Fixes issue 8052: Stackoverflow in toExampleValue() for python client (#8054)

Added a Set<String> in toExampleValueRecursive() to keep track of which models we have
generated to avoid an infinite recursion for recursive models.  An example of a recursive
model would be a GeoJson GeometryCollection.

Co-authored-by: Frank Levine <frank.levine@blacklynx.tech>

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java

@@ -16,6 +16,7 @@
 
 package org.openapitools.codegen.languages;
 
+import com.google.common.collect.Sets;
 import io.swagger.v3.core.util.Json;
 import io.swagger.v3.oas.models.media.*;
 import io.swagger.v3.oas.models.media.ArraySchema;
@@ -879,7 +880,7 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
 
     public String toExampleValue(Schema schema, Object objExample) {
         String modelName = getModelName(schema);
-        return toExampleValueRecursive(modelName, schema, objExample, 1, "", 0);
+        return toExampleValueRecursive(modelName, schema, objExample, 1, "", 0, Sets.newHashSet());
     }
 
     private Boolean simpleStringSchema(Schema schema) {
@@ -925,9 +926,12 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
      *                    ModelName( line 0
      *                        some_property='some_property_example' line 1
      *                    ) line 2
+     * @param seenSchemas This set contains all the schemas passed into the recursive function. It is used to check
+     *                    if a schema was already passed into the function and breaks the infinite recursive loop. The
+     *                    only schemas that are not added are ones that contain $ref != null
      * @return the string example
      */
-    private String toExampleValueRecursive(String modelName, Schema schema, Object objExample, int indentationLevel, String prefix, Integer exampleLine) {
+    private String toExampleValueRecursive(String modelName, Schema schema, Object objExample, int indentationLevel, String prefix, Integer exampleLine, Set<Schema> seenSchemas) {
         final String indentionConst = "    ";
         String currentIndentation = "";
         String closingIndentation = "";
@@ -951,6 +955,27 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
         if (objExample != null) {
             example = objExample.toString();
         }
+        // checks if the current schema has already been passed in. If so, breaks the current recursive pass
+        if (seenSchemas.contains(schema)){
+            if (modelName != null) {
+                return fullPrefix + modelName + closeChars;
+            } else {
+                // this is a recursive schema
+                // need to add a reasonable example to avoid
+                // infinite recursion
+                if(ModelUtils.isNullable(schema)) {
+                    // if the schema is nullable, then 'None' is a valid value
+                    return fullPrefix + "None" + closeChars;
+                } else if(ModelUtils.isArraySchema(schema)) {
+                    // the schema is an array, add an empty array
+                    return fullPrefix + "[]" + closeChars;
+                } else {
+                    // the schema is an object, make an empty object
+                    return fullPrefix + "{}" + closeChars;
+                }
+            }
+        }
+
         if (null != schema.get$ref()) {
             Map<String, Schema> allDefinitions = ModelUtils.getSchemas(this.openAPI);
             String ref = ModelUtils.getSimpleRef(schema.get$ref());
@@ -960,7 +985,7 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
                 return fullPrefix + "None" + closeChars;
             }
             String refModelName = getModelName(schema);
-            return toExampleValueRecursive(refModelName, refSchema, objExample, indentationLevel, prefix, exampleLine);
+            return toExampleValueRecursive(refModelName, refSchema, objExample, indentationLevel, prefix, exampleLine, seenSchemas);
         } else if (ModelUtils.isNullType(schema) || isAnyTypeSchema(schema)) {
             // The 'null' type is allowed in OAS 3.1 and above. It is not supported by OAS 3.0.x,
             // though this tooling supports it.
@@ -1058,7 +1083,8 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
             ArraySchema arrayschema = (ArraySchema) schema;
             Schema itemSchema = arrayschema.getItems();
             String itemModelName = getModelName(itemSchema);
-            example = fullPrefix + "[" + "\n" + toExampleValueRecursive(itemModelName, itemSchema, objExample, indentationLevel + 1, "", exampleLine + 1) + ",\n" + closingIndentation + "]" + closeChars;
+            seenSchemas.add(schema);
+            example = fullPrefix + "[" + "\n" + toExampleValueRecursive(itemModelName, itemSchema, objExample, indentationLevel + 1, "", exampleLine + 1, seenSchemas) + ",\n" + closingIndentation + "]" + closeChars;
             return example;
         } else if (ModelUtils.isMapSchema(schema)) {
             if (modelName == null) {
@@ -1080,7 +1106,8 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
                     addPropPrefix = ensureQuotes(key) + ": ";
                 }
                 String addPropsModelName = getModelName(addPropsSchema);
-                example = fullPrefix + "\n" + toExampleValueRecursive(addPropsModelName, addPropsSchema, addPropsExample, indentationLevel + 1, addPropPrefix, exampleLine + 1) + ",\n" + closingIndentation + closeChars;
+                seenSchemas.add(schema);
+                example = fullPrefix + "\n" + toExampleValueRecursive(addPropsModelName, addPropsSchema, addPropsExample, indentationLevel + 1, addPropPrefix, exampleLine + 1, seenSchemas) + ",\n" + closingIndentation + closeChars;
             } else {
                 example = fullPrefix + closeChars;
             }
@@ -1103,7 +1130,12 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
                     return fullPrefix + closeChars;
                 }
             }
-            return exampleForObjectModel(schema, fullPrefix, closeChars, null, indentationLevel, exampleLine, closingIndentation);
+            // Adds schema to seenSchemas before running example model function. romoves schema after running
+            // the function. It also doesnt keep track of any schemas within the ObjectModel.
+            seenSchemas.add(schema);
+            String exampleForObjectModel = exampleForObjectModel(schema, fullPrefix, closeChars, null, indentationLevel, exampleLine, closingIndentation, seenSchemas);
+            seenSchemas.remove(schema);
+            return exampleForObjectModel;
         } else if (ModelUtils.isComposedSchema(schema)) {
             // TODO add examples for composed schema models without discriminators
 
@@ -1117,7 +1149,12 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
                     CodegenProperty cp = new CodegenProperty();
                     cp.setName(disc.getPropertyName());
                     cp.setExample(discPropNameValue);
-                    return exampleForObjectModel(modelSchema, fullPrefix, closeChars, cp, indentationLevel, exampleLine, closingIndentation);
+                    // Adds schema to seenSchemas before running example model function. romoves schema after running
+                    // the function. It also doesnt keep track of any schemas within the ObjectModel.
+                    seenSchemas.add(modelSchema);
+                    String exampleForObjectModel = exampleForObjectModel(modelSchema, fullPrefix, closeChars, cp, indentationLevel, exampleLine, closingIndentation, seenSchemas);
+                    seenSchemas.remove(modelSchema);
+                    return exampleForObjectModel;
                 } else {
                     return fullPrefix + closeChars;
                 }
@@ -1130,7 +1167,7 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
         return example;
     }
 
-    private String exampleForObjectModel(Schema schema, String fullPrefix, String closeChars, CodegenProperty discProp, int indentationLevel, int exampleLine, String closingIndentation) {
+    private String exampleForObjectModel(Schema schema, String fullPrefix, String closeChars, CodegenProperty discProp, int indentationLevel, int exampleLine, String closingIndentation, Set<Schema> seenSchemas) {
         Map<String, Schema> requiredAndOptionalProps = schema.getProperties();
         if (requiredAndOptionalProps == null || requiredAndOptionalProps.isEmpty()) {
             return fullPrefix + closeChars;
@@ -1150,7 +1187,7 @@ public class PythonClientCodegen extends PythonLegacyClientCodegen {
                 propModelName = getModelName(propSchema);
                 propExample = exampleFromStringOrArraySchema(propSchema, null, propName);
             }
-            example += toExampleValueRecursive(propModelName, propSchema, propExample, indentationLevel + 1, propName + "=", exampleLine + 1) + ",\n";
+            example += toExampleValueRecursive(propModelName, propSchema, propExample, indentationLevel + 1, propName + "=", exampleLine + 1, seenSchemas) + ",\n";
         }
         // TODO handle additionalProperties also
         example += closingIndentation + closeChars;

modules/openapi-generator/src/test/java/org/openapitools/codegen/python/PythonClientTest.java

@@ -15,6 +15,18 @@
  */
 
 package org.openapitools.codegen.python;
+import com.google.common.io.Resources;
+import io.swagger.v3.oas.models.PathItem;
+import io.swagger.v3.oas.models.Paths;
+import io.swagger.v3.oas.models.parameters.RequestBody;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.nio.charset.StandardCharsets;
+import javax.validation.constraints.AssertTrue;
+import org.apache.commons.io.IOUtils;
 import org.openapitools.codegen.config.CodegenConfigurator;
 
 import com.google.common.collect.Sets;
@@ -33,6 +45,7 @@ import org.openapitools.codegen.*;
 import org.openapitools.codegen.languages.PythonClientCodegen;
 import org.openapitools.codegen.utils.ModelUtils;
 import org.testng.Assert;
+import org.testng.TestNGAntTask.Mode;
 import org.testng.annotations.Test;
 
 @SuppressWarnings("static-method")
@@ -425,4 +438,30 @@ public class PythonClientTest {
         final CodegenModel model = codegen.fromModel(modelName, modelSchema);
         Assert.assertEquals((int) model.getMinProperties(), 1);
     }
+
+    @Test(description = "tests RecursiveToExample")
+    public void testRecursiveToExample() throws IOException {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/issue_8052_recursive_model.yaml");
+        final PythonClientCodegen codegen = new PythonClientCodegen();
+        codegen.setOpenAPI(openAPI);
+
+        final Operation operation = openAPI.getPaths().get("/geojson").getPost();
+        Schema schema = ModelUtils.getSchemaFromRequestBody(operation.getRequestBody());
+        String exampleValue = codegen.toExampleValue(schema, null);
+
+        // uncomment if you need to regenerate the expected value
+        //        PrintWriter printWriter = new PrintWriter("src/test/resources/3_0/issue_8052_recursive_model_expected_value.txt");
+        //        printWriter.write(exampleValue);
+        //        printWriter.close();
+        //        org.junit.Assert.assertTrue(false);
+
+        String expectedValue = Resources.toString(
+                Resources.getResource("3_0/issue_8052_recursive_model_expected_value.txt"),
+                StandardCharsets.UTF_8);
+
+
+        Assert.assertEquals(expectedValue.trim(), exampleValue.trim());
+
+    }
+
 }

modules/openapi-generator/src/test/resources/3_0/issue_8052_recursive_model.yaml

@@ -0,0 +1,83 @@
+openapi: 3.0.0
+info:
+  version: 01.01.00
+  title: APITest API documentation.
+  termsOfService: http://api.apitest.com/party/tos/
+servers:
+  - url: https://api.apitest.com/v1
+paths:
+  /geojson:
+    post:
+      summary: Add a GeoJson Object
+      operationId: post-geojson
+      responses:
+        '201':
+          description: Created
+          content:
+            application/json:
+              schema:
+                type: string
+                description: GeoJson ID
+        '400':
+          description: Bad Request
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/GeoJsonGeometry'
+      parameters: []
+components:
+  schemas:
+    GeoJsonGeometry:
+      title: GeoJsonGeometry
+      description: GeoJSON geometry
+      oneOf:
+        - $ref: '#/components/schemas/Point'
+        - $ref: '#/components/schemas/GeometryCollection'
+      discriminator:
+        propertyName: type
+        mapping:
+          Point: '#/components/schemas/Point'
+          GeometryCollection: '#/components/schemas/GeometryCollection'
+      externalDocs:
+        url: http://geojson.org/geojson-spec.html#geometry-objects
+    Point:
+      title: Point
+      type: object
+      description: GeoJSON geometry
+      externalDocs:
+        url: http://geojson.org/geojson-spec.html#id2
+      properties:
+        coordinates:
+          title: Point3D
+          type: array
+          description: Point in 3D space
+          externalDocs:
+            url: http://geojson.org/geojson-spec.html#id2
+          minItems: 2
+          maxItems: 3
+          items:
+            type: number
+            format: double
+        type:
+          type: string
+          default: Point
+      required:
+        - type
+    GeometryCollection:
+      title: GeometryCollection
+      type: object
+      description: GeoJSon geometry collection
+      required:
+        - type
+        - geometries
+      externalDocs:
+        url: http://geojson.org/geojson-spec.html#geometrycollection
+      properties:
+        type:
+          type: string
+          default: GeometryCollection
+        geometries:
+          type: array
+          items:
+            $ref: '#/components/schemas/GeoJsonGeometry'

modules/openapi-generator/src/test/resources/3_0/issue_8052_recursive_model_expected_value.txt

@@ -0,0 +1,9 @@
+GeoJsonGeometry(
+        type="GeometryCollection",
+        geometries=[
+            GeoJsonGeometry(
+                type="GeometryCollection",
+                geometries=[],
+            ),
+        ],
+    )