bkietz edited a comment on pull request #8256: URL: https://github.com/apache/arrow/pull/8256#issuecomment-724985123
@nealrichardson @romainfrancois I've refactored `r6_class_name` to a trait. For simple cases it's no longer necessary to declare the R6 class name- we correctly guess that `arrow::Field` corresponds to "Field". I've also added comments explaining why it's sometimes necessary to override this default and how, let me know if you'd like them more verbose. > How does it fail/error if you forget to add one For a new c++ function `shared_ptr<arrow::Widget> MakeWidget()`, the default R6 class name for the return value will be "Widget". If no such R6 class exists, we'll [`stop()`](https://github.com/apache/arrow/pull/8256/files#diff-ef920fdae5124d20b341b9710adf8a33367cd2d24e08510913419ead9c8bb40fR304-R306) anytime MakeWidget() is called (because we don't know how to box its return value). For example, when I tried to change the return type of `dataset___UnionDatasetFactory__Make` I got: ``` ══ Failed ══════════════════════════════════════════════════════════════════════ ── 1. Error: Assembling multiple DatasetFactories with DatasetFactory (@test-dat No arrow R6 class named 'UnionDatasetFactory' Backtrace: 1. DatasetFactory$create(list(factory1, factory2)) testthat/test-dataset.R:723:2 2. arrow:::dataset___UnionDatasetFactory__Make(x) ``` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
