fix: allow renaming between main entrypoint files

src/renderer/components/sidebar-file-tree.tsx

@@ -206,10 +206,8 @@ export const SidebarFileTree = observer(
         return;
       }
 
-      const contents = appState.editorMosaic.value(editorId).trim();
       try {
-        appState.editorMosaic.addNewFile(id, contents);
-        appState.editorMosaic.remove(editorId);
+        appState.editorMosaic.renameFile(editorId, id);
 
         if (visible) appState.editorMosaic.show(id);
       } catch (err) {

src/renderer/editor-mosaic.ts

@@ -83,6 +83,7 @@ export class EditorMosaic {
       addEditor: action,
       setEditorFromBackup: action,
       addNewFile: action,
+      renameFile: action,
     });
 
     // whenever the mosaics are changed,
@@ -291,6 +292,28 @@ export class EditorMosaic {
     this.addFile(id, value);
   }
 
+  /** Rename a file in the mosaic */
+  public renameFile(oldId: EditorId, newId: EditorId) {
+    if (!this.files.has(oldId)) {
+      throw new Error(`Cannot rename file "${oldId}": File doesn't exist`);
+    }
+
+    if (this.files.has(newId)) {
+      throw new Error(`Cannot rename file to "${newId}": File already exists`);
+    }
+
+    const entryPoint = this.mainEntryPointFile();
+
+    if (isMainEntryPoint(newId) && entryPoint !== oldId) {
+      throw new Error(
+        `Cannot rename file to "${newId}": Main entry point ${entryPoint} exists`,
+      );
+    }
+
+    this.addFile(newId, this.value(oldId).trim());
+    this.remove(oldId);
+  }
+
   /** Get the contents of a single file. */
   public value(id: EditorId): string {
     const { backups, editors } = this;

tests/renderer/components/sidebar-file-tree-spec.tsx

@@ -103,6 +103,23 @@ describe('SidebarFileTree component', () => {
     );
   });
 
+  it('can rename one main entry point file to another main entry point file', async () => {
+    const wrapper = shallow(<SidebarFileTree appState={store} />);
+    const instance: any = wrapper.instance();
+
+    const EDITOR_NAME = MAIN_JS;
+    const EDITOR_NEW_NAME = MAIN_CJS;
+
+    store.showInputDialog = jest.fn().mockResolvedValueOnce(EDITOR_NEW_NAME);
+
+    await instance.renameEditor(EDITOR_NAME);
+
+    expect(editorMosaic.files.get(EDITOR_NAME)).toBe(undefined);
+    expect(editorMosaic.files.get(EDITOR_NEW_NAME)).toBe(
+      EditorPresence.Pending,
+    );
+  });
+
   it('fails if trying to rename an editor to package(-lock).json', async () => {
     const wrapper = shallow(<SidebarFileTree appState={store} />);
     const instance: any = wrapper.instance();
@@ -153,7 +170,7 @@ describe('SidebarFileTree component', () => {
     await instance.renameEditor(TO_BE_NAMED);
 
     expect(store.showErrorDialog).toHaveBeenCalledWith(
-      `Cannot add file "${EDITOR_NEW_NAME}": File already exists`,
+      `Cannot rename file to "${EDITOR_NEW_NAME}": File already exists`,
     );
     expect(editorMosaic.files.get(TO_BE_NAMED)).toBe(EditorPresence.Pending);
   });
@@ -171,7 +188,7 @@ describe('SidebarFileTree component', () => {
     await instance.renameEditor(TO_BE_NAMED);
 
     expect(store.showErrorDialog).toHaveBeenCalledWith(
-      `Cannot add file "${EDITOR_NEW_NAME}": Main entry point ${MAIN_JS} exists`,
+      `Cannot rename file to "${EDITOR_NEW_NAME}": Main entry point ${MAIN_JS} exists`,
     );
     expect(editorMosaic.files.get(TO_BE_NAMED)).toBe(EditorPresence.Pending);
   });

tests/renderer/editor-mosaic-spec.ts

@@ -248,6 +248,15 @@ describe('EditorMosaic', () => {
     });
   });
 
+  describe('renameFile()', () => {
+    it('sets isEdited to true', () => {
+      editorMosaic.set(createEditorValues());
+      editorMosaic.isEdited = false;
+      editorMosaic.renameFile('renderer.js', 'bar.js');
+      expect(editorMosaic.isEdited).toBe(true);
+    });
+  });
+
   describe('remove()', () => {
     it('sets isEdited to true', () => {
       editorMosaic.set(createEditorValues());