Added option for custom JSON parser, and test cases for json reviver …

…option and custom parser option

README.md

@@ -89,6 +89,14 @@ specifies the number of bytes; if it is a string, the value is passed to the
 [bytes](https://www.npmjs.com/package/bytes) library for parsing. Defaults
 to `'100kb'`.
 
+##### parser
+
+The `parser` option can be used to supply a custom JSON parser used to 
+convert the request body to a Javascript object. If a `reviver` is 
+supplied, it is supplied as the second argument to this function.
+
+Defaults to `JSON.parse`.
+
 ##### reviver
 
 The `reviver` option is passed directly to `JSON.parse` as the second

lib/types/json.js

@@ -57,6 +57,7 @@ function json (options) {
     ? bytes.parse(opts.limit || '100kb')
     : opts.limit
   var inflate = opts.inflate !== false
+  var parser = opts.parser || JSON.parse
   var reviver = opts.reviver
   var strict = opts.strict !== false
   var type = opts.type || 'application/json'
@@ -89,12 +90,18 @@ function json (options) {
 
     try {
       debug('parse json')
-      return JSON.parse(body, reviver)
+      return parser(body, reviver)
     } catch (e) {
-      throw normalizeJsonSyntaxError(e, {
-        message: e.message,
-        stack: e.stack
-      })
+      // Only normalize errors if using default parser
+      // Custom parsers might throw custom errors
+      if (parser === JSON.parse) {
+        throw normalizeJsonSyntaxError(e, {
+          message: e.message,
+          stack: e.stack
+        })
+      } else {
+        throw e
+      }
     }
   }
 

test/json.js

@@ -305,6 +305,38 @@ describe('bodyParser.json()', function () {
     })
   })
 
+  describe('with reviver option', function () {
+    it('should use custom reviver', function (done) {
+      request(createServer({
+        reviver: function () {
+          return 'bar'
+        }
+      }))
+        .post('/')
+        .set('Content-Type', 'application/json')
+        .send('{"foo":""}')
+        .expect(200, '"bar"', done)
+    })
+
+  })
+
+  describe('with parser option', function () {
+    it('should use custom parser and pass reviver to it', function (done) {
+      request(createServer({
+        parser: function (body, reviver) {
+          return { foo: reviver() }
+        },
+        reviver: function () {
+          return 'bar'
+        }
+      }))
+        .post('/')
+        .set('Content-Type', 'application/json')
+        .send('{"str":""}')
+        .expect(200, '{"foo":"bar"}', done)
+    })
+  })
+
   describe('with type option', function () {
     describe('when "application/vnd.api+json"', function () {
       before(function () {