Querier/Ingester: Fixing json expression parser bug (#3928)

* Fixing json expression parser bug

Signed-off-by: Danny Kopping <danny.kopping@grafana.com>

* UNRELATED CHANGE: pulling main to fix linter issue

Signed-off-by: Danny Kopping <danny.kopping@grafana.com>

pkg/distributor/http.go

@@ -6,9 +6,10 @@ import (
 
 	util_log "github.com/cortexproject/cortex/pkg/util/log"
 	"github.com/go-kit/kit/log/level"
-	"github.com/grafana/loki/pkg/loghttp/push"
 	"github.com/weaveworks/common/httpgrpc"
 	"github.com/weaveworks/common/user"
+
+	"github.com/grafana/loki/pkg/loghttp/push"
 )
 
 // PushHandler reads a snappy-compressed proto from the HTTP body.

pkg/logql/log/jsonexpr/jsonexpr_test.go

@@ -113,6 +113,12 @@ func TestJSONExpressionParser(t *testing.T) {
 			nil,
 			fmt.Errorf("syntax error: unexpected DOT, expecting FIELD"),
 		},
+		{
+			"syntax error on key access",
+			`["key`,
+			nil,
+			fmt.Errorf("syntax error: unexpected $end, expecting RSB"),
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/logql/log/jsonexpr/lexer.go

@@ -97,7 +97,7 @@ func (sc *Scanner) scanField() string {
 			break
 		}
 
-		if r == '.' || r == scanner.EOF || r == rune(0) {
+		if r == '.' || isEndOfInput(r) {
 			sc.unread()
 			break
 		}
@@ -118,6 +118,10 @@ func (sc *Scanner) scanStr() string {
 
 	for {
 		r := sc.read()
+		if isEndOfInput(r) {
+			break
+		}
+
 		if r == '"' || r == ']' {
 			break
 		}
@@ -150,6 +154,11 @@ func (sc *Scanner) scanInt() (int, error) {
 	return strconv.Atoi(string(number))
 }
 
+// input is either terminated by EOF or null byte
+func isEndOfInput(r rune) bool {
+	return r == scanner.EOF || r == rune(0)
+}
+
 func (sc *Scanner) read() rune {
 	ch, _, _ := sc.buf.ReadRune()
 	return ch