fix(dependency-dashboard): skip unnecessary cache bust when unchanged (…

…renovatebot#26794)

Co-authored-by: Michael Kriese <[email protected]>

lib/workers/repository/dependency-dashboard.spec.ts

@@ -839,6 +839,10 @@ describe('workers/repository/dependency-dashboard', () => {
       config.dependencyDashboard = true;
       config.dependencyDashboardChecks = { branchName2: 'approve-branch' };
       config.dependencyDashboardIssue = 1;
+      mockedFunction(platform.getIssue).mockResolvedValueOnce({
+        title: 'Dependency Dashboard',
+        body: '',
+      });
       mockedFunction(platform.getIssue).mockResolvedValueOnce({
         title: 'Dependency Dashboard',
         body: `This issue contains a list of Renovate updates and their statuses.
@@ -863,6 +867,31 @@ describe('workers/repository/dependency-dashboard', () => {
       expect(platform.ensureIssue.mock.calls[0][0].body).toMatchSnapshot();
     });
 
+    it('skips fetching issue if content unchanged', async () => {
+      const branches: BranchConfig[] = [];
+      config.dependencyDashboard = true;
+      config.dependencyDashboardChecks = {};
+      config.dependencyDashboardIssue = 1;
+      mockedFunction(platform.getIssue).mockResolvedValueOnce({
+        title: 'Dependency Dashboard',
+        body: `This issue lists Renovate updates and detected dependencies. Read the [Dependency Dashboard](https://docs.renovatebot.com/key-concepts/dashboard/) docs to learn more.
+
+This repository currently has no open or pending branches.
+
+## Detected dependencies
+
+None detected
+
+`,
+      });
+      mockedFunction(platform.getIssue).mockResolvedValueOnce({
+        title: 'Dependency Dashboard',
+        body: '',
+      });
+      await dependencyDashboard.ensureDependencyDashboard(config, branches);
+      expect(platform.ensureIssue).not.toHaveBeenCalled();
+    });
+
     it('forwards configured labels to the ensure issue call', async () => {
       const branches: BranchConfig[] = [];
       config.dependencyDashboard = true;

lib/workers/repository/dependency-dashboard.ts

@@ -423,6 +423,18 @@ export async function ensureDependencyDashboard(
   issueBody += footer;
 
   if (config.dependencyDashboardIssue) {
+    // If we're not changing the dashboard issue then we can skip checking if the user changed it
+    // The cached issue we get back here will reflect its state at the _start_ of our run
+    const cachedIssue = await platform.getIssue?.(
+      config.dependencyDashboardIssue,
+    );
+    if (cachedIssue?.body === issueBody) {
+      logger.debug('No changes to dependency dashboard issue needed');
+      return;
+    }
+
+    // Skip cache when getting the issue to ensure we get the latest body,
+    // including any updates the user made after we started the run
     const updatedIssue = await platform.getIssue?.(
       config.dependencyDashboardIssue,
       false,