feature: include ranged code lines

lib/plugins/tag/include_code.js

@@ -7,6 +7,8 @@ const { highlight } = require('hexo-util');
 
 const rCaptionTitleFile = /(.*)?(?:\s+|^)(\/*\S+)/;
 const rLang = /\s*lang:(\w+)/i;
+const rFrom = /\s*from:(\d+)/i;
+const rTo = /\s*to:(\d+)/i;
 
 /**
 * Include code tag
@@ -28,6 +30,16 @@ module.exports = ctx => function includeCodeTag(args) {
     lang = _lang;
     return '';
   });
+  let from = 0;
+  arg = arg.replace(rFrom, (match, _from) => {
+    from = _from - 1;
+    return '';
+  });
+  let to = Number.MAX_VALUE;
+  arg = arg.replace(rTo, (match, _to) => {
+    to = _to;
+    return '';
+  });
 
   const match = arg.match(rCaptionTitleFile);
 
@@ -59,7 +71,9 @@ module.exports = ctx => function includeCodeTag(args) {
   }).then(code => {
     if (!code) return;
 
-    code = stripIndent(code).trim();
+    code = stripIndent(code);
+    const lines = code.split('\n');
+    code = lines.slice(from, to).join('\n').trim();
 
     if (!config.enable) {
       return `<pre><code>${code}</code></pre>`;

test/scripts/tags/include_code.js

@@ -58,6 +58,49 @@ describe('include_code', () => {
     });
   });
 
+  it('from', () => {
+    const fixture = [
+      '}'
+    ].join('\n');
+    const expected = highlight(fixture, {
+      lang: 'js',
+      caption: '<span>Hello world</span><a href="/downloads/code/test.js">view raw</a>'
+    });
+
+    return code('Hello world lang:js from:3 test.js').then(result => {
+      result.should.eql(expected);
+    });
+  });
+
+  it('to', () => {
+    const fixture = [
+      'if (tired && night){',
+      '  sleep();'
+    ].join('\n');
+    const expected = highlight(fixture, {
+      lang: 'js',
+      caption: '<span>Hello world</span><a href="/downloads/code/test.js">view raw</a>'
+    });
+
+    return code('Hello world lang:js to:2 test.js').then(result => {
+      result.should.eql(expected);
+    });
+  });
+
+  it('from and to', () => {
+    const fixture = [
+      'sleep();'
+    ].join('\n');
+    const expected = highlight(fixture, {
+      lang: 'js',
+      caption: '<span>Hello world</span><a href="/downloads/code/test.js">view raw</a>'
+    });
+
+    return code('Hello world lang:js from:2 to:2 test.js').then(result => {
+      result.should.eql(expected);
+    });
+  });
+
   it('file not found', () => code('nothing').then(result => {
     should.not.exist(result);
   }));