Crate fieldx_aux 

Helper crate for fieldx and any third-party crates that extend its functionality. Can be used either to extend FieldX functionality or to implement your own proc-macros.

fieldx is heavily based on the darling crate, which greatly simplifies proc-macro development, but also imposes some constraints on attribute argument syntax. This crate overcomes these limitations and provides support for attribute kinds required to implement fieldx.

Here is a brief breakdown of what is provided:

• Support for nested arguments, i.e. those that look like arg1("value", trigger, subarg(...)).
• Support for syntax elements not covered by the darling crate, such as some_type(crate::types::Foo) and error(crate::error::Error, crate::error::Error::SomeProblem("with details"))¹.
• A set of types implementing standard fieldx arguments like helpers or literal values.

Usage

Imagine we are implementing a field-level attribute foo using the darling::FromField trait, and we want it to accept the following arguments:

• trigger: enables or disables certain functionality
• action: specifies a method with special meaning
• comment: accepts arbitrary text
• vis: indicates whether field-related code should be public, and if so, which kind of pub modifier to use

A field declaration may take the following form with the attribute:

    #[foo(
        trigger,
        action("method_name", private),
        comment("Whatever we consider useful."),
        vis(pub(crate))
    )]
    bar: usize,

For this, you’ll need the following declaration somewhere in your proc-macro implementation:

#derive(FromField)
#[darling(attributes(foo))]
struct FooField {
    // ... skipping some darling default fields ...

    trigger: Option<FXBool>,
    action: Option<FXHelper>,
    comment: Option<FXString>,
    vis: Option<FXSynValue<syn::Visibility>>,
}

That’s all; this crate will take care of implementing the arguments for you!

Read the FieldX Object Manager book for the introduction on how to use this crate.

---

1. Here, the first argument of error()—Error—is an enum, and SomeProblem is one of its variants. ↩

Re-exports

pub use crate::accessor_helper::FXAccessorHelper;

pub use crate::accessor_helper::FXAccessorMode;

pub use crate::attributes::FXAttribute;

pub use crate::base_helper::FXBaseHelper;

pub use crate::builder_helper::FXBuilderHelper;

pub use crate::default_arg::FXDefault;

pub use crate::doc_arg::FXDocArg;

pub use crate::fallible::FXFallible;

pub use crate::nesting_attr::FXNestingAttr;

pub use crate::nesting_attr::FromNestAttr;

pub use crate::serde_helper::FXSerdeHelper;

pub use crate::setter_helper::FXSetterHelper;

pub use crate::syn_value::FXPunctuated;

pub use crate::syn_value::FXSynTupleArg;

pub use crate::syn_value::FXSynValueArg;

pub use crate::value::FXValueArg;

pub use crate::with_origin::FXOrig;

pub use crate::property::*;

pub use crate::traits::*;

Modules

accessor_helper

Implementation of accessor helper (get argument of fxstruct/fieldx attributes).

attributes

attributes* family of arguments.

base_helper

The most basic helper declaration

builder_helper

Parameters of builder pattern and builder object.

default_arg

Default value.

doc_arg

fallible

Argument that signals possibility of errors.

nesting_attr

Argument nesting support module.

property

serde_helper

setter_helper

syn_value

Support for types that are not supported by darling but implement syn::parse::Parse

traits

value

Literal value arguments

with_origin

Trait for objects that know their origins.

Macros

ident_or_alias

join_token_list

set_literals

Generate implementation of set_literals method for FromNestAttr trait.

to_tokens_vec

validate_exclusives

Generate validate_exclusives that would return a darling::Result if two arguments of an attribute are conflicting with each other.

validate_no_subarg_at_level

Generate code error out on sub-arguments that are invalid at a given level.

Structs

FXSyncMode

Enums

FXSyncModeVariant

Concurrency mode

Type Aliases

FXAccessor

Accessor helper

FXAttributes

FXBool

Boolean literal

FXBuilder

Builder helper

FXDoc

doc argument

FXHelper

Standard helper

FXSerde

serde argument

FXSetter

Setter helper

FXString

String literal

FXSynTuple

Standard tuple for types implementing syn::parse::Parse

FXSynValue

Standard type implementing syn::parse::Parse

FXValue

Standard literal value

Attribute Macros

fxhelper

This macro is used to generate helper structs. It adds the following fields to support related helper functionality: