radiovisual · December 21, 2022 10:09 · Dec 21, 2022 · Dec 21, 2022
diff --git a/README.md b/README.md
@@ -0,0 +1,2 @@
+This is a slightly modified version of [Kent C. Dodd's (and friends) take on getting to meaningful Error
+messages](https://kentcdodds.com/blog/get-a-catch-block-error-message-with-typescript) when the nature of the errorobject is `unknown`
diff --git a/util-errors.spec.ts b/util-errors.spec.ts
@@ -0,0 +1,26 @@
+import { getErrorMessage } from './util-errors';
+
+describe('getErrorMessage', () => {
+  it('should get the error message from a legit error object', () => {
+    const message = 'Not enough vegetables.';
+    const error = new Error(message);
+    expect(getErrorMessage(error)).toEqual(message);
+  });  
+
+  it('should get the error message from a string', () => {
+    const message = 'Not enough pizza.';
+    expect(getErrorMessage(message)).toEqual(JSON.stringify(message));
+  });  
+
+  it('should stringify a JSON object as the message', () => {
+    const json = { foo: 'bar' };
+    expect(getErrorMessage(json)).toEqual(JSON.stringify(json));
+  });
+
+  it('should fallback to returning a string when the object cannot be JSON-stringified', () => {
+    const json = { a: 1, b: 2, c: {} };
+    // create a circular reference so that the JSON cant be stringified
+    json.c = json;
+    expect(getErrorMessage(json)).toEqual(String(json));
+  });
+});
diff --git a/util-errors.ts b/util-errors.ts
@@ -0,0 +1,30 @@
+type ErrorWithMessageType = {
+  message: string
+}
+
+function isErrorWithMessage(error: unknown): boolean {
+  return (
+    typeof error === 'object' &&
+    error !== null &&
+    'message' in error &&
+    typeof (error as Record<string, unknown>)['message'] === 'string'
+  )
+}
+
+function toErrorWithMessage(maybeError: unknown): ErrorWithMessageType {
+  if (isErrorWithMessage(maybeError)) {
+    return maybeError as ErrorWithMessageType
+  }
+
+  try {
+    return new Error(JSON.stringify(maybeError))
+  } catch {
+    // Fallback in case there's an error stringifying the 
+    // maybeError (for example, with circular references).
+    return new Error(String(maybeError))
+  }
+}
+
+export function getErrorMessage(error: unknown) {
+  return toErrorWithMessage(error).message
+}
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		This is a slightly modified version of [Kent C. Dodd's (and friends) take on getting to meaningful Error
		messages](https://kentcdodds.com/blog/get-a-catch-block-error-message-with-typescript) when the nature of the errorobject is `unknown`
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