Add support for links to lines

Closes GH-23.

Author: raipc

index.js

@@ -44,6 +44,13 @@ var headingPrefixes = {
   bitbucket: '#markdown-header-'
 }
 
+var lineLinks = {
+  github: true,
+  gitlab: true
+}
+
+var lineExpression = /^#?l\d/i
+
 function validateLinks(options, fileSet) {
   var repo = (options || {}).repository
   var info
@@ -179,7 +186,11 @@ function transformerFactory(fileSet, info) {
     function mark(node) {
       var data = node.data || {}
       var props = data.hProperties || {}
-      var id = props.name || props.id || data.id || slugs.slug(toString(node))
+      var id = props.name || props.id || data.id
+
+      if (!id && node.type === 'heading') {
+        id = slugs.slug(toString(node))
+      }
 
       if (id) {
         landmarks[filePath + '#' + id] = true
@@ -251,6 +262,7 @@ function gatherReferences(file, tree, info, fileSet) {
   var getDefinition = definitions(tree)
   var prefix = ''
   var headingPrefix = '#'
+  var lines
 
   if (info && info.type in viewPaths) {
     prefix = '/' + info.path() + '/' + viewPaths[info.type] + '/'
@@ -260,6 +272,8 @@ function gatherReferences(file, tree, info, fileSet) {
     headingPrefix = headingPrefixes[info.type]
   }
 
+  lines = info && info.type in lineLinks ? lineLinks[info.type] : false
+
   visit(tree, ['link', 'linkReference'], onlink)
 
   return cache
@@ -291,6 +305,10 @@ function gatherReferences(file, tree, info, fileSet) {
     }
 
     if (!uri.hostname) {
+      if (lines && lineExpression.test(uri.hash)) {
+        uri.hash = ''
+      }
+
       /* Handle hashes, or relative files. */
       if (!uri.pathname && uri.hash) {
         link = file.path + uri.hash
@@ -301,6 +319,7 @@ function gatherReferences(file, tree, info, fileSet) {
         if (uri.hash) {
           link += uri.hash
         }
+
         uri = parse(link)
       }
     }
@@ -340,6 +359,10 @@ function gatherReferences(file, tree, info, fileSet) {
     } else {
       pathname = link.slice(0, index)
       hash = link.slice(index + headingPrefix.length)
+
+      if (lines && lineExpression.test(hash)) {
+        hash = null
+      }
     }
 
     if (!cache[pathname]) {
@@ -360,7 +383,7 @@ function gatherReferences(file, tree, info, fileSet) {
   }
 }
 
-/* Utilitity to warn `reason` for each node in `nodes` on `file`. */
+/* Utility to warn `reason` for each node in `nodes` on `file`. */
 function warnAll(file, nodes, reason, ruleId) {
   nodes.forEach(one)
 

test/fixtures/examples/example.js

@@ -0,0 +1 @@
+console.log('Hello world!')

test/fixtures/line-links.md

@@ -0,0 +1,9 @@
+# Source Code Link
+
+Link to [a line](./examples/example.js#L1)
+
+Link to [a line in a missing file](./examples/missing.js#L1)
+
+[a](https://github.com/wooorm/test/blob/master/examples/example.js#L1).
+
+[b](https://github.com/wooorm/test/blob/master/examples/missing.js#L1).

test/index.js

@@ -445,5 +445,29 @@ test('remark-validate-links', function(t) {
     }, st.error)
   })
 
+  t.test('should recognize github links to particular lines', function(st) {
+    st.plan(1)
+
+    execa(bin, [
+      '--no-config',
+      '--no-ignore',
+      '--use',
+      '../..=repository:"wooorm/test"',
+      'line-links.md'
+    ]).then(function(result) {
+      st.equal(
+        strip(result.stderr),
+        [
+          'line-links.md',
+          '  5:9-5:61  warning  Link to unknown file: `examples/missing.js`  missing-file  remark-validate-links',
+          '  9:1-9:71  warning  Link to unknown file: `examples/missing.js`  missing-file  remark-validate-links',
+          '',
+          '⚠ 2 warnings'
+        ].join('\n'),
+        'should report'
+      )
+    }, st.error)
+  })
+
   t.end()
 })