Revert "Make the parse list key to lowercase when insert the keys"

This reverts commit b3d8518.

src/env.rs

@@ -155,10 +155,10 @@ impl Environment {
     /// To switch the default type back to type Strings you need to provide the keys which should be [`Vec<String>`] using this function.
     pub fn with_list_parse_key(mut self, key: &str) -> Self {
         if self.list_parse_keys.is_none() {
-            self.list_parse_keys = Some(vec![key.to_lowercase()]);
+            self.list_parse_keys = Some(vec![key.into()]);
         } else {
             self.list_parse_keys = self.list_parse_keys.map(|mut keys| {
-                keys.push(key.to_lowercase());
+                keys.push(key.into());
                 keys
             });
         }
@@ -289,9 +289,6 @@ impl Source for Environment {
                     ValueKind::Float(parsed)
                 } else if let Some(separator) = &self.list_separator {
                     if let Some(keys) = &self.list_parse_keys {
-                        #[cfg(feature = "convert-case")]
-                        let key = key.to_lowercase();
-
                         if keys.contains(&key) {
                             let v: Vec<Value> = value
                                 .split(separator)

tests/testsuite/env.rs

@@ -1,5 +1,7 @@
-use config::{Config, Environment, Source};
 use serde_derive::Deserialize;
+use snapbox::{assert_data_eq, str};
+
+use config::{Config, Environment, Source};
 
 /// Reminder that tests using env variables need to use different env variable names, since
 /// tests can be run in parallel
@@ -474,11 +476,13 @@ fn test_parse_string_and_list_ignore_list_parse_key_case() {
     // using a struct in an enum here to make serde use `deserialize_any`
     #[derive(Deserialize, Debug)]
     #[serde(tag = "tag")]
+    #[allow(dead_code)]
     enum TestStringEnum {
         String(TestString),
     }
 
     #[derive(Deserialize, Debug)]
+    #[allow(dead_code)]
     struct TestString {
         string_val: String,
         string_list: Vec<String>,
@@ -503,20 +507,13 @@ fn test_parse_string_and_list_ignore_list_parse_key_case() {
                 .build()
                 .unwrap();
 
-            let config: TestStringEnum = config.try_deserialize().unwrap();
+            let res = config.try_deserialize::<TestStringEnum>();
 
-            match config {
-                TestStringEnum::String(TestString {
-                    string_val,
-                    string_list,
-                }) => {
-                    assert_eq!(String::from("test,string"), string_val);
-                    assert_eq!(
-                        vec![String::from("test"), String::from("string")],
-                        string_list
-                    );
-                }
-            }
+            assert!(res.is_err());
+            assert_data_eq!(
+                res.unwrap_err().to_string(),
+                str![[r#"invalid type: string "test,string", expected a sequence"#]]
+            );
         },
     );
 }