Change $ref to be part of a SchemaObject.

This allows other keyworlds to be used alongside $ref, as allowed in Json Schema 2019-09

schemars/src/flatten.rs

@@ -4,9 +4,9 @@ use crate::{JsonSchemaError, Map, Result, Set};
 impl Schema {
     pub fn flatten(self, other: Self) -> Result {
         if is_null_type(&self) {
-            return Ok(other)
+            return Ok(other);
         } else if is_null_type(&other) {
-            return Ok(self)
+            return Ok(self);
         }
         let s1 = ensure_object_type(self)?;
         let s2 = ensure_object_type(other)?;
@@ -38,7 +38,7 @@ 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,
+        if_schema then_schema else_schema reference,
 });
 
 impl_merge!(NumberValidation {

schemars/src/gen.rs

@@ -18,6 +18,16 @@ pub enum BoolSchemas {
 
 impl Default for SchemaSettings {
     fn default() -> SchemaSettings {
+        SchemaSettings::new()
+    }
+}
+
+impl SchemaSettings {
+    pub fn new() -> SchemaSettings {
+        Self::draft07()
+    }
+
+    pub fn draft07() -> SchemaSettings {
         SchemaSettings {
             option_nullable: false,
             option_add_null_type: true,
@@ -25,14 +35,7 @@ impl Default for SchemaSettings {
             definitions_path: "#/definitions/".to_owned(),
         }
     }
-}
 
-impl SchemaSettings {
-    pub fn new() -> SchemaSettings {
-        SchemaSettings {
-            ..Default::default()
-        }
-    }
     pub fn openapi3() -> SchemaSettings {
         SchemaSettings {
             option_nullable: true,
@@ -66,21 +69,20 @@ impl SchemaGenerator {
     }
 
     pub fn schema_for_any(&self) -> Schema {
+        let schema: Schema = true.into();
         if self.settings().bool_schemas == BoolSchemas::Enable {
-            true.into()
+            schema
         } else {
-            Schema::Object(Default::default())
+            Schema::Object(schema.into())
         }
     }
 
     pub fn schema_for_none(&self) -> Schema {
+        let schema: Schema = false.into();
         if self.settings().bool_schemas == BoolSchemas::Enable {
-            false.into()
+            schema
         } else {
-            Schema::Object(SchemaObject {
+            Schema::Object(schema.into())
-                not: Some(Schema::Object(Default::default()).into()),
-                ..Default::default()
-            })
         }
     }
 
@@ -94,7 +96,7 @@ impl SchemaGenerator {
         if !self.definitions.contains_key(&name) {
             self.insert_new_subschema_for::<T>(name)?;
         }
-        Ok(Ref { reference }.into())
+        Ok(Schema::new_ref(reference))
     }
 
     fn insert_new_subschema_for<T: ?Sized + JsonSchema>(&mut self, name: String) -> Result<()> {
@@ -148,49 +150,41 @@ impl SchemaGenerator {
         })
     }
 
-    pub fn get_schema_object(&self, mut schema: Schema) -> Result<SchemaObject> {
+    pub fn dereference_once(&self, schema: Schema) -> Result<Schema> {
-        for _ in 0..100 {
         match schema {
-                Schema::Object(obj) => return Ok(obj),
+            Schema::Object(SchemaObject {
-                Schema::Bool(true) => return Ok(Default::default()),
+                reference: Some(ref schema_ref),
-                Schema::Bool(false) => {
+                ..
-                    return Ok(SchemaObject {
+            }) => {
-                        not: Some(Schema::Bool(true).into()),
-                        ..Default::default()
-                    })
-                }
-                Schema::Ref(schema_ref) => {
                 let definitions_path = &self.settings().definitions_path;
-                    if !schema_ref.reference.starts_with(definitions_path) {
+                if !schema_ref.starts_with(definitions_path) {
                     return Err(JsonSchemaError::new(
                         "Could not extract referenced schema name.",
-                            Schema::Ref(schema_ref),
-                        ));
-                    }
-
-                    let name = &schema_ref.reference[definitions_path.len()..];
-                    schema = self
-                        .definitions
-                        .get(name)
-                        .ok_or_else(|| {
-                            JsonSchemaError::new(
-                                "Could not find referenced schema.",
-                                Schema::Ref(schema_ref.clone()),
-                            )
-                        })?
-                        .clone();
-
-                    if schema == Schema::Ref(schema_ref) {
-                        return Err(JsonSchemaError::new(
-                            "Schema is referencing itself.",
                         schema,
                     ));
                 }
+
+                let name = &schema_ref[definitions_path.len()..];
+                self.definitions.get(name).cloned().ok_or_else(|| {
+                    JsonSchemaError::new("Could not find referenced schema.", schema)
+                })
             }
+            s => Ok(s),
+        }
+    }
+
+    pub fn dereference(&self, mut schema: Schema) -> Result<Schema> {
+        if !schema.is_ref() {
+            return Ok(schema);
+        }
+        for _ in 0..100 {
+            schema = self.dereference_once(schema)?;
+            if !schema.is_ref() {
+                return Ok(schema);
             }
         }
         Err(JsonSchemaError::new(
-            "Failed to dereference schema after 100 iterations - reference may be cyclic.",
+            "Failed to dereference schema after 100 iterations - references may be cyclic.",
             schema,
         ))
     }

schemars/src/json_schema_impls/core.rs

@@ -34,7 +34,7 @@ impl<T: JsonSchema> JsonSchema for Option<T> {
             }
         }
         if gen.settings().option_nullable {
-            let mut deref = gen.get_schema_object(schema)?;
+            let mut deref: SchemaObject = gen.dereference(schema)?.into();
             deref.extensions.insert("nullable".to_owned(), json!(true));
             schema = Schema::Object(deref);
         };
@@ -110,12 +110,7 @@ mod tests {
         assert_eq!(schema.any_of.is_some(), true);
         let any_of = schema.any_of.unwrap();
         assert_eq!(any_of.len(), 2);
-        assert_eq!(
+        assert_eq!(any_of[0], Schema::new_ref("#/definitions/Foo".to_string()));
-            any_of[0],
-            Schema::Ref(Ref {
-                reference: "#/definitions/Foo".to_string()
-            })
-        );
         assert_eq!(any_of[1], schema_for::<()>());
     }
 

schemars/src/schema.rs

@@ -7,10 +7,22 @@ use serde_json::Value;
 #[serde(untagged)]
 pub enum Schema {
     Bool(bool),
-    Ref(Ref),
     Object(SchemaObject),
 }
 
+impl Schema {
+    pub fn new_ref(reference: String) -> Self {
+        SchemaObject::new_ref(reference).into()
+    }
+
+    pub fn is_ref(&self) -> bool {
+        match self {
+            Schema::Object(o) => o.is_ref(),
+            _ => false,
+        }
+    }
+}
+
 impl From<SchemaObject> for Schema {
     fn from(o: SchemaObject) -> Self {
         Schema::Object(o)
@@ -23,18 +35,6 @@ impl From<bool> for Schema {
     }
 }
 
-impl From<Ref> for Schema {
-    fn from(r: Ref) -> Self {
-        Schema::Ref(r)
-    }
-}
-
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema)]
-pub struct Ref {
-    #[serde(rename = "$ref")]
-    pub reference: String,
-}
-
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema)]
 #[serde(rename_all = "camelCase", default)]
 pub struct SchemaObject {
@@ -68,7 +68,7 @@ pub struct SchemaObject {
     pub then_schema: Option<Box<Schema>>,
     #[serde(rename = "else", skip_serializing_if = "Option::is_none")]
     pub else_schema: Option<Box<Schema>>,
-    #[serde(skip_serializing_if = "Map::is_empty")]
+    #[serde(alias = "$defs", skip_serializing_if = "Map::is_empty")]
     pub definitions: Map<String, Schema>,
     #[serde(flatten)]
     pub number: NumberValidation,
@@ -78,10 +78,45 @@ pub struct SchemaObject {
     pub array: ArrayValidation,
     #[serde(flatten)]
     pub object: ObjectValidation,
+    #[serde(rename = "$ref", skip_serializing_if = "Option::is_none")]
+    pub reference: Option<String>,
     #[serde(flatten)]
     pub extensions: Map<String, Value>,
 }
 
+impl SchemaObject {
+    pub fn new_ref(reference: String) -> Self {
+        SchemaObject {
+            reference: Some(reference),
+            ..Default::default()
+        }
+    }
+
+    pub fn is_ref(&self) -> bool {
+        if self.reference.is_none() {
+            return false;
+        }
+        let only_ref = SchemaObject {
+            reference: self.reference.clone(),
+            ..Default::default()
+        };
+        *self == only_ref
+    }
+}
+
+impl From<Schema> for SchemaObject {
+    fn from(schema: Schema) -> Self {
+        match schema {
+            Schema::Object(o) => o,
+            Schema::Bool(true) => SchemaObject::default(),
+            Schema::Bool(false) => SchemaObject {
+                not: Some(Schema::Object(Default::default()).into()),
+                ..Default::default()
+            },
+        }
+    }
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema)]
 #[serde(rename_all = "camelCase", default)]
 pub struct NumberValidation {
@@ -144,7 +179,9 @@ pub struct ObjectValidation {
     pub property_names: Option<Box<Schema>>,
 }
 
-#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, JsonSchema)]
+#[derive(
+    Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, JsonSchema,
+)]
 #[serde(rename_all = "camelCase")]
 pub enum InstanceType {
     Null,

schemars/tests/expected/schema-openapi3.json

@@ -5,9 +5,6 @@
     {
       "type": "boolean"
     },
-    {
-      "$ref": "#/components/schemas/Ref"
-    },
     {
       "$ref": "#/components/schemas/SchemaObject"
     }
@@ -24,25 +21,11 @@
         "integer"
       ]
     },
-    "Ref": {
-      "type": "object",
-      "required": [
-        "$ref"
-      ],
-      "properties": {
-        "$ref": {
-          "type": "string"
-        }
-      }
-    },
     "Schema": {
       "anyOf": [
         {
           "type": "boolean"
         },
-        {
-          "$ref": "#/components/schemas/Ref"
-        },
         {
           "$ref": "#/components/schemas/SchemaObject"
         }
@@ -55,6 +38,10 @@
           "type": "string",
           "nullable": true
         },
+        "$ref": {
+          "type": "string",
+          "nullable": true
+        },
         "$schema": {
           "type": "string",
           "nullable": true
@@ -64,9 +51,6 @@
             {
               "type": "boolean"
             },
-            {
-              "$ref": "#/components/schemas/Ref"
-            },
             {
               "$ref": "#/components/schemas/SchemaObject"
             }
@@ -78,9 +62,6 @@
             {
               "type": "boolean"
             },
-            {
-              "$ref": "#/components/schemas/Ref"
-            },
             {
               "$ref": "#/components/schemas/SchemaObject"
             }
@@ -109,9 +90,6 @@
             {
               "type": "boolean"
             },
-            {
-              "$ref": "#/components/schemas/Ref"
-            },
             {
               "$ref": "#/components/schemas/SchemaObject"
             }
@@ -133,9 +111,6 @@
             {
               "type": "boolean"
             },
-            {
-              "$ref": "#/components/schemas/Ref"
-            },
             {
               "$ref": "#/components/schemas/SchemaObject"
             }
@@ -166,9 +141,6 @@
             {
               "type": "boolean"
             },
-            {
-              "$ref": "#/components/schemas/Ref"
-            },
             {
               "$ref": "#/components/schemas/SchemaObject"
             }
@@ -239,9 +211,6 @@
             {
               "type": "boolean"
             },
-            {
-              "$ref": "#/components/schemas/Ref"
-            },
             {
               "$ref": "#/components/schemas/SchemaObject"
             }
@@ -276,9 +245,6 @@
             {
               "type": "boolean"
             },
-            {
-              "$ref": "#/components/schemas/Ref"
-            },
             {
               "$ref": "#/components/schemas/SchemaObject"
             }
@@ -296,9 +262,6 @@
             {
               "type": "boolean"
             },
-            {
-              "$ref": "#/components/schemas/Ref"
-            },
             {
               "$ref": "#/components/schemas/SchemaObject"
             }

schemars/tests/expected/schema.json

@@ -5,9 +5,6 @@
     {
       "type": "boolean"
     },
-    {
-      "$ref": "#/definitions/Ref"
-    },
     {
       "$ref": "#/definitions/SchemaObject"
     }
@@ -24,25 +21,11 @@
         "integer"
       ]
     },
-    "Ref": {
-      "type": "object",
-      "required": [
-        "$ref"
-      ],
-      "properties": {
-        "$ref": {
-          "type": "string"
-        }
-      }
-    },
     "Schema": {
       "anyOf": [
         {
           "type": "boolean"
         },
-        {
-          "$ref": "#/definitions/Ref"
-        },
         {
           "$ref": "#/definitions/SchemaObject"
         }
@@ -57,6 +40,12 @@
             "null"
           ]
         },
+        "$ref": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
         "$schema": {
           "type": [
             "string",