WEBDEV-8508: Migrate result-type into elements

src/types/result.test.ts

@@ -0,0 +1,35 @@
+import { describe, expect, test } from 'vitest';
+
+import type { Result } from './result';
+
+describe('Result', () => {
+  test('can be initialized with a success value', () => {
+    const result: Result<string, Error> = {
+      success: 'foo',
+    };
+    expect(result.success).toBe('foo');
+    expect(result.error).toBeUndefined();
+  });
+
+  test('can be initialized with an error', () => {
+    const FooErrorType = {
+      networkError: 0,
+      decodingError: 1,
+    } as const;
+    type FooErrorType = (typeof FooErrorType)[keyof typeof FooErrorType];
+
+    class FooError extends Error {
+      type?: FooErrorType;
+
+      constructor(type: FooErrorType) {
+        super();
+        this.type = type;
+      }
+    }
+    const result: Result<string, FooError> = {
+      error: new FooError(FooErrorType.decodingError),
+    };
+    expect(result.success).toBeUndefined();
+    expect(result.error?.type).toBe(FooErrorType.decodingError);
+  });
+});

src/types/result.ts

@@ -0,0 +1,18 @@
+/**
+ * The Result is a container for a response.
+ *
+ * It contains an optional success result which is generic
+ * and can be anything depending on the context,
+ * or an Error or subclass of an error.
+ *
+ * This allows us to return rich, typed errors instead of
+ * an untyped Promise rejection.
+ *
+ * This is modeled after Swift's Result type:
+ * https://developer.apple.com/documentation/swift/result
+ */
+export interface Result<T, E extends Error> {
+  success?: T;
+
+  error?: E;
+}