How to find a package name from given call in runtime? - go

Question

For logging purpose I want to write a function which will print a package name.
I can do it for a directory name:
// file is the full file name
// 4 - how many calls we want to go up in a stack trace.
_, file, line, ok := runtime.Caller(4)
... but can't find a way for package name (package name can be different from directory name).

Answer 1

I came across a similar problem - from a package path how do you get the package name. The best solution I found is to exec the "go list" command. Not ideal but I came up blank elsewhere.
In my case I also had a problem that sometimes the package is an empty directory. With no source files, "go list" throws an error, so I added a function to create a sensible package name from the path.
Here's the code:
func getPackageName(path string) string {
output, err := exec.Command("go", "list", "-f", "{{.Name}}", path).CombinedOutput()
if err != nil {
return guessPackageName(path)
}
return strings.TrimSpace(string(output))
}
func guessPackageName(path string) string {
preferred := path
if strings.HasSuffix(preferred, "/") {
// training slashes are usually tolerated, so we can get rid of one if it exists
preferred = preferred[:len(preferred)-1]
}
if strings.Contains(preferred, "/") {
// if the path contains a "/", use the last part
preferred = preferred[strings.LastIndex(preferred, "/")+1:]
}
if strings.Contains(preferred, "-") {
// the name usually follows a hyphen - e.g. github.com/foo/go-bar
// if the package name contains a "-", use the last part
preferred = preferred[strings.LastIndex(preferred, "-")+1:]
}
if strings.Contains(preferred, ".") {
// dot is commonly usually used as a version - e.g. github.com/foo/bar.v1
// if the package name contains a ".", use the first part
preferred = preferred[:strings.LastIndex(preferred, ".")]
}
return preferred
}