Use LinkedHashMap in place of HashMap

Author: David Orchard

Cargo.toml

@@ -35,6 +35,7 @@ serde-hjson = { version = "0.9", default-features = false, optional = true }
 rust-ini = { version = "0.17", optional = true }
 ron = { version = "0.6", optional = true }
 json5_rs = { version = "0.3", optional = true, package = "json5" }
+linked-hash-map = { version = "0.5.4", features = ["serde_impl"] }
 
 [dev-dependencies]
 serde_derive = "1.0.8"

examples/async_source/main.rs

@@ -1,4 +1,5 @@
-use std::{collections::HashMap, error::Error};
+use linked_hash_map::LinkedHashMap;
+use std::error::Error;
 
 use config::{builder::AsyncState, AsyncSource, ConfigBuilder, ConfigError, FileFormat};
 
@@ -56,7 +57,7 @@ struct HttpSource {
 
 #[async_trait]
 impl AsyncSource for HttpSource {
-    async fn collect(&self) -> Result<HashMap<String, config::Value>, ConfigError> {
+    async fn collect(&self) -> Result<LinkedHashMap<String, config::Value>, ConfigError> {
         reqwest::get(&self.uri)
             .await
             .map_err(|e| ConfigError::Foreign(Box::new(e)))? // error conversion is possible from custom AsyncSource impls

examples/glob/src/main.rs

@@ -1,5 +1,5 @@
 use std::path::Path;
-use std::collections::HashMap;
+use std::collections::LinkedHashMap;
 use config::*;
 use glob::glob;
 
@@ -14,9 +14,9 @@ fn main() {
         .merge(File::from(Path::new("conf/05-some.yml"))).unwrap()
         .merge(File::from(Path::new("conf/99-extra.json"))).unwrap();
 
-    // Print out our settings (as a HashMap)
+    // Print out our settings (as a LinkedHashMap)
     println!("\n{:?} \n\n-----------",
-             settings.try_into::<HashMap<String, String>>().unwrap());
+             settings.try_into::<LinkedHashMap<String, String>>().unwrap());
 
     // Option 2
     // --------
@@ -28,9 +28,9 @@ fn main() {
                     File::from(Path::new("conf/99-extra.json"))])
         .unwrap();
 
-    // Print out our settings (as a HashMap)
+    // Print out our settings (as a LinkedHashMap)
     println!("\n{:?} \n\n-----------",
-             settings.try_into::<HashMap<String, String>>().unwrap());
+             settings.try_into::<LinkedHashMap<String, String>>().unwrap());
 
     // Option 3
     // --------
@@ -43,7 +43,7 @@ fn main() {
                    .collect::<Vec<_>>())
         .unwrap();
 
-    // Print out our settings (as a HashMap)
+    // Print out our settings (as a LinkedHashMap)
     println!("\n{:?} \n\n-----------",
-             settings.try_into::<HashMap<String, String>>().unwrap());
+             settings.try_into::<LinkedHashMap<String, String>>().unwrap());
 }

examples/simple/src/main.rs

@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use std::collections::LinkedHashMap;
 
 fn main() {
     let mut settings = config::Config::default();
@@ -9,7 +9,7 @@ fn main() {
         // Eg.. `APP_DEBUG=1 ./target/app` would set the `debug` key
         .merge(config::Environment::with_prefix("APP")).unwrap();
 
-    // Print out our settings (as a HashMap)
+    // Print out our settings (as a LinkedHashMap)
     println!("{:?}",
-             settings.try_into::<HashMap<String, String>>().unwrap());
+             settings.try_into::<LinkedHashMap<String, String>>().unwrap());
 }

examples/watch/src/main.rs

@@ -1,5 +1,5 @@
 use config::*;
-use std::collections::HashMap;
+use std::collections::LinkedHashMap;
 use std::sync::RwLock;
 use notify::{RecommendedWatcher, DebouncedEvent, Watcher, RecursiveMode};
 use std::sync::mpsc::channel;
@@ -20,7 +20,7 @@ fn show() {
                  .read()
                  .unwrap()
                  .clone()
-                 .try_into::<HashMap<String, String>>()
+                 .try_into::<LinkedHashMap<String, String>>()
                  .unwrap());
 }
 

src/builder.rs

@@ -1,5 +1,6 @@
+use linked_hash_map::LinkedHashMap;
+use std::iter::IntoIterator;
 use std::str::FromStr;
-use std::{collections::HashMap, iter::IntoIterator};
 
 use crate::error::Result;
 use crate::source::AsyncSource;
@@ -87,8 +88,8 @@ use crate::{config::Config, path::Expression, source::Source, value::Value};
 /// ```
 #[derive(Debug, Clone, Default)]
 pub struct ConfigBuilder<St: BuilderState> {
-    defaults: HashMap<Expression, Value>,
-    overrides: HashMap<Expression, Value>,
+    defaults: LinkedHashMap<Expression, Value>,
+    overrides: LinkedHashMap<Expression, Value>,
     state: St,
 }
 
@@ -120,8 +121,8 @@ pub struct DefaultState {
 /// Refer to [`ConfigBuilder`] for similar API sample usage or to the examples folder of the crate, where such a source is implemented.
 #[derive(Debug, Clone, Default)]
 pub struct AsyncConfigBuilder {
-    defaults: HashMap<Expression, Value>,
-    overrides: HashMap<Expression, Value>,
+    defaults: LinkedHashMap<Expression, Value>,
+    overrides: LinkedHashMap<Expression, Value>,
     sources: Vec<SourceType>,
 }
 
@@ -244,11 +245,11 @@ impl ConfigBuilder<DefaultState> {
     }
 
     fn build_internal(
-        defaults: HashMap<Expression, Value>,
-        overrides: HashMap<Expression, Value>,
+        defaults: LinkedHashMap<Expression, Value>,
+        overrides: LinkedHashMap<Expression, Value>,
         sources: &[Box<dyn Source + Send + Sync>],
     ) -> Result<Config> {
-        let mut cache: Value = HashMap::<String, Value>::new().into();
+        let mut cache: Value = LinkedHashMap::<String, Value>::new().into();
 
         // Add defaults
         for (key, val) in defaults.into_iter() {
@@ -322,11 +323,11 @@ impl ConfigBuilder<AsyncState> {
     }
 
     async fn build_internal(
-        defaults: HashMap<Expression, Value>,
-        overrides: HashMap<Expression, Value>,
+        defaults: LinkedHashMap<Expression, Value>,
+        overrides: LinkedHashMap<Expression, Value>,
         sources: &[SourceType],
     ) -> Result<Config> {
-        let mut cache: Value = HashMap::<String, Value>::new().into();
+        let mut cache: Value = LinkedHashMap::<String, Value>::new().into();
 
         // Add defaults
         for (key, val) in defaults.into_iter() {

src/config.rs

@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::fmt::Debug;
 
 use crate::builder::{ConfigBuilder, DefaultState};
@@ -16,8 +16,8 @@ use crate::value::{Table, Value};
 /// them according to the source's priority.
 #[derive(Clone, Debug)]
 pub struct Config {
-    defaults: HashMap<path::Expression, Value>,
-    overrides: HashMap<path::Expression, Value>,
+    defaults: LinkedHashMap<path::Expression, Value>,
+    overrides: LinkedHashMap<path::Expression, Value>,
     sources: Vec<Box<dyn Source + Send + Sync>>,
 
     /// Root of the cached configuration.
@@ -83,7 +83,7 @@ impl Config {
     #[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();
+            let mut cache: Value = LinkedHashMap::<String, Value>::new().into();
 
             // Add defaults
             for (key, val) in self.defaults.iter() {
@@ -181,7 +181,7 @@ impl Config {
         self.get(key).and_then(Value::into_bool)
     }
 
-    pub fn get_table(&self, key: &str) -> Result<HashMap<String, Value>> {
+    pub fn get_table(&self, key: &str) -> Result<LinkedHashMap<String, Value>> {
         self.get(key).and_then(Value::into_table)
     }
 
@@ -212,7 +212,7 @@ impl Source for Config {
         Box::new((*self).clone())
     }
 
-    fn collect(&self) -> Result<HashMap<String, Value>> {
+    fn collect(&self) -> Result<LinkedHashMap<String, Value>> {
         self.cache.clone().into_table()
     }
 }

src/de.rs

@@ -1,4 +1,5 @@
-use std::collections::{HashMap, VecDeque};
+use linked_hash_map::LinkedHashMap;
+use std::collections::VecDeque;
 use std::iter::Enumerate;
 
 use serde::de;
@@ -199,7 +200,7 @@ struct MapAccess {
 }
 
 impl MapAccess {
-    fn new(table: HashMap<String, Value>) -> Self {
+    fn new(table: LinkedHashMap<String, Value>) -> Self {
         MapAccess {
             elements: table.into_iter().collect(),
         }

src/env.rs

@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::env;
 
 use crate::error::*;
@@ -79,8 +79,8 @@ impl Source for Environment {
         Box::new((*self).clone())
     }
 
-    fn collect(&self) -> Result<HashMap<String, Value>> {
-        let mut m = HashMap::new();
+    fn collect(&self) -> Result<LinkedHashMap<String, Value>> {
+        let mut m = LinkedHashMap::new();
         let uri: String = "the environment".into();
 
         let separator = self.separator.as_deref().unwrap_or("");

src/file/format/hjson.rs

@@ -1,19 +1,19 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 
 use crate::value::{Value, ValueKind};
 
 pub fn parse(
     uri: Option<&String>,
     text: &str,
-) -> Result<HashMap<String, Value>, Box<dyn Error + Send + Sync>> {
+) -> Result<LinkedHashMap<String, Value>, Box<dyn Error + Send + Sync>> {
     // Parse a JSON object value from the text
     // TODO: Have a proper error fire if the root of a file is ever not a Table
     let value = from_hjson_value(uri, &serde_hjson::from_str(text)?);
     match value.kind {
         ValueKind::Table(map) => Ok(map),
 
-        _ => Ok(HashMap::new()),
+        _ => Ok(LinkedHashMap::new()),
     }
 }
 
@@ -30,7 +30,7 @@ fn from_hjson_value(uri: Option<&String>, value: &serde_hjson::Value) -> Value {
         serde_hjson::Value::Bool(value) => Value::new(uri, ValueKind::Boolean(value)),
 
         serde_hjson::Value::Object(ref table) => {
-            let mut m = HashMap::new();
+            let mut m = LinkedHashMap::new();
 
             for (key, value) in table {
                 m.insert(key.clone(), from_hjson_value(uri, value));