core-app-api: fix base url rewriting

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/green-deers-turn.md

@@ -0,0 +1,5 @@
+---
+'@backstage/core-app-api': patch
+---
+
+Fix for the automatic rewriting of base URLs.

packages/core-app-api/src/app/AppManager.test.tsx

@@ -624,21 +624,18 @@ describe('Integration Test', () => {
   describe('relative url resolvers', () => {
     it.each([
       [
-        [document.location.href, document.location.href],
+        ['http://localhost', 'http://localhost'],
         {
           backend: {
-            baseUrl: 'http://localhost:8008/',
+            baseUrl: 'http://localhost:8008',
           },
           app: {
-            baseUrl: 'http://localhost:8008/',
+            baseUrl: 'http://localhost:8008',
           },
         },
       ],
       [
-        [
-          `${document.location.origin}/backstage`,
-          `${document.location.origin}/backstage`,
-        ],
+        ['http://localhost/backstage', 'http://localhost/backstage'],
         {
           backend: {
             baseUrl: 'http://test.com/backstage',
@@ -650,8 +647,8 @@ describe('Integration Test', () => {
       ],
       [
         [
-          `${document.location.origin}/backstage/instance`,
-          `${document.location.origin}/backstage/instance`,
+          'http://localhost/backstage/instance',
+          'http://localhost/backstage/instance',
         ],
         {
           backend: {
@@ -664,8 +661,8 @@ describe('Integration Test', () => {
       ],
       [
         [
-          `${document.location.origin}/backstage/instance`,
-          `http://test.com/backstage/instance`,
+          'http://localhost/backstage/instance',
+          'http://test.com/backstage/instance',
         ],
         {
           backend: {

packages/core-app-api/src/app/AppManager.tsx

@@ -179,7 +179,7 @@ function useConfigLoader(
       return new URL(
         fullUrl.replace(getOrigin(fullUrl), ''),
         document.location.origin,
-      ).href;
+      ).href.replace(/\/$/, '');
     };
 
     /**
@@ -199,15 +199,17 @@ function useConfigLoader(
       const backendOrigin = getOrigin(backendBaseUrl);
 
       if (appOrigin === backendOrigin) {
-        relativeResolverConfig.data.backend = {
-          baseUrl: overrideOrigin(backendBaseUrl),
-        };
+        const newBackendBaseUrl = overrideOrigin(backendBaseUrl);
+        if (backendBaseUrl !== newBackendBaseUrl) {
+          relativeResolverConfig.data.backend = { baseUrl: newBackendBaseUrl };
+        }
       }
     }
     if (appBaseUrl) {
-      relativeResolverConfig.data.app = {
-        baseUrl: overrideOrigin(appBaseUrl),
-      };
+      const newAppBaseUrl = overrideOrigin(appBaseUrl);
+      if (appBaseUrl !== newAppBaseUrl) {
+        relativeResolverConfig.data.app = { baseUrl: newAppBaseUrl };
+      }
     }
     /**
      * Only add the relative config if there is actually data to add.