feat(spanner/spansql): support JSON literals

spanner/spansql/parser.go

@@ -2975,6 +2975,11 @@ func (p *parser) parseLit() (Expr, *parseError) {
 			p.back()
 			return p.parseTimestampLit()
 		}
+	case tok.caseEqual("JSON"):
+		if p.sniffTokenType(stringToken) {
+			p.back()
+			return p.parseJSONLit()
+		}
 	}
 
 	// TODO: struct literals
@@ -3140,6 +3145,19 @@ func (p *parser) parseTimestampLit() (TimestampLiteral, *parseError) {
 	return TimestampLiteral{}, p.errorf("invalid timestamp literal %q", s)
 }
 
+func (p *parser) parseJSONLit() (JSONLiteral, *parseError) {
+	if err := p.expect("JSON"); err != nil {
+		return JSONLiteral{}, err
+	}
+	s, err := p.parseStringLit()
+	if err != nil {
+		return JSONLiteral{}, err
+	}
+	// It is not guaranteed that the returned JSONLiteral is a valid JSON document
+	// to avoid error due to parsing SQL generated with an invalid JSONLiteral like JSONLiteral("")
+	return JSONLiteral(s), nil
+}
+
 func (p *parser) parseStringLit() (StringLiteral, *parseError) {
 	tok := p.next()
 	if tok.err != nil {

spanner/spansql/parser_test.go

@@ -427,6 +427,9 @@ func TestParseExpr(t *testing.T) {
 		{`[1, 2, 3]`, Array{IntegerLiteral(1), IntegerLiteral(2), IntegerLiteral(3)}},
 		{`['x', 'y', 'xy']`, Array{StringLiteral("x"), StringLiteral("y"), StringLiteral("xy")}},
 		{`ARRAY[1, 2, 3]`, Array{IntegerLiteral(1), IntegerLiteral(2), IntegerLiteral(3)}},
+		// JSON literals:
+		// https://cloud.google.com/spanner/docs/reference/standard-sql/lexical#json_literals
+		{`JSON '{"a": 1}'`, JSONLiteral(`{"a": 1}`)},
 
 		// OR is lower precedence than AND.
 		{`A AND B OR C`, LogicalOp{LHS: LogicalOp{LHS: ID("A"), Op: And, RHS: ID("B")}, Op: Or, RHS: ID("C")}},

spanner/spansql/sql.go

@@ -738,3 +738,8 @@ func (tl TimestampLiteral) SQL() string { return buildSQL(tl) }
 func (tl TimestampLiteral) addSQL(sb *strings.Builder) {
 	fmt.Fprintf(sb, "TIMESTAMP '%s'", time.Time(tl).Format("2006-01-02 15:04:05.000000 -07:00"))
 }
+
+func (jl JSONLiteral) SQL() string { return buildSQL(jl) }
+func (jl JSONLiteral) addSQL(sb *strings.Builder) {
+	fmt.Fprintf(sb, "JSON '%s'", jl)
+}

spanner/spansql/sql_test.go

@@ -559,6 +559,11 @@ func TestSQL(t *testing.T) {
 			`TIMESTAMP '2014-09-27 12:34:56.123456 -07:00'`,
 			reparseExpr,
 		},
+		{
+			JSONLiteral(`{"a": 1}`),
+			`JSON '{"a": 1}'`,
+			reparseExpr,
+		},
 		{
 			Query{
 				Select: Select{

spanner/spansql/types.go

@@ -771,6 +771,12 @@ type TimestampLiteral time.Time
 
 func (TimestampLiteral) isExpr() {}
 
+// JSONLiteral represents a JSON literal
+// https://cloud.google.com/spanner/docs/reference/standard-sql/lexical#json_literals
+type JSONLiteral []byte
+
+func (JSONLiteral) isExpr() {}
+
 type StarExpr int
 
 // Star represents a "*" in an expression.