Fix emoji parsing and allow them only if they are surrounded by spaces (issue #15)

src/Markdig.Tests/Specs/EmojiSpecs.md

@@ -11,3 +11,11 @@ This is a test with a :) and a :angry: smiley
 .
 <p>This is a test with a 😃 and a 😠 smiley</p>
 ````````````````````````````````
+
+An emoji needs to be preceded by a space and followed by a space:
+
+```````````````````````````````` example
+These are not:) an :)emoji with a:) x:angry:x
+.
+<p>These are not:) an :)emoji with a:) x:angry:x</p>
+````````````````````````````````

src/Markdig.Tests/Specs/Specs.cs

@@ -5387,8 +5387,8 @@ namespace Markdig.Tests
 			TestParser.TestSpec("    > # Foo\n    > bar\n    > baz", "<pre><code>&gt; # Foo\n&gt; bar\n&gt; baz\n</code></pre>", "");
         }
     }
-        // The Laziness clause allows us to omit the `>` before a
-        // paragraph continuation line:
+        // The Laziness clause allows us to omit the `>` before
+        // [paragraph continuation text]:
     [TestFixture]
     public partial class TestContainerblocksBlockquotes
     {
@@ -5561,8 +5561,8 @@ namespace Markdig.Tests
 			TestParser.TestSpec("> ```\nfoo\n```", "<blockquote>\n<pre><code></code></pre>\n</blockquote>\n<p>foo</p>\n<pre><code></code></pre>", "");
         }
     }
-        // Note that in the following case, we have a paragraph
-        // continuation line:
+        // Note that in the following case, we have a [lazy
+        // continuation line]:
     [TestFixture]
     public partial class TestContainerblocksBlockquotes
     {
@@ -5595,7 +5595,7 @@ namespace Markdig.Tests
         //
         // the `- bar` is indented too far to start a list, and can't
         // be an indented code block because indented code blocks cannot
-        // interrupt paragraphs, so it is a [paragraph continuation line].
+        // interrupt paragraphs, so it is [paragraph continuation text].
         //
         // A block quote can be empty:
     [TestFixture]
@@ -13868,7 +13868,7 @@ namespace Markdig.Tests
         // [link reference definition] elsewhere in the
         // document and is not followed by `[]` or a link label.
         // The contents of the first link label are parsed as inlines,
-        // which are used as the link's text.  the link's URI and title
+        // which are used as the link's text.  The link's URI and title
         // are provided by the matching link reference definition.
         // Thus, `[foo]` is equivalent to `[foo][]`.
     [TestFixture]
@@ -17978,6 +17978,26 @@ namespace Markdig.Tests
             Console.WriteLine("Example {0}" + Environment.NewLine + "Section: {0}" + Environment.NewLine, 1, "Extensions Emoji");
 			TestParser.TestSpec("This is a test with a :) and a :angry: smiley", "<p>This is a test with a 😃 and a 😠 smiley</p>", "emojis");
         }
+    }
+        // An emoji needs to be preceded by a space and followed by a space
+    [TestFixture]
+    public partial class TestExtensionsEmoji
+    {
+        [Test]
+        public void Example002()
+        {
+            // Example 2
+            // Section: Extensions Emoji
+            //
+            // The following CommonMark:
+            //     These are not:) an :)emoji with a:) x:angry:x
+            //
+            // Should be rendered as:
+            //     <p>These are not:) an :)emoji with a:) x:angry:x</p>
+
+            Console.WriteLine("Example {0}" + Environment.NewLine + "Section: {0}" + Environment.NewLine, 2, "Extensions Emoji");
+			TestParser.TestSpec("These are not:) an :)emoji with a:) x:angry:x", "<p>These are not:) an :)emoji with a:) x:angry:x</p>", "emojis");
+        }
     }
         // # Extensions
         //

src/Markdig/Extensions/Emoji/EmojiParser.cs

@@ -67,18 +67,34 @@ namespace Markdig.Extensions.Emoji
         public override bool Match(InlineProcessor processor, ref StringSlice slice)
         {
             string match;
+
+            // Previous char must be a space
+            if (!slice.PeekCharExtra(-1).IsWhiteSpaceOrZero())
+            {
+                return false;
+            }
+
+            // Try to match an existing emoji
             var startPosition = slice.Start;
             if (!textMatchHelper.TryMatch(slice.Text, slice.Start, slice.Length, out match))
             {
                 return false;
             }
 
+            // Following char must be a space
+            if (!slice.PeekCharExtra(match.Length).IsWhiteSpaceOrZero())
+            {
+                return false;
+            }
+
+            // If we have a smiley, we decode it to emoji
             string emoji;
             if (!SmileyToEmoji.TryGetValue(match, out emoji))
             {
                 emoji = match;
             }
 
+            // Decode the eomji to unicode
             string unicode;
             if (!EmojiToUnicode.TryGetValue(emoji, out unicode))
             {