feat(openapi): an object type with discriminator reflected as an interface

.changeset/beige-timers-explain.md

@@ -0,0 +1,6 @@
+---
+"@omnigraph/json-schema": minor
+"@omnigraph/openapi": minor
+---
+
+If an object type has a discriminator, it becomes an interface type and any other allOf references with that implements that interface

packages/loaders/json-schema/src/getComposerFromJSONSchema.ts

@@ -14,6 +14,7 @@ import {
   ComposeOutputType,
   ComposeInputType,
   EnumTypeComposer,
+  InterfaceTypeComposer,
 } from 'graphql-compose';
 import {
   getNamedType,
@@ -498,6 +499,20 @@ export function getComposerFromJSONSchema(schema: JSONSchema, logger: Logger): P
             default: subSchema.default,
           };
         }
+        const config = {
+          name: getValidTypeName({
+            schemaComposer,
+            isInput: false,
+            subSchema,
+          }),
+          description: subSchema.description,
+          fields: {},
+          extensions: {
+            validateWithJSONSchema,
+            examples: subSchema.examples,
+            default: subSchema.default,
+          },
+        };
         return {
           input: schemaComposer.createInputTC({
             name: getValidTypeName({
@@ -512,20 +527,14 @@ export function getComposerFromJSONSchema(schema: JSONSchema, logger: Logger): P
               default: subSchema.default,
             },
           }),
-          output: schemaComposer.createObjectTC({
-            name: getValidTypeName({
-              schemaComposer,
-              isInput: false,
-              subSchema,
-            }),
-            description: subSchema.description,
-            fields: {},
-            extensions: {
-              validateWithJSONSchema,
-              examples: subSchema.examples,
-              default: subSchema.default,
-            },
-          }),
+          output: subSchema.discriminator
+            ? schemaComposer.createInterfaceTC({
+                ...config,
+                resolveType(root: any) {
+                  return root[subSchema.discriminator];
+                },
+              })
+            : schemaComposer.createObjectTC(config),
           ...subSchema,
           ...(subSchema.properties ? { properties: { ...subSchema.properties } } : {}),
           ...(subSchema.allOf ? { allOf: [...subSchema.allOf] } : {}),
@@ -615,6 +624,9 @@ export function getComposerFromJSONSchema(schema: JSONSchema, logger: Logger): P
               }
             }
           } else {
+            if (outputTypeComposer instanceof InterfaceTypeComposer) {
+              (subSchemaAndTypeComposers.output as ObjectTypeComposer).addInterface(outputTypeComposer);
+            }
             const typeElemFieldMap = outputTypeComposer.getFields();
             for (const fieldName in typeElemFieldMap) {
               const field = typeElemFieldMap[fieldName];

packages/loaders/openapi/tests/__snapshots__/pet.test.ts.snap

@@ -0,0 +1,30 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Pet should generate the correct schema 1`] = `
+"schema {
+  query: Query
+}
+
+type Query {
+  pets_by_id(id: String!): Pet
+  dogs_by_id(id: String!): Dog
+  cats_by_id(id: String!): Cat
+}
+
+interface Pet {
+  name: String!
+  petType: String
+}
+
+type Dog implements Pet {
+  name: String!
+  petType: String
+  dog_exclusive: String
+}
+
+type Cat implements Pet {
+  name: String!
+  petType: String
+  cat_exclusive: String
+}"
+`;

packages/loaders/openapi/tests/fixtures/pet.yml

@@ -0,0 +1,93 @@
+openapi: 3.0.0
+info:
+  version: 1.0.0
+  title: Swagger Petstore
+  license:
+    name: MIT
+paths:
+  /pets/{id}:
+    get:
+      parameters:
+        - name: id
+          required: true
+          in: path
+          schema:
+            type: string
+      responses:
+        200:
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Pet'
+  /dogs/{id}:
+    get:
+      parameters:
+        - name: id
+          required: true
+          in: path
+          schema:
+            type: string
+      responses:
+        200:
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Dog'
+  /cats/{id}:
+    get:
+      parameters:
+        - name: id
+          required: true
+          in: path
+          schema:
+            type: string
+      responses:
+        200:
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Cat'
+
+components:
+  schemas:
+    Pet:
+      required:
+        - name
+      type: object
+      discriminator:
+        propertyName: petType
+        mapping:
+          Dog: '#/components/schemas/Dog'
+          Cat: '#/components/schemas/Cat'
+      properties:
+        name:
+          type: string
+        petType:
+          type: string
+    Cat:
+      allOf:
+        - $ref: '#/components/schemas/Pet'
+        - type: object
+          properties:
+            cat_exclusive:
+              type: string
+    Dog:
+      allOf:
+        - $ref: '#/components/schemas/Pet'
+        - type: object
+          properties:
+            dog_exclusive:
+              type: string
+  requestBodies:
+    Pet:
+      required: true
+      content:
+        application/vnd.api+json:
+          schema:
+            type: object
+            properties:
+              data:
+                type: object
+                properties:
+                  attributes:
+                    $ref: '#/components/schemas/Pet'

packages/loaders/openapi/tests/pet.test.ts

@@ -0,0 +1,12 @@
+import { printSchemaWithDirectives } from '@graphql-tools/utils';
+import loadGraphQLSchemaFromOpenAPI from '../src';
+
+describe('Pet', () => {
+  it('should generate the correct schema', async () => {
+    const schema = await loadGraphQLSchemaFromOpenAPI('toto', {
+      source: './fixtures/pet.yml',
+      cwd: __dirname,
+    });
+    expect(printSchemaWithDirectives(schema)).toMatchSnapshot();
+  });
+});