Add error on unsupported OpenAPI versions

src/parser/spec.js

@@ -1,5 +1,17 @@
 import OpenAPIParser from '@readme/openapi-parser';
 
 export const validateSpec = async options => {
-  return await OpenAPIParser.validate(options.spec);
+  const spec = await OpenAPIParser.validate(options.spec);
+
+  if (spec.swagger) {
+    throw new TypeError(`Unsupported OpenAPI version: ${spec.swagger}`);
+  }
+
+  const majorVersion = Number(spec.openapi?.split('.')[0] ?? '0');
+
+  if (majorVersion < 3 || majorVersion >= 4) {
+    throw new TypeError(`Unsupported OpenAPI version: ${spec.openapi ?? 'n/a'}`);
+  }
+
+  return spec;
 };

src/parser/spec.test.js

@@ -9,6 +9,31 @@ describe('validateSpec()', () => {
     );
   });
 
+  it('should throw an error on unsupported OpenAPI versions', async () => {
+    const specSwagger20 = {
+      info: {
+        title: 'Title',
+        version: '1'
+      },
+      paths: {},
+      swagger: '2.0'
+    };
+    const specOpenApi20 = {
+      info: {},
+      openapi: '2.0.0',
+      paths: {}
+    };
+    const specOpenApi40 = {
+      info: {},
+      openapi: '4.0.0',
+      paths: {}
+    };
+
+    await expect(validateSpec({ spec: specSwagger20 })).rejects.toThrowError(/Unsupported OpenAPI version: 2\.0/);
+    await expect(validateSpec({ spec: specOpenApi20 })).rejects.toThrowError(/Unsupported OpenAPI version: 2\.0\.0/);
+    await expect(validateSpec({ spec: specOpenApi40 })).rejects.toThrowError(/Unsupported OpenAPI version: 4\.0\.0/);
+  });
+
   it('should return a parsed spec', async () => {
     const spec = {
       info: {