Return cache keys with exact hits from downloadDependencyCaches

Author: mbg

lib/init-action.js

@@ -237,15 +237,17 @@ test("downloadDependencyCaches - does not restore caches with feature keys if no
     .resolves(CSHARP_BASE_PATTERNS);
   makePatternCheckStub.withArgs(CSHARP_EXTRA_PATTERNS).resolves(undefined);
 
-  const results = await downloadDependencyCaches(
+  const result = await downloadDependencyCaches(
     codeql,
     createFeatures([]),
     [KnownLanguage.csharp],
     logger,
   );
-  t.is(results.length, 1);
-  t.is(results[0].language, KnownLanguage.csharp);
-  t.is(results[0].hit_kind, CacheHitKind.Miss);
+  const statusReport = result.statusReport;
+  t.is(statusReport.length, 1);
+  t.is(statusReport[0].language, KnownLanguage.csharp);
+  t.is(statusReport[0].hit_kind, CacheHitKind.Miss);
+  t.deepEqual(result.exactKeys, []);
   t.assert(restoreCacheStub.calledOnce);
 });
 
@@ -257,7 +259,8 @@ test("downloadDependencyCaches - restores caches with feature keys if features a
   const logger = getRecordingLogger(messages);
   const features = createFeatures([Feature.CsharpNewCacheKey]);
 
-  sinon.stub(glob, "hashFiles").resolves("abcdef");
+  const mockHash = "abcdef";
+  sinon.stub(glob, "hashFiles").resolves(mockHash);
 
   const keyWithFeature = await cacheKey(
     codeql,
@@ -277,15 +280,28 @@ test("downloadDependencyCaches - restores caches with feature keys if features a
     .resolves(CSHARP_BASE_PATTERNS);
   makePatternCheckStub.withArgs(CSHARP_EXTRA_PATTERNS).resolves(undefined);
 
-  const results = await downloadDependencyCaches(
+  const result = await downloadDependencyCaches(
     codeql,
     features,
     [KnownLanguage.csharp],
     logger,
   );
-  t.is(results.length, 1);
-  t.is(results[0].language, KnownLanguage.csharp);
-  t.is(results[0].hit_kind, CacheHitKind.Exact);
+
+  // Check that the status report for telemetry indicates that one cache was restored with an exact match.
+  const statusReport = result.statusReport;
+  t.is(statusReport.length, 1);
+  t.is(statusReport[0].language, KnownLanguage.csharp);
+  t.is(statusReport[0].hit_kind, CacheHitKind.Exact);
+
+  // Check that the exact key match has been returned.
+  const exactKeys = result.exactKeys;
+  t.is(exactKeys.length, 1);
+  t.assert(
+    exactKeys[0].endsWith(mockHash),
+    "Expected exact key match to end with hash returned by `hashFiles`",
+  );
+
+  // `restoreCache` should have been called exactly once.
   t.assert(restoreCacheStub.calledOnce);
 });
 
@@ -319,15 +335,17 @@ test("downloadDependencyCaches - restores caches with feature keys if features a
     .resolves(CSHARP_BASE_PATTERNS);
   makePatternCheckStub.withArgs(CSHARP_EXTRA_PATTERNS).resolves(undefined);
 
-  const results = await downloadDependencyCaches(
+  const result = await downloadDependencyCaches(
     codeql,
     features,
     [KnownLanguage.csharp],
     logger,
   );
-  t.is(results.length, 1);
-  t.is(results[0].language, KnownLanguage.csharp);
-  t.is(results[0].hit_kind, CacheHitKind.Partial);
+  const statusReport = result.statusReport;
+  t.is(statusReport.length, 1);
+  t.is(statusReport[0].language, KnownLanguage.csharp);
+  t.is(statusReport[0].hit_kind, CacheHitKind.Partial);
+  t.deepEqual(result.exactKeys, []);
   t.assert(restoreCacheStub.calledOnce);
 });
 

src/dependency-caching.test.ts

@@ -193,6 +193,14 @@ export interface DependencyCacheRestoreStatus {
 /** An array of `DependencyCacheRestoreStatus` objects for each analysed language with a caching configuration. */
 export type DependencyCacheRestoreStatusReport = DependencyCacheRestoreStatus[];
 
+/* Represents the results of `downloadDependencyCaches`. */
+export interface DownloadDependencyCachesResult {
+  /* The status report for telemetry */
+  statusReport: DependencyCacheRestoreStatusReport;
+  /* An array of cache keys that we had exact cache hits for. */
+  exactKeys: string[];
+}
+
 /**
  * A wrapper around `cacheConfig.getHashPatterns` which logs when there are no files to calculate
  * a hash for the cache key from.
@@ -239,8 +247,9 @@ export async function downloadDependencyCaches(
   features: FeatureEnablement,
   languages: Language[],
   logger: Logger,
-): Promise<DependencyCacheRestoreStatusReport> {
+): Promise<DownloadDependencyCachesResult> {
   const status: DependencyCacheRestoreStatusReport = [];
+  const exactKeys: string[] = [];
 
   for (const language of languages) {
     const cacheConfig = defaultCacheConfigs[language];
@@ -288,16 +297,28 @@ export async function downloadDependencyCaches(
 
     if (hitKey !== undefined) {
       logger.info(`Cache hit on key ${hitKey} for ${language}.`);
-      const hit_kind =
-        hitKey === primaryKey ? CacheHitKind.Exact : CacheHitKind.Partial;
-      status.push({ language, hit_kind, download_duration_ms });
+
+      // We have a partial cache hit, unless the key of the restored cache matches the
+      // primary restore key. In that case we have an exact hit and track the restored
+      // cache key so that we can skip storing the same cache again later.
+      let hit_kind = CacheHitKind.Partial;
+      if (hitKey === primaryKey) {
+        hit_kind = CacheHitKind.Exact;
+        exactKeys.push(hitKey);
+      }
+
+      status.push({
+        language,
+        hit_kind,
+        download_duration_ms,
+      });
     } else {
       status.push({ language, hit_kind: CacheHitKind.Miss });
       logger.info(`No suitable cache found for ${language}.`);
     }
   }
 
-  return status;
+  return { statusReport: status, exactKeys };
 }
 
 /** Enumerates possible outcomes for storing caches. */

src/dependency-caching.ts

@@ -371,7 +371,7 @@ async function run() {
   }
 
   let overlayBaseDatabaseStats: OverlayBaseDatabaseDownloadStats | undefined;
-  let dependencyCachingResults: DependencyCacheRestoreStatusReport | undefined;
+  let dependencyCachingStatus: DependencyCacheRestoreStatusReport | undefined;
   try {
     if (
       config.overlayDatabaseMode === OverlayDatabaseMode.Overlay &&
@@ -579,12 +579,13 @@ async function run() {
 
     // Restore dependency cache(s), if they exist.
     if (shouldRestoreCache(config.dependencyCachingEnabled)) {
-      dependencyCachingResults = await downloadDependencyCaches(
+      const dependencyCachingResult = await downloadDependencyCaches(
         codeql,
         features,
         config.languages,
         logger,
       );
+      dependencyCachingStatus = dependencyCachingResult.statusReport;
     }
 
     // Suppress warnings about disabled Python library extraction.
@@ -732,7 +733,7 @@ async function run() {
       toolsSource,
       toolsVersion,
       overlayBaseDatabaseStats,
-      dependencyCachingResults,
+      dependencyCachingStatus,
       logger,
       error,
     );
@@ -755,7 +756,7 @@ async function run() {
     toolsSource,
     toolsVersion,
     overlayBaseDatabaseStats,
-    dependencyCachingResults,
+    dependencyCachingStatus,
     logger,
   );
 }