Crate optional_struct

This crate provides the user with a macro, optional_struct, which allows the user to generate structures with optional fields, as well as functions for “fusing” such structures to form a concrete instance of the original, user-defined structure. This was developed with the goal of simplifying aggregating configurations coming from different sources, such as e.g. file, env, CLI, etc.

Traits

Applicable

The trait is implemented for every generated structure. Thanks to this, you can use optional_struct in generic contexts. You should never have to implement this manually.

Attribute Macros

optional_struct

The core of this crate. Call this proc macro on your structures to generate another structure containing Optional fields, as well as helpers functions to convert those optional_struct to their base, or even update only fields that have been set. This makes aggregating structures from different sources (e.g. configuration from file/env/CLI) simple. The generated struct by default will wrap all fields in an Option, unless the field already is an Option. There are however other attributes that one can use to enforce a different behaviour: optional_rename => rename the type in the generated structure. Useful when the nested structure itself has an optional_struct. This enables arbitrary nesting of optional_struct (see tests for examples). optional_skip_wrap => this force not wrapping a value, e.g. T stays T. This is enabled by default if T is a Optiona<U>. optional_wrap => this forces wrapping a value, e.g. U becomes Option<U>. Enabling this allows nested Option, e.g. Option<V> can become Option<Option<V>> optional_serde_skip_none => This generate an extra #[serde(skip_serializing_if = ... )] to the generated structures. Useful if you want to (de)serialize those structures with serde.