Handle promise exceptions

Author: mattphillips

src/__snapshots__/index.test.js.snap

@@ -9,6 +9,16 @@ exports[`jest-expect-message should fail with custom message 1`] = `
 Received: <red>false</color>"
 `;
 
+exports[`jest-expect-message should fail with custom message for async test 1`] = `
+"Custom message:
+  hello
+
+<dim>expect(</intensity><red>received</color><dim>).</intensity>rejects<dim>.</intensity>toBe<dim>(</intensity><green>expected</color><dim>) // Object.is equality</intensity>
+
+Expected: <green>false</color>
+Received: <red>true</color>"
+`;
+
 exports[`jest-expect-message should fail without custom message 1`] = `
 "<dim>expect(</intensity><red>received</color><dim>).</intensity>toBeTruthy<dim>()</intensity>
 

src/index.test.js

@@ -5,6 +5,12 @@ describe('jest-expect-message', () => {
     expect(() => expect(false, 'Woah this should be false!').toBeTruthy()).toThrowErrorMatchingSnapshot();
   });
 
+  test('should fail with custom message for async test', async () => {
+    await expect(
+      async () => await expect(Promise.reject(true), 'hello').rejects.toBe(false)
+    ).rejects.toThrowErrorMatchingSnapshot();
+  });
+
   test('should fail without custom message', () => {
     expect(() => expect(false).toBeTruthy()).toThrowErrorMatchingSnapshot();
   });

src/withMessage.js

@@ -12,8 +12,20 @@ class JestAssertionError extends Error {
 const wrapMatcher = (matcher, customMessage, config) => {
   const newMatcher = (...args) => {
     try {
-      return matcher(...args);
-    } catch (error) {
+      const result = matcher(...args);
+
+      if (result && typeof result.then === 'function') {
+        return result.catch(rethrowWithMessage).catch(function handleError(error) {
+          throw new JestAssertionError(error.matcherResult, handleError);
+        });
+      } else {
+        return result;
+      }
+    } catch (e) {
+      rethrowWithMessage(e);
+    }
+
+    function rethrowWithMessage(error) {
       if (!error.matcherResult) {
         throw error;
       }