Return detailed C* error for USE query. More test comments

Author: lukasz-antoniak

parser/lexer_test.go

@@ -86,11 +86,15 @@ func TestLexerIdentifiers(t *testing.T) {
 		{`"system"`, tkIdentifier, "system"},
 		{`"system"`, tkIdentifier, "system"},
 		{`"System"`, tkIdentifier, "System"},
-		{`""""`, tkIdentifier, "\""},
-		{`""""""`, tkIdentifier, "\"\""},
-		{`"A"""""`, tkIdentifier, "A\"\""},
-		{`"""A"""`, tkIdentifier, "\"A\""},
-		{`"""""A"`, tkIdentifier, "\"\"A"},
+		// below test verify correct escaping double quote character as per CQL definition:
+		//    identifier ::= unquoted_identifier | quoted_identifier
+		//    unquoted_identifier ::= re('[a-zA-Z][link:[a-zA-Z0-9]]*')
+		//    quoted_identifier ::= '"' (any character where " can appear if doubled)+ '"'
+		{`""""`, tkIdentifier, "\""},       // outermost quotes indicate quoted string, inner two double quotes shall be treated as single quote
+		{`""""""`, tkIdentifier, "\"\""},   // same as above, but 4 inner quotes result in 2 quotes
+		{`"A"""""`, tkIdentifier, "A\"\""}, // outermost quotes indicate quoted string, 4 quotes after A result in 2 quotes
+		{`"""A"""`, tkIdentifier, "\"A\""}, // outermost quotes indicate quoted string, 2 quotes before and after A result in single quotes
+		{`"""""A"`, tkIdentifier, "\"\"A"}, // analogical to previous tests
 		{`";`, tkInvalid, ""},
 		{`"""`, tkIdentifier, ""},
 	}

proxy/proxy.go

@@ -812,7 +812,14 @@ func (c *client) interceptSystemQuery(hdr *frame.Header, stmt interface{}) {
 		}
 	case *parser.UseStatement:
 		if _, err := c.proxy.maybeCreateSession(hdr.Version, s.Keyspace); err != nil {
-			c.send(hdr, &message.ServerError{ErrorMessage: "Proxy unable to create new session for keyspace"})
+			var cqlError *proxycore.CqlError
+			switch {
+			case errors.As(err, &cqlError):
+				errMsg := cqlError.Message
+				c.send(hdr, errMsg)
+			default:
+				c.send(hdr, &message.ServerError{ErrorMessage: "Proxy unable to create new session for keyspace"})
+			}
 		} else {
 			c.keyspace = s.Keyspace
 			// We might have received a quoted keyspace name in the UseStatement so remove any

proxy/proxy_test.go

@@ -219,6 +219,37 @@ func TestProxy_UseKeyspace(t *testing.T) {
 	}
 }
 
+func TestProxy_UseKeyspace_Error(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	tester, proxyContactPoint, err := setupProxyTest(ctx, 1, proxycore.MockRequestHandlers{
+		primitive.OpCodeQuery: func(cl *proxycore.MockClient, frm *frame.Frame) message.Message {
+			qry := frm.Body.Message.(*message.Query)
+			if qry.Query == "USE non_existing" {
+				return &message.ServerError{
+					ErrorMessage: "Keyspace 'non_existing' does not exist",
+				}
+			}
+			return cl.InterceptQuery(frm.Header, frm.Body.Message.(*message.Query))
+		}})
+	defer func() {
+		cancel()
+		tester.shutdown()
+	}()
+	require.NoError(t, err)
+
+	cl := connectTestClient(t, ctx, proxyContactPoint)
+
+	resp, err := cl.SendAndReceive(ctx, frame.NewFrame(primitive.ProtocolVersion4, 0, &message.Query{Query: "USE non_existing"}))
+	require.NoError(t, err)
+
+	assert.Equal(t, primitive.OpCodeError, resp.Header.OpCode)
+	res, ok := resp.Body.Message.(*message.ServerError)
+	require.True(t, ok)
+	// make sure that CQL Proxy returns the same error of 'USE keyspace' command
+	// as backend C* cluster has and does not wrap it inside a custom one
+	assert.Equal(t, "Keyspace 'non_existing' does not exist", res.ErrorMessage)
+}
+
 func TestProxy_NegotiateProtocolV5(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	tester, proxyContactPoint, err := setupProxyTest(ctx, 1, nil)