feat!: resolve extension conflicts with mime-score, close #116

index.js

@@ -14,6 +14,7 @@
 
 var db = require('mime-db')
 var extname = require('path').extname
+var mimeScore = require('./mimeScore')
 
 /**
  * Module variables.
@@ -171,11 +172,11 @@ function populateMaps (extensions, types) {
       var extension = exts[i]
 
       if (types[extension]) {
-        var from = preference.indexOf(db[types[extension]].source)
-        var to = preference.indexOf(mime.source)
+        var from = mimeScore(types[extension])
+        var to = mimeScore(type)
 
         if (types[extension] !== 'application/octet-stream' &&
-          (from > to || (from === to && types[extension].slice(0, 12) === 'application/'))) {
+        from > to) {
           // skip the remapping
           continue
         }

mimeScore.js

@@ -0,0 +1,48 @@
+// 'mime-score' back-ported to CommonJS
+
+// Score RFC facets (see https://tools.ietf.org/html/rfc6838#section-3)
+var FACET_SCORES = {
+  'prs.': 100,
+  'x-': 200,
+  'x.': 300,
+  'vnd.': 400,
+  default: 900,
+}
+
+// Score mime source (Logic originally from `jshttp/mime-types` module)
+var SOURCE_SCORES = {
+  nginx: 10,
+  apache: 20,
+  iana: 40,
+  default: 30, // definitions added by `jshttp/mime-db` project?
+}
+
+var TYPE_SCORES = {
+  // prefer application/xml over text/xml
+  // prefer application/rtf over text/rtf
+  application: 1,
+
+  // prefer font/woff over application/font-woff
+  font: 2,
+
+  default: 0,
+}
+
+/**
+ * Get each component of the score for a mime type.  The sum of these is the
+ * total score.  The higher the score, the more "official" the type.
+ */
+module.exports = function mimeScore(mimeType, source = 'default') {
+  let [type, subtype] = mimeType.split('/')
+
+  const facet = subtype.replace(/(\.|x-).*/, '$1')
+
+  const facetScore = FACET_SCORES[facet] || FACET_SCORES.default
+  const sourceScore = SOURCE_SCORES[source] || SOURCE_SCORES.default
+  const typeScore = TYPE_SCORES[type] || TYPE_SCORES.default
+
+  // All else being equal prefer shorter types
+  const lengthScore = 1 - mimeType.length / 100
+
+  return facetScore + sourceScore + typeScore + lengthScore
+}

test/test.js

@@ -1,4 +1,3 @@
-
 var assert = require('assert')
 var mimeTypes = require('..')
 
@@ -220,7 +219,23 @@ describe('mimeTypes', function () {
       })
 
       it('should return mime type when there is extension, but no path', function () {
-        assert.strictEqual(mimeTypes.lookup('.config.json'), 'application/json')
+        assert.strictEqual(
+          mimeTypes.lookup('.config.json'),
+          'application/json'
+        )
+      })
+    })
+
+    describe('extension conflicts', function () {
+      it('should use mime-score', function () {
+        // Test extension conflicts where the lookup has changed as a result of the switch to mime-score
+        assert.strictEqual(mimeTypes.lookup('exe'), 'application/x-msdownload') // was application/x-msdos-program
+        assert.strictEqual(mimeTypes.lookup('prc'), 'application/x-pilot') // was application/x-mobipocket-ebook
+        assert.strictEqual(mimeTypes.lookup('mp3'), 'audio/mp3') // was audio/mpeg
+        assert.strictEqual(mimeTypes.lookup('wav'), 'audio/wav') // was audio/wave
+        assert.strictEqual(mimeTypes.lookup('ra'), 'audio/x-realaudio') // was audio/x-pn-realaudio
+        assert.strictEqual(mimeTypes.lookup('x3db'), 'model/x3d+binary') // was model/x3d+fastinfoset
+        assert.strictEqual(mimeTypes.lookup('jpm'), 'video/jpm') // was image/jpm
       })
     })
   })