolveTrailUpdateBody(t.Context(), client, "gh", "acme", "repo", found)
+	if err != nil {
+		t.Fatalf("resolveTrailUpdateBody: %v", err)
+	}
 	if body != "list body" {
 		t.Fatalf("body = %q, want %q", body, "list body")
 	}
 }
 
+func TestResolveTrailUpdateBody_ReturnsErrorOnFetchFailure(t *testing.T) {
+	t.Parallel()
+	// A detail-fetch failure must be surfaced (not swallowed) so the caller can
+	// warn: a blank baseline could otherwise silently overwrite an unseen body.
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusInternalServerError)
+	}))
+	defer srv.Close()
+
+	client := api.NewClientWithBaseURL("tok", srv.URL)
+	found := &api.TrailResource{Number: 42, Body: "list body"}
+	body, err := resolveTrailUpdateBody(t.Context(), client, "gh", "acme", "repo", found)
+	if err == nil {
+		t.Fatal("expected error on fetch failure, got nil")
+	}
+	if body != "list body" {
+		t.Fatalf("body = %q, want fallback %q", body, "list body")
+	}
+}
+
 func TestResolveCreateBranch(t *testing.T) {
 	t.Parallel()
 	tests := []struct {