Only update the details view when data has changed

extensions/ql-vscode/src/data-extensions-editor/model-details/model-details-data-provider.ts

@@ -34,17 +34,28 @@ export class ModelDetailsDataProvider
     return this.onDidChangeTreeDataEmitter.event;
   }
 
+  /**
+   * Update the data displayed in the tree view.
+   *
+   * Will only trigger an update if the data has changed. This relies on
+   * object identity, so be sure to not mutate the data passed to this
+   * method and instead always pass new objects/arrays.
+   */
   public async setState(
     externalApiUsages: ExternalApiUsage[],
     databaseItem: DatabaseItem,
   ): Promise<void> {
+    if (
+      this.externalApiUsages !== externalApiUsages ||
+      this.databaseItem !== databaseItem
+    ) {
       this.externalApiUsages = externalApiUsages;
       this.databaseItem = databaseItem;
-    this.sourceLocationPrefix = await this.databaseItem.getSourceLocationPrefix(
-      this.cliServer,
-    );
+      this.sourceLocationPrefix =
+        await this.databaseItem.getSourceLocationPrefix(this.cliServer);
       this.onDidChangeTreeDataEmitter.fire();
     }
+  }
 
   getTreeItem(item: ModelDetailsTreeViewItem): TreeItem {
     if (isExternalApiUsage(item)) {

extensions/ql-vscode/test/vscode-tests/no-workspace/data-extensions-editor/model-details/model-details-data-provider.test.ts

@@ -0,0 +1,66 @@
+import { CodeQLCliServer } from "../../../../../src/codeql-cli/cli";
+import { ExternalApiUsage } from "../../../../../src/data-extensions-editor/external-api-usage";
+import { ModelDetailsDataProvider } from "../../../../../src/data-extensions-editor/model-details/model-details-data-provider";
+import { DatabaseItem } from "../../../../../src/databases/local-databases";
+import { mockedObject } from "../../../utils/mocking.helpers";
+
+describe("ModelDetailsDataProvider", () => {
+  const mockCliServer = mockedObject<CodeQLCliServer>({});
+
+  describe("setState", () => {
+    it("should emit onDidChangeTreeData event when state has changed", async () => {
+      const externalApiUsages: ExternalApiUsage[] = [];
+      const dbItem = mockedObject<DatabaseItem>({
+        getSourceLocationPrefix: () => "test",
+      });
+
+      const dataProvider = new ModelDetailsDataProvider(mockCliServer);
+      await dataProvider.setState(externalApiUsages, dbItem);
+
+      const onDidChangeTreeDataListener = jest.fn();
+      dataProvider.onDidChangeTreeData(onDidChangeTreeDataListener);
+
+      await dataProvider.setState(externalApiUsages, dbItem);
+
+      expect(onDidChangeTreeDataListener).toHaveBeenCalledTimes(0);
+    });
+
+    it("should emit onDidChangeTreeData event when externalApiUsages has changed", async () => {
+      const externalApiUsages1: ExternalApiUsage[] = [];
+      const externalApiUsages2: ExternalApiUsage[] = [];
+      const dbItem = mockedObject<DatabaseItem>({
+        getSourceLocationPrefix: () => "test",
+      });
+
+      const dataProvider = new ModelDetailsDataProvider(mockCliServer);
+      await dataProvider.setState(externalApiUsages1, dbItem);
+
+      const onDidChangeTreeDataListener = jest.fn();
+      dataProvider.onDidChangeTreeData(onDidChangeTreeDataListener);
+
+      await dataProvider.setState(externalApiUsages2, dbItem);
+
+      expect(onDidChangeTreeDataListener).toHaveBeenCalledTimes(1);
+    });
+
+    it("should emit onDidChangeTreeData event when dbItem has changed", async () => {
+      const externalApiUsages: ExternalApiUsage[] = [];
+      const dbItem1 = mockedObject<DatabaseItem>({
+        getSourceLocationPrefix: () => "test",
+      });
+      const dbItem2 = mockedObject<DatabaseItem>({
+        getSourceLocationPrefix: () => "test",
+      });
+
+      const dataProvider = new ModelDetailsDataProvider(mockCliServer);
+      await dataProvider.setState(externalApiUsages, dbItem1);
+
+      const onDidChangeTreeDataListener = jest.fn();
+      dataProvider.onDidChangeTreeData(onDidChangeTreeDataListener);
+
+      await dataProvider.setState(externalApiUsages, dbItem2);
+
+      expect(onDidChangeTreeDataListener).toHaveBeenCalledTimes(1);
+    });
+  });
+});