Further reduce memory footprint of SchemaObject.

More fields are now wrapped in Option<Box<_>>, reducing size of JsonSchema (depending on system) from 424 to 240 bytes.

schemars/src/flatten.rs

@@ -36,9 +36,16 @@ macro_rules! impl_merge {
 
 impl_merge!(SchemaObject {
     merge: definitions extensions instance_type enum_values
-        number string array object,
-    or: schema id title description format const_value all_of any_of one_of not
-        if_schema then_schema else_schema reference,
+        metadata subschemas number string array object,
+    or: format const_value reference,
+});
+
+impl_merge!(Metadata {
+    or: schema id title description,
+});
+
+impl_merge!(SubschemaValidation {
+    or: all_of any_of one_of not if_schema then_schema else_schema,
 });
 
 impl_merge!(NumberValidation {

schemars/src/gen.rs

@@ -124,30 +124,22 @@ impl SchemaGenerator {
         self.definitions
     }
 
-    pub fn root_schema_for<T: ?Sized + JsonSchema>(&mut self) -> Result {
-        let schema = T::json_schema(self)?;
-        Ok(match schema {
-            Schema::Object(mut o) => {
-                o.schema = Some("http://json-schema.org/draft-07/schema#".to_owned());
-                o.title = Some(T::schema_name());
-                o.definitions.extend(self.definitions().clone());
-                Schema::Object(o)
-            }
-            schema => schema,
-        })
+    pub fn root_schema_for<T: ?Sized + JsonSchema>(&mut self) -> Result<SchemaObject> {
+        let mut schema: SchemaObject = T::json_schema(self)?.into();
+        let metadata = schema.metadata.get_or_insert_with(Default::default);
+        metadata.schema = Some("http://json-schema.org/draft-07/schema#".to_owned());
+        metadata.title = Some(T::schema_name());
+        schema.definitions.extend(self.definitions().clone());
+        Ok(schema)
     }
 
-    pub fn into_root_schema_for<T: ?Sized + JsonSchema>(mut self) -> Result {
-        let schema = T::json_schema(&mut self)?;
-        Ok(match schema {
-            Schema::Object(mut o) => {
-                o.schema = Some("http://json-schema.org/draft-07/schema#".to_owned());
-                o.title = Some(T::schema_name());
-                o.definitions.extend(self.into_definitions());
-                Schema::Object(o)
-            }
-            schema => schema,
-        })
+    pub fn into_root_schema_for<T: ?Sized + JsonSchema>(mut self) -> Result<SchemaObject> {
+        let mut schema: SchemaObject = T::json_schema(&mut self)?.into();
+        let metadata = schema.metadata.get_or_insert_with(Default::default);
+        metadata.schema = Some("http://json-schema.org/draft-07/schema#".to_owned());
+        metadata.title = Some(T::schema_name());
+        schema.definitions.extend(self.into_definitions());
+        Ok(schema)
     }
 
     pub fn dereference_once(&self, schema: Schema) -> Result<Schema> {

schemars/src/json_schema_impls/core.rs

@@ -27,8 +27,11 @@ impl<T: JsonSchema> JsonSchema for Option<T> {
                     },
                 ) => Schema::Object(with_null_type(obj)),
                 schema => SchemaObject {
+                    subschemas: Some(Box::new(SubschemaValidation {
                         any_of: Some(vec![schema, <()>::json_schema(gen)?]),
                         ..Default::default()
+                    })),
+                    ..Default::default()
                 }
                 .into(),
             }
@@ -99,7 +102,7 @@ mod tests {
             Some(vec![InstanceType::Integer, InstanceType::Null].into())
         );
         assert_eq!(schema.extensions.get("nullable"), None);
-        assert_eq!(schema.any_of.is_none(), true);
+        assert_eq!(schema.subschemas.is_none(), true);
     }
 
     #[test]
@@ -111,8 +114,8 @@ mod tests {
         let schema = schema_object_for::<Option<Foo>>();
         assert_eq!(schema.instance_type, None);
         assert_eq!(schema.extensions.get("nullable"), None);
-        assert_eq!(schema.any_of.is_some(), true);
-        let any_of = schema.any_of.unwrap();
+        assert_eq!(schema.subschemas.is_some(), true);
+        let any_of = schema.subschemas.unwrap().any_of.unwrap();
         assert_eq!(any_of.len(), 2);
         assert_eq!(any_of[0], Schema::new_ref("#/definitions/Foo".to_string()));
         assert_eq!(any_of[1], schema_for::<()>());
@@ -131,6 +134,6 @@ mod tests {
             Some(SingleOrVec::from(InstanceType::Integer))
         );
         assert_eq!(schema.extensions.get("nullable"), Some(&json!(true)));
-        assert_eq!(schema.any_of.is_none(), true);
+        assert_eq!(schema.subschemas.is_none(), true);
     }
 }

schemars/src/schema.rs

@@ -38,14 +38,8 @@ impl From<bool> for Schema {
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema)]
 #[serde(rename_all = "camelCase", default)]
 pub struct SchemaObject {
-    #[serde(rename = "$schema", skip_serializing_if = "Option::is_none")]
-    pub schema: Option<String>,
-    #[serde(rename = "$id", skip_serializing_if = "Option::is_none")]
-    pub id: Option<String>,
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub title: Option<String>,
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub description: Option<String>,
+    #[serde(flatten, deserialize_with = "skip_if_default")]
+    pub metadata: Option<Box<Metadata>>,
     #[serde(rename = "type", skip_serializing_if = "Option::is_none")]
     pub instance_type: Option<SingleOrVec<InstanceType>>,
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -54,23 +48,11 @@ pub struct SchemaObject {
     pub enum_values: Option<Vec<Value>>,
     #[serde(rename = "const", skip_serializing_if = "Option::is_none")]
     pub const_value: Option<Value>,
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub all_of: Option<Vec<Schema>>,
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub any_of: Option<Vec<Schema>>,
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub one_of: Option<Vec<Schema>>,
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub not: Option<Box<Schema>>,
-    #[serde(rename = "if", skip_serializing_if = "Option::is_none")]
-    pub if_schema: Option<Box<Schema>>,
-    #[serde(rename = "then", skip_serializing_if = "Option::is_none")]
-    pub then_schema: Option<Box<Schema>>,
-    #[serde(rename = "else", skip_serializing_if = "Option::is_none")]
-    pub else_schema: Option<Box<Schema>>,
     #[serde(alias = "$defs", skip_serializing_if = "Map::is_empty")]
     pub definitions: Map<String, Schema>,
     #[serde(flatten, deserialize_with = "skip_if_default")]
+    pub subschemas: Option<Box<SubschemaValidation>>,
+    #[serde(flatten, deserialize_with = "skip_if_default")]
     pub number: Option<Box<NumberValidation>>,
     #[serde(flatten, deserialize_with = "skip_if_default")]
     pub string: Option<Box<StringValidation>>,
@@ -123,13 +105,48 @@ impl From<Schema> for SchemaObject {
             Schema::Object(o) => o,
             Schema::Bool(true) => SchemaObject::default(),
             Schema::Bool(false) => SchemaObject {
+                subschemas: Some(Box::new(SubschemaValidation {
                     not: Some(Schema::Object(Default::default()).into()),
                     ..Default::default()
+                })),
+                ..Default::default()
             },
         }
     }
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema)]
+#[serde(rename_all = "camelCase", default)]
+pub struct Metadata {
+    #[serde(rename = "$schema", skip_serializing_if = "Option::is_none")]
+    pub schema: Option<String>,
+    #[serde(rename = "$id", skip_serializing_if = "Option::is_none")]
+    pub id: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema)]
+#[serde(rename_all = "camelCase", default)]
+pub struct SubschemaValidation {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub all_of: Option<Vec<Schema>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub any_of: Option<Vec<Schema>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub one_of: Option<Vec<Schema>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub not: Option<Box<Schema>>,
+    #[serde(rename = "if", skip_serializing_if = "Option::is_none")]
+    pub if_schema: Option<Box<Schema>>,
+    #[serde(rename = "then", skip_serializing_if = "Option::is_none")]
+    pub then_schema: Option<Box<Schema>>,
+    #[serde(rename = "else", skip_serializing_if = "Option::is_none")]
+    pub else_schema: Option<Box<Schema>>,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema)]
 #[serde(rename_all = "camelCase", default)]
 pub struct NumberValidation {

schemars/tests/util/mod.rs

@@ -1,5 +1,5 @@
 use pretty_assertions::assert_eq;
-use schemars::{gen::SchemaSettings, schema::Schema, schema_for, JsonSchema};
+use schemars::{gen::SchemaSettings, schema::SchemaObject, schema_for, JsonSchema};
 use std::error::Error;
 use std::fs;
 use std::panic;
@@ -18,7 +18,7 @@ pub fn test_default_generated_schema<T: JsonSchema>(file: &str) -> TestResult {
     test_schema(&actual, file)
 }
 
-fn test_schema(actual: &Schema, file: &str) -> TestResult {
+fn test_schema(actual: &SchemaObject, file: &str) -> TestResult {
     let expected_json = match fs::read_to_string(format!("tests/expected/{}.json", file)) {
         Ok(j) => j,
         Err(e) => {
@@ -36,7 +36,7 @@ fn test_schema(actual: &Schema, file: &str) -> TestResult {
     Ok(())
 }
 
-fn write_actual_to_file(schema: &Schema, file: &str) -> TestResult {
+fn write_actual_to_file(schema: &SchemaObject, file: &str) -> TestResult {
     let actual_json = serde_json::to_string_pretty(&schema)?;
     fs::write(format!("tests/actual/{}.json", file), actual_json)?;
     Ok(())

schemars_derive/src/lib.rs

@@ -159,7 +159,10 @@ fn schema_for_external_tagged_enum<'a>(
     }));
 
     wrap_schema_fields(quote! {
+        subschemas: Some(Box::new(schemars::schema::SubschemaValidation {
             any_of: Some(vec![#(#schemas),*]),
+            ..Default::default()
+        })),
     })
 }
 
@@ -208,7 +211,10 @@ fn schema_for_internal_tagged_enum<'a>(
     });
 
     wrap_schema_fields(quote! {
+        subschemas: Some(Box::new(schemars::schema::SubschemaValidation {
             any_of: Some(vec![#(#schemas),*]),
+            ..Default::default()
+        })),
     })
 }
 
@@ -219,7 +225,10 @@ fn schema_for_untagged_enum<'a>(
     let schemas = variants.map(|v| schema_for_untagged_enum_variant(v, cattrs));
 
     wrap_schema_fields(quote! {
+        subschemas: Some(Box::new(schemars::schema::SubschemaValidation {
             any_of: Some(vec![#(#schemas),*]),
+            ..Default::default()
+        })),
     })
 }