Issue with boolean type (bool)

[strmaks]

If struct has a boolean fields, merge result is prefer true value, but this is not correct.
Example:

package main

import (
    "fmt"
    "github.com/imdario/mergo"
)

type Foo struct {
    A string
    B int64
    C bool
}

func main() {
    src := Foo{
        A: "one",
        C: true,
    }

    dest := Foo{
        A: "two",
        B: 2,
        C: false,
    }

    mergo.Merge(&dest, src)

    fmt.Println(dest)
    // Will print
    // {two 2 true}
    // but expected result is {two 2 false}
}

[darccio]

This is the expected behavior. As stated in README:

Mergo is intended to assign only zero value fields on destination with source value.

The zero value of a boolean field is false. It isn't possible to avoid it even with a pointer because Merge follows the pointers too. So, when it finds a pointer to bool with false value, it will overwrite with a true value if src matching field is true.

If you have any doubt, don't hesitate to ask me.

[strmaks]

Thank you.

[TomOperator]

For those of you who need it, @Pothulapati built a fork that solves this here.

[PamelaKelly]

This is the expected behavior.

@darccio does this mean it is not possible to merge booleans at all using this tool then? If we cannot rely on it respecting a legitimate value of false? Or do you have a recommendation for how to get around this?

It would be unfortunate if so as it would make it unusable for anyone with boolean values in their yaml, and otherwise the tool is brilliant. :(

[vtolstov]

i think that for bool case we need to add additional logic

[PamelaKelly]

i think that for bool case we need to add additional logic

Do you mean in the mergo repo or where it is being called?

[vtolstov]

i think that for bool case we need to add additional logic

Do you mean in the mergo repo or where it is being called?

in mergo repo, but i dont know how to detect false vs not set =)

[emirot]

Here is 3 ways to handle merge boolean the way we would like:

• Using mergo.WithOverwriteWithEmptyValue Merge Boolean #129 (comment) but the drawback is that empty values won't be kept
• Using a customBoolean Type see Merge Boolean #129 (comment)
• Treat boolean as string