shim private methods

lib/Error.js

@@ -4,40 +4,63 @@
  * Generic Error class to wrap any errors returned by stripe-node
  */
 class GenericError extends Error {
-  constructor(message) {
+  constructor(type, message) {
     super(message);
     // Saving class name in the property of our custom error as a shortcut.
-    this.type = this.constructor.name;
-    this.name = this.constructor.name;
+    this.type = type || this.constructor.name;
+    this.name = type || this.constructor.name;
 
     // Capturing stack trace, excluding constructor call from it.
     Error.captureStackTrace(this, this.constructor);
   }
+
+  populate(raw) {
+    if (!raw || typeof raw !== 'object' || Object.keys(raw).length < 1) {
+      return;
+    }
+    this.raw = raw;
+    this.rawType = raw.type;
+    this.code = raw.code;
+    this.param = raw.param;
+    this.message = raw.message;
+    this.detail = raw.detail;
+    this.headers = raw.headers;
+    this.requestId = raw.requestId;
+    this.statusCode = raw.statusCode;
+  }
+
+  /**
+   * @param {{ type: string, message?: string, [k:string]: any }} options
+   */
+  static extend(options) {
+    class customError extends GenericError {
+      constructor(raw = {}) {
+        super(options.type, raw.message);
+        this.populate(raw);
+      }
+    }
+    for (const property in options) {
+      customError.prototype[property] = options[property];
+    }
+    return customError;
+  }
 }
 
 /**
  * StripeError is the base error from which all other more specific Stripe
  * errors derive.
  * (Specifically for errors returned from Stripe's REST API)
  *
- * @typedef {{ message: string, type?: string, code?: number, param?: string, detail: string, headers?: Record<string, string>, requestId?: string, statusCode?: number }} ErrorParams
+ * @typedef {{ message?: string, type?: string, code?: number, param?: string, detail?: string, headers?: Record<string, string>, requestId?: string, statusCode?: number }} ErrorParams
  */
 class StripeError extends GenericError {
   /**
    *
    * @param {ErrorParams} raw
    */
   constructor(raw) {
-    super(raw.message);
-    this.rawType = raw.type;
-    this.code = raw.code;
-    this.param = raw.param;
-    this.message = raw.message;
-    this.detail = raw.detail;
-    this.raw = raw;
-    this.headers = raw.headers;
-    this.requestId = raw.requestId;
-    this.statusCode = raw.statusCode;
+    super(undefined, raw.message);
+    this.populate(raw);
   }
 
   /**
@@ -144,4 +167,5 @@ module.exports = {
   StripeSignatureVerificationError,
   StripeIdempotencyError,
   StripeInvalidGrantError,
+  extend: GenericError.extend.bind(GenericError),
 };

test/Error.spec.js

@@ -7,8 +7,8 @@ const expect = require('chai').expect;
 
 describe('Error', () => {
   it('Populates with type and message params', () => {
-    const e = new Error.GenericError('Foo happened');
-    expect(e).to.have.property('type', 'GenericError');
+    const e = new Error.GenericError('FooError', 'Foo happened');
+    expect(e).to.have.property('type', 'FooError');
     expect(e).to.have.property('message', 'Foo happened');
     expect(e).to.have.property('stack');
   });
@@ -53,5 +53,33 @@ describe('Error', () => {
       });
       expect(e).to.have.property('statusCode', 400);
     });
+
+    it('can be extended via .extend method', () => {
+      const Custom = Error.GenericError.extend({type: 'MyCustomErrorType'});
+      const err = new Custom({message: 'byaka'});
+      expect(err).to.be.instanceOf(Error.GenericError);
+      expect(err).to.have.property('type', 'MyCustomErrorType');
+      expect(err).to.have.property('name', 'MyCustomErrorType');
+      expect(err).to.have.property('message', 'byaka');
+    });
+
+    it('can create custom error via `extend` export', () => {
+      const Custom = Error.extend({
+        type: 'MyCardError',
+        populate(raw) {
+          this.detail = 'hello';
+          this.customField = 'hi';
+        },
+      });
+      const err = new Custom({
+        message: 'ee',
+      });
+      expect(err).to.be.instanceOf(Error.GenericError);
+      expect(err).to.have.property('type', 'MyCardError');
+      expect(err).to.have.property('name', 'MyCardError');
+      expect(err).to.have.property('message', 'ee');
+      expect(err).to.have.property('detail', 'hello');
+      expect(err).to.have.property('customField', 'hi');
+    });
   });
 });