feat: Implement Type on the char primitive

poem-openapi/src/types/external/char.rs

@@ -0,0 +1,60 @@
+use std::borrow::Cow;
+
+use serde_json::Value;
+
+use crate::{
+    registry::{MetaSchema, MetaSchemaRef},
+    types::{ParseError, ParseFromJSON, ParseFromParameter, ParseResult, ToJSON, Type},
+};
+
+impl Type for char {
+    const IS_REQUIRED: bool = true;
+
+    type RawValueType = Self;
+
+    type RawElementValueType = Self;
+
+    fn name() -> Cow<'static, str> {
+        "char".into()
+    }
+
+    fn schema_ref() -> MetaSchemaRef {
+        MetaSchemaRef::Inline(Box::new(MetaSchema::new("char")))
+    }
+
+    fn as_raw_value(&self) -> Option<&Self::RawValueType> {
+        Some(self)
+    }
+
+    fn raw_element_iter<'a>(
+        &'a self,
+    ) -> Box<dyn Iterator<Item = &'a Self::RawElementValueType> + 'a> {
+        Box::new(self.as_raw_value().into_iter())
+    }
+}
+
+impl ParseFromJSON for char {
+    fn parse_from_json(value: Option<Value>) -> ParseResult<Self> {
+        let value = value.unwrap_or_default();
+        if let Value::String(value) = value {
+            match value.chars().next() {
+                Some(ch) => Ok(ch),
+                None => Err(ParseError::expected_input()),
+            }
+        } else {
+            Err(ParseError::expected_type(value))
+        }
+    }
+}
+
+impl ParseFromParameter for char {
+    fn parse_from_parameter(value: &str) -> ParseResult<Self> {
+        value.parse().map_err(ParseError::custom)
+    }
+}
+
+impl ToJSON for char {
+    fn to_json(&self) -> Option<Value> {
+        Some(Value::String(self.to_string()))
+    }
+}

poem-openapi/src/types/external/mod.rs

@@ -4,6 +4,7 @@ mod bool;
 mod bson;
 mod btreemap;
 mod btreeset;
+mod char;
 #[cfg(feature = "chrono")]
 mod chrono;
 #[cfg(feature = "rust_decimal")]