Adding CustomFn layer (#34)

* Deriving `Default` trait on a number of tests, so that `cargo test --all-features` test will pass

* Adding CustomFn layer, where any Fn type, (functions or immutable closures) can provide a values.  This is useful to support additional data sources, for example a database or an unsupported file format, e.g. hjson

* Converting from Fn to FnOnce, because the 'static lifetime bound requirement on the closure makes an Fn version no better than a static fn.
Fixing a wrong doc comment

* Feature-gating tests, depending on cfg, so `cargo test` should pass, regardless of which combination of features are enabled

* Adding mention of custom_fn feature in README
Synchronizing 3 copies of README.md in the repo

README.md

@@ -11,9 +11,10 @@ For now it supports :
 
 - Default settings (inside your codebase with `#[serde(default = ...)]` coming from [serde](https://serde.rs))
 - Reading from `TOML`, `YAML`, `JSON`, `DHALL`, `INI` files
+- Executing a custom function or closure to supply values via a [serde_json::Value]
 - Reading from environment variables: it supports `HashMap` structure with `MY_VARIABLE="mykey=myvalue,mykey2=myvalue2"` and also array like `MY_VARIABLE=first,second` thanks to [envy](https://github.com/softprops/envy).
 - All [serde](https://serde.rs) attributes can be used in your struct to customize your configuration as you wish
-- Reading your configuration from your command line built with [clap](https://github.com/clap-rs/clap) (ATTENTION: if you're using version < v3 use the `twelf@0.1.8` version, if you're using `[email protected]` please use `[email protected]`)
+- Reading your configuration from your command line built with [clap](https://github.com/clap-rs/clap) (ATTENTION: if you're using version < v3 use the `[email protected]` version)
 
 # Usage
 
@@ -23,6 +24,7 @@ For now it supports :
 use twelf::{config, Layer};
 
 #[config]
+#[derive(Default)]
 struct Conf {
     test: String,
     another: usize,
@@ -49,7 +51,6 @@ struct Conf {
 
 // Will generate global arguments for each of your fields inside your configuration struct
 let app = clap::Command::new("test").args(&Conf::clap_args());
-// If you're looking for how to use with clap derive feature, check in the examples directory (twelf/examples/clap_derive.rs)
 
 // Init configuration with layers, each layers override only existing fields
 let config = Conf::with_layers(&[
@@ -68,9 +69,13 @@ Check [here](./twelf/examples) for more examples.
 Twelf supports crate features, if you only want support for `json`, `env` and `toml` then you just have to add this to your `Cargo.toml`
 
 ```toml
-twelf = { version = "0.4", default-features = false, features = ["json", "toml", "env"] }
+twelf = { version = "0.11", default-features = false, features = ["json", "toml", "env"] }
 ```
 
+`default_trait` enables code for a layer that integrate fields derived with the [std::default::Default] trait.
+
+`custom_fn` enables code for a layer that allows a custom closure to be executed.
+
 Default features are `["env", "clap"]`
 
 # Contributing

config-derive/Cargo.toml

@@ -34,3 +34,4 @@
     toml  = []
     yaml  = []
     default_trait = []
+    custom_fn = []

config-derive/README.md

@@ -11,9 +11,10 @@ For now it supports :
 
 - Default settings (inside your codebase with `#[serde(default = ...)]` coming from [serde](https://serde.rs))
 - Reading from `TOML`, `YAML`, `JSON`, `DHALL`, `INI` files
+- Executing a custom function or closure to supply values via a [serde_json::Value]
 - Reading from environment variables: it supports `HashMap` structure with `MY_VARIABLE="mykey=myvalue,mykey2=myvalue2"` and also array like `MY_VARIABLE=first,second` thanks to [envy](https://github.com/softprops/envy).
 - All [serde](https://serde.rs) attributes can be used in your struct to customize your configuration as you wish
-- Reading your configuration from your command line built with [clap](https://github.com/clap-rs/clap) (ATTENTION: if you're using version < v3 use the `twelf@1.8` version)
+- Reading your configuration from your command line built with [clap](https://github.com/clap-rs/clap) (ATTENTION: if you're using version < v3 use the `twelf@0.8` version)
 
 # Usage
 
@@ -23,6 +24,7 @@ For now it supports :
 use twelf::{config, Layer};
 
 #[config]
+#[derive(Default)]
 struct Conf {
     test: String,
     another: usize,
@@ -67,9 +69,13 @@ Check [here](./twelf/examples) for more examples.
 Twelf supports crate features, if you only want support for `json`, `env` and `toml` then you just have to add this to your `Cargo.toml`
 
 ```toml
-twelf = { version = "0.3", default-features = false, features = ["json", "toml", "env"] }
+twelf = { version = "0.11", default-features = false, features = ["json", "toml", "env"] }
 ```
 
+`default_trait` enables code for a layer that integrate fields derived with the [std::default::Default] trait.
+
+`custom_fn` enables code for a layer that allows a custom closure to be executed.
+
 Default features are `["env", "clap"]`
 
 # Contributing

config-derive/src/lib.rs

@@ -119,6 +119,7 @@ pub fn config(_attrs: TokenStream, item: TokenStream) -> TokenStream {
     let yaml_branch = build_yaml_branch();
     let dhall_branch = build_dhall_branch();
     let default_trait_branch = build_default_trait_branch();
+    let custom_fn_branch = build_custom_fn_branch();
 
     #[cfg(not(feature = "ini"))]
     let ini_branch = quote! {};
@@ -141,9 +142,9 @@ pub fn config(_attrs: TokenStream, item: TokenStream) -> TokenStream {
         docs,
     );
 
-    #[cfg(not(feature = "default_trait"))]
+    #[cfg(all(not(feature = "default_trait"), not(feature = "custom_fn")))]
     let derive_serialize = quote! {};
-    #[cfg(feature = "default_trait")]
+    #[cfg(any(feature = "default_trait", feature = "custom_fn"))]
     let derive_serialize = quote! { #[derive(::twelf::reexports::serde::Serialize)] };
 
     let code = quote! {
@@ -192,6 +193,7 @@ pub fn config(_attrs: TokenStream, item: TokenStream) -> TokenStream {
                     #ini_branch
                     #clap_branch
                     #default_trait_branch
+                    #custom_fn_branch
                     other => unimplemented!("{:?}", other)
                 };
 
@@ -327,3 +329,11 @@ fn build_default_trait_branch() -> proc_macro2::TokenStream {
     let default_trait_branch = quote! {};
     default_trait_branch
 }
+
+fn build_custom_fn_branch() -> proc_macro2::TokenStream {
+    #[cfg(feature = "custom_fn")]
+    let custom_branch = quote! { ::twelf::Layer::CustomFn(custom_fn) => (custom_fn.clone().0(),None), };
+    #[cfg(not(feature = "custom_fn"))]
+    let custom_branch = quote! {};
+    custom_branch
+}

twelf/Cargo.toml

@@ -23,6 +23,7 @@
     serde_yaml    = { version = "0.8.23", optional = true }
     thiserror     = "1"
     toml_rs       = { version = "0.5.8", package = "toml", optional = true }
+    dyn-clone     = { version = "1.0.0", optional = true }
 
 [features]
     clap    = ["clap_rs", "config-derive/clap", "envy"]
@@ -34,3 +35,4 @@
     toml    = ["toml_rs", "config-derive/toml"]
     yaml    = ["serde_yaml", "config-derive/yaml"]
     default_trait = ["config-derive/default_trait"]
+    custom_fn = ["dyn-clone", "config-derive/custom_fn"]

twelf/README.md

@@ -11,6 +11,7 @@ For now it supports :
 
 - Default settings (inside your codebase with `#[serde(default = ...)]` coming from [serde](https://serde.rs))
 - Reading from `TOML`, `YAML`, `JSON`, `DHALL`, `INI` files
+- Executing a custom function or closure to supply values via a [serde_json::Value]
 - Reading from environment variables: it supports `HashMap` structure with `MY_VARIABLE="mykey=myvalue,mykey2=myvalue2"` and also array like `MY_VARIABLE=first,second` thanks to [envy](https://github.com/softprops/envy).
 - All [serde](https://serde.rs) attributes can be used in your struct to customize your configuration as you wish
 - Reading your configuration from your command line built with [clap](https://github.com/clap-rs/clap) (ATTENTION: if you're using version < v3 use the `[email protected]` version)
@@ -23,6 +24,7 @@ For now it supports :
 use twelf::{config, Layer};
 
 #[config]
+#[derive(Default)]
 struct Conf {
     test: String,
     another: usize,
@@ -67,9 +69,13 @@ Check [here](./twelf/examples) for more examples.
 Twelf supports crate features, if you only want support for `json`, `env` and `toml` then you just have to add this to your `Cargo.toml`
 
 ```toml
-twelf = { version = "0.3", default-features = false, features = ["json", "toml", "env"] }
+twelf = { version = "0.11", default-features = false, features = ["json", "toml", "env"] }
 ```
 
+`default_trait` enables code for a layer that integrate fields derived with the [std::default::Default] trait.
+
+`custom_fn` enables code for a layer that allows a custom closure to be executed.
+
 Default features are `["env", "clap"]`
 
 # Contributing

twelf/examples/advanced_struct.rs

@@ -6,15 +6,15 @@ use twelf::reexports::serde::{Deserialize, Serialize};
 use twelf::{config, Layer};
 
 #[config]
-#[derive(Debug)]
+#[derive(Debug, Default)]
 struct Config {
     list: Vec<String>,
     labels: HashMap<String, String>,
     #[serde(flatten)]
     nested: Nested,
 }
 
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Default, Deserialize, Serialize)]
 struct Nested {
     inner: String,
 }

twelf/examples/clap.rs

@@ -4,7 +4,7 @@ use clap_rs as clap;
 use twelf::{config, Layer};
 
 #[config]
-#[derive(Debug)]
+#[derive(Debug, Default)]
 struct Config {
     /// Documentation inside clap, to specifiy db_host
     db_host: String,

twelf/examples/clap_derive.rs

@@ -5,7 +5,7 @@ use clap_rs as clap;
 use twelf::{config, Layer};
 
 #[config]
-#[derive(Parser, Debug)]
+#[derive(Parser, Debug, Default)]
 #[clap(author, version, about, long_about = None)]
 struct Config {
     #[clap(long, help = "Documentation inside clap, to specifiy db_host")]

twelf/examples/default_env.rs

@@ -3,7 +3,7 @@
 use twelf::{config, Layer};
 
 #[config]
-#[derive(Debug)]
+#[derive(Debug, Default)]
 struct Config {
     db_host: String,
     threads: usize,

twelf/examples/simple_env_json.rs

@@ -3,7 +3,7 @@
 use twelf::{config, Layer};
 
 #[config]
-#[derive(Debug)]
+#[derive(Debug, Default)]
 struct Config {
     db_host: String,
     threads: usize,

twelf/src/lib.rs

@@ -61,4 +61,36 @@ pub enum Layer {
     /// Default layer, using std::default::Default trait
     #[cfg(feature = "default_trait")]
     DefaultTrait,
+    /// Custom layer, takes any function or closure that outputs a [serde_json::Value].
+    #[cfg(feature = "custom_fn")]
+    CustomFn(custom_fn::CustomFn),
+}
+
+#[cfg(feature = "custom_fn")]
+pub mod custom_fn {
+    use dyn_clone::{DynClone, clone_box};
+
+    pub struct CustomFn(pub Box<dyn CustomFnTrait>);
+
+    impl<T> From<T> for CustomFn where T: FnOnce() -> crate::reexports::serde_json::Value + Clone + 'static {
+        fn from(func: T) -> Self {
+            CustomFn(Box::new(func) as Box<dyn CustomFnTrait>)
+        }
+    }
+
+    pub trait CustomFnTrait: FnOnce() -> crate::reexports::serde_json::Value + DynClone {}
+
+    impl<T> CustomFnTrait for T where T: Clone + FnOnce() -> crate::reexports::serde_json::Value {}
+
+    impl Clone for CustomFn {
+        fn clone(&self) -> Self {
+            CustomFn(clone_box(&*self.0) as Box<dyn CustomFnTrait>)
+        }
+    }
+
+    impl core::fmt::Debug for CustomFn {
+        fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+            write!(f, "CustomFn")
+        } 
+    }
 }

twelf/tests/clap.rs

@@ -1,3 +1,5 @@
+#![cfg(feature = "clap")]
+
 use std::collections::HashMap;
 
 use clap_rs as clap;
@@ -10,7 +12,7 @@ const JSON_TEST_FILE: &str = "./tests/fixtures/test.json";
 #[test]
 fn clap_with_array_and_hashmap() {
     #[config]
-    #[derive(Debug)]
+    #[derive(Debug, Default)]
     struct Conf {
         /// My custom documentation on elements-snake in clap
         elements_snake: HashMap<String, String>,
@@ -50,7 +52,7 @@ fn clap_with_array_and_hashmap() {
 #[test]
 fn clap_derive_array() {
     #[config]
-    #[derive(Parser,Debug)]
+    #[derive(Parser,Debug, Default)]
     #[clap(author, version, about, long_about = None)]
     struct Conf {
         #[clap(long, default_value_t = 55)]

twelf/tests/custom_fn.rs

@@ -0,0 +1,32 @@
+#![cfg(feature = "custom_fn")]
+
+use config_derive::config;
+use twelf::Layer;
+
+use serde_json::value::to_value;
+
+#[test]
+fn simple_custom_fn() {
+    #[config]
+    #[derive(Debug, Default)]
+    struct TestCfg {
+        test: String,
+        another: usize,
+    }
+
+    std::env::set_var("ANOTHER", "5");
+
+    let func = || {
+        to_value(TestCfg{test: "from func".to_string(), another: 25}).unwrap()
+    };
+
+    let prio = vec![Layer::CustomFn(func.into()), Layer::Env(None)];
+    let config = TestCfg::with_layers(&prio).unwrap();
+    assert_eq!(config.test, String::from("from func"));
+    assert_eq!(config.another, 5usize);
+
+    let prio = vec![Layer::Env(None), Layer::CustomFn(func.into())];
+    let config = TestCfg::with_layers(&prio).unwrap();
+    assert_eq!(config.test, String::from("from func"));
+    assert_eq!(config.another, 25usize);
+}

twelf/tests/default.rs

@@ -1,4 +1,4 @@
-#![cfg(features = "default_trait")]
+#![cfg(feature = "default_trait")]
 use config_derive::config;
 use twelf::Layer;
 

twelf/tests/dhall.rs

@@ -1,3 +1,5 @@
+#![cfg(feature = "dhall")]
+
 use std::collections::HashMap;
 
 use config_derive::config;
@@ -12,7 +14,7 @@ const DHALL_TEST_FILE: &str = "./tests/fixtures/test.dhall";
 #[test]
 fn dhall_simple_types() {
     #[config]
-    #[derive(Debug)]
+    #[derive(Debug, Default)]
     struct TestCfg {
         test: String,
         another: usize,
@@ -32,7 +34,7 @@ fn dhall_simple_types() {
 #[test]
 fn dhall_simple_with_prefix() {
     #[config]
-    #[derive(Debug)]
+    #[derive(Debug, Default)]
     struct Conf {
         elements_def: HashMap<String, String>,
         #[serde(default = "default_array")]
@@ -57,7 +59,7 @@ fn dhall_simple_with_prefix() {
 #[test]
 fn dhall_simple_with_option() {
     #[config]
-    #[derive(Debug)]
+    #[derive(Debug, Default)]
     struct Conf {
         elements_def: Option<HashMap<String, String>>,
         array_def: Option<Vec<String>>,
@@ -80,7 +82,7 @@ fn dhall_simple_with_option() {
 #[test]
 fn dhall_with_array_and_hashmap_string() {
     #[config]
-    #[derive(Debug)]
+    #[derive(Debug, Default)]
     struct Conf {
         elements: HashMap<String, String>,
         #[serde(default = "default_array")]
@@ -113,7 +115,7 @@ fn dhall_with_array_and_hashmap_string() {
 #[test]
 fn dhall_with_array_and_hashmap_with_default() {
     #[config]
-    #[derive(Debug)]
+    #[derive(Debug, Default)]
     struct Conf {
         elements_def: HashMap<String, String>,
         #[serde(default = "default_array")]