Prevent stack overflow when using inline_subschemas

schemars/src/gen.rs

@@ -11,7 +11,7 @@ use crate::flatten::Merge;
 use crate::schema::*;
 use crate::{visit::*, JsonSchema, Map};
 use dyn_clone::DynClone;
-use std::{any::Any, fmt::Debug};
+use std::{any::Any, collections::HashSet, fmt::Debug};
 
 /// Settings to customize how Schemas are generated.
 ///
@@ -146,10 +146,21 @@ impl SchemaSettings {
 /// let gen = SchemaGenerator::default();
 /// let schema = gen.into_root_schema_for::<MyStruct>();
 /// ```
-#[derive(Debug, Default, Clone)]
+#[derive(Debug, Default)]
 pub struct SchemaGenerator {
     settings: SchemaSettings,
     definitions: Map<String, Schema>,
+    pending_schema_names: HashSet<String>,
+}
+
+impl Clone for SchemaGenerator {
+    fn clone(&self) -> Self {
+        Self {
+            settings: self.settings.clone(),
+            definitions: self.definitions.clone(),
+            pending_schema_names: HashSet::new(),
+        }
+    }
 }
 
 impl From<SchemaSettings> for SchemaGenerator {
@@ -203,23 +214,28 @@ impl SchemaGenerator {
     /// If `T`'s schema depends on any [referenceable](JsonSchema::is_referenceable) schemas, then this method will
     /// add them to the `SchemaGenerator`'s schema definitions.
     pub fn subschema_for<T: ?Sized + JsonSchema>(&mut self) -> Schema {
-        if !T::is_referenceable() || self.settings.inline_subschemas {
-            return T::json_schema(self);
-        }
-
         let name = T::schema_name();
-        let reference = format!("{}{}", self.settings().definitions_path, name);
-        if !self.definitions.contains_key(&name) {
-            self.insert_new_subschema_for::<T>(name);
+        let return_ref = T::is_referenceable()
+            && (!self.settings.inline_subschemas || self.pending_schema_names.contains(&name));
+
+        if return_ref {
+            let reference = format!("{}{}", self.settings().definitions_path, name);
+            if !self.definitions.contains_key(&name) {
+                self.insert_new_subschema_for::<T>(name);
+            }
+            Schema::new_ref(reference)
+        } else {
+            self.json_schema_internal::<T>(&name)
         }
-        Schema::new_ref(reference)
     }
 
     fn insert_new_subschema_for<T: ?Sized + JsonSchema>(&mut self, name: String) {
         let dummy = Schema::Bool(false);
         // insert into definitions BEFORE calling json_schema to avoid infinite recursion
         self.definitions.insert(name.clone(), dummy);
-        let schema = T::json_schema(self);
+
+        let schema = self.json_schema_internal::<T>(&name);
+
         self.definitions.insert(name, schema);
     }
 
@@ -259,8 +275,9 @@ impl SchemaGenerator {
     /// add them to the `SchemaGenerator`'s schema definitions and include them in the returned `SchemaObject`'s
     /// [`definitions`](../schema/struct.Metadata.html#structfield.definitions)
     pub fn root_schema_for<T: ?Sized + JsonSchema>(&mut self) -> RootSchema {
-        let mut schema = T::json_schema(self).into_object();
-        schema.metadata().title.get_or_insert_with(T::schema_name);
+        let name = T::schema_name();
+        let mut schema = self.json_schema_internal::<T>(&name).into_object();
+        schema.metadata().title.get_or_insert(name);
         let mut root = RootSchema {
             meta_schema: self.settings.meta_schema.clone(),
             definitions: self.definitions.clone(),
@@ -279,8 +296,9 @@ impl SchemaGenerator {
     /// If `T`'s schema depends on any [referenceable](JsonSchema::is_referenceable) schemas, then this method will
     /// include them in the returned `SchemaObject`'s [`definitions`](../schema/struct.Metadata.html#structfield.definitions)
     pub fn into_root_schema_for<T: ?Sized + JsonSchema>(mut self) -> RootSchema {
-        let mut schema = T::json_schema(&mut self).into_object();
-        schema.metadata().title.get_or_insert_with(T::schema_name);
+        let name = T::schema_name();
+        let mut schema = self.json_schema_internal::<T>(&name).into_object();
+        schema.metadata().title.get_or_insert(name);
         let mut root = RootSchema {
             meta_schema: self.settings.meta_schema,
             definitions: self.definitions,
@@ -352,6 +370,14 @@ impl SchemaGenerator {
             }
         }
     }
+
+    fn json_schema_internal<T: ?Sized + JsonSchema>(&mut self, name: &str) -> Schema {
+        self.pending_schema_names.insert(name.to_owned());
+        let schema = T::json_schema(self);
+        // FIXME schema name not removed if previous line panics
+        self.pending_schema_names.remove(name);
+        schema
+    }
 }
 
 /// A [Visitor](Visitor) which implements additional traits required to be included in a [SchemaSettings].

schemars/tests/expected/inline-subschemas-recursive.json

@@ -0,0 +1,95 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "RecursiveOuter",
+  "type": "object",
+  "properties": {
+    "direct": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/RecursiveOuter"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "indirect": {
+      "type": [
+        "object",
+        "null"
+      ],
+      "required": [
+        "recursive"
+      ],
+      "properties": {
+        "recursive": {
+          "type": "object",
+          "properties": {
+            "direct": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/RecursiveOuter"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
+            "indirect": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/RecursiveInner"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            }
+          }
+        }
+      }
+    }
+  },
+  "definitions": {
+    "RecursiveOuter": {
+      "type": "object",
+      "properties": {
+        "direct": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/RecursiveOuter"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
+        "indirect": {
+          "type": [
+            "object",
+            "null"
+          ],
+          "required": [
+            "recursive"
+          ],
+          "properties": {
+            "recursive": {
+              "$ref": "#/definitions/RecursiveOuter"
+            }
+          }
+        }
+      }
+    },
+    "RecursiveInner": {
+      "type": "object",
+      "required": [
+        "recursive"
+      ],
+      "properties": {
+        "recursive": {
+          "$ref": "#/definitions/RecursiveOuter"
+        }
+      }
+    }
+  }
+}

schemars/tests/expected/inline-subschemas.json

@@ -1,23 +1,23 @@
 {
-  "$schema":  "https://spec.openapis.org/oas/3.0/schema/2019-04-02#/definitions/Schema",
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "MyJob",
+  "type": "object",
+  "required": [
+    "spec"
+  ],
   "properties": {
     "spec": {
+      "type": "object",
+      "required": [
+        "replicas"
+      ],
       "properties": {
         "replicas": {
+          "type": "integer",
           "format": "uint32",
-          "minimum": 0,
-          "type": "integer"
+          "minimum": 0.0
         }
-      },
-      "required": [
-        "replicas"
-      ],
-      "type": "object"
+      }
     }
-  },
-  "required": [
-     "spec"
-  ],
-  "title": "MyJob",
-  "type": "object"
+  }
 }

schemars/tests/inline_subschemas.rs

@@ -15,7 +15,25 @@ pub struct MyJobSpec {
 
 #[test]
 fn struct_normal() -> TestResult {
-    let mut settings = SchemaSettings::openapi3();
+    let mut settings = SchemaSettings::default();
     settings.inline_subschemas = true;
     test_generated_schema::<MyJob>("inline-subschemas", settings)
 }
+
+#[derive(Debug, JsonSchema)]
+pub struct RecursiveOuter {
+    pub direct: Option<Box<RecursiveOuter>>,
+    pub indirect: Option<Box<RecursiveInner>>,
+}
+
+#[derive(Debug, JsonSchema)]
+pub struct RecursiveInner {
+    pub recursive: RecursiveOuter,
+}
+
+#[test]
+fn struct_recursive() -> TestResult {
+    let mut settings = SchemaSettings::default();
+    settings.inline_subschemas = true;
+    test_generated_schema::<RecursiveOuter>("inline-subschemas-recursive", settings)
+}