Handle null PostgreSQL JSON values (#1145)

* codegen/golang: Handle NULL JSON values

lib/pq: For nullable values, use pqtype.NullRawMessage
pgx/v4: Always use pgtype.JSON[B]

* endtoend: Update test cases

Author: kyleconroy

internal/codegen/golang/imports.go

@@ -135,14 +135,17 @@ var stdlibTypes = map[string]string{
 var pgtypeTypes = map[string]struct{}{
 	"pgtype.CIDR":    {},
 	"pgtype.Inet":    {},
+	"pgtype.JSON":    {},
+	"pgtype.JSONB":   {},
 	"pgtype.Macaddr": {},
 	"pgtype.Numeric": {},
 }
 
 var pqtypeTypes = map[string]struct{}{
-	"pqtype.CIDR":    {},
-	"pqtype.Inet":    {},
-	"pqtype.Macaddr": {},
+	"pqtype.CIDR":           {},
+	"pqtype.Inet":           {},
+	"pqtype.Macaddr":        {},
+	"pqtype.NullRawMessage": {},
 }
 
 func buildImports(settings config.CombinedSettings, queries []Query, uses func(string) bool) (map[string]struct{}, map[ImportSpec]struct{}) {

internal/codegen/golang/postgresql_type.go

@@ -76,8 +76,33 @@ func postgresType(r *compiler.Result, col *compiler.Column, settings config.Comb
 		}
 		return "sql.NullBool"
 
-	case "json", "jsonb":
-		return "json.RawMessage"
+	case "json":
+		switch driver {
+		case SQLDriverPGXV4:
+			return "pgtype.JSON"
+		case SQLDriverLibPQ:
+			if notNull {
+				return "json.RawMessage"
+			} else {
+				return "pqtype.NullRawMessage"
+			}
+		default:
+			return "interface{}"
+		}
+
+	case "jsonb":
+		switch driver {
+		case SQLDriverPGXV4:
+			return "pgtype.JSONB"
+		case SQLDriverLibPQ:
+			if notNull {
+				return "json.RawMessage"
+			} else {
+				return "pqtype.NullRawMessage"
+			}
+		default:
+			return "interface{}"
+		}
 
 	case "bytea", "blob", "pg_catalog.bytea":
 		return "[]byte"