检查来自os.Remove的错误消息

Question

What's the most idiomatic way to check error messages? My use case is that in err := os.Remove(path), I consider a success either:

A) if err == nil

or

B) if err != nil but the error is thrown because the file was not found.

any other error should cause the removal to retry. Currently I've wrapped this in a for { ... } loop and am checking:

if err == nil || strings.Contains(err.Error(), "no such file") {
    // Success
} else {
    // Fail
}

Since the docs say:

If there is an error, it will be of type *PathError.

I don't think there's a way to check by type assertion. Am I missing something fundamental? My error handling in Go has always felt somewhat slapdash.

Answer 1

The "type" error is an interface. Interfaces don't have an concrete type. To get the type of the value you could use a type assertion or a type switch:

// Type assertion
_, ok := err.(*PathError)

// Type switch
switch err.(type) {
case *PathError:
    // You know the type now
}

This is an idiomatic way to find out of which type an error is. As in the comments specified there is already a function inside the os package which does this for you (https://golang.org/pkg/os/#IsNotExist)