How to handle replacement of single config entries inside a nested configuration? about figment HOT 2 CLOSED

All you need to do is ensure that the CLI arguments structure serializes in such a way that's compatible with the structure of your other configuration options. Serde has an incredible number of options to configure the automatic derivation of Serialize; see https://serde.rs for all of its docs, in particular https://serde.rs/attributes.html and the following pages.

Alternatively, you could manually convert your CLI config structure into a Config and merge the resulting value.

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Thanks for your answer - I didn't know about serde attributes, yet. That looks very promising.
I worked around my issue by building a PartialConfigBuilder which converts my CLI-config into a HashMap-representation of the config. This works well, but needs quite a lot of boilerplate, so I'll definitely see, if I can solve this with attributes. (They reason why my CLI currently can't exactly match the config is, because I want these arguments to be optional, but the config itself requires them and sets defaults instead when initializing the Figment - Maybe this is bad design? I am not quite sure. I just didn't want to handle lots of Options inside my code...)

Edit:
I tried to refactor my code and use serde attributes instead, as you suggested. It works like a charm and I could get rid of a lot of boilerplate. Here is what I did:

1. Add additional sub-structs to my clap parser to match the structure of my configuration
2. Because these sub-structs are named differently than the actual structs used inside my real config, I used `#[serde(rename(serialize = ))] container attributes, to make sure they match after serialization.
3. Because my parser arguments are wrappen with Option I also added #[serde(skip_serializing_if = "Option::is_none")] to each field, so that they are simply ignored if they are not set.

ApparentlySerde + Figment take care of the rest of the work and make sure, the arguments are unwrapped correctly to their inner values and merging the result with my base figment works like a charm.

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