chore: prlinter crashes if it runs alongside itself

tools/@aws-cdk/prlint/linter-base.ts

@@ -168,6 +168,11 @@ export class PullRequestLinterBase {
           message,
         });
       } catch (e: any) {
+        if (githubResponseErrors(e).includes('Can not dismiss a dismissed pull request review')) {
+          // Can happen because of race conditions. We already achieved the result we wanted, so ignore.
+          continue;
+        }
+
         // This can fail with a "not found" for some reason
         throw new Error(`Dismissing review failed, user is probably not authorized: ${JSON.stringify(e, undefined, 2)}`);
       }
@@ -386,4 +391,11 @@ export function mergeLinterActions(a: LinterActions, b: LinterActions): LinterAc
 
 function nonEmpty<A>(xs: A[]): A[] | undefined {
   return xs.length > 0 ? xs : undefined;
+}
+
+/**
+ * Return error messages from an exception thrown by GitHub
+ */
+function githubResponseErrors(e: Error): string[] {
+  return (e as any).response?.data?.errors ?? [];
 }

tools/@aws-cdk/prlint/test/linter-base.test.ts

@@ -21,7 +21,7 @@ const linter = new PullRequestLinterBase({
 });
 
 beforeEach(() => {
-  jest.clearAllMocks();
+  jest.resetAllMocks();
 
   octomock.pulls.get.mockReturnValue({
     data: {
@@ -34,6 +34,66 @@ beforeEach(() => {
   octomock.repos.listCommitStatusesForRef.mockReturnValue({ data: [] });
 });
 
+test('ignore if dismissing reviews throws a specific "already dismissed" error', async () => {
+  // GIVEN
+  octomock.pulls.listReviews.mockReturnValue({
+    data: [
+      {
+        id: 1111,
+        user: { login: 'aws-cdk-automation' },
+        state: 'CHANGES_REQUESTED',
+        body: 'some comment',
+      },
+    ]
+  });
+  octomock.pulls.dismissReview.mockRejectedValue({
+    status: 422,
+    response: {
+      data: {
+        errors: [
+          'Can not dismiss a dismissed pull request review',
+        ],
+      },
+    },
+  });
+
+  // WHEN
+  await linter.executeActions({
+    dismissPreviousReview: true,
+  });
+
+  // THEN: no error
+});
+
+test('throw if dismissing reviews throws any other error', async () => {
+  // GIVEN
+  octomock.pulls.listReviews.mockReturnValue({
+    data: [
+      {
+        id: 1111,
+        user: { login: 'aws-cdk-automation' },
+        state: 'CHANGES_REQUESTED',
+        body: 'some comment',
+      },
+    ]
+  });
+  octomock.pulls.dismissReview.mockRejectedValue({
+    status: 422,
+    response: {
+      data: {
+        errors: [
+          'Review not found',
+        ],
+      },
+    },
+  });
+
+  // THEN
+  await expect(linter.executeActions({
+    dismissPreviousReview: true,
+  })).rejects.toThrow(/Dismissing review failed/);
+});
+
 test('dismissing a review dismisses and changes the text of all previous reviews', async () => {
   // GIVEN
   octomock.pulls.listReviews.mockReturnValue({