Add DiagnosticMessage support API

Change-Id: I0ae8d37e48951a58bd2d9016397baeee916857ee
Reviewed-on: https://dart-review.googlesource.com/c/78063
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Auto-Submit: Peter von der Ahé <ahe@google.com>

pkg/analyzer_fe_comparison/lib/src/kernel.dart

@@ -8,10 +8,9 @@ import 'package:analyzer_fe_comparison/src/comparison_node.dart';
 import 'package:front_end/src/api_prototype/compiler_options.dart'
     show CompilerOptions;
 import 'package:front_end/src/api_prototype/diagnostic_message.dart'
-    show DiagnosticMessage, DiagnosticMessageHandler;
+    show DiagnosticMessage, DiagnosticMessageHandler, getMessageHeaderText;
 import 'package:front_end/src/api_prototype/kernel_generator.dart';
 import 'package:front_end/src/api_prototype/standard_file_system.dart';
-import 'package:front_end/src/fasta/messages.dart' show FormattedMessage;
 import 'package:kernel/ast.dart';
 import 'package:kernel/target/targets.dart';
 
@@ -60,10 +59,7 @@ Future<ComparisonNode> analyzeProgram(Uri input, Uri packagesFileUri,
 }
 
 ComparisonNode _diagnosticMessageToNode(DiagnosticMessage message) {
-  // TODO(ahe): Temporarily using FormattedMessage until DiagnosticMessage
-  // is extended to support this use case.
-  FormattedMessage formatted = message;
-  return ComparisonNode(formatted.message);
+  return ComparisonNode(getMessageHeaderText(message));
 }
 
 CompilerOptions _makeCompilerOptions(Uri packagesFileUri, Uri platformUri,

pkg/front_end/lib/src/api_prototype/diagnostic_message.dart

@@ -4,6 +4,8 @@
 
 library front_end.diagnostic_message;
 
+import '../fasta/fasta_codes.dart' show Code, FormattedMessage;
+
 import '../fasta/severity.dart' show Severity;
 
 /// The type of a diagnostic message callback. For example:
@@ -32,7 +34,29 @@ abstract class DiagnosticMessage {
   Iterable<String> get plainTextFormatted;
 
   Severity get severity;
-
-  // TODO(ahe): Rename this, it's actually an error code.
-  int get index;
+}
+
+/// This method is subject to change.
+Uri getMessageUri(DiagnosticMessage message) {
+  return message is FormattedMessage ? message.uri : null;
+}
+
+/// This method is subject to change.
+Code getMessageCodeObject(DiagnosticMessage message) {
+  return message is FormattedMessage ? message.code : null;
+}
+
+/// This method is subject to change.
+String getMessageHeaderText(DiagnosticMessage message) {
+  return message is FormattedMessage ? message.message : null;
+}
+
+/// This method is subject to change.
+int getMessageCode(DiagnosticMessage message) {
+  return message is FormattedMessage ? message.code.index : -1;
+}
+
+/// This method is subject to change.
+Map<String, dynamic> getMessageArguments(DiagnosticMessage message) {
+  return message is FormattedMessage ? message.arguments : null;
 }

pkg/front_end/lib/src/api_prototype/terminal_color_support.dart

@@ -10,11 +10,22 @@ import 'dart:io' show Platform, Process, ProcessResult, stderr, stdout;
 
 import '../fasta/colors.dart' show ALL_CODES, TERMINAL_CAPABILITIES;
 
+import 'diagnostic_message.dart' show DiagnosticMessage;
+
 /// True if we should enable colors in output.
 ///
 /// We enable colors only when both [stdout] and [stderr] support ANSI escapes.
 final bool enableTerminalColors = _computeEnableColors();
 
+void printDiagnosticMessage(
+    DiagnosticMessage message, void Function(String) println) {
+  if (enableTerminalColors) {
+    message.ansiFormatted.forEach(println);
+  } else {
+    message.plainTextFormatted.forEach(println);
+  }
+}
+
 /// On Windows, colors are enabled if both stdout and stderr supports ANSI
 /// escapes.  On other platforms, we rely on the external programs `tty` and
 /// `tput` to compute if ANSI colors are supported.

pkg/front_end/lib/src/api_unstable/vm.dart

@@ -2,17 +2,10 @@
 // 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.
 
-import '../api_prototype/diagnostic_message.dart' show DiagnosticMessage;
-
-import '../api_prototype/terminal_color_support.dart' show enableTerminalColors;
-
-import '../fasta/fasta_codes.dart' show FormattedMessage;
-
-export '../api_prototype/compiler_options.dart'
-    show CompilerOptions, ProblemHandler;
+export '../api_prototype/compiler_options.dart' show CompilerOptions;
 
 export '../api_prototype/diagnostic_message.dart'
-    show DiagnosticMessage, DiagnosticMessageHandler;
+    show DiagnosticMessage, DiagnosticMessageHandler, getMessageUri;
 
 export '../api_prototype/file_system.dart'
     show FileSystem, FileSystemEntity, FileSystemException;
@@ -27,6 +20,9 @@ export '../api_prototype/memory_file_system.dart' show MemoryFileSystem;
 
 export '../api_prototype/standard_file_system.dart' show StandardFileSystem;
 
+export '../api_prototype/terminal_color_support.dart'
+    show printDiagnosticMessage;
+
 export '../base/processed_options.dart' show ProcessedOptions;
 
 export '../compute_platform_binaries_location.dart'
@@ -59,14 +55,3 @@ export '../fasta/hybrid_file_system.dart' show HybridFileSystem;
 export '../fasta/kernel/utils.dart' show serializeComponent, serializeProcedure;
 
 export '../fasta/severity.dart' show Severity;
-
-Uri getMessageUri(FormattedMessage message) => message.uri;
-
-void printDiagnosticMessage(
-    DiagnosticMessage message, void Function(String) println) {
-  if (enableTerminalColors) {
-    message.ansiFormatted.forEach(println);
-  } else {
-    message.plainTextFormatted.forEach(println);
-  }
-}

pkg/front_end/lib/src/fasta/fasta_codes.dart

@@ -181,9 +181,6 @@ class FormattedMessage implements DiagnosticMessage {
     // TODO(ahe): Implement this correctly.
     return ansiFormatted;
   }
-
-  @override
-  int get index => code.index;
 }
 
 String relativizeUri(Uri uri) {