Using Meta to Specify time.Time Type Causes Code Generation Error

[Kahoulam]

Description

In my design file, I use the following code to specify a date-time format field as time.Time type:

Attribute(name, String, func() {
    Meta("struct:field:type", "time.Time", "time") // Specify struct field type metadata
    Description(desc)                              // Set description of the attribute
    Format(FormatDateTime)                         // Set format for date and time
    Example("2024-01-01T11:53:54Z")                // Provide example value
})

The reason for writing it this way is to avoid repeatedly converting between time.Time and string.

However, the generated code produces the following error:

cannot use *body.Timestamp (variable of type time.Time) as string value in argument to goa.ValidateFormat

Example

Below is the complete design file example:

package design

import (
    . "goa.design/goa/v3/dsl"
)

var _ = API("example", func() {
    Title("Example API")
    Server("example", func() {
        Host("localhost", func() {
            URI("http://localhost:8080")
        })
    })
})

var ExampleType = Type("ExampleType", func() {
    Attribute("timestamp", String, func() {
        Meta("struct:field:type", "time.Time", "time") // Specify struct field type metadata
        Description("Timestamp in RFC3339 format")
        Format(FormatDateTime)
        Example("2024-01-01T11:53:54Z")
    })
    Required("timestamp")
})

var _ = Service("example", func() {
    Method("show", func() {
        Payload(ExampleType)
        Result(ExampleType)
        HTTP(func() {
            GET("/example")
            Response(StatusOK)
        })
    })
})

Expected Solution

I hope to be able to specify a date-time format field as time.Time type in the design file using Meta, and have the generated code work without the above error.

Additional Information

goa version: v3.16.2
Golang version: go1.22.6
Operating System: linux/arm64

I would appreciate any solutions or guidance. Thank you!

[raphael]

Hello, the type specified with struct:field:type must be structurally compatible with the type defined in the design, here time.Time isn't compatible with String.