Fix JSON strict violation error to match native parse error

HISTORY.md

@@ -1,6 +1,7 @@
 unreleased
 ==========
 
+  * Fix JSON strict violation error to match native parse error
   * deps: [email protected]
   * deps: [email protected]
   * deps: depd@~1.1.1

lib/types/json.js

@@ -80,7 +80,7 @@ function json (options) {
 
       if (first !== '{' && first !== '[') {
         debug('strict violation')
-        throw new SyntaxError('Unexpected token ' + first)
+        throw createStrictSyntaxError(body, first)
       }
     }
 
@@ -133,6 +133,27 @@ function json (options) {
   }
 }
 
+/**
+ * Create strict violation syntax error matching native error.
+ *
+ * @param {string} str
+ * @param {string} char
+ * @return {Error}
+ * @private
+ */
+
+function createStrictSyntaxError (str, char) {
+  var index = str.indexOf(char)
+  var partial = str.substring(0, index) + '#'
+
+  try {
+    JSON.parse(partial); /* istanbul ignore next */ throw new SyntaxError('strict violation')
+  } catch (e) {
+    e.message = e.message.replace('#', char)
+    return e
+  }
+}
+
 /**
  * Get the first non-whitespace character in a string.
  *

test/json.js

@@ -20,7 +20,7 @@ describe('bodyParser.json()', function () {
     .post('/')
     .set('Content-Type', 'application/json')
     .send('{"user"')
-    .expect(400, /unexpected end/i, done)
+    .expect(400, parseError('{"user"'), done)
   })
 
   it('should handle Content-Length: 0', function (done) {
@@ -52,7 +52,7 @@ describe('bodyParser.json()', function () {
     .post('/')
     .set('Content-Type', 'application/json')
     .send('{:')
-    .expect(400, /unexpected token/i, done)
+    .expect(400, parseError('{:'), done)
   })
 
   it('should 400 when invalid content-length', function (done) {
@@ -106,15 +106,15 @@ describe('bodyParser.json()', function () {
       .post('/')
       .set('Content-Type', 'application/json')
       .send('true')
-      .expect(400, /unexpected token/i, done)
+      .expect(400, parseError('#rue').replace('#', 't'), done)
     })
 
     it('should not parse primitives with leading whitespaces', function (done) {
       request(server)
       .post('/')
       .set('Content-Type', 'application/json')
       .send('    true')
-      .expect(400, /unexpected token/i, done)
+      .expect(400, parseError('    #rue').replace('#', 't'), done)
     })
 
     it('should allow leading whitespaces in JSON', function (done) {
@@ -132,7 +132,7 @@ describe('bodyParser.json()', function () {
       .post('/')
       .set('Content-Type', 'application/json')
       .send('true')
-      .expect(400, /unexpected token/i, done)
+      .expect(400, parseError('#rue').replace('#', 't'), done)
     })
   })
 
@@ -487,3 +487,11 @@ function createServer (opts) {
     })
   })
 }
+
+function parseError (str) {
+  try {
+    JSON.parse(str); throw new SyntaxError('strict violation')
+  } catch (e) {
+    return e.message
+  }
+}