Prevent creating views with duplicate URL (#17871)

src/panels/lovelace/editor/config-util.ts

@@ -3,6 +3,7 @@ import {
   LovelaceConfig,
   LovelaceViewConfig,
 } from "../../../data/lovelace";
+import type { HomeAssistant } from "../../../types";
 
 export const addCard = (
   config: LovelaceConfig,
@@ -253,23 +254,44 @@ export const moveCard = (
 };
 
 export const addView = (
+  hass: HomeAssistant,
   config: LovelaceConfig,
   viewConfig: LovelaceViewConfig
-): LovelaceConfig => ({
-  ...config,
-  views: config.views.concat(viewConfig),
-});
+): LovelaceConfig => {
+  if (viewConfig.path && config.views.some((v) => v.path === viewConfig.path)) {
+    throw new Error(
+      hass.localize("ui.panel.lovelace.editor.edit_view.error_same_url")
+    );
+  }
+  return {
+    ...config,
+    views: config.views.concat(viewConfig),
+  };
+};
 
 export const replaceView = (
+  hass: HomeAssistant,
   config: LovelaceConfig,
   viewIndex: number,
   viewConfig: LovelaceViewConfig
-): LovelaceConfig => ({
-  ...config,
-  views: config.views.map((origView, index) =>
-    index === viewIndex ? viewConfig : origView
-  ),
-});
+): LovelaceConfig => {
+  if (
+    viewConfig.path &&
+    config.views.some(
+      (v, idx) => v.path === viewConfig.path && idx !== viewIndex
+    )
+  ) {
+    throw new Error(
+      hass.localize("ui.panel.lovelace.editor.edit_view.error_same_url")
+    );
+  }
+  return {
+    ...config,
+    views: config.views.map((origView, index) =>
+      index === viewIndex ? viewConfig : origView
+    ),
+  };
+};
 
 export const swapView = (
   config: LovelaceConfig,

src/panels/lovelace/editor/view-editor/hui-dialog-edit-view.ts

@@ -405,8 +405,13 @@ export class HuiDialogEditView extends LitElement {
     try {
       await lovelace.saveConfig(
         this._creatingView
-          ? addView(lovelace.config, viewConf)
-          : replaceView(lovelace.config, this._params.viewIndex!, viewConf)
+          ? addView(this.hass!, lovelace.config, viewConf)
+          : replaceView(
+              this.hass!,
+              lovelace.config,
+              this._params.viewIndex!,
+              viewConf
+            )
       );
       if (this._params.saveCallback) {
         this._params.saveCallback(
@@ -417,7 +422,9 @@ export class HuiDialogEditView extends LitElement {
       this.closeDialog();
     } catch (err: any) {
       showAlertDialog(this, {
-        text: `Saving failed: ${err.message}`,
+        text: `${this.hass!.localize(
+          "ui.panel.lovelace.editor.edit_view.saving_failed"
+        )}: ${err.message}`,
       });
     } finally {
       this._saving = false;

src/translations/en.json

@@ -4641,7 +4641,9 @@
             "subview": "Subview",
             "subview_helper": "Subviews don't appear in tabs and have a back button.",
             "edit_ui": "Edit in visual editor",
-            "edit_yaml": "Edit in YAML"
+            "edit_yaml": "Edit in YAML",
+            "saving_failed": "Saving failed",
+            "error_same_url": "You cannot save a view with the same URL as a different existing view."
           },
           "edit_badges": {
             "view_no_badges": "Badges are not be supported by the current view type."