[messages] Clean up representation of analyzer code.

Changes the code generation logic for messages so that there is no
longer an `analyzerCodes` getter in the `CfeStyleErrorCodeInfo` base
class, because only the derived class `SharedErrorCodeInfo` can have
an analyzer code.

Also, removes the logic that used to exist for allowing a front-end
error code to have multiple analyzer codes. It no longer makes sense
to support this, since instances of `SharedErrorCodeInfo` must always
have exactly one analyzer code.

Finally, removes the unused `analyzerCodes` field from the
`_TemplateCompiler` class.

These clean-ups simplisy the logic for supporting
`SharedErrorCodeInfo.analyzerCode`, so they should make that support
easier to maintain in the future.

Change-Id: I6a6a6964a800f3c01d7585cf2129b5af736b4ca2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/452848
Commit-Queue: Paul Berry <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>

Author: stereotype441

pkg/analyzer_utilities/lib/messages.dart

@@ -233,10 +233,6 @@ class AnalyzerCode implements Comparable<AnalyzerCode> {
 /// In-memory representation of error code information obtained from a
 /// `messages.yaml` file in `pkg/front_end` or `pkg/_fe_analyzer_shared`.
 abstract class CfeStyleErrorCodeInfo extends ErrorCodeInfo {
-  /// The set of analyzer error codes that corresponds to this error code, if
-  /// any.
-  final List<AnalyzerCode> analyzerCodes;
-
   /// The index of the error in the analyzer's `fastaAnalyzerErrorCodes` table.
   final int? index;
 
@@ -245,45 +241,14 @@ abstract class CfeStyleErrorCodeInfo extends ErrorCodeInfo {
   final String? cfeSeverity;
 
   CfeStyleErrorCodeInfo.fromYaml(YamlMap yaml)
-    : analyzerCodes = _decodeAnalyzerCodes(yaml['analyzerCode']),
-      index = _decodeIndex(yaml['index']),
+    : index = _decodeIndex(yaml['index']),
       cfeSeverity = _decodeSeverity(yaml['severity']),
       super.fromYaml(yaml) {
     if (yaml['problemMessage'] == null) {
       throw 'Missing problemMessage';
     }
   }
 
-  static AnalyzerCode _decodeAnalyzerCode(String s) {
-    switch (s.split('.')) {
-      case [var errorName] when errorName == errorName.toUpperCase():
-        return AnalyzerCode(className: null, snakeCaseErrorName: errorName);
-      case [var className, var errorName]
-          when errorName == errorName.toUpperCase():
-        return AnalyzerCode(
-          className: className,
-          snakeCaseErrorName: errorName,
-        );
-      default:
-        throw StateError(
-          'Analyzer codes must take the form DIAGNOSTIC_NAME or '
-          'ClassName.DIAGNOSTIC_NAME. Found ${json.encode(s)} instead.',
-        );
-    }
-  }
-
-  static List<AnalyzerCode> _decodeAnalyzerCodes(Object? value) {
-    if (value == null) {
-      return const [];
-    } else if (value is String) {
-      return [_decodeAnalyzerCode(value)];
-    } else if (value is List) {
-      return [for (var s in value) _decodeAnalyzerCode(s as String)];
-    } else {
-      throw 'Unrecognized analyzer code: $value';
-    }
-  }
-
   static int? _decodeIndex(Object? value) {
     switch (value) {
       case null:
@@ -870,11 +835,11 @@ class FrontEndErrorCodeInfo extends CfeStyleErrorCodeInfo {
   // codes.
   final String? pseudoSharedCode;
 
-  FrontEndErrorCodeInfo.fromYaml(super.yaml)
+  FrontEndErrorCodeInfo.fromYaml(YamlMap yaml)
     : pseudoSharedCode = yaml['pseudoSharedCode'] as String?,
-      super.fromYaml() {
-    if (analyzerCodes.isNotEmpty) {
-      throw StateError('Only shared messages can have analyzer codes');
+      super.fromYaml(yaml) {
+    if (yaml['analyzerCode'] != null) {
+      throw StateError('Only shared messages can have an analyzer code');
     }
     if (index != null) {
       throw StateError('Non-shared messages must not have an index');
@@ -1039,26 +1004,43 @@ class ParsedPlaceholder {
 /// In-memory representation of error code information obtained from the file
 /// `pkg/_fe_analyzer_shared/messages.yaml`.
 class SharedErrorCodeInfo extends CfeStyleErrorCodeInfo {
-  SharedErrorCodeInfo.fromYaml(super.yaml) : super.fromYaml() {
-    if (analyzerCodes.length != 1) {
-      throw StateError('Shared messages must have exactly one analyzerCode');
-    }
-    if (super.index == null) {
-      throw StateError('Shared messages must have an index');
-    }
-  }
-
   /// The analyzer error code that corresponds to this shared error code.
   ///
   /// Shared error codes are required to have exactly one analyzer error code
   /// associated with them.
-  AnalyzerCode get analyzerCode => analyzerCodes.single;
+  final AnalyzerCode analyzerCode;
+
+  SharedErrorCodeInfo.fromYaml(super.yaml)
+    : analyzerCode = _decodeAnalyzerCode(yaml['analyzerCode'] as String),
+      super.fromYaml() {
+    if (super.index == null) {
+      throw StateError('Shared messages must have an index');
+    }
+  }
 
   /// The index of the error in the analyzer's `fastaAnalyzerErrorCodes` table.
   ///
   /// Shared error codes are required to have a non-null index.
   @override
   int get index => super.index!;
+
+  static AnalyzerCode _decodeAnalyzerCode(String s) {
+    switch (s.split('.')) {
+      case [var errorName] when errorName == errorName.toUpperCase():
+        return AnalyzerCode(className: null, snakeCaseErrorName: errorName);
+      case [var className, var errorName]
+          when errorName == errorName.toUpperCase():
+        return AnalyzerCode(
+          className: className,
+          snakeCaseErrorName: errorName,
+        );
+      default:
+        throw StateError(
+          'Analyzer codes must take the form DIAGNOSTIC_NAME or '
+          'ClassName.DIAGNOSTIC_NAME. Found ${json.encode(s)} instead.',
+        );
+    }
+  }
 }
 
 /// Data tables mapping between shared errors and their corresponding

pkg/front_end/test/messages_suite.dart

@@ -198,7 +198,7 @@ class MessageTestSuite extends ChainContext {
       bool includeErrorContext = false;
       List<Example> examples = <Example>[];
       String? externalTest;
-      List<String>? analyzerCodes;
+      String? analyzerCode;
       CfeSeverity? severity;
       YamlNode? badSeverity;
       YamlNode? unnecessarySeverity;
@@ -325,9 +325,12 @@ class MessageTestSuite extends ChainContext {
             break;
 
           case "analyzerCode":
-            analyzerCodes = value is String
-                ? <String>[value]
-                : new List<String>.from(value);
+            if (value is! String) {
+              throw new ArgumentError(
+                'analyzerCode should be a string: $value',
+              );
+            }
+            analyzerCode = value;
             if (!analyzerCodeRequired) {
               throw new ArgumentError(
                 'analyzerCode not allowed in package ${json.encode(package)}',
@@ -706,7 +709,7 @@ class MessageTestSuite extends ChainContext {
         createDescription(
           "analyzerCode",
           null,
-          analyzerCodeRequired && analyzerCodes == null
+          analyzerCodeRequired && analyzerCode == null
               ? (
                   expectation: KnownExpectation.missingAnalyzerCode,
                   message:

pkg/front_end/tool/generate_messages_lib.dart

@@ -168,7 +168,6 @@ class _TemplateCompiler {
   final int? index;
   final String problemMessage;
   final String? correctionMessage;
-  final List<AnalyzerCode> analyzerCodes;
   final String? severity;
   final Map<String, ErrorCodeParameter> parameters;
   final String? pseudoSharedCode;
@@ -199,7 +198,6 @@ class _TemplateCompiler {
     required this.pseudoSharedCodeValues,
   }) : problemMessage = errorCodeInfo.problemMessage,
        correctionMessage = errorCodeInfo.correctionMessage,
-       analyzerCodes = errorCodeInfo.analyzerCodes,
        severity = errorCodeInfo.cfeSeverity,
        parameters = errorCodeInfo.parameters,
        pseudoSharedCode = errorCodeInfo is FrontEndErrorCodeInfo