在GO中毒化套件/功能

Question

TLDR: Is there a way in golang (even if it is a bit non-standard), to "poison" a function or import of a certain package altogether.

The longer version: I am writing a thrift service, which all public facing functions return results, or an error of a certain type, declared in the thrift file. The code generator generates code for the interface like this:

publicFacingFunc(...) (returnType, error)

This would be great, until someone I am working with decides to check for another condition, and when that condition is not met does something like this:

if conditionIsNotMet {
    return nil, errors.New(...)
}

The code compiles, but when the error arises, the received message is undocumented random string. So in these files, I want to prevent usage of "errors" and "fmt" packages.

And yes, I tried, and still have I a blaring warning at the top of the file, but nobody seems to read.

BTW, the public errors all have a respective "constructor", which is external to these files, and only those should be used, in my case.

Answer 1

If you're only concerned with a packages use within a file, you could import it under a silly name, like 'NEVER'... and people could use it, but they'd get the idea I think.

 import (
      NEVER "fmt"
 )

OR, if you want to be less silly, you could use the _ underscore, https://golang.org/doc/effective_go.html#blank_import

import (
    _ "fmt"
)

which will load the import, but only it's side effects (that is, not for explicit use.

---

To stop the input of all errors not of a certain type, you could use reflect in order to stop the undesirable types with type assertion, https://golang.org/ref/spec#Type_assertions

v, ok = x.(T)

So if an err comes up in the public facing function, that you don't want passed through, check what kind of error it is,

 specialError, ok := err.(mypackage.ErrorType)
    if !ok {
        // don't send this error on
    }