From decb887b0a35fa8fd758cc1e3a08341e99441d12 Mon Sep 17 00:00:00 2001
From: Patrik Svensson <patrik@patriksvensson.se>
Date: Wed, 26 Aug 2020 21:15:52 +0200
Subject: [PATCH] Throw if markup contains unescaped close tag

---
 src/Spectre.Console.Tests/Unit/MarkupTests.cs | 40 +++++++++++++++++++
 .../Internal/Text/Markup/MarkupTokenizer.cs   | 26 ++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 src/Spectre.Console.Tests/Unit/MarkupTests.cs

diff --git a/src/Spectre.Console.Tests/Unit/MarkupTests.cs b/src/Spectre.Console.Tests/Unit/MarkupTests.cs
new file mode 100644
index 0000000..4909570
--- /dev/null
+++ b/src/Spectre.Console.Tests/Unit/MarkupTests.cs
@@ -0,0 +1,40 @@
+using System;
+using Shouldly;
+using Xunit;
+
+namespace Spectre.Console.Tests.Unit
+{
+    public sealed class MarkupTests
+    {
+        [Theory]
+        [InlineData("Hello [[ World ]")]
+        [InlineData("Hello [[ World ] !")]
+        public void Should_Throw_If_Closing_Tag_Is_Not_Properly_Escaped(string input)
+        {
+            // Given
+            var fixture = new PlainConsole();
+
+            // When
+            var result = Record.Exception(() => new Markup(input));
+
+            // Then
+            result.ShouldNotBeNull();
+            result.ShouldBeOfType<InvalidOperationException>();
+            result.Message.ShouldBe("Encountered unescaped ']' token at position 16");
+        }
+
+        [Fact]
+        public void Should_Escape_Markup_Blocks_As_Expected()
+        {
+            // Given
+            var fixture = new PlainConsole();
+            var markup = new Markup("Hello [[ World ]] !");
+
+            // When
+            fixture.Render(markup);
+
+            // Then
+            fixture.Output.ShouldBe("Hello [ World ] !");
+        }
+    }
+}
diff --git a/src/Spectre.Console/Internal/Text/Markup/MarkupTokenizer.cs b/src/Spectre.Console/Internal/Text/Markup/MarkupTokenizer.cs
index 5737a8a..228ce85 100644
--- a/src/Spectre.Console/Internal/Text/Markup/MarkupTokenizer.cs
+++ b/src/Spectre.Console/Internal/Text/Markup/MarkupTokenizer.cs
@@ -91,6 +91,8 @@ namespace Spectre.Console.Internal
             {
                 var position = _reader.Position;
                 var builder = new StringBuilder();
+
+                var encounteredClosing = false;
                 while (!_reader.Eof)
                 {
                     current = _reader.Peek();
@@ -98,10 +100,34 @@ namespace Spectre.Console.Internal
                     {
                         break;
                     }
+                    else if (current == ']')
+                    {
+                        if (encounteredClosing)
+                        {
+                            _reader.Read();
+                            encounteredClosing = false;
+                            continue;
+                        }
+
+                        encounteredClosing = true;
+                    }
+                    else
+                    {
+                        if (encounteredClosing)
+                        {
+                            throw new InvalidOperationException(
+                                $"Encountered unescaped ']' token at position {_reader.Position}");
+                        }
+                    }
 
                     builder.Append(_reader.Read());
                 }
 
+                if (encounteredClosing)
+                {
+                    throw new InvalidOperationException($"Encountered unescaped ']' token at position {_reader.Position}");
+                }
+
                 Current = new MarkupToken(MarkupTokenKind.Text, builder.ToString(), position);
                 return true;
             }