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Francesco Di Donato
Francesco Di Donato

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go:generate 101

#go #github #metaprogram #beginners

How to use go:generate?

support code

Setup

terminal

go mod init github.com/<username>/<reponame>
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Create two files. main.go will use gen.go as generator.

terminal

touch main.go gen.go
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main.go simply logs "World!" and runs the generator via the special comment.

main.go

package main

//go:generate go run gen.go

import "fmt"

func init() {
    fmt.Println("main.go#main.init")
}

func main() {
    fmt.Println("World!")
}
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NOTE: There is no space between the slashes and go:generate.

NOTE: not only gen.go, but go run gen.go.

gen.go declares package main, which would be forbidden were it not for the special comment.

gen.go

//go:build ignore

package main

import "fmt"

func init() {
    fmt.Println("gen.go#main.init")
}

func main() {
    fmt.Println("Hello")
}
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NOTE: There is not space between the slashes and go:build.

Usage

terminal

go generate ./...
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Output

gen.go#main.init
Hello
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terminal

go run .
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terminal

main.go#main.init
World!
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Although the subcommand name is generate, the **generator* need not generate a file.*

References

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