gogen
AST rewrite powered generics for Go
Usage
Somewhere in your code you need to define one or more generic types. Something like:
type I interface{}
type F interface{}
From here, you can write any code that uses those generic type (including tests):
func Add(left, right I) I {
return left + right
}
func Sub(left, right F) F {
return left - right
}
Using the gogen
CLI you can then render the generic code with concrete types:
gogen -source github.com/username/package -destination . -rewrite "I=uint16" -rewrite "F=float64
The source code will be rewritten without the type I interface{}
lines and
with all references to generic types replaced with concrete types.
func Add(left, right uint16) uint16 {
return left + right
}
func Sub(left, right float64) float64 {
return left - right
}
The output will be formatted with gofmt
(but not goimports
).
More Options
In addition to direct rewrites, the CLI also offers the following options:
-
-unstar T
This option triggers the rewrite of *T
within the source to T
before
being rewritten as the concrete type. This is useful if rendering a generic
as an interface type (such as `-rewrite "T=io.Reader"). The option may be
given multiple times to unstar multiple generic types.
-
-rewrite "T=*int"
If the concrete type given in a rewrite rule is prefixed with an *
then
a pointer type will be used. If the generic type is already a pointer then
this could result in a double pointer to the concrete type. Use the
unstar
flag to prevent this. Any number of rewrites may be given per
invocation.
-
-rewrite "T=pkg.Name"
If the concrete type has a package prefix then the resulting code will
correctly select the type from the target package. However, the rewrite
will not change import statements or add new ones. It is recommended to
use something like goimports
to correct any missing or excess import
statements after rewrites.
-
-package newname
The package option causes the renderer to set a custom package name in
all files rendered. By default, the original package name is reused.
License
This project is available under the Apache2.0 license. See the LICENSE
file
in this repository for the complete license text.