From 3a53f5165b8121f193b9fdbe67a8f9db7daba1f3 Mon Sep 17 00:00:00 2001
From: Simon Warta <simon@warta.it>
Date: Tue, 29 Nov 2022 11:48:10 +0100
Subject: [PATCH 1/3] Add #[serde(flatten)] tests for serialization and
 deserialization

---
 src/de/mod.rs  | 35 ++++++++++++++++++++++++++++++++++-
 src/ser/mod.rs | 34 +++++++++++++++++++++++++++++++++-
 2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/src/de/mod.rs b/src/de/mod.rs
index edb56131..1c6fd50d 100644
--- a/src/de/mod.rs
+++ b/src/de/mod.rs
@@ -687,7 +687,7 @@ where
 #[cfg(test)]
 mod tests {
     use super::from_str;
-    use serde_derive::Deserialize;
+    use serde_derive::{Deserialize, Serialize};
 
     #[derive(Debug, Deserialize, PartialEq)]
     enum Type {
@@ -1018,6 +1018,39 @@ mod tests {
         assert_eq!(serde_json::from_str::<Nothing>(r#"null"#).unwrap(), Nothing);
     }
 
+    #[test]
+    fn struct_with_flatten() {
+        #[derive(Serialize, Deserialize, Debug, PartialEq, Eq)]
+        struct Pagination {
+            limit: u64,
+            offset: u64,
+            total: u64,
+        }
+
+        #[derive(Serialize, Deserialize, Debug, PartialEq, Eq)]
+        struct Users {
+            users: Vec<String>,
+
+            #[serde(flatten)]
+            pagination: Pagination,
+        }
+
+        let expected = Users {
+            users: vec!["joe".to_string(), "alice".to_string()],
+            pagination: Pagination {
+                offset: 100,
+                limit: 20,
+                total: 102,
+            },
+        };
+
+        assert_eq!(
+            from_str::<Users>(r#"{"users":["joe","alice"],"limit":20,"offset":100,"total":102}"#)
+                .unwrap(),
+            expected,
+        );
+    }
+
     #[test]
     fn ignoring_extra_fields() {
         #[derive(Debug, Deserialize, PartialEq)]
diff --git a/src/ser/mod.rs b/src/ser/mod.rs
index db009914..fbe1d746 100644
--- a/src/ser/mod.rs
+++ b/src/ser/mod.rs
@@ -539,7 +539,7 @@ impl ser::SerializeStructVariant for Unreachable {
 mod tests {
 
     use super::to_string;
-    use serde_derive::Serialize;
+    use serde_derive::{Deserialize, Serialize};
 
     #[test]
     fn bool() {
@@ -988,6 +988,38 @@ mod tests {
         );
     }
 
+    #[test]
+    fn struct_with_flatten() {
+        #[derive(Serialize, Deserialize, Debug, PartialEq, Eq)]
+        struct Pagination {
+            limit: u64,
+            offset: u64,
+            total: u64,
+        }
+
+        #[derive(Serialize, Deserialize, Debug, PartialEq, Eq)]
+        struct Users {
+            users: Vec<String>,
+
+            #[serde(flatten)]
+            pagination: Pagination,
+        }
+
+        let users = Users {
+            users: vec!["joe".to_string(), "alice".to_string()],
+            pagination: Pagination {
+                offset: 100,
+                limit: 20,
+                total: 102,
+            },
+        };
+
+        assert_eq!(
+            to_string(&users).unwrap(),
+            r#"{"users":["joe","alice"],"limit":20,"offset":100,"total":102}"#
+        );
+    }
+
     #[test]
     fn btree_map() {
         use std::collections::BTreeMap;

From 5ac78a2b539fb117cbb768a8512e57e606d35776 Mon Sep 17 00:00:00 2001
From: Simon Warta <simon@warta.it>
Date: Tue, 29 Nov 2022 11:49:32 +0100
Subject: [PATCH 2/3] Test serde_json compliance

---
 src/ser/mod.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/ser/mod.rs b/src/ser/mod.rs
index fbe1d746..f6160638 100644
--- a/src/ser/mod.rs
+++ b/src/ser/mod.rs
@@ -1018,6 +1018,11 @@ mod tests {
             to_string(&users).unwrap(),
             r#"{"users":["joe","alice"],"limit":20,"offset":100,"total":102}"#
         );
+        assert_eq!(
+            to_string(&users).unwrap(),
+            serde_json::to_string(&users).unwrap(),
+            "serialization must match serde_json implementation"
+        );
     }
 
     #[test]

From 56c81ec1aa0b7e18a2046147896c4dfb1044926c Mon Sep 17 00:00:00 2001
From: Simon Warta <simon@warta.it>
Date: Tue, 29 Nov 2022 11:54:47 +0100
Subject: [PATCH 3/3] Add CHANGELOG

---
 CHANGELOG.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index da435c86..3c54589d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,9 @@ project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 - Add support for map (de)serialization.
+- Add support for `#[serde(flatten)]` (de)serialization ([#20]).
+
+[#20]: https://github.com/CosmWasm/serde-json-wasm/issues/20
 
 ### Changed