From 51c01b83aec1256421db25257f1671b2fc7fa8f2 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Mon, 4 Feb 2019 12:38:18 +0100
Subject: [PATCH] rpc: respond to invalid JSON

---
 rpc/client.go                    | 3 +++
 rpc/errors.go                    | 7 +++++++
 rpc/testdata/invalid-syntax.json | 5 +++++
 3 files changed, 15 insertions(+)
 create mode 100644 rpc/testdata/invalid-syntax.json

diff --git a/rpc/client.go b/rpc/client.go
index 1b3c3ada0c..02029dc8f6 100644
--- a/rpc/client.go
+++ b/rpc/client.go
@@ -612,6 +612,9 @@ func (c *Client) drainRead() {
 func (c *Client) read(codec ServerCodec) {
 	for {
 		msgs, batch, err := codec.Read()
+		if _, ok := err.(*json.SyntaxError); ok {
+			codec.Write(context.Background(), errorMessage(&parseError{err.Error()}))
+		}
 		if err != nil {
 			c.readErr <- err
 			return
diff --git a/rpc/errors.go b/rpc/errors.go
index 1166a5540a..c3aa826cc8 100644
--- a/rpc/errors.go
+++ b/rpc/errors.go
@@ -36,6 +36,13 @@ func (e *subscriptionNotFoundError) Error() string {
 	return fmt.Sprintf("no %q subscription in %s namespace", e.subscription, e.namespace)
 }
 
+// Invalid JSON was received by the server.
+type parseError struct{ message string }
+
+func (e *parseError) ErrorCode() int { return -32700 }
+
+func (e *parseError) Error() string { return e.message }
+
 // received message isn't a valid request
 type invalidRequestError struct{ message string }
 
diff --git a/rpc/testdata/invalid-syntax.json b/rpc/testdata/invalid-syntax.json
new file mode 100644
index 0000000000..b194299603
--- /dev/null
+++ b/rpc/testdata/invalid-syntax.json
@@ -0,0 +1,5 @@
+// This test checks that an error is written for invalid JSON requests.
+
+--> 'f
+<-- {"jsonrpc":"2.0","id":null,"error":{"code":-32700,"message":"invalid character '\\'' looking for beginning of value"}}
+