restore cache if cacheValidityDecidingFile is missing

src/main/java/jenkins/plugins/jobcacher/ArbitraryFileCache.java

@@ -195,13 +195,13 @@ private FilePath resolvePath(FilePath workspace, EnvVars initialEnvironment) {
     }
 
     private ExistingCache resolveExistingValidCache(ObjectPath cachesRoot, ObjectPath fallbackCachesRoot, FilePath workspace, TaskListener listener) throws IOException, InterruptedException {
-        ExistingCache cache = resolveExistingValidCache(cachesRoot, workspace);
+        ExistingCache cache = resolveExistingValidCache(cachesRoot, workspace, listener);
         if (cache != null) {
             logMessage("Found cache in job specific caches", listener);
             return cache;
         }
 
-        cache = resolveExistingValidCache(fallbackCachesRoot, workspace);
+        cache = resolveExistingValidCache(fallbackCachesRoot, workspace, listener);
         if (cache != null) {
             logMessage("Found cache in default caches", listener);
             return cache;
@@ -210,17 +210,22 @@ private ExistingCache resolveExistingValidCache(ObjectPath cachesRoot, ObjectPat
         return null;
     }
 
-    private ExistingCache resolveExistingValidCache(ObjectPath cachesRoot, FilePath workspace) throws IOException, InterruptedException {
+    private ExistingCache resolveExistingValidCache(ObjectPath cachesRoot, FilePath workspace, TaskListener listener) throws IOException, InterruptedException {
         ExistingCache existingCache = resolveExistingCache(cachesRoot);
         if (existingCache == null) {
             return null;
         }
 
-        if (isCacheValidityDecidingFileConfigured() && isCacheOutdated(cachesRoot, workspace)) {
-            return null;
+        if (!isCacheValidityDecidingFileConfigured()) {
+            return existingCache;
+        }
+
+        if (!isOneCacheValidityDecidingFilePresent(workspace)) {
+            logMessage("cacheValidityDecidingFile configured, but file(s) not present in workspace - considering cache anyway", listener);
+            return existingCache;
         }
 
-        return existingCache;
+        return isCacheOutdated(cachesRoot, workspace) ? null : existingCache;
     }
 
     private ExistingCache resolveExistingCache(ObjectPath cachesRoot) throws IOException, InterruptedException {
@@ -327,7 +332,7 @@ public void save(ObjectPath cachesRoot, Run<?, ?> build, FilePath workspace, Lau
             }
 
             if (isCacheValidityDecidingFileConfigured()) {
-                ExistingCache existingValidCache = resolveExistingValidCache(cachesRoot, workspace);
+                ExistingCache existingValidCache = resolveExistingValidCache(cachesRoot, workspace, listener);
                 if (existingValidCache != null) {
                     logMessage("Skip cache creation as the cache is up-to-date", listener);
                     return;

src/test/java/jenkins/plugins/jobcacher/ArbitraryFileCachePipelineTest.java

@@ -33,6 +33,30 @@ public static void startAgent() throws Exception {
         agent = jenkins.createSlave(Label.get("test-agent"));
     }
 
+    @Test
+    @WithTimeout(600)
+    public void testMissingCacheValidityDecidingFile() throws Exception {
+        String cacheDefinition = "arbitraryFileCache(path: 'test-path', cacheValidityDecidingFile: 'cacheValidityDecidingFile.txt')";
+        WorkflowJob project = createTestProject(cacheDefinition);
+
+        WorkflowRun run1 = jenkins.assertBuildStatus(Result.SUCCESS, project.scheduleBuild2(0));
+        assertThat(run1.getLog())
+                .contains("[Cache for test-path] Skip restoring cache as no up-to-date cache exists")
+                .doesNotContain("expected output from test file")
+                .contains("[Cache for test-path] Creating cache...");
+
+        deleteCachedDirectoryInWorkspace(project);
+        setProjectDefinition(project, cacheDefinition, null);
+
+        WorkflowRun run2 = jenkins.assertBuildStatus(Result.SUCCESS, project.scheduleBuild2(0));
+        assertThat(run2.getLog())
+                .contains("[Cache for test-path] cacheValidityDecidingFile configured, but file(s) not present in workspace - considering cache anyway")
+                .contains("[Cache for test-path] Found cache in job specific caches")
+                .contains("[Cache for test-path] Restoring cache...")
+                .contains("expected output from test file")
+                .contains("[Cache for test-path] Skip cache creation as the cache is up-to-date");
+    }
+
     @Test
     @WithTimeout(600)
     public void testMultipleCacheValidityDecidingFiles() throws Exception {
@@ -147,9 +171,11 @@ public void testNonExistingCacheValidityDecidingFile() throws Exception {
 
         WorkflowRun run2 = jenkins.assertBuildStatus(Result.SUCCESS, project.scheduleBuild2(0));
         assertThat(run2.getLog())
-                .contains("[Cache for test-path] Skip restoring cache as no up-to-date cache exists")
-                .doesNotContain("expected output from test file")
-                .contains("[Cache for test-path] Creating cache...");
+                .contains("[Cache for test-path] cacheValidityDecidingFile configured, but file(s) not present in workspace - considering cache anyway")
+                .contains("[Cache for test-path] Found cache in job specific caches")
+                .contains("[Cache for test-path] Restoring cache...")
+                .contains("expected output from test file")
+                .contains("[Cache for test-path] Skip cache creation as the cache is up-to-date");
     }
 
     @Test
@@ -209,14 +235,30 @@ private void setProjectDefinition(WorkflowJob project, String cacheDefinition) {
     private void setProjectDefinition(WorkflowJob project, String cacheDefinition, String cacheValidityDecidingFileContent) {
         String scriptedPipeline = ""
                 + "node('test-agent') {\n"
-                + "    writeFile text: '" + cacheValidityDecidingFileContent + "', file: 'cacheValidityDecidingFile.txt'\n"
+                + "   " + cacheValidityDecidingFileCode(cacheValidityDecidingFileContent) + "\n"
                 + "    cache(maxCacheSize: 100, caches: [" + cacheDefinition + "]) {\n"
                 + "        " + fileCreationCode("test-path", "test-file") + "\n"
                 + "    }\n"
                 + "}";
         project.setDefinition(new CpsFlowDefinition(scriptedPipeline, true));
     }
 
+    private String cacheValidityDecidingFileCode(String cacheValidityDecidingFileContent) {
+        if (cacheValidityDecidingFileContent != null) {
+            return "writeFile text: '" + cacheValidityDecidingFileContent + "', file: 'cacheValidityDecidingFile.txt'";
+        } else {
+            return fileDeletionCode("cacheValidityDecidingFile.txt");
+        }
+    }
+
+    private String fileDeletionCode(String file) {
+        if (SystemUtils.IS_OS_WINDOWS) {
+            return "bat '''del " + file + "'''";
+        } else {
+            return "sh '''rm " + file + "'''";
+        }
+    }
+
     private String fileCreationCode(String folder, String file) {
         if (SystemUtils.IS_OS_WINDOWS) {
             return "bat '''" + fileCreationCodeForWindows(folder, file + ".bat") + "'''";