Use patterns and null safety to omprove request routing code style.

Change-Id: I2747e7cfd982430f0d1c72a29b58945722533638
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/346905
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/services/correction/dart/destructure_local_variable_assignment.dart

@@ -11,7 +11,7 @@ import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
-import 'package:analyzer/src/utilities/extensions/map.dart';
+import 'package:analyzer/src/utilities/extensions/collection.dart';
 import 'package:analyzer_plugin/utilities/assist/assist.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
 import 'package:analyzer_plugin/utilities/range_factory.dart';

pkg/analyzer/lib/src/dart/analysis/driver.dart

@@ -1159,8 +1159,7 @@ class AnalysisDriver {
     _discoverDartCore();
     _discoverLibraries();
 
-    if (_resolveForCompletionRequests.isNotEmpty) {
-      final request = _resolveForCompletionRequests.removeLast();
+    if (_resolveForCompletionRequests.removeLastOrNull() case var request?) {
       try {
         final result = await _resolveForCompletion(request);
         request.completer.complete(result);
@@ -1173,55 +1172,45 @@ class AnalysisDriver {
     }
 
     // Analyze a requested file.
-    if (_requestedFiles.isNotEmpty) {
-      final path = _requestedFiles.keys.first;
+    if (_requestedFiles.firstKey case var path?) {
       await _analyzeFile(path);
       return;
     }
 
     // Analyze a requested library.
-    if (_requestedLibraries.isNotEmpty) {
-      final library = _requestedLibraries.keys.first;
+    if (_requestedLibraries.firstKey case var library?) {
       await _getResolvedLibrary(library);
       return;
     }
 
     // Process an error request.
-    if (_errorsRequestedFiles.isNotEmpty) {
-      final path = _errorsRequestedFiles.keys.first;
+    if (_errorsRequestedFiles.firstKey case var path?) {
       await _getErrors(path);
       return;
     }
 
     // Process an index request.
-    if (_indexRequestedFiles.isNotEmpty) {
-      final path = _indexRequestedFiles.keys.first;
+    if (_indexRequestedFiles.firstKey case var path?) {
       await _getIndex(path);
       return;
     }
 
     // Process a unit element request.
-    if (_unitElementRequestedFiles.isNotEmpty) {
-      String path = _unitElementRequestedFiles.keys.first;
-      var completers = _unitElementRequestedFiles.remove(path)!;
-      final result = await _computeUnitElement(path);
-      for (var completer in completers) {
-        completer.complete(result);
-      }
+    if (_unitElementRequestedFiles.firstKey case var path?) {
+      await _getUnitElement(path);
       return;
     }
 
     // Discover available files.
-    if (_discoverAvailableFilesTask != null &&
-        !_discoverAvailableFilesTask!.isCompleted) {
-      _discoverAvailableFilesTask!.perform();
-      return;
+    if (_discoverAvailableFilesTask case var task?) {
+      if (!task.isCompleted) {
+        task.perform();
+        return;
+      }
     }
 
     // Compute files defining a name.
-    if (_definingClassMemberNameTasks.isNotEmpty) {
-      _FilesDefiningClassMemberNameTask task =
-          _definingClassMemberNameTasks.first;
+    if (_definingClassMemberNameTasks.firstOrNull case var task?) {
       bool isDone = task.perform();
       if (isDone) {
         _definingClassMemberNameTasks.remove(task);
@@ -1230,8 +1219,7 @@ class AnalysisDriver {
     }
 
     // Compute files referencing a name.
-    if (_referencingNameTasks.isNotEmpty) {
-      _FilesReferencingNameTask task = _referencingNameTasks.first;
+    if (_referencingNameTasks.firstOrNull case var task?) {
       bool isDone = task.perform();
       if (isDone) {
         _referencingNameTasks.remove(task);
@@ -1240,18 +1228,15 @@ class AnalysisDriver {
     }
 
     // Analyze a priority file.
-    if (_priorityFiles.isNotEmpty) {
-      for (String path in _priorityFiles) {
-        if (_fileTracker.isFilePending(path)) {
-          await _analyzeFile(path);
-          return;
-        }
+    for (var path in _priorityFiles) {
+      if (_fileTracker.isFilePending(path)) {
+        await _analyzeFile(path);
+        return;
       }
     }
 
     // Analyze a general file.
-    if (_fileTracker.hasPendingFiles) {
-      String path = _fileTracker.anyPendingFile;
+    if (_fileTracker.anyPendingFile case var path?) {
       await _produceErrors(path);
       return;
     }
@@ -1520,28 +1505,6 @@ class AnalysisDriver {
     _resolvedLibraryCache.clear();
   }
 
-  Future<UnitElementResult> _computeUnitElement(String path) async {
-    FileState file = _fsState.getFileForPath(path);
-
-    // Prepare the library - the file itself, or the known library.
-    final kind = file.kind;
-    final library = kind.library ?? kind.asLibrary;
-
-    return _logger.runAsync('Compute unit element for $path', () async {
-      _logger.writeln('Work in $name');
-      await libraryContext.load(
-        targetLibrary: library,
-        performance: OperationPerformanceImpl('<root>'),
-      );
-      var element = libraryContext.computeUnitElement(library, file);
-      return UnitElementResultImpl(
-        session: currentSession,
-        fileState: file,
-        element: element,
-      );
-    });
-  }
-
   ErrorsResultImpl _createErrorsResultFromBytes(
     FileState file,
     LibraryFileKind library,
@@ -1793,6 +1756,28 @@ class AnalysisDriver {
     return signature.toHex();
   }
 
+  Future<void> _getUnitElement(String path) async {
+    FileState file = _fsState.getFileForPath(path);
+
+    // Prepare the library - the file itself, or the known library.
+    final kind = file.kind;
+    final library = kind.library ?? kind.asLibrary;
+
+    await libraryContext.load(
+      targetLibrary: library,
+      performance: OperationPerformanceImpl('<root>'),
+    );
+
+    var element = libraryContext.computeUnitElement(library, file);
+    var result = UnitElementResultImpl(
+      session: currentSession,
+      fileState: file,
+      element: element,
+    );
+
+    _unitElementRequestedFiles.completeAll(path, result);
+  }
+
   bool _hasLibraryByUri(String uriStr) {
     var uri = uriCache.parse(uriStr);
     var fileOr = _fsState.getFileForUri(uri);

pkg/analyzer/lib/src/dart/analysis/file_tracker.dart

@@ -49,19 +49,12 @@ class FileTracker {
 
   FileTracker(this._logger, this._fsState, this._fileContentStrategy);
 
-  /// Returns the path to exactly one that needs analysis.  Throws a
-  /// [StateError] if no files need analysis.
-  String get anyPendingFile {
-    if (_pendingChangedFiles.isNotEmpty) {
-      return _pendingChangedFiles.first;
-    }
-    if (_pendingImportFiles.isNotEmpty) {
-      return _pendingImportFiles.first;
-    }
-    if (_pendingErrorFiles.isNotEmpty) {
-      return _pendingErrorFiles.first;
-    }
-    return _pendingFiles.first;
+  /// Returns the path to exactly one that needs analysis.
+  String? get anyPendingFile {
+    return _pendingChangedFiles.firstOrNull ??
+        _pendingImportFiles.firstOrNull ??
+        _pendingErrorFiles.firstOrNull ??
+        _pendingFiles.firstOrNull;
   }
 
   /// Returns a boolean indicating whether there are any files that have

pkg/analyzer/lib/src/utilities/extensions/collection.dart

@@ -92,6 +92,13 @@ extension ListExtension<E> on List<E> {
     }
   }
 
+  E? removeLastOrNull() {
+    if (isNotEmpty) {
+      return removeLast();
+    }
+    return null;
+  }
+
   /// Returns a new list with all elements of the target, arranged such that
   /// all elements for which the [predicate] specified returns `true` come
   /// before those for which the [predicate] returns `false`. The partitioning
@@ -110,6 +117,18 @@ extension ListQueueExtension<T> on ListQueue<T> {
   }
 }
 
+extension MapExtension<K, V> on Map<K, V> {
+  K? get firstKey {
+    return keys.firstOrNull;
+  }
+}
+
+extension MapOfListValuesExtension<K, V> on Map<K, List<V>> {
+  void add(K key, V value) {
+    (this[key] ??= []).add(value);
+  }
+}
+
 extension SetExtension<E> on Set<E> {
   void addIfNotNull(E? element) {
     if (element != null) {

pkg/analyzer/lib/src/utilities/extensions/map.dart

@@ -1,10 +0,0 @@
-// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-// TODO(pq): move to collections
-extension MapExtension<K, V> on Map<K, List<V>> {
-  void add(K key, V value) {
-    (this[key] ??= []).add(value);
-  }
-}

pkg/analyzer/test/src/utilities/extensions/collection_test.dart

@@ -12,6 +12,7 @@ main() {
     defineReflectiveTests(IterableIterableExtensionTest);
     defineReflectiveTests(IterableMapEntryExtensionTest);
     defineReflectiveTests(ListExtensionTest);
+    defineReflectiveTests(MapExtensionTest);
   });
 }
 
@@ -100,6 +101,12 @@ class ListExtensionTest {
     expect(elements.nextOrNull(3), null);
   }
 
+  test_removeLastOrNull() {
+    expect([0, 1, 2].removeLastOrNull(), 2);
+    expect([0].removeLastOrNull(), 0);
+    expect(<int>[].removeLastOrNull(), isNull);
+  }
+
   test_stablePartition() {
     expect(
       [0, 1, 2, 3, 4, 5].stablePartition((e) => e.isEven),
@@ -119,6 +126,14 @@ class ListExtensionTest {
   }
 }
 
+@reflectiveTest
+class MapExtensionTest {
+  test_firstKey() {
+    expect({0: 1, 2: 3}.firstKey, 0);
+    expect(<int, int>{}.firstKey, isNull);
+  }
+}
+
 @reflectiveTest
 class SetExtensionTest {
   test_addIfNotNull_notNull() {