Ensure new analysis drivers are seeded with existing priority files

Bug: Dart-Code/Dart-Code#2438
Change-Id: Ia1ca9a024b9d864d94ad7a9ee186fd9de0c536b5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/147183
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Danny Tuppeny <danny@tuppeny.com>

Author: DanTup

pkg/analysis_server/lib/src/analysis_server.dart

@@ -777,6 +777,7 @@ class ServerContextManagerCallbacks extends ContextManagerCallbacks {
       }
     });
     analysisDriver.exceptions.listen(analysisServer.logExceptionResult);
+    analysisDriver.priorityFiles = analysisServer.priorityFiles.toList();
     analysisServer.driverMap[folder] = analysisDriver;
     return analysisDriver;
   }

pkg/analysis_server/test/analysis/set_priority_files_test.dart

@@ -43,6 +43,14 @@ class SetPriorityFilesTest extends AbstractAnalysisTest {
     _verifyPriorityFiles(testFile);
   }
 
+  Future<void> test_fileInAnalysisRootAddedLater() async {
+    var path = convertPath('/other/file.dart');
+    newFile(path);
+    await _setPriorityFile(path);
+    await _setAnalysisRoots('/other');
+    _verifyPriorityFiles(path);
+  }
+
   Future<void> test_fileInSdk() async {
     addTestFile('');
     // set priority files
@@ -134,6 +142,11 @@ analyzer:
     expect(params.files, <String>[testFile]);
   }
 
+  Future<Response> _setAnalysisRoots(String folder) async {
+    var request = AnalysisSetAnalysisRootsParams([folder], []).toRequest('1');
+    return await serverChannel.sendRequest(request);
+  }
+
   Future<Response> _setPriorityFile(String file) async {
     var request = AnalysisSetPriorityFilesParams(<String>[file]).toRequest('0');
     return await serverChannel.sendRequest(request);