Use LinkedHashMap in place of HashMap

39 files changed, 144 insertions, 137 deletions

diff --git a/Cargo.toml b/Cargo.toml
index f72389f..68e6617 100644
--- a/Cargo.toml
+++ b/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"
diff --git a/examples/async_source/main.rs b/examples/async_source/main.rs
index 10befe0..6c836a3 100644
--- a/examples/async_source/main.rs
+++ b/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
diff --git a/examples/glob/src/main.rs b/examples/glob/src/main.rs
index b3183ef..c85f86e 100644
--- a/examples/glob/src/main.rs
+++ b/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());
 }
diff --git a/examples/simple/src/main.rs b/examples/simple/src/main.rs
index 1c7ddb7..698401a 100644
--- a/examples/simple/src/main.rs
+++ b/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());
 }
diff --git a/examples/watch/src/main.rs b/examples/watch/src/main.rs
index a197390..9e676ad 100644
--- a/examples/watch/src/main.rs
+++ b/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());
 }
 
diff --git a/src/builder.rs b/src/builder.rs
index bb88f44..65f49ae 100644
--- a/src/builder.rs
+++ b/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() {
diff --git a/src/config.rs b/src/config.rs
index b9c64b4..6302c45 100644
--- a/src/config.rs
+++ b/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()
     }
 }
diff --git a/src/de.rs b/src/de.rs
index a7a6fb4..7d66896 100644
--- a/src/de.rs
+++ b/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(),
         }
diff --git a/src/env.rs b/src/env.rs
index 3d95e17..2e48701 100644
--- a/src/env.rs
+++ b/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("");
diff --git a/src/file/format/hjson.rs b/src/file/format/hjson.rs
index f94b1d3..a61afef 100644
--- a/src/file/format/hjson.rs
+++ b/src/file/format/hjson.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 
 use crate::value::{Value, ValueKind};
@@ -6,14 +6,14 @@ 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));
diff --git a/src/file/format/ini.rs b/src/file/format/ini.rs
index b45695a..47f3499 100644
--- a/src/file/format/ini.rs
+++ b/src/file/format/ini.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 
 use ini::Ini;
@@ -8,13 +8,13 @@ use crate::value::{Value, ValueKind};
 pub fn parse(
     uri: Option<&String>,
     text: &str,
-) -> Result<HashMap<String, Value>, Box<dyn Error + Send + Sync>> {
-    let mut map: HashMap<String, Value> = HashMap::new();
+) -> Result<LinkedHashMap<String, Value>, Box<dyn Error + Send + Sync>> {
+    let mut map: LinkedHashMap<String, Value> = LinkedHashMap::new();
     let i = Ini::load_from_str(text)?;
     for (sec, prop) in i.iter() {
         match sec {
             Some(sec) => {
-                let mut sec_map: HashMap<String, Value> = HashMap::new();
+                let mut sec_map: LinkedHashMap<String, Value> = LinkedHashMap::new();
                 for (k, v) in prop.iter() {
                     sec_map.insert(
                         k.to_owned(),
diff --git a/src/file/format/json.rs b/src/file/format/json.rs
index 87a6e61..a6a9443 100644
--- a/src/file/format/json.rs
+++ b/src/file/format/json.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 
 use crate::value::{Value, ValueKind};
@@ -6,14 +6,14 @@ 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_json_value(uri, &serde_json::from_str(text)?);
     match value.kind {
         ValueKind::Table(map) => Ok(map),
 
-        _ => Ok(HashMap::new()),
+        _ => Ok(LinkedHashMap::new()),
     }
 }
 
@@ -34,7 +34,7 @@ fn from_json_value(uri: Option<&String>, value: &serde_json::Value) -> Value {
         serde_json::Value::Bool(value) => Value::new(uri, ValueKind::Boolean(value)),
 
         serde_json::Value::Object(ref table) => {
-            let mut m = HashMap::new();
+            let mut m = LinkedHashMap::new();
 
             for (key, value) in table {
                 m.insert(key.clone(), from_json_value(uri, value));
diff --git a/src/file/format/json5.rs b/src/file/format/json5.rs
index ea3390f..952b265 100644
--- a/src/file/format/json5.rs
+++ b/src/file/format/json5.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 
 use crate::error::{ConfigError, Unexpected};
@@ -13,13 +13,13 @@ pub enum Val {
     Float(f64),
     String(String),
     Array(Vec<Val>),
-    Object(HashMap<String, Val>),
+    Object(LinkedHashMap<String, Val>),
 }
 
 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>> {
     match json5_rs::from_str::<Val>(text)? {
         Val::String(ref value) => Err(Unexpected::Str(value.clone())),
         Val::Integer(value) => Err(Unexpected::Integer(value)),
@@ -29,7 +29,7 @@ pub fn parse(
         Val::Null => Err(Unexpected::Unit),
         Val::Object(o) => match from_json5_value(uri, Val::Object(o)).kind {
             ValueKind::Table(map) => Ok(map),
-            _ => Ok(HashMap::new()),
+            _ => Ok(LinkedHashMap::new()),
         },
     }
     .map_err(|err| ConfigError::invalid_root(uri, err))
diff --git a/src/file/format/mod.rs b/src/file/format/mod.rs
index 53bacf6..55d1c7a 100644
--- a/src/file/format/mod.rs
+++ b/src/file/format/mod.rs
@@ -2,7 +2,7 @@
 // BUG: ? For some reason this doesn't do anything if I try and function scope this
 #![allow(unused_mut)]
 
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 
 use crate::value::Value;
@@ -62,8 +62,8 @@ pub enum FileFormat {
 lazy_static! {
     #[doc(hidden)]
     // #[allow(unused_mut)] ?
-    pub static ref ALL_EXTENSIONS: HashMap<FileFormat, Vec<&'static str>> = {
-        let mut formats: HashMap<FileFormat, Vec<_>> = HashMap::new();
+    pub static ref ALL_EXTENSIONS: LinkedHashMap<FileFormat, Vec<&'static str>> = {
+        let mut formats: LinkedHashMap<FileFormat, Vec<_>> = LinkedHashMap::new();
 
         #[cfg(feature = "toml")]
         formats.insert(FileFormat::Toml, vec!["toml"]);
@@ -107,7 +107,7 @@ impl FileFormat {
         self,
         uri: Option<&String>,
         text: &str,
-    ) -> Result<HashMap<String, Value>, Box<dyn Error + Send + Sync>> {
+    ) -> Result<LinkedHashMap<String, Value>, Box<dyn Error + Send + Sync>> {
         match self {
             #[cfg(feature = "toml")]
             FileFormat::Toml => toml::parse(uri, text),
diff --git a/src/file/format/ron.rs b/src/file/format/ron.rs
index f7dbce3..a527d6f 100644
--- a/src/file/format/ron.rs
+++ b/src/file/format/ron.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 
 use crate::value::{Value, ValueKind};
@@ -6,12 +6,12 @@ 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>> {
     let value = from_ron_value(uri, ron::from_str(text)?)?;
     match value.kind {
         ValueKind::Table(map) => Ok(map),
 
-        _ => Ok(HashMap::new()),
+        _ => Ok(LinkedHashMap::new()),
     }
 }
 
@@ -56,7 +56,7 @@ fn from_ron_value(
 
                     Ok((key, value))
                 })
-                .collect::<Result<HashMap<_, _>, _>>()?;
+                .collect::<Result<LinkedHashMap<_, _>, _>>()?;
 
             ValueKind::Table(map)
         }
diff --git a/src/file/format/toml.rs b/src/file/format/toml.rs
index c7c5972..5468d97 100644
--- a/src/file/format/toml.rs
+++ b/src/file/format/toml.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 
 use crate::value::{Value, ValueKind};
@@ -6,14 +6,14 @@ 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 TOML value from the provided text
     // TODO: Have a proper error fire if the root of a file is ever not a Table
     let value = from_toml_value(uri, &toml::from_str(text)?);
     match value.kind {
         ValueKind::Table(map) => Ok(map),
 
-        _ => Ok(HashMap::new()),
+        _ => Ok(LinkedHashMap::new()),
     }
 }
 
@@ -25,7 +25,7 @@ fn from_toml_value(uri: Option<&String>, value: &toml::Value) -> Value {
         toml::Value::Boolean(value) => Value::new(uri, value),
 
         toml::Value::Table(ref table) => {
-            let mut m = HashMap::new();
+            let mut m = LinkedHashMap::new();
 
             for (key, value) in table {
                 m.insert(key.clone(), from_toml_value(uri, value));
diff --git a/src/file/format/yaml.rs b/src/file/format/yaml.rs
index 2526395..246758a 100644
--- a/src/file/format/yaml.rs
+++ b/src/file/format/yaml.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::error::Error;
 use std::fmt;
 use std::mem;
@@ -10,7 +10,7 @@ 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 YAML object from file
     let mut docs = yaml::YamlLoader::load_from_str(text)?;
     let root = match docs.len() {
@@ -26,7 +26,7 @@ pub fn parse(
     match value.kind {
         ValueKind::Table(map) => Ok(map),
 
-        _ => Ok(HashMap::new()),
+        _ => Ok(LinkedHashMap::new()),
     }
 }
 
@@ -40,7 +40,7 @@ fn from_yaml_value(uri: Option<&String>, value: &yaml::Yaml) -> Value {
         yaml::Yaml::Integer(value) => Value::new(uri, ValueKind::Integer(value)),
         yaml::Yaml::Boolean(value) => Value::new(uri, ValueKind::Boolean(value)),
         yaml::Yaml::Hash(ref table) => {
-            let mut m = HashMap::new();
+            let mut m = LinkedHashMap::new();
             for (key, value) in table {
                 if let Some(k) = key.as_str() {
                     m.insert(k.to_owned(), from_yaml_value(uri, value));
diff --git a/src/file/mod.rs b/src/file/mod.rs
index b00a271..02fd51f 100644
--- a/src/file/mod.rs
+++ b/src/file/mod.rs
@@ -1,7 +1,7 @@
 mod format;
 pub mod source;
 
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::path::{Path, PathBuf};
 
 use crate::error::*;
@@ -99,7 +99,7 @@ where
         Box::new((*self).clone())
     }
 
-    fn collect(&self) -> Result<HashMap<String, Value>> {
+    fn collect(&self) -> Result<LinkedHashMap<String, Value>> {
         // Coerce the file contents to a string
         let (uri, contents, format) = match self
             .source
@@ -110,7 +110,7 @@ where
 
             Err(error) => {
                 if !self.required {
-                    return Ok(HashMap::new());
+                    return Ok(LinkedHashMap::new());
                 }
 
                 return Err(error);
diff --git a/src/path/mod.rs b/src/path/mod.rs
index d58a6f2..04c424c 100644
--- a/src/path/mod.rs
+++ b/src/path/mod.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::str::FromStr;
 
 use crate::error::*;
@@ -135,7 +135,7 @@ impl Expression {
                     ),
 
                     _ => {
-                        *value = HashMap::<String, Value>::new().into();
+                        *value = LinkedHashMap::<String, Value>::new().into();
 
                         if let ValueKind::Table(ref mut map) = value.kind {
                             Some(
@@ -186,7 +186,7 @@ impl Expression {
                     ValueKind::Table(_) => {}
 
                     _ => {
-                        *root = HashMap::<String, Value>::new().into();
+                        *root = LinkedHashMap::<String, Value>::new().into();
                     }
                 }
 
@@ -195,7 +195,7 @@ impl Expression {
                         // Pull out another table
                         let mut target = if let ValueKind::Table(ref mut map) = root.kind {
                             map.entry(id.clone())
-                                .or_insert_with(|| HashMap::<String, Value>::new().into())
+                                .or_insert_with(|| LinkedHashMap::<String, Value>::new().into())
                         } else {
                             unreachable!();
                         };
@@ -224,7 +224,7 @@ impl Expression {
 
                         _ => {
                             // Didn't find a table. Oh well. Make a table and do this anyway
-                            *parent = HashMap::<String, Value>::new().into();
+                            *parent = LinkedHashMap::<String, Value>::new().into();
 
                             Expression::Identifier(key.clone()).set(parent, value);
                         }
diff --git a/src/source.rs b/src/source.rs
index 831e4c4..7d257d0 100644
--- a/src/source.rs
+++ b/src/source.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use linked_hash_map::LinkedHashMap;
 use std::fmt::Debug;
 use std::str::FromStr;
 
@@ -13,8 +13,8 @@ pub trait Source: Debug {
     fn clone_into_box(&self) -> Box<dyn Source + Send + Sync>;
 
     /// Collect all configuration properties available from this source and return
-    /// a HashMap.
-    fn collect(&self) -> Result<HashMap<String, Value>>;
+    /// a LinkedHashMap.
+    fn collect(&self) -> Result<LinkedHashMap<String, Value>>;
 
     /// Collects all configuration properties to a provided cache.
     fn collect_to(&self, cache: &mut Value) -> Result<()> {
@@ -55,8 +55,8 @@ pub trait AsyncSource: Debug + Sync {
     // Sync is supertrait due to https://docs.rs/async-trait/0.1.50/async_trait/index.html#dyn-traits
 
     /// Collects all configuration properties available from this source and return
-    /// a HashMap as an async operations.
-    async fn collect(&self) -> Result<HashMap<String, Value>>;
+    /// a LinkedHashMap as an async operations.
+    async fn collect(&self) -> Result<LinkedHashMap<String, Value>>;
 
     /// Collects all configuration properties to a provided cache.
     async fn collect_to(&self, cache: &mut Value) -> Result<()> {
@@ -86,8 +86,8 @@ impl Source for Vec<Box<dyn Source + Send + Sync>> {
         Box::new((*self).clone())
     }
 
-    fn collect(&self) -> Result<HashMap<String, Value>> {
-        let mut cache: Value = HashMap::<String, Value>::new().into();
+    fn collect(&self) -> Result<LinkedHashMap<String, Value>> {
+        let mut cache: Value = LinkedHashMap::<String, Value>::new().into();
 
         for source in self {
             source.collect_to(&mut cache)?;
@@ -106,8 +106,8 @@ impl Source for [Box<dyn Source + Send + Sync>] {
         Box::new(self.to_owned())
     }