Use civil.Date for date fields

[jpmeijers]

Describe the feature

Rather than using time.Time for sql date fields, shouldn't we rather use civil.Date from https://pkg.go.dev/cloud.google.com/go/civil. This latter type seems to be the standard way to handle dates in go.

Motivation

If one uses time.Time to represent dates, the time part is set to all 0's. If the end user isn't aware that the time part should be ignored, this can cause confusion, and even create errors if it's interpreted in a GMT+ve timezone.

Related Issues

Other

I tried defining a custom struct that uses civil.Date fields, and scanning the database result into this struct. This resulted in a date with value 0000-00-00.

[jpmeijers]

I ended up writing a custom type based on gorm's Date.

package customtypes

import (
	"cloud.google.com/go/civil"
	"database/sql"
	"database/sql/driver"
	"time"
)

type Date civil.Date

func (date *Date) Scan(value interface{}) (err error) {
	nullTime := &sql.NullTime{}
	err = nullTime.Scan(value)
	*date = Date(civil.DateOf(nullTime.Time))
	return
}

func (date Date) Value() (driver.Value, error) {
	return time.Date(date.Year, date.Month, date.Day, 0, 0, 0, 0, time.UTC), nil
}

// GormDataType gorm common data type
func (date Date) GormDataType() string {
	return "date"
}

func (date Date) GobEncode() ([]byte, error) {
	return civil.Date(date).In(time.UTC).GobEncode()
}

func (date *Date) GobDecode(b []byte) error {
	var timeVal time.Time
	err := timeVal.GobDecode(b)
	if err != nil {
		return err
	}
	dateVal := Date(civil.DateOf(timeVal))
	*date = dateVal
	return nil
}

func (date Date) MarshalJSON() ([]byte, error) {
	marshalled := make([]byte, 0)
	text, err := civil.Date(date).MarshalText()
	marshalled = append(marshalled, byte('"'))
	marshalled = append(marshalled, text...)
	marshalled = append(marshalled, byte('"'))
	return marshalled, err
}

func (date *Date) UnmarshalJSON(b []byte) error {
	c := civil.Date{}
	err := c.UnmarshalText(b[1 : len(b)-1])
	*date = Date(c)
	return err
}