Merge pull request #196 from szarykott/builder

Create the ConfigBuilder

Author: matthiasbeyer

src/builder.rs

@@ -0,0 +1,159 @@
+use std::str::FromStr;
+use std::{collections::HashMap, iter::IntoIterator};
+
+use crate::{config::Config, error, path::Expression, source::Source, value::Value};
+
+/// A configuration builder
+///
+/// It registers ordered sources of configuration to later build consistent [`Config`] from them.
+/// Configuration sources it defines are defaults, [`Source`]s and overrides.
+///
+/// Defaults are alaways loaded first and can be overwritten by any of two other sources.
+/// Overrides are always loaded last, thus cannot be overridden.
+/// Both can be only set explicitly key by key in code
+/// using [`set_default`](Self::set_default) or [`set_override`](Self::set_override).
+///
+/// An intermediate category, [`Source`], set groups of keys at once implicitly using data coming from external sources
+/// like files, environment variables or others that one implements. Defining a [`Source`] is as simple as implementing
+/// a trait for a struct.
+///
+/// Adding sources, setting defaults and overrides does not invoke any I/O nor builds a config.
+/// It happens on demand when [`build`](Self::build) (or its alternative) is called.
+/// Therefore all errors, related to any of the [`Source`] will only show up then.
+///
+/// # Examples
+///
+/// ```rust
+/// # use config::*;
+/// # use std::error::Error;
+/// # fn main() -> Result<(), Box<dyn Error>> {
+/// let mut builder = ConfigBuilder::default()
+///     .set_default("default", "1")?
+///     .add_source(File::new("config/settings", FileFormat::Json))
+///     .set_override("override", "1")?;
+///
+/// match builder.build() {
+///     Ok(config) => {
+///         // use your config
+///     },
+///     Err(e) => {
+///         // something went wrong
+///     }
+/// }
+/// # Ok(())
+/// # }
+/// ```
+///
+/// Calls can be not chained as well
+/// ```rust
+/// # use std::error::Error;
+/// # use config::*;
+/// # fn main() -> Result<(), Box<dyn Error>> {
+/// let mut builder = ConfigBuilder::default();
+/// builder = builder.set_default("default", "1")?;
+/// builder = builder.add_source(File::new("config/settings", FileFormat::Json));
+/// builder = builder.add_source(File::new("config/settings.prod", FileFormat::Json));
+/// builder = builder.set_override("override", "1")?;
+/// # Ok(())
+/// # }
+/// ```
+#[derive(Debug, Clone, Default)]
+pub struct ConfigBuilder {
+    defaults: HashMap<Expression, Value>,
+    overrides: HashMap<Expression, Value>,
+    sources: Vec<Box<dyn Source + Send + Sync>>,
+}
+
+impl ConfigBuilder {
+    /// Set a default `value` at `key`
+    ///
+    /// This value can be overwritten by any [`Source`] or override.
+    ///
+    /// # Errors
+    ///
+    /// Fails if `Expression::from_str(key)` fails.
+    pub fn set_default<S, T>(mut self, key: S, value: T) -> error::Result<ConfigBuilder>
+    where
+        S: AsRef<str>,
+        T: Into<Value>,
+    {
+        self.defaults
+            .insert(Expression::from_str(key.as_ref())?, value.into());
+        Ok(self)
+    }
+
+    /// Registers new [`Source`] in this builder.
+    ///
+    /// Calling this method does not invoke any I/O. [`Source`] is only saved in internal register for later use.
+    pub fn add_source<T>(mut self, source: T) -> Self
+    where
+        T: Source + Send + Sync + 'static,
+    {
+        self.sources.push(Box::new(source));
+        self
+    }
+
+    /// Set an override
+    ///
+    /// This function sets an overwrite value. It will not be altered by any default or [`Source`]
+    ///
+    /// # Errors
+    ///
+    /// Fails if `Expression::from_str(key)` fails.
+    pub fn set_override<S, T>(mut self, key: S, value: T) -> error::Result<ConfigBuilder>
+    where
+        S: AsRef<str>,
+        T: Into<Value>,
+    {
+        self.overrides
+            .insert(Expression::from_str(key.as_ref())?, value.into());
+        Ok(self)
+    }
+
+    /// Reads all registered [`Source`]s.
+    ///
+    /// This is the method that invokes all I/O operations.
+    /// For a non consuming alternative see [`build_cloned`](Self::build_cloned)
+    ///
+    /// # Errors
+    /// If source collection fails, be it technical reasons or related to inability to read data as `Config` for different reasons,
+    /// this method returns error.
+    pub fn build(self) -> error::Result<Config> {
+        Self::build_internal(self.defaults, self.overrides, &self.sources)
+    }
+
+    /// Reads all registered [`Source`]s.
+    ///
+    /// Similar to [`build`](Self::build), but it does not take ownership of `ConfigBuilder` to allow later reuse.
+    /// Internally it clones data to achieve it.
+    ///
+    /// # Errors
+    /// If source collection fails, be it technical reasons or related to inability to read data as `Config` for different reasons,
+    /// this method returns error.
+    pub fn build_cloned(&self) -> error::Result<Config> {
+        Self::build_internal(self.defaults.clone(), self.overrides.clone(), &self.sources)
+    }
+
+    fn build_internal(
+        defaults: HashMap<Expression, Value>,
+        overrides: HashMap<Expression, Value>,
+        sources: &[Box<dyn Source + Send + Sync>],
+    ) -> error::Result<Config> {
+        let mut cache: Value = HashMap::<String, Value>::new().into();
+
+        // Add defaults
+        for (key, val) in defaults.into_iter() {
+            key.set(&mut cache, val);
+        }
+
+        // Add sources
+        sources.collect_to(&mut cache)?;
+
+        // Add overrides
+        for (key, val) in overrides.into_iter() {
+            key.set(&mut cache, val);
+        }
+
+        Ok(Config::new(cache))
+    }
+}

src/config.rs

@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 use std::fmt::Debug;
 
+use crate::builder::ConfigBuilder;
 use serde::de::Deserialize;
 use serde::ser::Serialize;
 
@@ -35,23 +36,41 @@ impl Default for Config {
 }
 
 impl Config {
+    pub(crate) fn new(value: Value) -> Self {
+        Config {
+            cache: value,
+            ..Default::default()
+        }
+    }
+
+    /// Creates new [`ConfigBuilder`] instance
+    pub fn builder() -> ConfigBuilder {
+        ConfigBuilder::default()
+    }
+
     /// Merge in a configuration property source.
+    #[deprecated(since = "0.12.0", note = "please use 'ConfigBuilder' instead")]
     pub fn merge<T>(&mut self, source: T) -> Result<&mut Config>
     where
         T: 'static,
         T: Source + Send + Sync,
     {
         self.sources.push(Box::new(source));
+
+        #[allow(deprecated)]
         self.refresh()
     }
 
     /// Merge in a configuration property source.
+    #[deprecated(since = "0.12.0", note = "please use 'ConfigBuilder' instead")]
     pub fn with_merged<T>(mut self, source: T) -> Result<Self>
     where
         T: 'static,
         T: Source + Send + Sync,
     {
         self.sources.push(Box::new(source));
+
+        #[allow(deprecated)]
         self.refresh()?;
         Ok(self)
     }
@@ -61,6 +80,7 @@ impl Config {
     ///
     /// Configuration is automatically refreshed after a mutation
     /// operation (`set`, `merge`, `set_default`, etc.).
+    #[deprecated(since = "0.12.0", note = "please use 'ConfigBuilder' instead")]
     pub fn refresh(&mut self) -> Result<&mut Config> {
         self.cache = {
             let mut cache: Value = HashMap::<String, Value>::new().into();
@@ -85,11 +105,14 @@ impl Config {
     }
 
     /// Set a default `value` at `key`
+    #[deprecated(since = "0.12.0", note = "please use 'ConfigBuilder' instead")]
     pub fn set_default<T>(&mut self, key: &str, value: T) -> Result<&mut Config>
     where
         T: Into<Value>,
     {
         self.defaults.insert(key.parse()?, value.into());
+
+        #[allow(deprecated)]
         self.refresh()
     }
 
@@ -101,14 +124,18 @@ impl Config {
     /// # Warning
     ///
     /// Errors if config is frozen
+    #[deprecated(since = "0.12.0", note = "please use 'ConfigBuilder' instead")]
     pub fn set<T>(&mut self, key: &str, value: T) -> Result<&mut Config>
     where
         T: Into<Value>,
     {
         self.overrides.insert(key.parse()?, value.into());
+
+        #[allow(deprecated)]
         self.refresh()
     }
 
+    #[deprecated(since = "0.12.0", note = "please use 'ConfigBuilder' instead")]
     pub fn set_once(&mut self, key: &str, value: Value) -> Result<()> {
         let expr: path::Expression = key.parse()?;
 

src/lib.rs

@@ -51,6 +51,7 @@ extern crate ini;
 #[cfg(feature = "ron")]
 extern crate ron;
 
+mod builder;
 mod config;
 mod de;
 mod env;
@@ -61,6 +62,7 @@ mod ser;
 mod source;
 mod value;
 
+pub use crate::builder::ConfigBuilder;
 pub use crate::config::Config;
 pub use crate::env::Environment;
 pub use crate::error::ConfigError;

src/ser.rs

@@ -27,6 +27,8 @@ impl ConfigSerializer {
                 )))
             }
         };
+
+        #[allow(deprecated)]
         self.output.set(&key, value.into())?;
         Ok(())
     }

src/source.rs

@@ -55,6 +55,26 @@ impl Source for Vec<Box<dyn Source + Send + Sync>> {
     }
 }
 
+impl Source for [Box<dyn Source + Send + Sync>] {
+    fn clone_into_box(&self) -> Box<dyn Source + Send + Sync> {
+        Box::new(self.to_owned())
+    }
+
+    fn collect(&self) -> Result<HashMap<String, Value>> {
+        let mut cache: Value = HashMap::<String, Value>::new().into();
+
+        for source in self {
+            source.collect_to(&mut cache)?;
+        }
+
+        if let ValueKind::Table(table) = cache.kind {
+            Ok(table)
+        } else {
+            unreachable!();
+        }
+    }
+}
+
 impl<T> Source for Vec<T>
 where
     T: Source + Sync + Send,

tests/datetime.rs

@@ -14,56 +14,51 @@ use chrono::{DateTime, TimeZone, Utc};
 use config::*;
 
 fn make() -> Config {
-    Config::default()
-        .merge(File::from_str(
+    Config::builder()
+        .add_source(File::from_str(
             r#"
             {
                 "json_datetime": "2017-05-10T02:14:53Z"
             }
             "#,
             FileFormat::Json,
         ))
-        .unwrap()
-        .merge(File::from_str(
+        .add_source(File::from_str(
             r#"
             yaml_datetime: 2017-06-12T10:58:30Z
             "#,
             FileFormat::Yaml,
         ))
-        .unwrap()
-        .merge(File::from_str(
+        .add_source(File::from_str(
             r#"
             toml_datetime = 2017-05-11T14:55:15Z
             "#,
             FileFormat::Toml,
         ))
-        .unwrap()
-        .merge(File::from_str(
+        .add_source(File::from_str(
             r#"
             {
                 "hjson_datetime": "2017-05-10T02:14:53Z"
             }
             "#,
             FileFormat::Hjson,
         ))
-        .unwrap()
-        .merge(File::from_str(
+        .add_source(File::from_str(
             r#"
                 ini_datetime = 2017-05-10T02:14:53Z
             "#,
             FileFormat::Ini,
         ))
-        .unwrap()
-        .merge(File::from_str(
+        .add_source(File::from_str(
             r#"
             (
                 ron_datetime: "2021-04-19T11:33:02Z"
             )
             "#,
             FileFormat::Ron,
         ))
+        .build()
         .unwrap()
-        .clone()
 }
 
 #[test]