Arbitrary struct field name for belongs_to relation leads to error with eager creation.

[aeneasr]

Description

When using a has_many relation, it seems to be impossible to set the child's struct field name of the foreign key, instead <name>ID is apparently required.

Steps to Reproduce the Problem

type Request struct {
	ID            uuid.UUID `json:"id" db:"id" rw:"r"`
	CreatedAt     time.Time `json:"created_at" db:"created_at"`
	UpdatedAt time.Time `json:"updated_at" db:"updated_at"`
	Methods    Methods               `json:"-" has_many:"methods"`
}

type Method struct {
	ID        uuid.UUID `json:"id" db:"id" rw:"r"`

	CreatedAt time.Time `json:"created_at" db:"created_at"`
	UpdatedAtF time.Time `json:"updated_at" db:"updated_at"`

	
	RequestFoo  uuid.UUID  `json:"-" db:"request_id"`
	
	Request   *Request  `json:"request" belongs_to:"request" fk_id:"RequestFoo"`

	// Doesn't work either:
	// Request   *Request  `json:"request" belongs_to:"request" fk_id:"request_id"`
}

func TestRequest(t *testing.T) {
	req := models.Request{
		Methods: []models.Method{{}},
	}
	_, err = tx.Eager().ValidateAndSave(&req)
	require.NoError(t, err)
}

With fizz

create_table("requests") {
	t.Column("id", "uuid", {primary: true})
	t.Timestamps()
}

create_table("methods") {
	t.Column("id", "uuid", {primary: true})
	t.Timestamps()
	t.Column("request_id", "uuid")
       t.ForeignKey("request_id", {"requests": ["id"]}, {"on_delete": "cascade"})
}

Will always result in: could not set '3aecf318-0fb6-43b3-b3fe-a0de91042f65' in '<invalid reflect.Value>' (or some other uuid value).

Only changing RequestFoo to RequestID resolves the issue:

Expected Behavior

I would expect the struct field name to be customizable. I would also expect this to work if RequestID was missing from the struct:

type Method struct {
	ID        uuid.UUID `json:"id" db:"id" rw:"r"`

	CreatedAt time.Time `json:"created_at" db:"created_at"`
	UpdatedAt time.Time `json:"updated_at" db:"updated_at"`

	Request   *Request  `json:"request" belongs_to:"request" fk_id:"request_id"`
}

I would also expect the behavior to reflect other struct fields with db tags. This works with eager fetching, but not eager creation.

Actual Behavior

It seems like this is some fixed behavior. This is also not explained in the docs.

Info

Using pop latest master without buffalo.

[stanislas-m]

Fixed with #546.