[expect] Protect against undefined matcher when extending

jestjs · Feb 23, 2022 · ec0cb2e · ec0cb2e
1 parent d472868
commit ec0cb2e
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Showing 3 changed files with 61 additions and 46 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -41,6 +41,7 @@
 - `[jest-jasmine2, jest-types]` [**BREAKING**] Move all `jasmine` specific types from `@jest/types` to its own package ([#12125](https://github.com/facebook/jest/pull/12125))
 - `[jest-matcher-utils]` Pass maxWidth to `pretty-format` to avoid printing every element in arrays by default ([#12402](https://github.com/facebook/jest/pull/12402))
 - `[jest-mock]` Fix function overloads for `spyOn` to allow more correct type inference in complex object ([#12442](https://github.com/facebook/jest/pull/12442))
+- `[expect]` Protect against undefined `matcher` when extending ([#12481](https://github.com/facebook/jest/pull/12481))
 
 ### Chore & Maintenance
 

diff --git a/packages/expect/src/__tests__/extend.test.ts b/packages/expect/src/__tests__/extend.test.ts
@@ -184,3 +184,11 @@ it('allows overriding existing extension', () => {
 
   jestExpect('foo').toAllowOverridingExistingMatcher();
 });
+
+it('does not explode if matcher is undefined', () => {
+  expect(() =>
+    jestExpect.extend({
+      default: undefined,
+    }),
+  ).not.toThrow();
+});
diff --git a/packages/expect/src/jestMatchersObject.ts b/packages/expect/src/jestMatchersObject.ts
@@ -56,57 +56,63 @@ export const setMatchers = (
 ): void => {
   Object.keys(matchers).forEach(key => {
     const matcher = matchers[key];
-    Object.defineProperty(matcher, INTERNAL_MATCHER_FLAG, {
-      value: isInternal,
-    });
-
-    if (!isInternal) {
-      // expect is defined
-
-      class CustomMatcher extends AsymmetricMatcher<
-        [unknown, ...Array<unknown>]
-      > {
-        constructor(inverse = false, ...sample: [unknown, ...Array<unknown>]) {
-          super(sample, inverse);
-        }
-
-        asymmetricMatch(other: unknown) {
-          const {pass} = matcher.call(
-            this.getMatcherContext(),
-            other,
-            ...this.sample,
-          ) as SyncExpectationResult;
 
-          return this.inverse ? !pass : pass;
-        }
-
-        toString() {
-          return `${this.inverse ? 'not.' : ''}${key}`;
-        }
+    if (matcher) {
+      Object.defineProperty(matcher, INTERNAL_MATCHER_FLAG, {
+        value: isInternal,
+      });
 
-        getExpectedType() {
-          return 'any';
+      if (!isInternal) {
+        // expect is defined
+
+        class CustomMatcher extends AsymmetricMatcher<
+          [unknown, ...Array<unknown>]
+        > {
+          constructor(
+            inverse = false,
+            ...sample: [unknown, ...Array<unknown>]
+          ) {
+            super(sample, inverse);
+          }
+
+          asymmetricMatch(other: unknown) {
+            const {pass} = matcher.call(
+              this.getMatcherContext(),
+              other,
+              ...this.sample,
+            ) as SyncExpectationResult;
+
+            return this.inverse ? !pass : pass;
+          }
+
+          toString() {
+            return `${this.inverse ? 'not.' : ''}${key}`;
+          }
+
+          getExpectedType() {
+            return 'any';
+          }
+
+          toAsymmetricMatcher() {
+            return `${this.toString()}<${this.sample.map(String).join(', ')}>`;
+          }
         }
 
-        toAsymmetricMatcher() {
-          return `${this.toString()}<${this.sample.map(String).join(', ')}>`;
-        }
+        Object.defineProperty(expect, key, {
+          configurable: true,
+          enumerable: true,
+          value: (...sample: [unknown, ...Array<unknown>]) =>
+            new CustomMatcher(false, ...sample),
+          writable: true,
+        });
+        Object.defineProperty(expect.not, key, {
+          configurable: true,
+          enumerable: true,
+          value: (...sample: [unknown, ...Array<unknown>]) =>
+            new CustomMatcher(true, ...sample),
+          writable: true,
+        });
       }
-
-      Object.defineProperty(expect, key, {
-        configurable: true,
-        enumerable: true,
-        value: (...sample: [unknown, ...Array<unknown>]) =>
-          new CustomMatcher(false, ...sample),
-        writable: true,
-      });
-      Object.defineProperty(expect.not, key, {
-        configurable: true,
-        enumerable: true,
-        value: (...sample: [unknown, ...Array<unknown>]) =>
-          new CustomMatcher(true, ...sample),
-        writable: true,
-      });
     }
   });