Encode version to the header of generated files

[Mossaka]

Essentially, replace

// Code generated by wit-bindgen-go. DO NOT EDIT.

to

// Code generated by wit-bindgen-go version v0.3.0. DO NOT EDIT.

[ydnar]

Because generated Go code is written to the filesystem and committed, this means that updating the version of wasm-tools-go can create (noisy) diffs for otherwise unchanged files.

Second, this is only available when examining the source code.

What if we implemented something for each generated package along the lines of Go’s debug.ReadBuildInfo(), but for generated Go packages? Thinking something along the lines of:

package cm

// BuildInfo contains debugging information about the WIT package
// and toolchain that generated a Go package.
type BuildInfo struct {
	WITPackage       string // "wasi:http"
	WITVersion       string // "0.2.0"
	Generator        string // "wit-bindgen-go"
	GeneratorVersion string // "0.3.1"
}

Then each generated Go package could have a build.go file with a single export func ReadBuildInfo() cm.BuildInfo.

[Mossaka]

I like the idea of reducing noisy diffs. How will this impact our release process? Do we need to bump up this version whenever we release a new version?

The release CI knows the tag version. Maybe BuildInfo could pick up the tag version at linking time and populate the GeneratorVersion field?

[ydnar]

We can generate this in code. The package cm struct would only be used for the API. The values would be generated in a build.go file.

[Mossaka]

Ah okay that makes sense!