Add support for commonmark mode

Author: wooorm

index.js

@@ -1,28 +1,35 @@
 'use strict';
 
 var visit = require('unist-util-visit');
+var has = require('has');
 
 module.exports = getDefinitionFactory;
 
 /* Get a definition in `node` by `identifier`. */
-function getDefinitionFactory(node) {
-  return getterFactory(gather(node));
+function getDefinitionFactory(node, options) {
+  return getterFactory(gather(node, options));
 }
 
 /* Gather all definitions in `node` */
-function gather(node) {
+function gather(node, options) {
   var cache = {};
 
   if (!node || !node.type) {
     throw new Error('mdast-util-definitions expected node');
   }
 
-  visit(node, 'definition', check);
+  visit(node, 'definition', options && options.commonmark ? commonmark : normal);
 
   return cache;
 
-  /* Add `definition` to `cache` if it has an identifier. */
-  function check(definition) {
+  function commonmark(definition) {
+    var id = normalise(definition.identifier);
+    if (!has(cache, id)) {
+      cache[id] = definition;
+    }
+  }
+
+  function normal(definition) {
     cache[normalise(definition.identifier)] = definition;
   }
 }
@@ -33,7 +40,8 @@ function getterFactory(cache) {
 
   /* Get a node from the bound definition-cache. */
   function getter(identifier) {
-    return (identifier && cache[normalise(identifier)]) || null;
+    var id = identifier && normalise(identifier);
+    return id && has(cache, id) ? cache[id] : null;
   }
 }
 

package.json

@@ -13,6 +13,7 @@
     "cache"
   ],
   "dependencies": {
+    "has": "^1.0.1",
     "unist-util-visit": "^1.0.0"
   },
   "repository": "https://github.com/wooorm/mdast-util-definitions",

readme.md

@@ -30,13 +30,15 @@ definition('foo');
 
 ## API
 
-### `definitions(node)`
+### `definitions(node[, options])`
 
-Create a cache of all `definition`s in `node`.
+Create a cache of all `definition`s in [`node`][node].
 
-###### Parameters
+###### `options`
 
-*   `node` ([`Node`][node]) — Ancestor of definitions.
+*   `commonmark` (`boolean`, default: false) — Turn on to use CommonMark
+    precedence: ignore later found definitions for duplicate definitions.
+    The default behaviour is to prefer the last found definition.
 
 ###### Returns
 

test.js

@@ -66,5 +66,22 @@ test('mdast-util-definitions', function (t) {
     'should work on weird identifiers when not found'
   );
 
+  tree = remark().parse([
+    '[example]: http://one.com',
+    '[example]: http://two.com'
+  ].join('\n'));
+
+  t.deepEqual(
+    definitions(tree)('example').url,
+    'http://two.com',
+    'should prefer the last of duplicate definitions by default'
+  );
+
+  t.deepEqual(
+    definitions(tree, {commonmark: true})('example').url,
+    'http://one.com',
+    'should prefer the first of duplicate definitions in commonmark mode'
+  );
+
   t.end();
 });