Merge pull request #456 from graphql-go/fix-panic-blockstring

language/lexer: fixes panic on empty blockstrings

Author: chris-ramon

language/lexer/lexer.go

@@ -404,19 +404,13 @@ func blockStringValue(in string) string {
 	}
 
 	// Remove leading blank lines.
-	for {
-		if isBlank := lineIsBlank(lines[0]); !isBlank {
-			break
-		}
+	for len(lines) > 0 && lineIsBlank(lines[0]) {
 		lines = lines[1:]
 	}
 
 	// Remove trailing blank lines.
-	for {
+	for len(lines) > 0 && lineIsBlank(lines[len(lines)-1]) {
 		i := len(lines) - 1
-		if isBlank := lineIsBlank(lines[i]); !isBlank {
-			break
-		}
 		lines = append(lines[:i], lines[i+1:]...)
 	}
 

language/lexer/lexer_test.go

@@ -449,6 +449,15 @@ func TestLexer_ReportsUsefulStringErrors(t *testing.T) {
 
 func TestLexer_LexesBlockStrings(t *testing.T) {
 	tests := []Test{
+		{
+			Body: `""""""`,
+			Expected: Token{
+				Kind:  BLOCK_STRING,
+				Start: 0,
+				End:   6,
+				Value: "",
+			},
+		},
 		{
 			Body: `"""simple"""`,
 			Expected: Token{