patch 7.4.1278

Problem:    When jsonencode() fails it still returns something.
Solution:   Return an empty string on failure.

src/testdir/test_channel.py

@@ -93,6 +93,13 @@ class ThreadedTCPRequestHandler(socketserver.BaseRequestHandler):
                         print("sending: {}".format(cmd))
                         self.request.sendall(cmd.encode('utf-8'))
                         response = "ok"
+                    elif decoded[1] == 'eval-error':
+                        # Send an eval request that works but the result can't
+                        # be encoded.
+                        cmd = '["eval","function(\\"tr\\")", -3]'
+                        print("sending: {}".format(cmd))
+                        self.request.sendall(cmd.encode('utf-8'))
+                        response = "ok"
                     elif decoded[1] == 'eval-bad':
                         # Send an eval request missing the third argument.
                         cmd = '["eval","xxx"]'

src/testdir/test_channel.vim

@@ -118,10 +118,15 @@ func Test_communicate()
   sleep 10m
   call assert_equal([-2, 'ERROR'], ch_sendexpr(handle, 'eval-result'))
 
+  " Send an eval request that works but can't be encoded.
+  call assert_equal('ok', ch_sendexpr(handle, 'eval-error'))
+  sleep 10m
+  call assert_equal([-3, 'ERROR'], ch_sendexpr(handle, 'eval-result'))
+
   " Send a bad eval request. There will be no response.
   call assert_equal('ok', ch_sendexpr(handle, 'eval-bad'))
   sleep 10m
-  call assert_equal([-2, 'ERROR'], ch_sendexpr(handle, 'eval-result'))
+  call assert_equal([-3, 'ERROR'], ch_sendexpr(handle, 'eval-result'))
 
   " Send an expr request
   call assert_equal('ok', ch_sendexpr(handle, 'an expr'))

src/testdir/test_json.vim

@@ -75,6 +75,9 @@ func Test_encode()
   call assert_fails('echo jsonencode(function("tr"))', 'E474:')
   call assert_fails('echo jsonencode([function("tr")])', 'E474:')
   call assert_fails('echo jsonencode({"key":v:none})', 'E474:')
+
+  silent! let res = jsonencode(function("tr"))
+  call assert_equal("", res)
 endfunc
 
 func Test_decode()