1 files changed, 80 insertions, 0 deletions
diff --git a/vendor/icu_provider/src/serde/borrow_de_utils.rs b/vendor/icu_provider/src/serde/borrow_de_utils.rs
new file mode 100644
index 000000000..afce7641e
--- /dev/null
+++ b/vendor/icu_provider/src/serde/borrow_de_utils.rs
@@ -0,0 +1,80 @@
+// This file is part of ICU4X. For terms of use, please see the file
+// called LICENSE at the top level of the ICU4X source tree
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+use alloc::borrow::Cow;
+use serde::de::Deserializer;
+use serde::Deserialize;
+
+#[derive(Deserialize)]
+#[serde(transparent)]
+// Cows fail to borrow in some situations (array, option), but structs of Cows don't.
+#[allow(clippy::exhaustive_structs)] // newtype
+pub struct CowWrap<'data>(#[serde(borrow)] pub Cow<'data, str>);
+
+#[derive(Deserialize)]
+#[serde(transparent)]
+// Cows fail to borrow in some situations (array, option), but structs of Cows don't.
+#[allow(clippy::exhaustive_structs)] // newtype
+pub struct CowBytesWrap<'data>(#[serde(borrow)] pub Cow<'data, [u8]>);
+
+pub fn array_of_cow<'de, D, const N: usize>(deserializer: D) -> Result<[Cow<'de, str>; N], D::Error>
+where
+    D: Deserializer<'de>,
+    [CowWrap<'de>; N]: Deserialize<'de>,
+{
+    <[CowWrap<'de>; N]>::deserialize(deserializer).map(|array| array.map(|wrap| wrap.0))
+}
+
+pub fn option_of_cow<'de, D>(deserializer: D) -> Result<Option<Cow<'de, str>>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    <Option<CowWrap<'de>>>::deserialize(deserializer).map(|opt| opt.map(|wrap| wrap.0))
+}
+
+pub fn tuple_of_cow<'de, D>(deserializer: D) -> Result<(Cow<'de, str>, Cow<'de, str>), D::Error>
+where
+    D: Deserializer<'de>,
+    (CowWrap<'de>, CowWrap<'de>): Deserialize<'de>,
+{
+    <(CowWrap<'de>, CowWrap<'de>)>::deserialize(deserializer).map(|x| (x.0 .0, x.1 .0))
+}
+
+#[test]
+fn test_option() {
+    #[derive(Debug, PartialEq, serde::Serialize, serde::Deserialize)]
+    struct Demo<'s>(#[serde(borrow, deserialize_with = "option_of_cow")] Option<Cow<'s, str>>);
+
+    let data_orig = Demo(Some("Hello world".into()));
+    let json = serde_json::to_string(&data_orig).expect("serialize");
+    let data_new = serde_json::from_str::<Demo>(&json).expect("deserialize");
+    assert_eq!(data_orig, data_new);
+    assert!(matches!(data_new.0, Some(Cow::Borrowed(_))));
+}
+
+#[test]
+fn test_tuple() {
+    #[derive(Debug, PartialEq, serde::Serialize, serde::Deserialize)]
+    struct Demo<'s>(
+        #[serde(borrow, deserialize_with = "tuple_of_cow")] (Cow<'s, str>, Cow<'s, str>),
+    );
+
+    let data_orig = Demo(("Hello world".into(), "Hello earth".into()));
+    let json = serde_json::to_string(&data_orig).expect("serialize");
+    let data_new = serde_json::from_str::<Demo>(&json).expect("deserialize");
+    assert_eq!(data_orig, data_new);
+    assert!(matches!(data_new.0, (Cow::Borrowed(_), Cow::Borrowed(_))));
+}
+
+#[test]
+fn test_array() {
+    #[derive(Debug, PartialEq, serde::Serialize, serde::Deserialize)]
+    struct Demo<'s>(#[serde(borrow, deserialize_with = "array_of_cow")] [Cow<'s, str>; 1]);
+
+    let data_orig = Demo(["Hello world".into()]);
+    let json = serde_json::to_string(&data_orig).expect("serialize");
+    let data_new = serde_json::from_str::<Demo>(&json).expect("deserialize");
+    assert_eq!(data_orig, data_new);
+    assert!(matches!(data_new.0, [Cow::Borrowed(_)]));
+}