Allow dart.lineLength to control formatting for LSP

Noted at Dart-Code/Dart-Code#2286 (comment).

Change-Id: If45bede84a0a4414a16d1809a1aa0f81d18cebfb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154008
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Danny Tuppeny <danny@tuppeny.com>

Author: DanTup

pkg/analysis_server/lib/src/lsp/client_configuration.dart

@@ -8,6 +8,7 @@ class LspClientConfiguration {
   final Map<String, dynamic> _settings = <String, dynamic>{};
 
   bool get enableSdkFormatter => _settings['enableSdkFormatter'] ?? true;
+  int get lineLength => _settings['lineLength'];
 
   void replace(Map<String, dynamic> newConfig) {
     _settings

pkg/analysis_server/lib/src/lsp/handlers/handler_format_on_type.dart

@@ -29,7 +29,8 @@ class FormatOnTypeHandler
     }
 
     final unformattedSource = file.readAsStringSync();
-    return success(generateEditsForFormatting(unformattedSource));
+    return success(generateEditsForFormatting(
+        unformattedSource, server.clientConfiguration.lineLength));
   }
 
   @override

pkg/analysis_server/lib/src/lsp/handlers/handler_formatting.dart

@@ -29,7 +29,8 @@ class FormattingHandler
     }
 
     final unformattedSource = file.readAsStringSync();
-    return success(generateEditsForFormatting(unformattedSource));
+    return success(generateEditsForFormatting(
+        unformattedSource, server.clientConfiguration.lineLength));
   }
 
   @override

pkg/analysis_server/lib/src/lsp/source_edits.dart

@@ -8,7 +8,7 @@ import 'package:analyzer_plugin/protocol/protocol_common.dart' as plugin;
 import 'package:analyzer_plugin/utilities/pair.dart';
 import 'package:dart_style/dart_style.dart';
 
-final DartFormatter formatter = DartFormatter();
+DartFormatter formatter = DartFormatter();
 
 /// Transforms a sequence of LSP document change events to a sequence of source
 /// edits used by analysis plugins.
@@ -66,12 +66,17 @@ ErrorOr<Pair<String, List<plugin.SourceEdit>>> applyAndConvertEditsToServer(
   return ErrorOr.success(Pair(newContent, serverEdits));
 }
 
-List<TextEdit> generateEditsForFormatting(String unformattedSource) {
+List<TextEdit> generateEditsForFormatting(
+    String unformattedSource, int lineLength) {
   final lineInfo = LineInfo.fromContent(unformattedSource);
   final code =
       SourceCode(unformattedSource, uri: null, isCompilationUnit: true);
   SourceCode formattedResult;
   try {
+    // If the lineLength has changed, recreate the formatter with the new setting.
+    if (lineLength != formatter.pageWidth) {
+      formatter = DartFormatter(pageWidth: lineLength);
+    }
     formattedResult = formatter.formatSource(code);
   } on FormatterException {
     // If the document fails to parse, just return no edits to avoid the the

pkg/analysis_server/test/lsp/format_test.dart

@@ -18,6 +18,13 @@ void main() {
 
 @reflectiveTest
 class FormatTest extends AbstractLspAnalysisServerTest {
+  Future<void> expectFormattedContents(
+      Uri uri, String original, String expected) async {
+    final formatEdits = await formatDocument(uri.toString());
+    final formattedContents = applyTextEdits(original, formatEdits);
+    expect(formattedContents, equals(expected));
+  }
+
   Future<void> test_alreadyFormatted() async {
     const contents = '''main() {
   print('test');
@@ -149,6 +156,32 @@ class FormatTest extends AbstractLspAnalysisServerTest {
     expect(formatEdits, isNull);
   }
 
+  Future<void> test_lineLength() async {
+    const contents = '''
+    main() =>
+    print(
+    '123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789'
+    );
+    ''';
+    final expectedDefault = '''main() => print(
+    '123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789');\n''';
+    final expectedLongLines =
+        '''main() => print('123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789');\n''';
+
+    // Initialize with config support, supplying an empty config when requested.
+    await provideConfig(
+      () => initialize(
+          workspaceCapabilities: withDidChangeConfigurationDynamicRegistration(
+              withConfigurationSupport(emptyWorkspaceClientCapabilities))),
+      {}, // empty config
+    );
+    await openFile(mainFileUri, contents);
+
+    await expectFormattedContents(mainFileUri, contents, expectedDefault);
+    await updateConfig({'lineLength': 500});
+    await expectFormattedContents(mainFileUri, contents, expectedLongLines);
+  }
+
   Future<void> test_nonDartFile() async {
     await initialize();
     await openFile(pubspecFileUri, simplePubspecContent);
@@ -201,11 +234,7 @@ class FormatTest extends AbstractLspAnalysisServerTest {
 ''';
     await initialize();
     await openFile(mainFileUri, contents);
-
-    final formatEdits = await formatDocument(mainFileUri.toString());
-    expect(formatEdits, isNotNull);
-    final formattedContents = applyTextEdits(contents, formatEdits);
-    expect(formattedContents, equals(expected));
+    await expectFormattedContents(mainFileUri, contents, expected);
   }
 
   Future<void> test_unopenFile() async {
@@ -222,10 +251,6 @@ class FormatTest extends AbstractLspAnalysisServerTest {
 ''';
     newFile(mainFilePath, content: contents);
     await initialize();
-
-    final formatEdits = await formatDocument(mainFileUri.toString());
-    expect(formatEdits, isNotNull);
-    final formattedContents = applyTextEdits(contents, formatEdits);
-    expect(formattedContents, equals(expected));
+    await expectFormattedContents(mainFileUri, contents, expected);
   }
 }