From 1447c8a40aad7fe475293728c2e9cd8df527e7bc Mon Sep 17 00:00:00 2001
From: Anton Wilhelm <timaschew@users.noreply.github.com>
Date: Wed, 23 Jan 2019 03:54:50 +0100
Subject: [PATCH] feat: Provide code fragments feature (#748)

---
 docs/_media/example.js      | 16 ++++++++++++++++
 docs/embed-files.md         | 15 +++++++++++++++
 src/core/render/compiler.js |  1 +
 src/core/render/embed.js    |  5 +++++
 4 files changed, 37 insertions(+)
 create mode 100644 docs/_media/example.js

diff --git a/docs/_media/example.js b/docs/_media/example.js
new file mode 100644
index 000000000..7b6f668cc
--- /dev/null
+++ b/docs/_media/example.js
@@ -0,0 +1,16 @@
+import fetch from 'fetch'
+
+const URL = 'https://example.com'
+const PORT = 8080
+
+/// [demo]
+const result = fetch(`${URL}:${PORT}`)
+  .then(function(response) {
+    return response.json();
+  })
+  .then(function(myJson) {
+    console.log(JSON.stringify(myJson));
+  });
+/// [demo]
+
+result.then(console.log).catch(console.error)
diff --git a/docs/embed-files.md b/docs/embed-files.md
index a935dd374..dab2efe4e 100644
--- a/docs/embed-files.md
+++ b/docs/embed-files.md
@@ -39,6 +39,21 @@ You will get it
 
 [filename](_media/example.md ':include :type=code')
 
+## Embedded code fragments
+Sometimes you don't want to embed a whole file. Maybe because you need just a few lines but you want to compile and test the file in CI.
+
+```markdown
+[filename](_media/example.js ':include :type=code :fragment=demo')
+```
+
+In your code file you need to surround the fragment between `/// [demo]` lines (before and after the fragment).  
+Alternatively you can use `### [demo]`.
+
+Example:
+
+[filename](_media/example.js ':include :type=code :fragment=demo')
+
+
 ## Tag attribute
 
 If you embed the file as `iframe`, `audio` and `video`, then you may need to set the attributes of these tags.
diff --git a/src/core/render/compiler.js b/src/core/render/compiler.js
index 9d6536d0f..b086b1476 100644
--- a/src/core/render/compiler.js
+++ b/src/core/render/compiler.js
@@ -164,6 +164,7 @@ export class Compiler {
         embed = compileMedia[type].call(this, href, title)
         embed.type = type
       }
+      embed.fragment = config.fragment
 
       return embed
     }
diff --git a/src/core/render/embed.js b/src/core/render/embed.js
index 85afbe646..821837488 100644
--- a/src/core/render/embed.js
+++ b/src/core/render/embed.js
@@ -20,6 +20,11 @@ function walkFetchEmbed({embedTokens, compile, fetch}, cb) {
           if (token.embed.type === 'markdown') {
             embedToken = compile.lexer(text)
           } else if (token.embed.type === 'code') {
+            if (token.embed.fragment) {
+              const fragment = token.embed.fragment
+              const pattern = new RegExp(`(?:###|\\/\\/\\/)\\s*\\[${fragment}\\]([\\s\\S]*)(?:###|\\/\\/\\/)\\s*\\[${fragment}\\]`)
+              text = ((text.match(pattern) || [])[1] || '').trim()
+            }
             embedToken = compile.lexer(
               '```' +
                 token.embed.lang +