Fix template name collision between new and legacy frontend plugin templates

The legacy frontend plugin template had the same name (`frontend-plugin`) as
the new frontend plugin template, causing a conflict error when both were shown
(e.g. when the frontend system could not be auto-detected). Rename the legacy
template to `frontend-plugin-legacy` so both can coexist.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Vincenzo Scamporlino <vincenzos@spotify.com>

.changeset/angry-clouds-tell.md

@@ -2,4 +2,4 @@
 '@backstage/cli-module-new': patch
 ---
 
-Rename the legacy `frontend-plugin` to `legacy-frontend-plugin`
+Rename the legacy `frontend-plugin` to `frontend-plugin-legacy`

packages/cli-module-new/src/lib/preparation/loadPortableTemplateConfig.test.ts

@@ -374,14 +374,14 @@ describe('loadPortableTemplateConfig', () => {
       },
       node_modules: Object.fromEntries(
         defaultTemplates.map(t => {
-          // Match the real behavior: both frontend-plugin and legacy-frontend-plugin
-          // have the same template name "frontend-plugin"
           const name = t.endsWith('/legacy-frontend-plugin')
-            ? 'frontend-plugin'
+            ? 'frontend-plugin-legacy'
             : basename(t);
           return [
             t,
-            { [TEMPLATE_FILE_NAME]: `name: ${name}\nrole: web-library\n` },
+            {
+              [TEMPLATE_FILE_NAME]: `name: ${name}\nrole: web-library\n`,
+            },
           ];
         }),
       ),
@@ -398,14 +398,7 @@ describe('loadPortableTemplateConfig', () => {
     expect(templateNames).toContain('frontend-plugin-module');
     expect(templateNames).toContain('backend-plugin');
     // Legacy template should be filtered out
-    expect(templateNames).not.toContain('legacy-frontend-plugin');
-
-    // The frontend-plugin in the list should be from the new template, not legacy
-    const frontendPlugin = config.templatePointers.find(
-      t => t.name === 'frontend-plugin',
-    );
-    expect(frontendPlugin?.target).toContain('/frontend-plugin/');
-    expect(frontendPlugin?.target).not.toContain('/legacy-frontend-plugin/');
+    expect(templateNames).not.toContain('frontend-plugin-legacy');
   });
 
   it('should filter out new frontend templates for legacy frontend system apps', async () => {
@@ -424,11 +417,13 @@ describe('loadPortableTemplateConfig', () => {
       node_modules: Object.fromEntries(
         defaultTemplates.map(t => {
           const name = t.endsWith('/legacy-frontend-plugin')
-            ? 'frontend-plugin'
+            ? 'frontend-plugin-legacy'
             : basename(t);
           return [
             t,
-            { [TEMPLATE_FILE_NAME]: `name: ${name}\nrole: web-library\n` },
+            {
+              [TEMPLATE_FILE_NAME]: `name: ${name}\nrole: web-library\n`,
+            },
           ];
         }),
       ),
@@ -441,17 +436,12 @@ describe('loadPortableTemplateConfig', () => {
     expect(config.isUsingDefaultTemplates).toBe(true);
 
     const templateNames = config.templatePointers.map(t => t.name);
-    // Legacy template should be present (shown as "frontend-plugin")
-    expect(templateNames).toContain('frontend-plugin');
+    // Legacy template should be present
+    expect(templateNames).toContain('frontend-plugin-legacy');
     expect(templateNames).toContain('backend-plugin');
     // New frontend templates should be filtered out
+    expect(templateNames).not.toContain('frontend-plugin');
     expect(templateNames).not.toContain('frontend-plugin-module');
-
-    // The frontend-plugin in the list should be from the legacy template
-    const frontendPlugin = config.templatePointers.find(
-      t => t.name === 'frontend-plugin',
-    );
-    expect(frontendPlugin?.target).toContain('/legacy-frontend-plugin/');
   });
 
   it('should not filter templates when using explicit configuration', async () => {

packages/cli-module-new/src/lib/preparation/loadPortableTemplateConfig.ts

@@ -177,8 +177,6 @@ export async function loadPortableTemplateConfig(
   );
 
   // Auto-filter frontend templates based on detected frontend system.
-  // This must happen before the conflict check since both the new and legacy
-  // frontend plugin templates have the same name, but only one will be shown.
   if (isUsingDefaultTemplates) {
     const frontendSystem = await detectFrontendSystem(basePath);
     templatePointerEntries = filterTemplateEntriesForFrontendSystem(

packages/cli-module-new/templates/legacy-frontend-plugin/portable-template.yaml

@@ -1,4 +1,4 @@
-name: legacy-frontend-plugin
+name: frontend-plugin-legacy
 role: frontend-plugin
 description: A new frontend plugin (legacy system)
 values: