fix: ArgResults.operator[] should throw Exception not Error

pkgs/args/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 3.0.0
+
+* Breaking: ArgResults.operator[] and ArgResults.option now correctly throw
+  Exceptions rather than Errors when defined arguments are missing values.
+
 ## 2.7.0
 
 * Remove sorting of the `allowedHelp` argument in usage output. Ordering will

pkgs/args/lib/src/arg_results.dart

@@ -5,6 +5,7 @@
 import 'dart:collection';
 
 import 'arg_parser.dart';
+import 'arg_parser_exception.dart';
 
 /// Creates a new [ArgResults].
 ///
@@ -71,7 +72,7 @@ class ArgResults {
 
     final option = _parser.options[name]!;
     if (option.mandatory && !_parsed.containsKey(name)) {
-      throw ArgumentError('Option $name is mandatory.');
+      throw ArgParserException('Option $name is mandatory.');
     }
 
     return option.valueOrDefault(_parsed[name]);
@@ -103,7 +104,7 @@ class ArgResults {
       throw ArgumentError('"$name" is a multi-option.');
     }
     if (option.mandatory && !_parsed.containsKey(name)) {
-      throw ArgumentError('Option $name is mandatory.');
+      throw ArgParserException('Option $name is mandatory.');
     }
     return option.valueOrDefault(_parsed[name]) as String?;
   }

pkgs/args/test/command_runner_test.dart

@@ -2,6 +2,7 @@
 // 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 'package:args/args.dart';
 import 'package:args/command_runner.dart';
 import 'package:test/test.dart';
 
@@ -736,7 +737,7 @@ Run "test help" to see global options.'''));
     runner.addCommand(subcommand);
     expect(
         () => runner.run([subcommand.name]),
-        throwsA(isA<ArgumentError>().having((e) => e.message, 'message',
+        throwsA(isA<ArgParserException>().having((e) => e.message, 'message',
             contains('Option mandatory-option is mandatory'))));
     expect(await runner.run([subcommand.name, '--mandatory-option', 'foo']),
         'foo');

pkgs/args/test/parse_test.dart

@@ -595,7 +595,10 @@ void main() {
           var parser = ArgParser();
           parser.addOption('username', mandatory: true);
           var results = parser.parse([]);
-          expect(() => results['username'], throwsA(isA<ArgumentError>()));
+          expect(
+              () => results['username'],
+              throwsA(isA<ArgParserException>().having((e) => e.message,
+                  'message', 'Option username is mandatory.')));
         });
 
         test('throw if no mandatory args', () {
@@ -604,7 +607,10 @@ void main() {
           parser.addOption('username', mandatory: true);
           var results = parser.parse(['--test', 'test']);
           expect(results['test'], equals('test'));
-          expect(() => results['username'], throwsA(isA<ArgumentError>()));
+          expect(
+              () => results['username'],
+              throwsA(isA<ArgParserException>().having((e) => e.message,
+                  'message', 'Option username is mandatory.')));
         });
 
         test('parse successfully', () {
@@ -620,8 +626,9 @@ void main() {
           parser.addOption('test', mandatory: true);
           var results = parser.parse(['-h']);
           expect(results['help'], true);
-          expect(() => results['test'], throwsA(isA<ArgumentError>()));
-          expect(() => results.option('test'), throwsA(isA<ArgumentError>()));
+          expect(() => results['test'], throwsA(isA<ArgParserException>()));
+          expect(
+              () => results.option('test'), throwsA(isA<ArgParserException>()));
         });
       });
     });