Omry Yadan

String concatenation is already supported directly: ```yaml url: http://${host}:${port}:${path} ``` It might still be worth supporting it, but some other things does not make immediate sense, for example: ```yaml a:...

Supporting + for arbitrary values may be incompatible with existing strings: ```yaml foo: FOO bar: BAR key: ${foo}+${bar} ``` current interpretation is `FOO+BAR`, new interpretation will be FOOBAR. limiting to...

@odelalleau, I was thinking about introducing an eval resolver later to do arithmetic operations. It could also be using a different syntax, like `#{expression}`. ```yaml two : #{1 * 2}...

The main concern is backward compatibility. Interpreting all configs as expressions means that you can't have a config value that is an expression: ```yaml x: 10 * 2 ``` Quoting...

Makes sense. I don't think we need to deprecate anything at this time (since we are not sure about the final design yet). We can deprecate things in between 2.1...

Cool. A few surface area points to test/consider: - Unions with optional: ``` Optional[Union[int, str]] Union[int,str,None] # I think this is legal to define Optional ``` - Union with containers,...

Re-request review when you want me to review again. 

FYI: I am still working on the recursive defaults in Hydra. It's a very large pull request and I am delaying reviewing of other large changes in Hydra and OmegaConf...

I bounced the Union support to OmegaConf 2.2, we will resume working on it after 2.1 is released. Thanks for working on it. Since many things have changed in 2.1,...

@till-varoquaux, would love to chat with you about this to see what is currently possible. I would like to start with the Doc annotation, and I saw multiple suggestion on...