From 2a653b4a8d2cddc7164f079ae1eff3b6ff616a55 Mon Sep 17 00:00:00 2001
From: Cemre Mengu <cemremengu@gmail.com>
Date: Wed, 22 Mar 2023 14:33:53 +0300
Subject: [PATCH] fix: handle null interface for json

When using `scany` I encountered the following case. This seems to fix it.

Looks like null `jsonb` columns cause the problem. If you create a table like below you can see that the following code fails. Is this expected?

```sql
CREATE TABLE test (
	a int4 NULL,
	b int4 NULL,
	c jsonb NULL
);

INSERT INTO test (a, b, c) VALUES (1, null, null);
```

```go
package main

import (
	"context"
	"log"

	"github.com/georgysavva/scany/v2/pgxscan"
	"github.com/jackc/pgx/v5"
)

func main() {
	var rows []map[string]interface{}
	conn, _ := pgx.Connect(context.Background(), , ts.PGURL().String())

	// this will fail with can't scan into dest[0]: cannot scan NULL into *interface {}
	err := pgxscan.Select(context.Background(), conn, &rows, `SELECT c from test`)

	// this works
	// err = pgxscan.Select(context.Background(), conn, &rows, `SELECT a,b from test`)

	if err != nil {
		panic(err)
	}

	log.Printf("%+v", rows)
}
```
---
 pgtype/json.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pgtype/json.go b/pgtype/json.go
index 69861bf8..753f2410 100644
--- a/pgtype/json.go
+++ b/pgtype/json.go
@@ -150,7 +150,7 @@ func (scanPlanJSONToJSONUnmarshal) Scan(src []byte, dst any) error {
 		if dstValue.Kind() == reflect.Ptr {
 			el := dstValue.Elem()
 			switch el.Kind() {
-			case reflect.Ptr, reflect.Slice, reflect.Map:
+			case reflect.Ptr, reflect.Slice, reflect.Map, reflect.Interface:
 				el.Set(reflect.Zero(el.Type()))
 				return nil
 			}