Add CJK-friendly Emphasis Extension

readme.md

@@ -51,6 +51,7 @@ You can **try Markdig online** and compare it to other implementations on [babel
   - [**Diagrams**](src/Markdig.Tests/Specs/DiagramsSpecs.md) extension whenever a fenced code block contains a special keyword, it will be converted to a div block with the content as-is (currently, supports [`mermaid`](https://mermaid.js.org) and [`nomnoml`](https://github.com/skanaar/nomnoml) diagrams)
   - [**YAML Front Matter**](src/Markdig.Tests/Specs/YamlSpecs.md) to parse without evaluating the front matter and to discard it from the HTML output (typically used for previewing without the front matter in MarkdownEditor)
   - [**JIRA links**](src/Markdig.Tests/Specs/JiraLinks.md) to automatically generate links for JIRA project references (Thanks to @clarkd: https://github.com/clarkd/MarkdigJiraLinker)
+  - [**CJK-friendly Emphasis**](src/Markdig.Tests/Specs/CJKFriendlyEmphasis.md) to mitigate a CommonMark specification issue in CJK languages (Thanks to @tats-u: https://github.com/tats-u/markdown-cjk-friendly)
 - Starting with Markdig version `0.20.0+`, Markdig is compatible only with `NETStandard 2.0`, `NETStandard 2.1`, `NETCoreApp 2.1` and `NETCoreApp 3.1`.
 
 If you are looking for support for an old .NET Framework 3.5 or 4.0, you can download Markdig `0.18.3`.

src/Markdig.Tests/Specs/CJKFriendlyEmphasis.generated.cs

@@ -0,0 +1,67 @@
+
+// --------------------------------
+//       CJK-friendly Emphasis
+// --------------------------------
+
+using System;
+using NUnit.Framework;
+
+namespace Markdig.Tests.Specs.CJKFriendlyEmphasis
+{
+    [TestFixture]
+    public class TestCJKFriendlyEmphasisExtension
+    {
+        // ## CJK-friendly Emphasis Extension
+        // 
+        // See https://github.com/tats-u/markdown-cjk-friendly/blob/main/specification.md for details about the spec of this extension.
+        // 
+        // This extension drastically mitigates [the long-standing issue (specification flaw)](https://github.com/commonmark/commonmark-spec/issues/650) in CommonMark that emphasis in CJK languages is often not parsed as expected.
+        // 
+        // The plain CommonMark cannot recognize even the following emphasis in CJK languages:
+        [Test]
+        public void CJKFriendlyEmphasisExtension_Example001()
+        {
+            // Example 1
+            // Section: CJK-friendly Emphasis Extension
+            //
+            // The following Markdown:
+            //     **この文を強調できますか（Can I emphasize this sentence）？**残念ながらこの文のせいでできません（Unfortunately not possible due to this sentence）。
+            //
+            // Should be rendered as:
+            //     <p><strong>この文を強調できますか（Can I emphasize this sentence）？</strong>残念ながらこの文のせいでできません（Unfortunately not possible due to this sentence）。</p>
+
+            TestParser.TestSpec("**この文を強調できますか（Can I emphasize this sentence）？**残念ながらこの文のせいでできません（Unfortunately not possible due to this sentence）。", "<p><strong>この文を強調できますか（Can I emphasize this sentence）？</strong>残念ながらこの文のせいでできません（Unfortunately not possible due to this sentence）。</p>", "cjk-friendly-emphasis", context: "Example 1\nSection CJK-friendly Emphasis Extension\n");
+        }
+
+        // ````````````````````````````````` example
+        // 我可以强调**这个`code`**吗（Can I emphasize **this `code`**）？
+        // .
+        // <p>我可以强调<code>这个`code`</code>吗（Can I emphasize <strong>this <code>code</code></strong>）？</p>
+        // `````````````````````````````````
+        [Test]
+        public void CJKFriendlyEmphasisExtension_Example002()
+        {
+            // Example 2
+            // Section: CJK-friendly Emphasis Extension
+            //
+            // The following Markdown:
+            //     **이 용어(This term)**를 강조해 주세요. (Please emphasize **this term**.)
+            //
+            // Should be rendered as:
+            //     <p><strong>이 용어(This term)</strong>를 강조해 주세요. (Please emphasize <strong>this term</strong>.)</p>
+
+            TestParser.TestSpec("**이 용어(This term)**를 강조해 주세요. (Please emphasize **this term**.)", "<p><strong>이 용어(This term)</strong>를 강조해 주세요. (Please emphasize <strong>this term</strong>.)</p>", "cjk-friendly-emphasis", context: "Example 2\nSection CJK-friendly Emphasis Extension\n");
+        }
+        // You can compare the results with and without this extension: https://tats-u.github.io/markdown-cjk-friendly/?sc8=KirjgZPjga7mlofjgpLlvLfoqr_jgafjgY3jgb7jgZnjgYvvvIhDYW4gSSBlbXBoYXNpemUgdGhpcyBzZW50ZW5jZe-8ie-8nyoq5q6L5b-144Gq44GM44KJ44GT44Gu5paH44Gu44Gb44GE44Gn44Gn44GN44G-44Gb44KT77yIVW5mb3J0dW5hdGVseSBub3QgcG9zc2libGUgZHVlIHRvIHRoaXMgc2VudGVuY2XvvInjgIIKCuaIkeWPr-S7peW8uuiwgyoq6L-Z5LiqYGNvZGVgKirlkJfvvIhDYW4gSSBlbXBoYXNpemUgKip0aGlzIGBjb2RlYCoq77yJ77yfCgoqKuydtCDsmqnslrQoVGhpcyB0ZXJtKSoq66W8IOqwleyhsO2VtCDso7zshLjsmpQuIChQbGVhc2UgZW1waGFzaXplICoqdGhpcyB0ZXJtKiouKQo&gfm=1&engine=markdown-it
+        // 
+        // You will find how poor the plain CommonMark is for CJK languages.
+        // 
+        // To use this extension, configure the pipeline as follows:
+        // 
+        // ```csharp
+        // var pipeline = new MarkdownPipelineBuilder()
+        //     .UseCJKFriendlyEmphasis() // Add this
+        //     .Build();
+        // ```
+    }
+}

src/Markdig.Tests/Specs/CJKFriendlyEmphasis.md

@@ -0,0 +1,37 @@
+## CJK-friendly Emphasis Extension
+
+See https://github.com/tats-u/markdown-cjk-friendly/blob/main/specification.md for details about the spec of this extension.
+
+This extension drastically mitigates [the long-standing issue (specification flaw)](https://github.com/commonmark/commonmark-spec/issues/650) in CommonMark that emphasis in CJK languages is often not parsed as expected.
+
+The plain CommonMark cannot recognize even the following emphasis in CJK languages:
+
+```````````````````````````````` example
+**この文を強調できますか（Can I emphasize this sentence）？**残念ながらこの文のせいでできません（Unfortunately not possible due to this sentence）。
+.
+<p><strong>この文を強調できますか（Can I emphasize this sentence）？</strong>残念ながらこの文のせいでできません（Unfortunately not possible due to this sentence）。</p>
+````````````````````````````````
+
+````````````````````````````````` example
+我可以强调**这个`code`**吗（Can I emphasize **this `code`**）？
+.
+<p>我可以强调<code>这个`code`</code>吗（Can I emphasize <strong>this <code>code</code></strong>）？</p>
+`````````````````````````````````
+
+```````````````````````````````` example
+**이 용어(This term)**를 강조해 주세요. (Please emphasize **this term**.)
+.
+<p><strong>이 용어(This term)</strong>를 강조해 주세요. (Please emphasize <strong>this term</strong>.)</p>
+````````````````````````````````
+
+You can compare the results with and without this extension: https://tats-u.github.io/markdown-cjk-friendly/?sc8=KirjgZPjga7mlofjgpLlvLfoqr_jgafjgY3jgb7jgZnjgYvvvIhDYW4gSSBlbXBoYXNpemUgdGhpcyBzZW50ZW5jZe-8ie-8nyoq5q6L5b-144Gq44GM44KJ44GT44Gu5paH44Gu44Gb44GE44Gn44Gn44GN44G-44Gb44KT77yIVW5mb3J0dW5hdGVseSBub3QgcG9zc2libGUgZHVlIHRvIHRoaXMgc2VudGVuY2XvvInjgIIKCuaIkeWPr-S7peW8uuiwgyoq6L-Z5LiqYGNvZGVgKirlkJfvvIhDYW4gSSBlbXBoYXNpemUgKip0aGlzIGBjb2RlYCoq77yJ77yfCgoqKuydtCDsmqnslrQoVGhpcyB0ZXJtKSoq66W8IOqwleyhsO2VtCDso7zshLjsmpQuIChQbGVhc2UgZW1waGFzaXplICoqdGhpcyB0ZXJtKiouKQo&gfm=1&engine=markdown-it
+
+You will find how poor the plain CommonMark is for CJK languages.
+
+To use this extension, configure the pipeline as follows:
+
+```csharp
+var pipeline = new MarkdownPipelineBuilder()
+    .UseCJKFriendlyEmphasis() // Add this
+    .Build();
+```

src/Markdig.Tests/Specs/readme.md

@@ -32,5 +32,6 @@ You will find from the following links the supported extensions in markdig and t
   - [**Diagrams**](DiagramsSpecs.md)
   - [**YAML frontmatter**](YamlSpecs.md)
   - [**JIRA links**](JiraLinks.md)
+  - [**CJK-friendly Emphasis**](CJKFriendlyEmphasis.md)
 
    > Notice that the links above are not yet the final documentation but are "specification" files used for testing the correctness of markdig for each extension