Merge pull request #710 from valterc/fix-line-group-oob

Add line count check to avoid out of range

src/Markdig.Tests/TestStringSliceList.cs

@@ -180,4 +180,39 @@ public class TestStringSliceList
             Assert.AreEqual('\0', iterator.CurrentChar); iterator.SkipChar();
         }
     }
+
+    [Test]
+    public void TestStringLineGroupCharIteratorAtCapacity()
+    {
+        string str = "ABCDEFGHI";
+        var text = new StringLineGroup(1)
+        {
+            // Will store the following line at capacity
+            new StringSlice(str, NewLine.CarriageReturnLineFeed) { Start = 0, End = 2 },
+        };
+
+        var iterator = text.ToCharIterator();
+        var chars = ToString(iterator);
+        TextAssert.AreEqual("ABC\r\n", chars.ToString());
+        TextAssert.AreEqual("ABC", text.ToString());
+    }
+
+    [Test]
+    public void TestStringLineGroupCharIteratorForcingIncreaseCapacity()
+    {
+        string str = "ABCDEFGHI";
+        var text = new StringLineGroup(1)
+        {
+            // Will store the following line at capacity
+            new StringSlice(str, NewLine.CarriageReturnLineFeed) { Start = 0, End = 2 },
+
+            // Will force increase capacity to 2 and store the line at capacity
+            new StringSlice(str, NewLine.CarriageReturnLineFeed) { Start = 3, End = 3 },
+        };
+
+        var iterator = text.ToCharIterator();
+        var chars = ToString(iterator);
+        TextAssert.AreEqual("ABC\r\nD\r\n", chars.ToString());
+        TextAssert.AreEqual("ABC\r\nD", text.ToString());
+    }
 }

src/Markdig.Tests/TestYamlFrontMatterExtension.cs

@@ -83,4 +83,28 @@ public class TestYamlFrontMatterExtension
             return null;
         }
     }
+
+    [TestCase("---\nkey1: value1\nkey2: value2\n---\n\n# Content\n")]
+    [TestCase("---\nkey1: value1\nkey2: value2\nkey3: value3\nkey4: value4\nkey5: value5\nkey6: value6\nkey7: value7\nkey8: value8\n---\n\n# Content\n")]
+    public void FrontMatterBlockLinesCharIterator(string value)
+    {
+        var builder = new MarkdownPipelineBuilder();
+        builder.Extensions.Add(new YamlFrontMatterExtension());
+        var markdownDocument = Markdown.Parse(value, builder.Build());
+
+        var yamlBlocks = markdownDocument.Descendants<YamlFrontMatterBlock>();
+        Assert.True(yamlBlocks.Any());
+
+        foreach (var yamlBlock in yamlBlocks)
+        {
+            var iterator = yamlBlock.Lines.ToCharIterator();
+            while(iterator.CurrentChar != '\0')
+            {
+                iterator.NextChar();
+            }
+        }
+
+        Assert.Pass("No exception parsing and iterating through YAML front matter block lines");
+    }
+
 }

src/Markdig/Helpers/StringLineGroup.cs

@@ -334,9 +334,12 @@ public struct StringLineGroup : IEnumerable
             goto Return;
 
         MoveToNewLine:
-            SliceIndex++;
-            _offset = -1;
-            _currentSlice = _lines.Lines[SliceIndex];
+            if (SliceIndex < _lines.Lines.Length - 1)
+            {
+                SliceIndex++;
+                _offset = -1;
+                _currentSlice = _lines.Lines[SliceIndex];
+            }
 
         Return:
             return CurrentChar;