Suggest command based on aliases (#235)

CHANGELOG.md

@@ -1,3 +1,9 @@
+## 2.4.0
+
+* Command suggestions will now also suggest based on aliases of a command.
+* Introduce getter `Command.suggestionAliases` for names that cannot be used as
+  aliases, but will trigger suggestions.
+
 ## 2.3.2
 
 * Require Dart 2.18

lib/command_runner.dart

@@ -220,10 +220,17 @@ class CommandRunner<T> {
         SplayTreeSet<Command<T>>((a, b) => distances[a]! - distances[b]!);
     for (var command in commands) {
       if (command.hidden) continue;
-      var distance = _editDistance(name, command.name);
-      if (distance <= suggestionDistanceLimit) {
-        distances[command] = distance;
-        candidates.add(command);
+      for (var alias in [
+        command.name,
+        ...command.aliases,
+        ...command.suggestionAliases
+      ]) {
+        var distance = _editDistance(name, alias);
+        if (distance <= suggestionDistanceLimit) {
+          distances[command] =
+              math.min(distances[command] ?? distance, distance);
+          candidates.add(command);
+        }
       }
     }
     if (candidates.isEmpty) return '';
@@ -412,6 +419,17 @@ abstract class Command<T> {
   /// This is intended to be overridden.
   List<String> get aliases => const [];
 
+  /// Alternate non-functional names for this command.
+  ///
+  /// These names won't be used in the documentation, and also they won't work
+  /// when invoked on the command line. But if an unknown command is used it
+  /// will be matched against this when creating suggestions.
+  ///
+  /// A name does not have to be repeated both here and in [aliases].
+  ///
+  /// This is intended to be overridden.
+  List<String> get suggestionAliases => const [];
+
   Command() {
     if (!argParser.allowsAnything) {
       argParser.addFlag('help',

pubspec.yaml

@@ -1,5 +1,5 @@
 name: args
-version: 2.3.2
+version: 2.4.0
 description: >-
  Library for defining parsers for parsing raw command-line arguments into a set
  of options and values using GNU and POSIX style options.

test/command_runner_test.dart

@@ -481,6 +481,28 @@ Did you mean one of these?
             throwsUsageException(
                 'Could not find a command named "hidde".', anything));
       });
+
+      test('Suggests based on aliases', () {
+        var command = AliasedCommand();
+        runner.addCommand(command);
+        expect(() => runner.run(['rename']), throwsUsageException('''
+Could not find a command named "rename".
+
+Did you mean one of these?
+  aliased
+''', anything));
+      });
+
+      test('Suggests based on suggestedAliases', () {
+        var command = SuggestionAliasedCommand();
+        runner.addCommand(command);
+        expect(() => runner.run(['renamed']), throwsUsageException('''
+Could not find a command named "renamed".
+
+Did you mean one of these?
+  aliased
+''', anything));
+      });
     });
 
     group('with --help', () {

test/test_utils.dart

@@ -266,7 +266,28 @@ class AliasedCommand extends Command {
   final takesArguments = false;
 
   @override
-  final aliases = const ['alias', 'als'];
+  final aliases = const ['alias', 'als', 'renamed'];
+
+  @override
+  void run() {
+    hasRun = true;
+  }
+}
+
+class SuggestionAliasedCommand extends Command {
+  bool hasRun = false;
+
+  @override
+  final name = 'aliased';
+
+  @override
+  final description = 'Set a value.';
+
+  @override
+  final takesArguments = false;
+
+  @override
+  final suggestionAliases = const ['renamed'];
 
   @override
   void run() {