I believe we can generated the following type to fix this issue

// NullRawMessage represents a json.RawMessage that may be null.
// NullRawMessage implements the Scanner interface so
// it can be used as a scan destination, similar to NullString.
type NullRawMessage struct {
	RawMessage json.RawMessage
	Valid bool // Valid is true if JSON is not NULL
}

// Scan implements the Scanner interface.
func (n *NullRawMessage) Scan(value interface{}) error {
	n.RawMessage = json.RawMessage{}
	if value == nil {
		n.Valid = false
		return nil
	}
	n.Valid = true
	return n.RawMessage.Scan(value)
}

// Value implements the driver Valuer interface.
func (n NullRawMessage) Value() (driver.Value, error) {
	if !n.Valid {
		return nil, nil
	}
	return n.RawMessage.Value()
}

It appears that json.RawMessage does not implement the Scanner interface.

# command-line-arguments
./foo.go:24:21: n.RawMessage.Scan undefined (type json.RawMessage has no field or method Scan)
./foo.go:32:2: not enough arguments to return
./foo.go:32:21: n.RawMessage.Value undefined (type json.RawMessage has no field or method Value

We ran into this issue earlier, but this isn't really anything wrong with sqlc. We just added a null check in our code and if it was nil, we put in an empty array.

	if params.SalesforceProducts == nil {
		params.SalesforceProducts = json.RawMessage([]byte("[]"))
	}

Definitely not ideal, but like you said, no Scanner.

But if you find a fix, I'd love to see it! I'll keep an eye out as well.

@mrcampbell,@kyleconroy, you can do something like this:

func (n *NullRawMessage) Scan(value interface{}) error {
	if value == nil {
		n.RawMessage, n.Valid = json.RawMessage{}, false
		return nil
	}
	buf, ok := value.([]byte)

	if !ok {
		return errors.New("canot parse to bytes")
	}

	n.RawMessage, n.Valid = buf, true

	return nil
}

Not sure if it is the best way, but I was able to work around the issue by adding a coalesce statement in the query.sql

// query.sql

-- name: GetSomething :one
select
  t."id",
  coalesce(t."data", '[]') as "data"
from
  "public"."something" t
where
  t.id = $1
limit 1;

Hi! Is someone working on this? I'm getting the same error when reading a jsonb value that can be null.

Would also love to see a fix for this. I'm having this issue when reading json data from postgres.

There is the same problem on mysql.

@koolay I solved this for mysql using overrides in sqlc.yaml:

overrides:
  - db_type: "json"
    go_type:
      type: "[]byte"  # workaround sqlc bug when reading null json columns
    nullable: true

Note that the documentation is not up to date - go_type is a struct and not a string.

Hey, @idan-stripe. I tried your fix but I still seem to be getting the same error as I was before. Have you changed anything else other than sqlc.yaml?

Edit: I'm using PostgreSQL

Bug still not resolved in 08/13/2023.

I did try the main with #129 fix, but no luck. The override works nicely.