Keep what was typed when a target or webhook edit is refused (closes #381)

A refused save on the target edit page answered with a bare text page, losing the form and everything typed, and the webhook edit page came back with the stored values instead of the submitted ones. A refused target edit now shows the edit form again with the reason above it and every value submitted, with the same status codes as before; a refused webhook edit keeps the submitted name, description and retention. Target edits use the same validation as new targets, with no second copy; an encoding or database failure stays a logged 500. The browser test covers a refused save on both pages, and its main function is now a plain list of checks.

Model: opus-5-5

internal/handlers/target_edit_test.go

@@ -565,6 +565,73 @@ func assertEditRejectsTimeout(
 	)
 }
 
+// TestHandleTargetEditSubmit_RefusedFormComesBack refuses an edit of
+// a target of each type and checks that the edit form comes back with
+// the reason and every value submitted, and that nothing is saved.
+func TestHandleTargetEditSubmit_RefusedFormComesBack(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	// fields is what the operator submitted, as a query string.
+	cases := []struct {
+		targetType database.TargetType
+		fields     string
+		reason     string
+	}{
+		{
+			database.TargetTypeHTTP,
+			"name=edited&url=" + editBlockedURL +
+				"&headers=X-Edited:+kept&timeout=12&max_retries=3",
+			"Invalid target URL",
+		},
+		{
+			database.TargetTypeSlack,
+			"name=edited&url=" + editOriginalURL + "&max_retries=25",
+			"Invalid max retries",
+		},
+		{
+			database.TargetTypeDatabase, "name=edited&expiry=7d",
+			"Invalid archive expiry",
+		},
+		{database.TargetTypeLog, "name=", "Name is required"},
+	}
+
+	for _, tc := range cases {
+		t.Run(string(tc.targetType), func(t *testing.T) {
+			t.Parallel()
+
+			webhook := seedWebhookWithRetention(t, env.db, 30)
+			target := seedTarget(t, env.db, webhook.ID, tc.targetType)
+
+			form, err := url.ParseQuery(tc.fields)
+			require.NoError(t, err)
+
+			w := submitTargetEdit(env, webhook.ID, target.ID, form)
+			assert.Equal(t, http.StatusBadRequest, w.Code)
+
+			page := w.Body.String()
+			assert.Contains(t, page, `class="alert-error">`+tc.reason)
+
+			// headers is the form's one textarea; every other field is
+			// an input.
+			for field := range form {
+				shown := `name="` + field + `" value="` + form.Get(field) + `"`
+				if field == "headers" {
+					shown = ">" + form.Get(field) + "</textarea>"
+				}
+
+				assert.Contains(t, page, shown)
+			}
+
+			assert.Equal(
+				t, target.Name, storedTarget(t, env, target.ID).Name,
+				"a refused edit must save nothing",
+			)
+		})
+	}
+}
+
 // TestHandleTargetEdit_Scoping keeps the edit routes scoped the way
 // the delete and toggle routes are: ownership is decided by the
 // webhook, and the target is then scoped to it.
@@ -700,6 +767,10 @@ func TestHandleTargetEditSubmit_RenamesArchive(t *testing.T) {
 	w = submitTargetEdit(env, wh.ID, archive.ID, again)
 	require.Equal(t, http.StatusConflict, w.Code)
 	assert.Contains(t, w.Body.String(), "archive-taken.db")
+	assert.Contains(
+		t, w.Body.String(), `name="name" value="Again"`,
+		"the form comes back with the name submitted",
+	)
 	assert.Equal(
 		t, renamedTargetName, storedTarget(t, env, archive.ID).Name,
 	)