Respect serialize_with attr when serializing default

schemars/tests/default.rs

@@ -14,11 +14,19 @@ fn six() -> i32 {
     6
 }
 
+fn custom_serialize<S>(value: &MyStruct2, ser: S) -> Result<S::Ok, S::Error>
+where
+    S: serde::Serializer,
+{
+    ser.collect_str(&format_args!("i:{} b:{}", value.my_int, value.my_bool))
+}
+
 #[derive(Default, Deserialize, Serialize, JsonSchema, Debug)]
 #[serde(default)]
 pub struct MyStruct {
     pub my_int: i32,
     pub my_bool: bool,
+    #[serde(serialize_with = "custom_serialize")]
     pub my_struct2: MyStruct2,
 }
 

schemars/tests/expected/default.json

@@ -4,24 +4,21 @@
   "type": "object",
   "properties": {
     "my_bool": {
-      "type": "boolean",
-      "default": false
+      "default": false,
+      "type": "boolean"
     },
     "my_int": {
+      "default": 0,
       "type": "integer",
-      "format": "int32",
-      "default": 0
+      "format": "int32"
     },
     "my_struct2": {
+      "default": "i:0 b:false",
       "allOf": [
         {
           "$ref": "#/definitions/MyStruct2"
         }
-      ],
-      "default": {
-        "my_bool": false,
-        "my_int": 0
-      }
+      ]
     }
   },
   "definitions": {
@@ -29,13 +26,13 @@
       "type": "object",
       "properties": {
         "my_bool": {
-          "type": "boolean",
-          "default": true
+          "default": true,
+          "type": "boolean"
         },
         "my_int": {
+          "default": 6,
           "type": "integer",
-          "format": "int32",
-          "default": 6
+          "format": "int32"
         }
       }
     }

schemars/tests/expected/remote_derive.json

@@ -4,8 +4,6 @@
   "type": "object",
   "required": [
     "command_line",
-    "system_cpu_time",
-    "user_cpu_time",
     "wall_time"
   ],
   "properties": {
@@ -13,10 +11,26 @@
       "type": "string"
     },
     "system_cpu_time": {
-      "$ref": "#/definitions/DurationDef"
+      "default": {
+        "nanos": 0,
+        "secs": 0
+      },
+      "allOf": [
+        {
+          "$ref": "#/definitions/DurationDef"
+        }
+      ]
     },
     "user_cpu_time": {
-      "$ref": "#/definitions/DurationDef"
+      "default": {
+        "nanos": 0,
+        "secs": 0
+      },
+      "allOf": [
+        {
+          "$ref": "#/definitions/DurationDef"
+        }
+      ]
     },
     "wall_time": {
       "$ref": "#/definitions/DurationDef"

schemars/tests/remote_derive.rs

@@ -2,31 +2,40 @@ mod util;
 
 use other_crate::Duration;
 use schemars::JsonSchema;
+use serde::Serialize;
 use util::*;
 
 mod other_crate {
-    #[derive(Debug)]
+    #[derive(Debug, Default)]
     pub struct Duration {
         pub secs: i64,
         pub nanos: i32,
     }
 }
 
-#[derive(Debug, JsonSchema)]
+#[derive(Debug, JsonSchema, Serialize)]
 #[serde(remote = "Duration")]
 struct DurationDef {
     secs: i64,
     nanos: i32,
 }
 
-#[derive(Debug, JsonSchema)]
+fn custom_serialize<S>(value: &Duration, ser: S) -> Result<S::Ok, S::Error>
+where
+    S: serde::Serializer,
+{
+    ser.collect_str(&format_args!("{}.{:09}s", value.secs, value.nanos))
+}
+
+#[derive(Debug, JsonSchema, Serialize)]
 struct Process {
     command_line: String,
     #[serde(with = "DurationDef")]
     wall_time: Duration,
-    #[serde(with = "DurationDef")]
+    #[serde(default, with = "DurationDef")]
     user_cpu_time: Duration,
-    #[serde(deserialize_with = "some_serialize_function")]
+    // FIXME this should serialize the default as "0.000000000s"
+    #[serde(default, serialize_with = "custom_serialize")]
     #[schemars(with = "DurationDef")]
     system_cpu_time: Duration,
 }

schemars_derive/src/lib.rs

@@ -292,7 +292,6 @@ fn schema_for_struct(fields: &[Field], cattrs: &attr::Container) -> TokenStream
         let name = field.attrs.name().deserialize_name();
         let ty = field.ty;
 
-        // TODO respect serialize_with on field
         let default = match field.attrs.default() {
             SerdeDefault::None if set_container_default.is_some() => {
                 let field_ident = field
@@ -305,7 +304,27 @@ fn schema_for_struct(fields: &[Field], cattrs: &attr::Container) -> TokenStream
             SerdeDefault::None => None,
             SerdeDefault::Default => Some(quote!(<#ty>::default())),
             SerdeDefault::Path(path) => Some(quote!(#path())),
-        };
+        }
+        .map(|d| match field.attrs.serialize_with() {
+            Some(ser_with) => quote! {
+                {
+                    struct _SchemarsDefaultSerialize<T>(T);
+
+                    impl serde::Serialize for _SchemarsDefaultSerialize<#ty>
+                    {
+                        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+                        where
+                            S: serde::Serializer
+                        {
+                            #ser_with(&self.0, serializer)
+                        }
+                    }
+
+                    _SchemarsDefaultSerialize(#d)
+                }
+            },
+            None => d,
+        });
 
         if default.is_none() {
             required.push(name.clone());

schemars_derive/src/metadata.rs

@@ -55,9 +55,9 @@ pub fn set_metadata_on_schema(schema_expr: TokenStream, metadata: &SchemaMetadat
 
     if let Some(default) = &metadata.default {
         setters.push(quote! {
-            metadata.default = match serde_json::json!(#default) {
-                serde_json::value::Value::Null => None,
-                d => Some(d),
+            metadata.default = match serde_json::value::to_value(#default) {
+                Ok(serde_json::value::Value::Null) | Err(_) => None,
+                Ok(d) => Some(d),
             };
         })
     }