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v0.2.2 ... main

3 changed files with 63 additions and 30 deletions

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@ -1,6 +1,6 @@
[package]
name = "serde-inline-default"
version = "0.2.2"
version = "0.2.3"
authors = ["bytedream"]
edition = "2021"
description = "Serde default values via inline declaration"

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@ -1,4 +1,4 @@
# serde-inline-default [![ci](https://github.com/ByteDream/serde-inline-default/actions/workflows/ci.yml/badge.svg)](https://github.com/ByteDream/serde-inline-default/actions/workflows/ci.yml) [![crates.io](https://img.shields.io/crates/v/serde-inline-default)](https://crates.io/crates/serde-inline-default) [![docs](https://img.shields.io/docsrs/serde-inline-default)](https://docs.rs/serde-inline-default/latest/serde_inline_default/)
# serde-inline-default [![ci](https://github.com/ByteDream/serde-inline-default/actions/workflows/ci.yml/badge.svg)](https://github.com/ByteDream/serde-inline-default/actions/workflows/ci.yml) [![crates.io](https://img.shields.io/crates/v/serde-inline-default)](https://crates.io/crates/serde-inline-default) [![crates.io downloads](https://img.shields.io/crates/d/serde-inline-default)](https://crates.io/crates/serde-inline-default) [![docs](https://img.shields.io/docsrs/serde-inline-default)](https://docs.rs/serde-inline-default/latest/serde_inline_default/)
Tiny crate to set default values for serde fields via inline attribute declaration.
@ -19,7 +19,7 @@ fn value_default() -> u32 { 42 }
That can get quiet messy if you have many fields with many (different) default values.
This crate tries to solve this issue by providing the `#[serde_inline_default]` proc macro.
With this macro set at the struct level (_**before `#[derive(Deserialize)]`/`#[derive(Serialize)]`!, otherwise it's not working correctly**_), you can set default values via `#[serde_inline_default(...)]` for your serde fields inline, without creating an extra function.
With this macro set at the struct level, you can set default values via `#[serde_inline_default(...)]` for your serde fields inline, without creating an extra function.
```rust
#[serde_inline_default]
@ -30,9 +30,54 @@ struct Test {
}
```
> [!IMPORTANT]
> **`#[serde_inline_default]` must be set before `#[derive(Deserialize)]`/`#[derive(Serialize)]`, otherwise it's not working correctly!**
Internally, `#[serde_inline_default(...)]` gets expanded to a function which returns the set value and the attribute is replaced with `#[serde(default = "<function name>")]`.
So this macro is just some syntax sugar for you, but can get quiet handy if you want to keep your code clean or write declarative macros / `macro_rules!`.
## Alternatives
This crate isn't perfect. Thus, you might be more satisfied with alternatives `serde` provides.
With `#[serde(default)]` + `impl Default` on a struct, `serde` uses the default implementation of the struct to get default values for each field ([docs](https://serde.rs/container-attrs.html#default)):
```rust
#[derive(Deserialize)]
#[serde(default)]
struct Test {
value: u32
}
impl Default for Test {
fn default() -> Self {
Self {
value: 42
}
}
}
```
If you still need/want `serde-inline-default` features, you also can combine them with `#[serde(default))` and `impl Default`:
```rust
#[serde_inline_default]
#[derive(Deserialize)]
#[serde(default)]
struct Test {
value: u32,
#[serde_inline_default(0)]
other_value: u32,
}
impl Default for Test {
fn default() -> Self {
Self {
value: 42,
other_value: 42
}
}
}
```
## License
This project is licensed under either of the following licenses, at your option:

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@ -4,7 +4,7 @@ use quote::quote;
use syn::{parse_quote, ItemStruct};
pub(crate) fn expand_struct(mut item: ItemStruct) -> proc_macro::TokenStream {
let mut inline_fns: Vec<(String, TokenStream, TokenStream)> = vec![];
let mut inline_fns: Vec<TokenStream> = vec![];
for (i, field) in item.fields.iter_mut().enumerate() {
for (j, attr) in field.attrs.iter_mut().enumerate() {
@ -14,14 +14,6 @@ pub(crate) fn expand_struct(mut item: ItemStruct) -> proc_macro::TokenStream {
let default: TokenStream = attr.parse_args().unwrap();
// we check here if a function with the exact same return value already exists. if so,
// this function gets used.
let fn_name_lit = if let Some((fn_name_lit, _, _)) = inline_fns
.iter()
.find(|(_, def, _)| def.to_string() == default.to_string())
{
fn_name_lit.clone()
} else {
let fn_name_lit = format!("__serde_inline_default_{}_{}", item.ident, i);
let fn_name_ident = Ident::new(&fn_name_lit, Span::call_site());
let mut return_type = field.ty.clone();
@ -29,16 +21,14 @@ pub(crate) fn expand_struct(mut item: ItemStruct) -> proc_macro::TokenStream {
// replaces most lifetimes with 'static
type_lifetimes_to_static(&mut return_type);
let inline_fn = quote! {
inline_fns.push(quote! {
#[doc(hidden)]
#[allow(non_snake_case)]
fn #fn_name_ident () -> #return_type {
#default
}
};
inline_fns.push((fn_name_lit.clone(), default, inline_fn));
fn_name_lit
};
});
field.attrs.remove(j);
field
.attrs
@ -47,10 +37,8 @@ pub(crate) fn expand_struct(mut item: ItemStruct) -> proc_macro::TokenStream {
}
}
let real_inline_fns: Vec<TokenStream> =
inline_fns.into_iter().map(|(_, _, func)| func).collect();
let expanded = quote! {
#( #real_inline_fns )*
#( #inline_fns )*
#item
};