chore: Release macroconf version 0.3.6

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "macroconf"
-version = "0.3.0"
+version = "0.3.6"
 edition = "2021"
 description = "macro for creating configurations using miniconf"
 license = "MIT OR Apache-2.0"
@@ -33,3 +33,5 @@ darling = "0.20"
 [dev-dependencies]
 miniconf = { version = "0.13", features = ["json-core"] }
 serde = "1.0"
+rstest = "0.22"
+serde-json-core = "0.5.1"

src/lib.rs

@@ -2,12 +2,41 @@
 //! extra information about the field.
 
 use darling::{util::PathList, FromMeta};
+use parser::Enum;
 use proc_macro::TokenStream;
 use quote::quote;
 use syn::{parse_macro_input, parse_quote, DataStruct, DeriveInput};
 
 mod parser;
 
+/// Implements `miniconf::Tree` for the given enum.
+///
+/// This implementation of `miniconf::Tree` adds a value and a variants path.
+/// The value path serializes the enum.
+/// The variants path serializes all possible variants as an array.
+/// Optionally default and description paths can be generated.
+/// The description is generated from the docstring describing the enum.
+///
+/// # Example
+/// ```
+/// use macroconf::ConfigEnum;
+/// use serde::{Serialize, Deserialize};
+///
+/// /// Description
+/// #[derive(Default, ConfigEnum, Serialize, Deserialize)]
+/// enum Test {
+///     #[default]
+///     Variant1,
+///     Variant2,
+///     Variant3,
+/// }
+/// ```
+#[proc_macro_derive(ConfigEnum, attributes(default))]
+pub fn config_enum(item: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(item as Enum);
+    input.generate_tree().into()
+}
+
 /// Creates structs for the values to extend them with extra metadata.
 ///
 /// supported metadata is `min`, `max` and `default`. Doc comments are parsed as `description`

src/parser.rs

@@ -1,14 +1,16 @@
 #![allow(clippy::option_if_let_else)]
 
+use std::convert::identity;
+
 use convert_case::{Case, Casing};
 use darling::{
     ast::{self, Data},
-    util::{Override, PathList},
+    util::{Flag, Override, PathList},
     Error, FromDeriveInput, FromField, FromMeta,
 };
 use proc_macro2::{Span, TokenStream};
 use quote::{format_ident, quote};
-use syn::parse_quote;
+use syn::{braced, parse::Parse, parse_quote, spanned::Spanned, Token};
 
 #[derive(Debug, FromField)]
 #[darling(attributes(config))]
@@ -21,6 +23,10 @@ pub struct ConfigField {
     min: Option<Override<syn::Expr>>,
     max: Option<Override<syn::Expr>>,
     default: Option<Override<syn::Expr>>,
+    typ: Option<syn::Type>,
+    get: Option<syn::Path>,
+    set: Option<syn::Path>,
+    no_serde: Flag,
     #[darling(skip)]
     description: Option<syn::Expr>,
     #[darling(skip)]
@@ -29,11 +35,12 @@ pub struct ConfigField {
 
 impl ConfigField {
     pub(crate) fn needs_newtype(&self) -> bool {
-        self.helper_keys().len() > 1
+        self.helper_keys().len() > 1 || self.typ.is_some()
     }
 
     pub(crate) fn helper(&self, attrs: &[syn::Attribute]) -> (Option<TokenStream>, syn::Type) {
         if self.needs_newtype() {
+            let default = self.helper_default();
             let derives = attrs
                 .iter()
                 .find(|attr| attr.path().is_ident("derive"))
@@ -45,6 +52,7 @@ impl ConfigField {
                             derive.contains("Tree")
                                 || derive.contains("Serialize")
                                 || derive.contains("Deserialize")
+                                || (default.is_some() && derive.contains("Default"))
                         }) == Some(false)
                     });
                     quote! {#[derive(#(#derives,)*)]}
@@ -54,7 +62,6 @@ impl ConfigField {
             let ty = &self.ty;
 
             let new = self.helper_new();
-            let default = self.helper_default();
             let serde = self.helper_serde();
             let tree = self.helper_tree();
 
@@ -88,7 +95,8 @@ impl ConfigField {
     }
 
     pub(crate) fn has_custom_limits(&self) -> bool {
-        !((self.min.is_none() || self.min == Some(Override::Inherit))
+        self.typ.is_none()
+            && !((self.min.is_none() || self.min == Some(Override::Inherit))
                 && (self.max.is_none() || self.max == Some(Override::Inherit)))
     }
 
@@ -146,9 +154,12 @@ impl ConfigField {
     }
 
     pub(crate) fn helper_default(&self) -> Option<TokenStream> {
+        if self.typ.is_some() {
+            return None;
+        }
         self.default.as_ref().map(|default| {
             let ident = self.helper_ident();
-            let default_default = parse_quote!(default::Default());
+            let default_default = parse_quote!(::core::default::Default::default());
             let default = default.as_ref().unwrap_or(&default_default);
             quote! {
                 impl ::core::default::Default for #ident {
@@ -160,7 +171,10 @@ impl ConfigField {
         })
     }
 
-    pub(crate) fn helper_serde(&self) -> TokenStream {
+    pub(crate) fn helper_serde(&self) -> Option<TokenStream> {
+        if self.no_serde.is_present() {
+            return None;
+        }
         let ident = self.helper_ident();
         let conversion = if self.has_custom_limits() {
             quote! {
@@ -174,7 +188,7 @@ impl ConfigField {
             }
         };
         let ty = &self.ty;
-        quote! {
+        Some(quote! {
             impl ::serde::Serialize for #ident {
                 fn serialize<S>(&self, serializer: S) -> ::core::result::Result::<S::Ok, S::Error>
                 where
@@ -194,7 +208,7 @@ impl ConfigField {
                     #conversion
                 }
             }
-        }
+        })
     }
 
     pub(crate) fn helper_tree(&self) -> TokenStream {
@@ -209,7 +223,7 @@ impl ConfigField {
         macro_rules! field_to_key {
             ($field: ident, $default: expr) => {
                 self.$field.as_ref().map(|value| {
-                    let ty = &self.ty;
+                    let ty = self.typ.as_ref().unwrap_or(&self.ty);
                     (stringify!($field),
                     value.clone().explicit().map(|val| {
                         parse_quote!({
@@ -288,6 +302,7 @@ impl ConfigField {
             .helper_keys()
             .iter()
             .enumerate()
+            .skip(1)
             .map(|(i, (_, expr))| {
                 quote! {
                     #i => ::serde::Serialize::serialize(&#expr, ser).map_err(|err| ::miniconf::Error::Inner(0, err)),
@@ -295,6 +310,10 @@ impl ConfigField {
             })
             .collect::<Vec<_>>();
         let ident = self.helper_ident();
+        let get = self
+            .get
+            .as_ref()
+            .map_or_else(|| quote! {self}, |getter| quote! {#getter(&self.0)});
         quote! {
             impl ::miniconf::TreeSerialize<1> for #ident {
                 fn serialize_by_key<K, S>(
@@ -307,13 +326,14 @@ impl ConfigField {
                     S: ::serde::Serializer,
                 {
                     let ::core::result::Result::Ok(key) = keys.next::<Self>() else {
-                        return ::serde::Serialize::serialize(&self, ser).map_err(|err| ::miniconf::Error::Inner(1, err)).map(|_| 1);
+                        return ::serde::Serialize::serialize(&#get, ser).map_err(|err| ::miniconf::Error::Inner(0, err)).map(|_| 0);
                     };
-                    let index = ::miniconf::Key::find::<Self>(&key).ok_or(::miniconf::Traversal::NotFound(1))?;
+                    let index = ::miniconf::Key::find::<Self>(&key).ok_or(::miniconf::Traversal::NotFound(0))?;
                     if !keys.finalize() {
-                        return ::core::result::Result::Err(::miniconf::Traversal::TooLong(1).into());
+                        return ::core::result::Result::Err(::miniconf::Traversal::TooLong(0).into());
                     }
                     match index {
+                        0 => ::serde::Serialize::serialize(&#get, ser).map_err(|err| ::miniconf::Error::Inner(0, err)),
                         #(#matches)*
                         _ => unreachable!(),
                     }?;
@@ -326,6 +346,21 @@ impl ConfigField {
     pub(crate) fn helper_tree_deserialize(&self) -> TokenStream {
         let ident = self.helper_ident();
         let num_keys = self.helper_keys().len();
+        let set = self.set.as_ref().map_or_else(
+            || quote!((|val| {*self = val; core::result::Result::<_, ::miniconf::Traversal>::Ok(())})),
+            |set| quote!((|val| #set(&mut self.0, val).map_err(|e| ::miniconf::Traversal::Invalid(0, e)))),
+        );
+        let typ = self
+            .typ
+            .as_ref()
+            .map_or_else(|| quote!(Self), |typ| quote!(#typ));
+        let match_range = if num_keys > 1 {
+            Some(
+                quote!(1..=#num_keys => ::core::result::Result::Err(::miniconf::Traversal::Access(0, "Cannot write limits").into()),),
+            )
+        } else {
+            None
+        };
         quote! {
             impl<'de> ::miniconf::TreeDeserialize<'de, 1> for #ident {
                 fn deserialize_by_key<K, D>(
@@ -338,7 +373,7 @@ impl ConfigField {
                     D: ::serde::Deserializer<'de>,
                 {
                     let ::core::result::Result::Ok(key) = keys.next::<Self>() else {
-                        *self = <Self as ::serde::Deserialize>::deserialize(de).map_err(|err| ::miniconf::Error::Inner(0, err))?;
+                        #set(<#typ as ::serde::Deserialize>::deserialize(de).map_err(|err| ::miniconf::Error::Inner(0, err))?)?;
                         return ::core::result::Result::Ok(0);
                     };
                     let index = ::miniconf::Key::find::<Self>(&key).ok_or(::miniconf::Traversal::NotFound(1))?;
@@ -347,11 +382,10 @@ impl ConfigField {
                     }
                     match index {
                         0 => {
-                            *self = <Self as ::serde::Deserialize>::deserialize(de).map_err(|err| ::miniconf::Error::Inner(0, err))?;
+                            #set(<#typ as ::serde::Deserialize>::deserialize(de).map_err(|err| ::miniconf::Error::Inner(0, err))?)?;
                             Ok(0)
                         }
-                        ,
-                        1..=#num_keys => ::core::result::Result::Err(::miniconf::Traversal::Access(0, "Cannot write limits").into()),
+                        #match_range
                         _ => unreachable!(),
                     }
                 }
@@ -367,6 +401,13 @@ impl ConfigField {
         } else {
             quote!(::core::result::Result::Ok(&mut *self))
         };
+        let match_range = if num_keys > 1 {
+            Some(
+                quote!(1..#num_keys => ::core::result::Result::Err(::miniconf::Traversal::Access(1, "cannot return reference to local variable")),),
+            )
+        } else {
+            None
+        };
         quote! {
             impl ::miniconf::TreeAny<1> for #ident {
                 fn ref_any_by_key<K>(&self, mut keys: K) -> ::core::result::Result<&dyn ::core::any::Any, ::miniconf::Traversal>
@@ -382,7 +423,7 @@ impl ConfigField {
                     }
                     match index {
                         0 => ::core::result::Result::Ok(&*self),
-                        1..#num_keys => ::core::result::Result::Err(::miniconf::Traversal::Access(1, "cannot return reference to local variable")),
+                        #match_range
                         _ => unreachable!(),
                     }
                 }
@@ -400,7 +441,7 @@ impl ConfigField {
                     }
                     match index {
                         0 => #ref_mut,
-                        1..#num_keys => ::core::result::Result::Err(::miniconf::Traversal::Access(1, "cannot return reference to local variable")),
+                        #match_range
                         _ => unreachable!(),
                     }
                 }
@@ -436,6 +477,26 @@ impl Config {
                     parse_quote!(#description)
                 });
             field.parent_ident = Some(ident.clone());
+            let get_set_typ = [
+                field.typ.is_some(),
+                field.get.is_some(),
+                field.set.is_some(),
+            ];
+            if get_set_typ.iter().copied().any(identity) && !get_set_typ.into_iter().all(identity) {
+                return Err(
+                    Error::custom("need all or none of 'typ', 'get', 'set'").with_span(
+                        &field.typ.as_ref().map_or_else(
+                            || {
+                                field.get.as_ref().map_or_else(
+                                    || field.set.as_ref().unwrap().span(),
+                                    Spanned::span,
+                                )
+                            },
+                            Spanned::span,
+                        ),
+                    ),
+                );
+            }
         }
         Ok(config)
     }
@@ -454,3 +515,256 @@ impl Config {
         &mut fields.fields
     }
 }
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub struct Enum {
+    doc: Option<String>,
+    ident: syn::Ident,
+    variants: Vec<syn::Ident>,
+    default: Option<syn::Ident>,
+}
+
+impl Enum {
+    pub fn generate_tree(&self) -> TokenStream {
+        let mut tokens = self.generate_tree_key();
+        tokens.extend(self.generate_tree_serialize());
+        tokens.extend(self.generate_tree_deserialize());
+        tokens.extend(self.generate_tree_any());
+        tokens
+    }
+
+    fn keys(&self) -> Vec<(&'static str, syn::Expr)> {
+        let variants = &self.variants;
+        let mut keys = vec![
+            ("value", parse_quote!(self)),
+            ("variants", parse_quote!([#(Self::#variants,)*])),
+        ];
+        if let Some(ref doc) = self.doc {
+            keys.push(("description", parse_quote!(#doc)));
+        }
+        if let Some(ref default) = self.default {
+            keys.push(("default", parse_quote!(Self::#default)));
+        }
+        keys
+    }
+
+    fn generate_tree_key(&self) -> TokenStream {
+        let ident = &self.ident;
+        let keys = self.keys();
+        let num_keys = keys.len();
+        let max_length = keys.iter().map(|(path, _)| path.len()).max();
+        let keys = keys.iter().map(|(path, _)| path);
+        quote! {
+            impl ::miniconf::KeyLookup for #ident {
+                const LEN: usize = #num_keys;
+                const NAMES: &'static [&'static str] = &[#(#keys,)*];
+
+                fn name_to_index(value: &str) -> Option<usize> {
+                    Self::NAMES.iter().position(|name| *name == value)
+                }
+            }
+
+            impl ::miniconf::TreeKey<1> for #ident {
+                fn metadata() -> ::miniconf::Metadata {
+                    let mut metadata = ::miniconf::Metadata::default();
+                    metadata.max_depth = 1;
+                    metadata.count = #num_keys;
+                    metadata.max_length = #max_length;
+                    metadata
+                }
+
+                fn traverse_by_key<K, F, E>(mut keys: K, mut func: F) -> ::core::result::Result<usize, ::miniconf::Error<E>>
+                where
+                    K: ::miniconf::Keys,
+                    // Writing this to return an iterator instead of using a callback
+                    // would have worse performance (O(n^2) instead of O(n) for matching)
+                    F: FnMut(usize, Option<&'static str>, usize) -> ::core::result::Result<(), E>,
+                {
+                    let ::core::result::Result::Ok(key) = keys.next::<Self>() else { return ::core::result::Result::Ok(0) };
+                    let index = ::miniconf::Key::find::<Self>(&key).ok_or(::miniconf::Traversal::NotFound(1))?;
+                    let name = <Self as ::miniconf::KeyLookup>::NAMES
+                        .get(index)
+                        .ok_or(::miniconf::Traversal::NotFound(1))?;
+                    func(index, Some(name), #num_keys).map_err(|err| ::miniconf::Error::Inner(1, err))?;
+                    ::core::result::Result::Ok(1)
+                }
+            }
+        }
+    }
+
+    fn generate_tree_serialize(&self) -> TokenStream {
+        let ident = &self.ident;
+        let matches = self
+            .keys()
+            .iter()
+            .enumerate()
+            .map(|(i, (_, expr))| {
+                quote! {
+                    #i => ::serde::Serialize::serialize(&#expr, ser).map_err(|err| ::miniconf::Error::Inner(0, err)),
+                }
+            })
+            .collect::<Vec<_>>();
+        quote! {
+            impl ::miniconf::TreeSerialize<1> for #ident {
+                fn serialize_by_key<K, S>(
+                    &self,
+                    mut keys: K,
+                    ser: S,
+                ) -> ::core::result::Result<usize, ::miniconf::Error<S::Error>>
+                where
+                    K: ::miniconf::Keys,
+                    S: ::serde::Serializer,
+                {
+                    let ::core::result::Result::Ok(key) = keys.next::<Self>() else {
+                        return ::serde::Serialize::serialize(self, ser).map_err(|err| ::miniconf::Error::Inner(0, err)).map(|_| 0);
+                    };
+                    let index = ::miniconf::Key::find::<Self>(&key).ok_or(::miniconf::Traversal::NotFound(0))?;
+                    if !keys.finalize() {
+                        return ::core::result::Result::Err(::miniconf::Traversal::TooLong(0).into());
+                    }
+                    match index {
+                        #(#matches)*
+                        _ => unreachable!(),
+                    }?;
+                    Ok(0)
+                }
+            }
+        }
+    }
+
+    fn generate_tree_deserialize(&self) -> TokenStream {
+        let ident = &self.ident;
+        let num_keys = self.keys().len();
+        quote! {
+            impl<'de> ::miniconf::TreeDeserialize<'de, 1> for #ident {
+                fn deserialize_by_key<K, D>(
+                    &mut self,
+                    mut keys: K,
+                    de: D,
+                ) -> ::core::result::Result<usize, ::miniconf::Error<D::Error>>
+                where
+                    K: ::miniconf::Keys,
+                    D: ::serde::Deserializer<'de>,
+                {
+                    let ::core::result::Result::Ok(key) = keys.next::<Self>() else {
+                        *self = <Self as ::serde::Deserialize>::deserialize(de).map_err(|err| ::miniconf::Error::Inner(0, err))?;
+                        return ::core::result::Result::Ok(0);
+                    };
+                    let index = ::miniconf::Key::find::<Self>(&key).ok_or(::miniconf::Traversal::NotFound(1))?;
+                    if !keys.finalize() {
+                        return ::core::result::Result::Err(::miniconf::Traversal::TooLong(1).into());
+                    }
+                    match index {
+                        0 => {
+                            *self = <Self as ::serde::Deserialize>::deserialize(de).map_err(|err| ::miniconf::Error::Inner(0, err))?;
+                            Ok(0)
+                        }
+                        1..=#num_keys => ::core::result::Result::Err(::miniconf::Traversal::Access(0, "Cannot write limits").into()),
+                        _ => unreachable!(),
+                    }
+                }
+            }
+        }
+    }
+
+    fn generate_tree_any(&self) -> TokenStream {
+        let ident = &self.ident;
+        let num_keys = self.keys().len();
+        quote! {
+            impl ::miniconf::TreeAny<1> for #ident {
+                fn ref_any_by_key<K>(&self, mut keys: K) -> ::core::result::Result<&dyn ::core::any::Any, ::miniconf::Traversal>
+                where
+                    K: ::miniconf::Keys,
+                {
+                    let ::core::result::Result::Ok(key) = keys.next::<Self>() else {
+                        return ::core::result::Result::Ok(self);
+                    };
+                    let index = ::miniconf::Key::find::<Self>(&key).ok_or(::miniconf::Traversal::NotFound(1))?;
+                    if !keys.finalize() {
+                        return ::core::result::Result::Err(::miniconf::Traversal::TooLong(1));
+                    }
+                    match index {
+                        0 => ::core::result::Result::Ok(self),
+                        1..#num_keys => ::core::result::Result::Err(::miniconf::Traversal::Access(1, "cannot return reference to local variable")),
+                        _ => unreachable!(),
+                    }
+                }
+
+                fn mut_any_by_key<K>(&mut self, mut keys: K) -> ::core::result::Result<&mut dyn ::core::any::Any, ::miniconf::Traversal>
+                where
+                    K: ::miniconf::Keys,
+                {
+                    let ::core::result::Result::Ok(key) = keys.next::<Self>() else {
+                        return Ok(self);
+                    };
+                    let index = ::miniconf::Key::find::<Self>(&key).ok_or(::miniconf::Traversal::NotFound(1))?;
+                    if !keys.finalize() {
+                        return ::core::result::Result::Err(::miniconf::Traversal::TooLong(1));
+                    }
+                    match index {
+                        0 => Ok(self),
+                        1..#num_keys => ::core::result::Result::Err(::miniconf::Traversal::Access(1, "cannot return reference to local variable")),
+                        _ => unreachable!(),
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl Parse for Enum {
+    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
+        let attrs = input.call(syn::Attribute::parse_outer)?;
+        let doc = attrs
+            .iter()
+            .find(|attr| attr.path().is_ident("doc"))
+            .map(|attr| {
+                let meta = attr.meta.require_name_value()?;
+                if let syn::Expr::Lit(syn::ExprLit {
+                    attrs: _,
+                    lit: syn::Lit::Str(ref lit),
+                }) = meta.value
+                {
+                    Ok(lit.value().trim().to_owned())
+                } else {
+                    Err(syn::Error::new_spanned(
+                        &meta.value,
+                        "Expected string literal for doc comment",
+                    ))
+                }
+            })
+            .transpose()?;
+
+        let _vis = input.parse::<syn::Visibility>()?;
+        let _enum_token = input.parse::<Token![enum]>()?;
+
+        let ident = input.parse::<syn::Ident>()?;
+
+        let content;
+        let _brace = braced!(content in input);
+        let variants = content.parse_terminated(syn::Variant::parse, Token![,])?;
+        if let Some(variant) = variants.iter().find(|variant| !variant.fields.is_empty()) {
+            return Err(syn::Error::new_spanned(
+                &variant.fields,
+                "only unit variants are supported for now",
+            ));
+        }
+        let default = variants
+            .iter()
+            .find(|variant| {
+                variant
+                    .attrs
+                    .iter()
+                    .any(|attr| attr.path().is_ident("default"))
+            })
+            .map(|variant| variant.ident.clone());
+        let variants = variants.into_iter().map(|variant| variant.ident).collect();
+
+        Ok(Self {
+            doc,
+            ident,
+            variants,
+            default,
+        })
+    }
+}

tests/enum.rs

@@ -0,0 +1,62 @@
+use macroconf::ConfigEnum;
+use miniconf::{Error::Traversal, JsonCoreSlash, JsonPath, Traversal::Access, TreeKey};
+use rstest::*;
+use serde::{Deserialize, Serialize};
+use std::str::from_utf8;
+
+/// Description
+#[derive(Debug, Default, PartialEq, Eq, ConfigEnum, Serialize, Deserialize)]
+enum Test {
+    #[default]
+    Variant1,
+    Variant2,
+    Variant3,
+}
+
+#[test]
+fn nodes() {
+    let nodes = Test::nodes::<JsonPath<String>>()
+        .map(|p| p.unwrap().0.into_inner())
+        .collect::<Vec<_>>();
+    assert_eq!(
+        nodes,
+        vec![".value", ".variants", ".description", ".default"]
+    );
+}
+
+#[fixture]
+#[once]
+fn test() -> Test {
+    Test::Variant2
+}
+
+#[rstest]
+#[case("/", "\"Variant2\"")]
+#[case("/value", "\"Variant2\"")]
+#[case("/description", "\"Description\"")]
+#[case("/default", "\"Variant1\"")]
+#[case("/variants", "[\"Variant1\",\"Variant2\",\"Variant3\"]")]
+fn serialize(test: &Test, #[case] path: &str, #[case] expected: &str) {
+    let mut buffer = [0u8; 64];
+    let len = test.get_json(path, &mut buffer).unwrap();
+    assert_eq!(from_utf8(&buffer[..len]), Ok(expected));
+}
+
+#[rstest]
+#[case("/", Ok(10))]
+#[case("/value", Ok(10))]
+#[case("/variants", Err(Traversal(Access(0, "Cannot write limits"))))]
+#[case("/default", Err(Traversal(Access(0, "Cannot write limits"))))]
+#[case("/description", Err(Traversal(Access(0, "Cannot write limits"))))]
+fn deserialize(
+    #[case] path: &str,
+    #[case] expected: Result<usize, miniconf::Error<serde_json_core::de::Error>>,
+) {
+    let mut config = Test::Variant2;
+
+    let res = config.set_json(path, b"\"Variant3\"");
+    assert_eq!(res, expected);
+    if res.is_ok() {
+        assert_eq!(config, Test::Variant3);
+    }
+}

tests/get_set.rs

@@ -0,0 +1,65 @@
+use std::{cell::Cell, str::from_utf8};
+
+use macroconf::config;
+use miniconf::JsonCoreSlash;
+
+fn set_cell<const MIN: i32, const MAX: i32>(
+    cell: &Cell<i32>,
+    val: i32,
+) -> Result<(), &'static str> {
+    if (MIN..=MAX).contains(&val) {
+        cell.set(val);
+        Ok(())
+    } else {
+        Err("value out of bounds")
+    }
+}
+
+#[config]
+struct Config {
+    #[config(
+        min = "-128",
+        max = "128",
+        default,
+        typ = "i32",
+        get = "Cell::get",
+        set = "set_cell::<-128,128>"
+    )]
+    field: Cell<i32>,
+}
+
+#[config]
+struct WithSetterAndDefault {
+    #[config(
+        default = "42",
+        typ = "i32",
+        get = "Cell::get",
+        set = "set_cell::<{i32::MIN}, {i32::MAX}>"
+    )]
+    field: Cell<i32>,
+}
+
+#[test]
+fn get() {
+    let mut buffer = [0u8; 32];
+    let config = Config {
+        field: __ConfigField::new(Cell::new(42)),
+    };
+    let len = config.get_json("/field", &mut buffer).unwrap();
+    assert_eq!(from_utf8(&buffer[..len]), Ok("42"));
+}
+
+#[test]
+fn set() {
+    let mut config = Config {
+        field: __ConfigField::new(Cell::new(42)),
+    };
+    config.set_json("/field", b"-32").unwrap();
+    assert_eq!(config.field.get(), -32);
+    config
+        .set_json("/field", b"256")
+        .expect_err("result not checked");
+    config
+        .set_json("/field", b"-256")
+        .expect_err("result not checked");
+}

tests/simple.rs

@@ -7,6 +7,7 @@ use miniconf::{
     Traversal::{Access, TooLong},
     Tree, TreeKey,
 };
+use rstest::*;
 use serde::{Deserialize, Serialize};
 
 #[config]
@@ -30,27 +31,47 @@ struct Config {
     sub_config: SubConfig,
 }
 
-#[test]
-fn keys() {
-    for (id, field) in ["skipped", "min", "max", "default", "description"]
-        .into_iter()
-        .enumerate()
-    {
+/// Config with default derive and default field
+#[config]
+#[derive(Default)]
+struct _DefaultConfig {
+    #[config(default)]
+    field: i32,
+}
+
+#[rstest]
+#[case(0, ["skipped"])]
+#[case(1, ["min"])]
+#[case(2, ["max"])]
+#[case(3, ["default"])]
+#[case(4, ["description"])]
+fn key<const N: usize>(#[case] id: usize, #[case] field: [&str; N]) {
     assert_eq!(
-            SubConfig::traverse_by_key([field].into_keys(), |index, name, _len| {
-                assert_eq!((id, Some(field)), (index, name));
+        SubConfig::traverse_by_key(field.into_keys(), |index, name, _len| {
+            assert_eq!((id, Some(field[field.len() - 1])), (index, name));
             Ok::<_, ()>(())
         }),
         Ok(1)
     );
-    }
 }
 
-#[test]
-fn sub_keys() {
+#[rstest]
+#[case(["skipped", "value"], Err(Traversal(TooLong(1))))]
+#[case(["min", "value"], Ok(2))]
+#[case(["max", "value"], Ok(2))]
+#[case(["default", "value"], Ok(2))]
+#[case(["description", "value"], Ok(2))]
+#[case(["min", "min"], Ok(2))]
+#[case(["max", "max"], Ok(2))]
+#[case(["default", "default"], Ok(2))]
+#[case(["description", "description"], Ok(2))]
+fn sub_keys<const N: usize>(
+    #[case] fields: [&str; N],
+    #[case] expected: Result<usize, miniconf::Error<()>>,
+) {
     assert_eq!(
-        SubConfig::traverse_by_key(["skipped", "value"].into_keys(), |_, _, _| Ok::<_, ()>(())),
-        Err(Traversal(TooLong(1)))
+        SubConfig::traverse_by_key(fields.into_keys(), |_, _, _| Ok::<_, ()>(())),
+        expected
     );
     assert_eq!(
         SubConfig::traverse_by_key(["skipped"].into_keys(), |_, _, _| Ok::<_, ()>(())),
@@ -68,39 +89,59 @@ fn sub_keys() {
     }
 }
 
-#[test]
-fn serialize() {
-    let mut buffer = [0u8; 32];
-    let config = SubConfig {
+#[fixture]
+#[once]
+fn sub_config() -> SubConfig {
+    SubConfig {
         skipped: 1,
         min: __SubConfigMin::new(2),
         max: __SubConfigMax::new(3),
         default: __SubConfigDefault::new(4),
         description: __SubConfigDescription::new(5),
-    };
-
-    for (input, output) in [
-        ("/skipped", "1"),
-        ("/min", "2"),
-        ("/min/value", "2"),
-        ("/min/min", "-2147483648"),
-        ("/max", "3"),
-        ("/max/value", "3"),
-        ("/max/max", "2147483647"),
-        ("/default", "4"),
-        ("/default/value", "4"),
-        ("/default/default", "0"),
-        ("/description", "5"),
-        ("/description/value", "5"),
-        ("/description/description", "\"This is a description\""),
-    ] {
-        let len = config.get_json(input, &mut buffer).unwrap();
-        assert_eq!(from_utf8(&buffer[..len]), Ok(output));
     }
 }
 
-#[test]
-fn deserialize() {
+#[rstest]
+#[case("/skipped", "1")]
+#[case("/min", "2")]
+#[case("/min/value", "2")]
+#[case("/min/min", "-2147483648")]
+#[case("/max", "3")]
+#[case("/max/value", "3")]
+#[case("/max/max", "2147483647")]
+#[case("/default", "4")]
+#[case("/default/value", "4")]
+#[case("/default/default", "0")]
+#[case("/description", "5")]
+#[case("/description/value", "5")]
+#[case("/description/description", "\"This is a description\"")]
+fn serialize(sub_config: &SubConfig, #[case] path: &str, #[case] expected: &str) {
+    let mut buffer = [0u8; 32];
+    let len = sub_config.get_json(path, &mut buffer).unwrap();
+    assert_eq!(from_utf8(&buffer[..len]), Ok(expected));
+}
+
+#[rstest]
+#[case("/skipped", Ok(2))]
+#[case("/min", Ok(2))]
+#[case("/min/value", Ok(2))]
+#[case("/max", Ok(2))]
+#[case("/max/value", Ok(2))]
+#[case("/default", Ok(2))]
+#[case("/default/value", Ok(2))]
+#[case("/description", Ok(2))]
+#[case("/description/value", Ok(2))]
+#[case("/min/min", Err(Traversal(Access(1, "Cannot write limits"))))]
+#[case("/max/max", Err(Traversal(Access(1, "Cannot write limits"))))]
+#[case("/default/default", Err(Traversal(Access(1, "Cannot write limits"))))]
+#[case(
+    "/description/description",
+    Err(Traversal(Access(1, "Cannot write limits")))
+)]
+fn deserialize(
+    #[case] path: &str,
+    #[case] expected: Result<usize, miniconf::Error<serde_json_core::de::Error>>,
+) {
     let mut config = SubConfig {
         skipped: 0,
         min: __SubConfigMin::new(0),
@@ -109,34 +150,12 @@ fn deserialize() {
         description: __SubConfigDescription::new(0),
     };
 
-    for input in [
-        "/skipped",
-        "/min",
-        "/min/value",
-        "/max",
-        "/max/value",
-        "/default",
-        "/default/value",
-        "/description",
-        "/description/value",
-    ] {
-        let res = config.set_json(input, b"10");
-        assert_eq!(res, Ok(2));
-    }
-
-    for input in [
-        "/min/min",
-        "/max/max",
-        "/default/default",
-        "/description/description",
-    ] {
-        let res = config.set_json(input, b"10");
-        assert_eq!(res, Err(Traversal(Access(1, "Cannot write limits"))));
-    }
+    let res = config.set_json(path, b"10");
+    assert_eq!(res, expected);
 }
 
 #[test]
-fn subconfig() {
+fn config_paths() {
     let control = vec![
         "/sub_config/skipped".to_owned(),
         "/sub_config/min/value".to_owned(),