Reject an empty pr edit title Gitea would ignore

cmd/agentpr/main.go

@@ -163,6 +163,11 @@ func newPREditCmd() *cobra.Command {
 			// leave the title as it is, not blank it.
 			var opts agent.EditPROptions
 			if cmd.Flags().Changed("title") {
+				// Gitea ignores an empty title, so sending one would report
+				// success while changing nothing.
+				if title == "" {
+					return fmt.Errorf("--title cannot be empty: a title can be set but not cleared")
+				}
 				opts.Title = &title
 			}
 			if cmd.Flags().Changed("body") {

cmd/agentpr/main_test.go

@@ -33,3 +33,19 @@ func TestPREditRequiresTitleOrBody(t *testing.T) {
 		t.Errorf("error = %q, want it to name the missing flags", err)
 	}
 }
+
+// Gitea silently ignores an empty title, so `pr edit --title ""` would report
+// success while changing nothing; it must fail before any Vault/Gitea call.
+func TestPREditRejectsEmptyTitle(t *testing.T) {
+	cmd := newRootCmd()
+	cmd.SetArgs([]string{"pr", "edit", "--repo", "unkin/repo", "--pr", "7", "--title", ""})
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+	err := cmd.Execute()
+	if err == nil {
+		t.Fatal("Execute() = nil, want an error for an empty --title")
+	}
+	if !strings.Contains(err.Error(), "--title cannot be empty") {
+		t.Errorf("error = %q, want it to reject the empty title", err)
+	}
+}

internal/agent/client_test.go

@@ -155,19 +155,19 @@ func TestEditPRSendsOnlySuppliedFields(t *testing.T) {
 func TestEditPRAPIError(t *testing.T) {
 	mux := http.NewServeMux()
 	mux.HandleFunc("/api/v1/repos/unkin/repo/pulls/7", func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusUnprocessableEntity)
-		_, _ = io.WriteString(w, `{"message":"title cannot be empty"}`)
+		w.WriteHeader(http.StatusNotFound)
+		_, _ = io.WriteString(w, `{"message":"pull request does not exist"}`)
 	})
 	srv := httptest.NewServer(mux)
 	defer srv.Close()
 
-	title := ""
+	title := "new title"
 	c := &GiteaClient{BaseURL: srv.URL, Token: "t", HTTP: srv.Client()}
 	_, err := c.EditPR("unkin/repo", 7, EditPROptions{Title: &title})
 	if err == nil {
-		t.Fatal("expected error on 422")
+		t.Fatal("expected error on 404")
 	}
-	if !strings.Contains(err.Error(), "title cannot be empty") {
+	if !strings.Contains(err.Error(), "pull request does not exist") {
 		t.Errorf("error %q should carry the API message", err)
 	}
 }

internal/agent/gitea.go

@@ -215,8 +215,10 @@ func (c *GiteaClient) CreatePR(repoPath string, opts CreatePROptions) (PullReque
 }
 
 // EditPROptions are the fields an edit may change. Pointers so an unset field
-// is omitted from the payload entirely: Gitea overwrites whatever it is sent,
-// so a nil Title leaves the title alone while a pointer to "" clears it.
+// is omitted from the payload entirely, leaving that field as it is. The two
+// fields are not symmetric: Gitea only applies a title when it is non-empty,
+// so Title can be set but never cleared and a "" title is a silent no-op,
+// while a pointer to "" Body really does blank the body.
 type EditPROptions struct {
 	Title *string `json:"title,omitempty"`
 	Body  *string `json:"body,omitempty"`