refactor: Drop lazy_static dependency

Fixes #514

Cargo.toml

@@ -25,7 +25,6 @@ preserve_order = ["indexmap", "toml?/preserve_order", "serde_json?/preserve_orde
 async = ["async-trait"]
 
 [dependencies]
-lazy_static = "1.4"
 serde = "1.0"
 nom = "7"
 

src/file/format/mod.rs

@@ -1,10 +1,6 @@
-// If no features are used, there is an "unused mut" warning in `ALL_EXTENSIONS`
-// BUG: ? For some reason this doesn't do anything if I try and function scope this
-#![allow(unused_mut)]
-
-use lazy_static::lazy_static;
 use std::collections::HashMap;
 use std::error::Error;
+use std::sync::OnceLock;
 
 use crate::map::Map;
 use crate::{file::FileStoredFormat, value::Value, Format};
@@ -57,10 +53,11 @@ pub enum FileFormat {
     Json5,
 }
 
-lazy_static! {
-    #[doc(hidden)]
-    // #[allow(unused_mut)] ?
-    pub static ref ALL_EXTENSIONS: HashMap<FileFormat, Vec<&'static str>> = {
+pub(crate) fn all_extensions() -> &'static HashMap<FileFormat, Vec<&'static str>> {
+    #![allow(unused_mut)] // If no features are used, there is an "unused mut" warning in `all_extensions`
+
+    static ALL_EXTENSIONS: OnceLock<HashMap<FileFormat, Vec<&'static str>>> = OnceLock::new();
+    ALL_EXTENSIONS.get_or_init(|| {
         let mut formats: HashMap<FileFormat, Vec<_>> = HashMap::new();
 
         #[cfg(feature = "toml")]
@@ -82,15 +79,15 @@ lazy_static! {
         formats.insert(FileFormat::Json5, vec!["json5"]);
 
         formats
-    };
+    })
 }
 
 impl FileFormat {
     pub(crate) fn extensions(&self) -> &'static [&'static str] {
         // It should not be possible for this to fail
         // A FileFormat would need to be declared without being added to the
-        // ALL_EXTENSIONS map.
-        ALL_EXTENSIONS.get(self).unwrap()
+        // all_extensions map.
+        all_extensions().get(self).unwrap()
     }
 
     pub(crate) fn parse(

src/file/source/file.rs

@@ -5,7 +5,7 @@ use std::io;
 use std::path::PathBuf;
 
 use crate::file::{
-    format::ALL_EXTENSIONS, source::FileSourceResult, FileSource, FileStoredFormat, Format,
+    format::all_extensions, source::FileSourceResult, FileSource, FileStoredFormat, Format,
 };
 
 /// Describes a file sourced from a file
@@ -38,7 +38,7 @@ impl FileSourceFile {
             return if let Some(format) = format_hint {
                 Ok((filename, Box::new(format)))
             } else {
-                for (format, extensions) in ALL_EXTENSIONS.iter() {
+                for (format, extensions) in all_extensions().iter() {
                     if extensions.contains(
                         &filename
                             .extension()
@@ -75,7 +75,7 @@ impl FileSourceFile {
             }
 
             None => {
-                for format in ALL_EXTENSIONS.keys() {
+                for format in all_extensions().keys() {
                     for ext in format.extensions() {
                         filename.set_extension(ext);