cli11 check never called after transform validator

[dhsu123]

Using CLI11 when i call a transform mutating validator followed by a call to the check validator, check never gets called. If a non mutating transform is called before check, everything is fine and check is called. for example the bad case:

grp->add_option_functionstd::string(
"--file_path",
[&](std::string_view str) {
//do something here
},
"File Path")
->transform(MutatingValidator())
->check(NonMutatingValidator());

// where MutatingValidator is defined as follows:

struct MutatingValidator : public Validator {
MutatingValidator() {
name_ = "MutatingValidator";
func_ = [](const std::string &str) {
return std::string("My Sample mutating validator");
};
}
};

I also posted on stackoverflow:
https://stackoverflow.com/questions/70104056/cli11-check-never-called-after-transform-validator

[phlptp]

For a validator the return string is an error message. Any changes to the string should be modified in place.

So since your function returns a string it will be interpreted as an error and cease processing at that point. so the check would never get called.

The signature of the function call for a mutation validator is std::string(std::string &)
The input is the argument to process (passed by reference so it can be modified) the output is an error string if any.

[dhsu123]

Thanks Philip for the quick response. This worked. i was confused by this statement where it talks about throwing a ValidationError when there is an error vs just returning a non empty string:

https://cliutils.github.io/CLI11/book/chapters/validators.html:
"A transform validator comes in one form, a function with the signature std::string(std::string). The function will take a string and return the modified version of the string. If there is an error, the function should throw a CLI::ValidationError with the appropriate reason as a message."

[phlptp]

That chapter probably needs an update then. Created an issue to address it.