[R-package] Update remaining internal function calls to use keyword arguments

[zenggyu]

Closes #3390 .

I didn't edit the following .R files because all internal function calls in these files are already using keyword arguments:

• lgb.plot.importance.R
• lgb.unloader.R
• metrics.R
• readRDS.lgb.Booster.R
• saveRDS.lgb.Booster.R

[jameslamb]

Thanks for doing this! These changes all look great. Could you please also add keyword arguments for these other calls?

Let me know if you get stuck and need help, some of these are R6 objects way nested in the attributes of other R6 objects.

lgb.Dataset.R

• self$set_categorical_feature()
• self$set_colnames()
• private$set_predictor()
• x$set_colnames()
• lgb.is.Dataset()
• dataset$set_categorical_feature()
• dataset$set_reference()
• dataset$save_binary()

lgb.convert_with_rules.R

• .get_column_classes()

lgb.cv.R

• Predictor$new()
• lgb.check_interaction_constraints()
• data$update_params()
• data$.__enclos_env__$private$set_predictor()
• data$set_colnames()
• data$set_categorical_feature()
• categorize.callbacks()

[zenggyu]

OK!

[zenggyu]

So I used regular expression to find all functions defined in .R files, then used those function names to find all function calls and inspected them one by one. I have updated almost every function call which uses positional arguments instead of keyword arguments. There is one exception though. In lgb.cv.R and lgb.train.R, there are these function calls:

for (f in cb$pre_iter) {
   f(env)
}

I think f() comes from categorize.callbacks() in the callback.R file, and its one and only argument is x. However, I am not sure. Is this correct? Do you want me to update these function calls as well?

[jameslamb]

This looks great, thanks so much! You can ignore the f(env) things in callbacks.R.

The only CI job that's failing is the check-docs task on Travis, which isn't related to your changes. It just fails sometimes. I manually restarted it. Once that succeeds, I'll merge this.

Thanks for all the hard work! Come back and contribute any time!

[github-actions]

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