setupDiffInformedQueryRun(): support Default Setup

Author: cklin

src/analyze.ts

@@ -8,7 +8,11 @@ import del from "del";
 import * as yaml from "js-yaml";
 
 import * as actionsUtil from "./actions-util";
-import { getApiClient } from "./api-client";
+import {
+  getApiClient,
+  getPullRequestBranchesFromApi,
+  PullRequestBranches,
+} from "./api-client";
 import { setupCppAutobuild } from "./autobuild";
 import { CodeQL, getCodeQL } from "./codeql";
 import * as configUtils from "./config-utils";
@@ -243,22 +247,35 @@ async function finalizeDatabaseCreation(
   };
 }
 
-interface PullRequestBranches {
-  baseRef: string;
-  headLabel: string;
-}
-
-function getPullRequestBranches(): PullRequestBranches | undefined {
+async function getPullRequestBranches(
+  logger: Logger,
+): Promise<PullRequestBranches | undefined> {
   const pullRequest = github.context.payload.pull_request;
   if (pullRequest) {
     return {
       baseRef: pullRequest.base.ref,
       headLabel: pullRequest.head.label,
     };
   }
+  const pullRequestNumber = getDefaultSetupPullRequestNumber();
+  if (pullRequestNumber) {
+    try {
+      return await getPullRequestBranchesFromApi(pullRequestNumber);
+    } catch (e) {
+      logger.warning(
+        `Cannot identify branches for PR #${pullRequestNumber}: ${e}`,
+      );
+    }
+  }
   return undefined;
 }
 
+function getDefaultSetupPullRequestNumber(): number | undefined {
+  const ref = process.env.CODE_SCANNING_REF;
+  const match = ref?.match(/^refs\/pull\/(\d+)\/head$/);
+  return match ? parseInt(match[1], 10) : undefined;
+}
+
 /**
  * Set up the diff-informed analysis feature.
  *
@@ -274,7 +291,7 @@ export async function setupDiffInformedQueryRun(
     return undefined;
   }
 
-  const branches = getPullRequestBranches();
+  const branches = await getPullRequestBranches(logger);
   if (!branches) {
     return undefined;
   }

src/api-client.ts

@@ -246,6 +246,31 @@ export async function deleteActionsCache(id: number) {
   });
 }
 
+export interface PullRequestBranches {
+  baseRef: string;
+  headLabel: string;
+}
+
+/** Get the base and head branches for a pull request. */
+export async function getPullRequestBranchesFromApi(
+  pullRequestNumber: number,
+): Promise<PullRequestBranches | undefined> {
+  const repositoryNwo = parseRepositoryNwo(
+    getRequiredEnvParam("GITHUB_REPOSITORY"),
+  );
+
+  const pullRequest = await getApiClient().rest.pulls.get({
+    owner: repositoryNwo.owner,
+    repo: repositoryNwo.repo,
+    pull_number: pullRequestNumber,
+  });
+
+  return {
+    baseRef: pullRequest.data.base.ref,
+    headLabel: pullRequest.data.head.label,
+  };
+}
+
 export function wrapApiConfigurationError(e: unknown) {
   if (isHTTPError(e)) {
     if (