Allow spaces when tokenizing option-value

Previous behavior split the incoming token long-name value using the equal sign as the separator.
This would cause an option's value containing spaces to get truncated.
New behavior does regex. match to make sure format is correct and gets the full value.

Author: billbogaiv

src/CommandLine/Core/Tokenizer.cs

@@ -6,6 +6,7 @@
 using CommandLine.Infrastructure;
 using CSharpx;
 using RailwaySharp.ErrorHandling;
+using System.Text.RegularExpressions;
 
 namespace CommandLine.Core
 {
@@ -188,9 +189,19 @@ private static IEnumerable<Token> TokenizeLongName(
                     onError(new BadFormatTokenError(value));
                     yield break;
                 }
-                var parts = text.Split('=');
-                yield return Token.Name(parts[0]);
-                yield return Token.Value(parts[1], true);
+
+                var tokenMatch = Regex.Match(text, "^([^=]+)=([^ ].*)$");
+
+                if (tokenMatch.Success)
+                {
+                    yield return Token.Name(tokenMatch.Groups[1].Value);
+                    yield return Token.Value(tokenMatch.Groups[2].Value, true);
+                }
+                else
+                {
+                    onError(new BadFormatTokenError(value));
+                    yield break;
+                }
             }
         }
     }

tests/CommandLine.Tests/Unit/Core/TokenizerTests.cs

@@ -92,6 +92,41 @@ public void Normalize_should_remove_all_value_with_explicit_assignment_of_existi
 
             // Teardown
         }
+
+        [Fact]
+        public void Should_properly_parse_option_with_equals_in_value()
+        {
+            /**
+             * This is how the arg. would look in `static void Main(string[] args)`
+             * if passed from the command-line and the option-value wrapped in quotes.
+             * Ex.) ./app --connectionString="Server=localhost;Data Source..."
+             */
+            var args = new[] { "--connectionString=Server=localhost;Data Source=(LocalDB)\v12.0;Initial Catalog=temp;" };
+
+            var result = Tokenizer.Tokenize(args, name => NameLookupResult.OtherOptionFound, token => token);
+
+            var tokens = result.SucceededWith();
+
+            Assert.NotNull(tokens);
+            Assert.Equal(2, tokens.Count());
+            Assert.Equal("connectionString", tokens.First().Text);
+            Assert.Equal("Server=localhost;Data Source=(LocalDB)\v12.0;Initial Catalog=temp;", tokens.Last().Text);
+        }
+
+        [Fact]
+        public void Should_return_error_if_option_format_with_equals_is_not_correct()
+        {
+            var args = new[] { "--option1 = fail", "--option2= fail" };
+
+            var result = Tokenizer.Tokenize(args, name => NameLookupResult.OtherOptionFound, token => token);
+
+            var tokens = result.SuccessfulMessages();
+
+            Assert.NotNull(tokens);
+            Assert.Equal(2, tokens.Count());
+            Assert.Equal(ErrorType.BadFormatTokenError, tokens.First().Tag);
+            Assert.Equal(ErrorType.BadFormatTokenError, tokens.Last().Tag);
+        }
     }
 
 }