Modifying a struct type inside vendor files

Question

I have to modify a struct inside a vendor file. Suppose this is how the struct is inside the vendor file

type sampleStruct struct {
    sampleStringvar1       string
    sampleStringvar2       string
}

I need to add one more field to it like this

type sampleStruct struct {
    sampleStringvar1       string
    sampleStringvar2       string
    sampleBoolVar          bool
}

How can I achieve this? Is it good practise to modify vendor variables like this? If not what is the best way to do this?

Answer 1

If you don't want to fork a vendored library and replace it with your own, the best practice would be, in your project, to use a wrapper.

The wrapper object would be struct:

• referencing a sampleStruct instance
• with a sampleBoolVar boolean

That is:

type MySampleStruct {
    ss            *sampleStruct 
    sampleBoolVar bool
}

That way, you can benefit from sampleBoolVar while the vendored library keep using a sampleStruct as usual.

But, blackgreen points out in the comments:

How would you be able to reference an unexported struct, as sampleStruct appears to be, outside its own package?

This is correct, and the aforementioned suggestion is not about exposing a private variable, but about managing that variable yourself, based on what you see from sampleStruct.
Depending on the library behavior, that might not be possible.

Answer 2

Is it good practise to modify vendor variables like this?

Absolutely not.

If not what is the best way to do this?

Fork the vendor module and reference the fork with a replace directive in your go.mod.