Fix the issue that PR changed files list is empty (#14202)

* Fix the issue that PR changed files list is empty

* Fix the issue that PR changed files list is empty

Co-authored-by: wyunchi <[email protected]>

Author: wyunchi-ms

tools/BuildPackagesTask/Microsoft.Azure.Build.Tasks/CIFilterTask.cs

@@ -414,9 +414,26 @@ public override bool Execute()
             var csprojMap = ReadMapFile(CsprojMapFilePath, "CsprojMapFilePath");
 
             Console.WriteLine(string.Format("FilesChanged: {0}", FilesChanged.Length));
-            if (FilesChanged != null && FilesChanged.Length > 0)
+            if (FilesChanged != null)
             {
-                return ProcessFileChanged(csprojMap);
+                if (FilesChanged.Length > 0)
+                {
+                    return ProcessFileChanged(csprojMap);
+                }
+                else
+                {
+                    Dictionary<string, HashSet<string>> influencedModuleInfo = new Dictionary<string, HashSet<string>>
+                    {
+                        [BUILD_PHASE] = new HashSet<string>() { ACCOUNT_MODULE_NAME },
+                        [ANALYSIS_BREAKING_CHANGE_PHASE] = new HashSet<string>() { ACCOUNT_MODULE_NAME },
+                        [ANALYSIS_DEPENDENCY_PHASE] = new HashSet<string>() { ACCOUNT_MODULE_NAME },
+                        [ANALYSIS_HELP_PHASE] = new HashSet<string>() { ACCOUNT_MODULE_NAME },
+                        [ANALYSIS_SIGNATURE_PHASE] = new HashSet<string>() { ACCOUNT_MODULE_NAME },
+                        [TEST_PHASE] = new HashSet<string>() { ACCOUNT_MODULE_NAME }
+                    };
+                    FilterTaskResult.PhaseInfo = CalculateCsprojForBuildAndTest(influencedModuleInfo, csprojMap);
+                    return true;
+                }
             }
             else if (!string.IsNullOrWhiteSpace(TargetModule))
             {