There's no way to unset an `Option` field from env variables about figment HOT 2 CLOSED

That's true, and intended. As described in the docs, environment variable value parsing is based on TOML, which has no notion of null whatsoever. I don't foresee this basis changing - I don't think Figment should be in the business of defining formats. I don't foresee Figment special-casing null, but we could consider parameterizing Env so that it accepts a value parser, however, and provide implementations based on TOML and YAML. That would enable what you're asking for with limited changes on your end and no hard-coded decision on ours.

In the mean time, you can trivially manage this in your end via any of the following options:

• Use a custom deserializing function for your field via #[serde(deserialize_with = "path")].
• Defining your own enum and using the appropriate serde attributes to get the serialization you want.
• Defining your own Provider that takes Env but converts whichever values you want into the None you desire.

from figment.

no hard-coded decision on ours.

Makes sense to me :)

environment variable value parsing is based on TOML, which has no notion of null whatsoever.

Just out of curiosity, how would the None variant in TOML work for the aforementioned option? Would it be option = "None"?

Use a custom deserializing function for your field via #[serde(deserialize_with = "path")].
Defining your own enum and using the appropriate serde attributes to get the serialization you want.

These 2 workarounds are a bit "expensive" for me, as my configuration struct is a collection of other configuration structs scattered around my codebase, so it's quite some significant amount of code to change. It also sounds incorrect to me that I have to modify the target struct to adapt it to the parser logic.

Perhaps would you be up for a contribution to provide a value parser for Env? One can then easily copy over the parse.rs from this project and adapt to its needs? Or maybe in the in the simple cases even wrapping over the current FromStr implementation is enough.

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