# protoc-gen-go-value-scan

Implements scanner and valuer interfaces for proto messages.

![README](./README.gif)

## What it does

Takes this proto

```proto
syntax = "proto3";

package foo.v1;

option go_package = "git.wobcom.de/smartmetering/protoc-gen-go-value-scan/test/go/foo/v1;foov1";

message Foo {
    string bar  = 1;
    string zonk = 2;
}

message ExcludeThis {
    string bar  = 1;
    string zonk = 2;
}
```

and creates this go code

```go
// Code generated by protoc-gen-go-value-scan. DO NOT EDIT.

package foov1

import (
	"database/sql/driver"
	"fmt"

	protojson "google.golang.org/protobuf/encoding/protojson"
)

func (x Foo) Value() (driver.Value, error) {
	f := &x

	opts := protojson.MarshalOptions{}
	opts.UseProtoNames = false
	opts.EmitUnpopulated = true

	return opts.Marshal(f)
}

func (x *Foo) Scan(value interface{}) error {
	switch v := value.(type) {
	case []byte:
		return protojson.Unmarshal(v, x)
	case string:
		return protojson.Unmarshal([]byte(v), x)
	default:
		return fmt.Errorf("type assertion failed")
	}
}
```

with this `buf.gen.yaml`

```yaml
version: v1
plugins:
  - name: go
    out: go/
    opt:
      - paths=source_relative
  - name: go-value-scan
    out: go/
    opt:
      - paths=source_relative,use_proto_names=false,emit_unpopulated=true,exclude=git.wobcom.de/smartmetering/protoc-gen-go-value-scan/test/go/foo/v1.ExcludeThis
```

## Configuration

| Option             | Meaning                                                                                | Default |
| ------------------ | -------------------------------------------------------------------------------------- | ------- |
| `use_proto_names`  | UseProtoNames uses proto field name instead of lowerCamelCase name in JSON field names | `true`  |
| `emit_unpopulated` | EmitUnpopulated specifies whether to emit unpopulated fields                           | `true`  |
| `exclude`          | Takes a message identifier. Can be multiple identifier delimited by `,`                | none    |