add option string trim

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_trim"
-version = "0.2.0"
+version = "0.3.0"
 authors = ["baoyachi <[email protected]>"]
 edition = "2021"
 description = "serde deserialize_with String trim"

README.md

@@ -12,13 +12,22 @@
 ## how to use
 ```rust
 fn main() {
-    #[derive(Debug, Deserialize)]
+    #[derive(Deserialize)]
     struct Foo {
         #[serde(deserialize_with = "string_trim")]
         name: String,
     }
     let json = r#"{"name":" "}"#;
     let foo = serde_json::from_str::<Foo>(json).unwrap();
     assert_eq!(foo.name, "");
+
+    #[derive(Deserialize)]
+    struct OptionFoo {
+        #[serde(deserialize_with = "option_string_trim")]
+        name: Option<String>,
+    }
+    let json = r#"{"name":" "}"#;
+    let foo = serde_json::from_str::<OptionFoo>(json).unwrap();
+    assert_eq!(foo.name, None);
 }
 ```

lib.rs

@@ -10,9 +10,22 @@ where
     Ok(de_string)
 }
 
+pub fn option_string_trim<'de, D>(d: D) -> Result<Option<String>, D::Error>
+where
+    D: de::Deserializer<'de>,
+{
+    let mut de_string: Option<String> = Option::deserialize(d)?;
+    if let Some(ref mut de_string) = de_string {
+        if de_string.trim_in_place().is_empty() {
+            return Ok(None);
+        }
+    }
+    Ok(de_string)
+}
+
 #[test]
 fn test_string_trim() {
-    #[derive(Debug, Deserialize)]
+    #[derive(Deserialize)]
     struct Foo {
         #[serde(deserialize_with = "string_trim")]
         name: String,
@@ -21,3 +34,15 @@ fn test_string_trim() {
     let foo = serde_json::from_str::<Foo>(json).unwrap();
     assert_eq!(foo.name, "");
 }
+
+#[test]
+fn test_option_string_trim() {
+    #[derive(Deserialize)]
+    struct OptionFoo {
+        #[serde(deserialize_with = "option_string_trim")]
+        name: Option<String>,
+    }
+    let json = r#"{"name":" "}"#;
+    let foo = serde_json::from_str::<OptionFoo>(json).unwrap();
+    assert_eq!(foo.name, None);
+}