How can I implement error message internalization?

[suhdonghwi]

Hello. I am writing a parser and I'd like to add non-English error message to the parser. But, it seems like it is not easy as I expected.

Do I have to implement custom errorBundlePretty function from scratch to completely change the whole error message? Or is it possible with custom error message system?

Also, the functions like Text.Megaparsec.Lexer.decimal, its digit is labeled as "digit" and I cannot change it unless I re-implement my own version of the function. This is another hardship.

[mrkkrp]

Yes indeed, it is hard. The library is not written with this sort of thing in mind. If we remember old parsec there was something for internationalization but only in the part that prints error messages and it made quite ridiculous assumptions about grammar of non-English languages, so it's never been practically useful, imo. This is why, I dropped any attempts at internationalization when I started the project.

It appears that you'll indeed have to write your own version of errorBundlePretty and in addition to that your own "internationalized" functions like decimal. You'll also want to define instances of ShowErrorComponent leaving a way to control localization, I guess it's only possible by using reflection.

As you can see, internationalization is rather hard to do. Now you might ask me if we could add support for this sort of thing in the library itself. To that I'd answer that it's unlikely. The reason is that software development is often about balancing things. Here, we would be balancing additional complexity with the value the new feature would provide.

It so happens that not many users really want localization of error messages. Otherwise it would be supported by other parsing libraries in Haskell ecosystem. It may be that the users are just OK with English-only output or indeed the community is not big enough to really have the need for this sort of thing in its libraries.

I welcome any input on the issue, so I'll leave it open.

[mrkkrp]

This one seems to be dead, I'm going to close it now.