Make rejects and resolves synchronous (#5364)

* Make `makeRejectMatcher` synchronizable (#5361) * Reorganize code using promise instaed of async/await * Update changelog * Move rejectedHandler onto then * Make `makeResolveMatcher` synchronizable * Update a snapshot * Update CHANGELOG.md * Update CHANGELOG.md
jestjs · Jan 24, 2018 · 4585c73 · 4585c73
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -13,6 +13,8 @@
   ([#5367](https://github.com/facebook/jest/pull/5367))
 * `[jest-cli]` Fix npm update command for snapshot summary.
   ([#5376](https://github.com/facebook/jest/pull/5376))
+* `[expect]` Make `rejects` and `resolves` synchronously validate its argument.
+  ([#5364](https://github.com/facebook/jest/pull/5364))
 
 ## jest 22.1.4
 

diff --git a/integration-tests/__tests__/__snapshots__/failures.test.js.snap b/integration-tests/__tests__/__snapshots__/failures.test.js.snap
@@ -118,7 +118,7 @@ exports[`works with async failures 1`] = `
     +   \\"foo\\": \\"bar\\",
       }
       
-      at ../../packages/expect/build/index.js:156:54
+      at ../../packages/expect/build/index.js:145:57
 
 "
 `;

diff --git a/packages/expect/src/__tests__/__snapshots__/matchers.test.js.snap b/packages/expect/src/__tests__/__snapshots__/matchers.test.js.snap
@@ -84,6 +84,14 @@ Received:
   string: <red>\\"a\\"</>"
 `;
 
+exports[`.resolves fails non-promise value "a" synchronously 1`] = `
+"<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
+
+<red>received</> value must be a Promise.
+Received:
+  string: <red>\\"a\\"</>"
+`;
+
 exports[`.resolves fails non-promise value [1] 1`] = `
 "<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
 
@@ -92,6 +100,14 @@ Received:
   array: <red>[1]</>"
 `;
 
+exports[`.resolves fails non-promise value [1] synchronously 1`] = `
+"<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
+
+<red>received</> value must be a Promise.
+Received:
+  array: <red>[1]</>"
+`;
+
 exports[`.resolves fails non-promise value [Function anonymous] 1`] = `
 "<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
 
@@ -100,6 +116,14 @@ Received:
   function: <red>[Function anonymous]</>"
 `;
 
+exports[`.resolves fails non-promise value [Function anonymous] synchronously 1`] = `
+"<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
+
+<red>received</> value must be a Promise.
+Received:
+  function: <red>[Function anonymous]</>"
+`;
+
 exports[`.resolves fails non-promise value {"a": 1} 1`] = `
 "<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
 
@@ -108,6 +132,14 @@ Received:
   object: <red>{\\"a\\": 1}</>"
 `;
 
+exports[`.resolves fails non-promise value {"a": 1} synchronously 1`] = `
+"<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
+
+<red>received</> value must be a Promise.
+Received:
+  object: <red>{\\"a\\": 1}</>"
+`;
+
 exports[`.resolves fails non-promise value 4 1`] = `
 "<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
 
@@ -116,13 +148,28 @@ Received:
   number: <red>4</>"
 `;
 
+exports[`.resolves fails non-promise value 4 synchronously 1`] = `
+"<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
+
+<red>received</> value must be a Promise.
+Received:
+  number: <red>4</>"
+`;
+
 exports[`.resolves fails non-promise value null 1`] = `
 "<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
 
 <red>received</> value must be a Promise.
 Received: <red>null</>"
 `;
 
+exports[`.resolves fails non-promise value null synchronously 1`] = `
+"<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
+
+<red>received</> value must be a Promise.
+Received: <red>null</>"
+`;
+
 exports[`.resolves fails non-promise value true 1`] = `
 "<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
 
@@ -131,13 +178,28 @@ Received:
   boolean: <red>true</>"
 `;
 
+exports[`.resolves fails non-promise value true synchronously 1`] = `
+"<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
+
+<red>received</> value must be a Promise.
+Received:
+  boolean: <red>true</>"
+`;
+
 exports[`.resolves fails non-promise value undefined 1`] = `
 "<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
 
 <red>received</> value must be a Promise.
 Received: <red>undefined</>"
 `;
 
+exports[`.resolves fails non-promise value undefined synchronously 1`] = `
+"<dim>expect(</><red>received</><dim>).resolves.toBeDefined(</><dim>)</>
+
+<red>received</> value must be a Promise.
+Received: <red>undefined</>"
+`;
+
 exports[`.toBe() does not crash on circular references 1`] = `
 "<dim>expect(</><red>received</><dim>).toBe(</><green>expected</><dim>)</>
 

diff --git a/packages/expect/src/__tests__/matchers.test.js b/packages/expect/src/__tests__/matchers.test.js
@@ -37,6 +37,18 @@ describe('.rejects', () => {
     await jestExpect(fn()).rejects.toThrow('some error');
   });
 
+  [4, [1], {a: 1}, 'a', true, null, undefined, () => {}].forEach(value => {
+    it(`fails non-promise value ${stringify(value)} synchronously`, () => {
+      let error;
+      try {
+        jestExpect(value).rejects.toBe(111);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+    });
+  });
+
   [4, [1], {a: 1}, 'a', true, null, undefined, () => {}].forEach(value => {
     it(`fails non-promise value ${stringify(value)}`, async () => {
       let error;
@@ -81,6 +93,19 @@ describe('.resolves', () => {
     ).resolves.toThrow();
   });
 
+  [4, [1], {a: 1}, 'a', true, null, undefined, () => {}].forEach(value => {
+    it(`fails non-promise value ${stringify(value)} synchronously`, () => {
+      let error;
+      try {
+        jestExpect(value).resolves.toBeDefined();
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toMatchSnapshot();
+    });
+  });
+
   [4, [1], {a: 1}, 'a', true, null, undefined, () => {}].forEach(value => {
     it(`fails non-promise value ${stringify(value)}`, async () => {
       let error;

diff --git a/packages/expect/src/index.js b/packages/expect/src/index.js
@@ -130,7 +130,7 @@ const makeResolveMatcher = (
   matcher: RawMatcherFn,
   isNot: boolean,
   actual: Promise<any>,
-): PromiseMatcherFn => async (...args) => {
+): PromiseMatcherFn => (...args) => {
   const matcherStatement = `.resolves.${isNot ? 'not.' : ''}${matcherName}`;
   if (!isPromise(actual)) {
     throw new JestAssertionError(
@@ -141,27 +141,27 @@ const makeResolveMatcher = (
     );
   }
 
-  let result;
-  try {
-    result = await actual;
-  } catch (e) {
-    throw new JestAssertionError(
-      utils.matcherHint(matcherStatement, 'received', '') +
-        '\n\n' +
-        `Expected ${utils.RECEIVED_COLOR('received')} Promise to resolve, ` +
-        'instead it rejected to value\n' +
-        `  ${utils.printReceived(e)}`,
-    );
-  }
-  return makeThrowingMatcher(matcher, isNot, result).apply(null, args);
+  return actual.then(
+    result => makeThrowingMatcher(matcher, isNot, result).apply(null, args),
+    reason => {
+      const err = new JestAssertionError(
+        utils.matcherHint(matcherStatement, 'received', '') +
+          '\n\n' +
+          `Expected ${utils.RECEIVED_COLOR('received')} Promise to resolve, ` +
+          'instead it rejected to value\n' +
+          `  ${utils.printReceived(reason)}`,
+      );
+      return Promise.reject(err);
+    },
+  );
 };
 
 const makeRejectMatcher = (
   matcherName: string,
   matcher: RawMatcherFn,
   isNot: boolean,
   actual: Promise<any>,
-): PromiseMatcherFn => async (...args) => {
+): PromiseMatcherFn => (...args) => {
   const matcherStatement = `.rejects.${isNot ? 'not.' : ''}${matcherName}`;
   if (!isPromise(actual)) {
     throw new JestAssertionError(
@@ -172,19 +172,18 @@ const makeRejectMatcher = (
     );
   }
 
-  let result;
-  try {
-    result = await actual;
-  } catch (e) {
-    return makeThrowingMatcher(matcher, isNot, e).apply(null, args);
-  }
-
-  throw new JestAssertionError(
-    utils.matcherHint(matcherStatement, 'received', '') +
-      '\n\n' +
-      `Expected ${utils.RECEIVED_COLOR('received')} Promise to reject, ` +
-      'instead it resolved to value\n' +
-      `  ${utils.printReceived(result)}`,
+  return actual.then(
+    result => {
+      const err = new JestAssertionError(
+        utils.matcherHint(matcherStatement, 'received', '') +
+          '\n\n' +
+          `Expected ${utils.RECEIVED_COLOR('received')} Promise to reject, ` +
+          'instead it resolved to value\n' +
+          `  ${utils.printReceived(result)}`,
+      );
+      return Promise.reject(err);
+    },
+    reason => makeThrowingMatcher(matcher, isNot, reason).apply(null, args),
   );
 };