inspect() and inspectErr() can mutate consumed value

[dcadea]

Both inspect and inspectErr have a potential side effect of mutating the value wrapped into Result. This is not a desired behavior.

var ok = Result.ok(new Mutable(5))
               .inspect(v -> v.a = 20);

assertThat(ok).hasValue(new Mutable(20)); // !!! should be 'Mutable(5)'

var err = Result.err(new Mutable(2))
                .inspectErr(e -> e.a *= 2);

Assertions.assertThat(errors).containsOnly(new Mutable(4)); // !!! should be 'Mutable(2)'

[nanobreaker]

Maybe we can try to create a deep copy of the object before passing it to the consumer functions just for for inspect and inspectErr methods, basically this solves the problem.

    default Result<O, E> inspect(Consumer<? super O> op) {
        if (this instanceof Ok(O value)) {
            O copy = deepCopy(value); 
            op.accept(copy);
        }

        return this;
    }

[dcadea]

Maybe we can try to create a deep copy of the object before passing it to the consumer functions just for for inspect and inspectErr methods, basically this solves the problem.

    default Result<O, E> inspect(Consumer<? super O> op) {
        if (this instanceof Ok(O value)) {
            O copy = deepCopy(value); 
            op.accept(copy);
        }

        return this;
    }

The value has to be either Serializable or deepCopy(v) should convert the object into a byte array and then construct a new instance out of it. And with byte array you also erase initial type of object and have to do an unsafe cast.