expect: Return false from asymmetric matchers if received value isn’t string

CHANGELOG.md

@@ -25,6 +25,7 @@
 - `[jest-jasmine2`] Fix crash when test return Promise rejected with null ([#7049](https://github.com/facebook/jest/pull/7049))
 - `[jest-runtime]` Check `_isMockFunction` is true rather than truthy on potential global mocks ([#7017](https://github.com/facebook/jest/pull/7017))
 - `[jest-jasmine]` Show proper error message from async `assert` errors ([#6821](https://github.com/facebook/jest/pull/6821))
+- `[expect]` Return false from asymmetric matchers if received value isn’t string ([#7107](https://github.com/facebook/jest/pull/7107))
 
 ### Chore & Maintenance
 

docs/ExpectAPI.md

@@ -347,31 +347,31 @@ describe('not.objectContaining', () => {
 
 ### `expect.not.stringContaining(string)`
 
-`expect.not.stringContaining(string)` matches the received string that does not contain the exact expected string.
+`expect.not.stringContaining(string)` matches the received value if it is not a string or if it is a string that does not contain the exact expected string.
 
 It is the inverse of `expect.stringContaining`.
 
 ```js
 describe('not.stringContaining', () => {
   const expected = 'Hello world!';
 
-  it('matches if the actual string does not contain the expected substring', () => {
+  it('matches if the received value does not contain the expected substring', () => {
     expect('How are you?').toEqual(expect.not.stringContaining(expected));
   });
 });
 ```
 
 ### `expect.not.stringMatching(string | regexp)`
 
-`expect.not.stringMatching(string | regexp)` matches the received string that does not match the expected regexp.
+`expect.not.stringMatching(string | regexp)` matches the received value if it is not a string or if it is a string that does not match the expected string or regular expression.
 
 It is the inverse of `expect.stringMatching`.
 
 ```js
 describe('not.stringMatching', () => {
   const expected = /Hello world!/;
 
-  it('matches if the actual string does not match the expected regex', () => {
+  it('matches if the received value does not match the expected regex', () => {
     expect('How are you?').toEqual(expect.not.stringMatching(expected));
   });
 });
@@ -400,11 +400,11 @@ test('onPress gets called with the right thing', () => {
 
 ### `expect.stringContaining(string)`
 
-`expect.stringContaining(string)` matches the received string that contains the exact expected string.
+`expect.stringContaining(string)` matches the received value if it is a string that contains the exact expected string.
 
 ### `expect.stringMatching(string | regexp)`
 
-`expect.stringMatching(string | regexp)` matches the received string that matches the expected regexp.
+`expect.stringMatching(string | regexp)` matches the received value if it is a string that matches the expected string or regular expression.
 
 You can use it instead of a literal value:
 

packages/expect/src/__tests__/asymmetric_matchers.test.js

@@ -199,29 +199,29 @@ test('StringContaining matches string against string', () => {
   jestExpect(stringContaining('en').asymmetricMatch('queue')).toBe(false);
 });
 
-test('StringContaining throws for non-strings', () => {
+test('StringContaining throws if expected value is not string', () => {
   jestExpect(() => {
     stringContaining([1]).asymmetricMatch('queen');
   }).toThrow();
+});
 
-  jestExpect(() => {
-    stringContaining('en*').asymmetricMatch(1);
-  }).toThrow();
+test('StringContaining returns false if received value is not string', () => {
+  jestExpect(stringContaining('en*').asymmetricMatch(1)).toBe(false);
 });
 
 test('StringNotContaining matches string against string', () => {
   jestExpect(stringNotContaining('en*').asymmetricMatch('queen*')).toBe(false);
   jestExpect(stringNotContaining('en').asymmetricMatch('queue')).toBe(true);
 });
 
-test('StringNotContaining throws for non-strings', () => {
+test('StringNotContaining throws if expected value is not string', () => {
   jestExpect(() => {
     stringNotContaining([1]).asymmetricMatch('queen');
   }).toThrow();
+});
 
-  jestExpect(() => {
-    stringNotContaining('en*').asymmetricMatch(1);
-  }).toThrow();
+test('StringNotContaining returns true if received value is not string', () => {
+  jestExpect(stringNotContaining('en*').asymmetricMatch(1)).toBe(true);
 });
 
 test('StringMatching matches string against regexp', () => {
@@ -234,16 +234,18 @@ test('StringMatching matches string against string', () => {
   jestExpect(stringMatching('en').asymmetricMatch('queue')).toBe(false);
 });
 
-test('StringMatching throws for non-strings and non-regexps', () => {
+test('StringMatching throws if expected value is neither string nor regexp', () => {
   jestExpect(() => {
     stringMatching([1]).asymmetricMatch('queen');
   }).toThrow();
 });
 
-test('StringMatching throws for non-string actual values', () => {
-  jestExpect(() => {
-    stringMatching('en').asymmetricMatch(1);
-  }).toThrow();
+test('StringMatching returns false if received value is not string', () => {
+  jestExpect(stringMatching('en').asymmetricMatch(1)).toBe(false);
+});
+
+test('StringMatching returns false even if coerced non-string received value matches pattern', () => {
+  jestExpect(stringMatching('null').asymmetricMatch(null)).toBe(false);
 });
 
 test('StringNotMatching matches string against regexp', () => {
@@ -256,14 +258,12 @@ test('StringNotMatching matches string against string', () => {
   jestExpect(stringNotMatching('en').asymmetricMatch('queue')).toBe(true);
 });
 
-test('StringNotMatching throws for non-strings and non-regexps', () => {
+test('StringNotMatching throws if expected value is neither string nor regexp', () => {
   jestExpect(() => {
     stringNotMatching([1]).asymmetricMatch('queen');
   }).toThrow();
 });
 
-test('StringNotMatching throws for non-string actual values', () => {
-  jestExpect(() => {
-    stringNotMatching('en').asymmetricMatch(1);
-  }).toThrow();
+test('StringNotMatching returns true if received value is not string', () => {
+  jestExpect(stringNotMatching('en').asymmetricMatch(1)).toBe(true);
 });

packages/expect/src/asymmetric_matchers.js

@@ -216,12 +216,8 @@ class StringContaining extends AsymmetricMatcher {
     this.inverse = inverse;
   }
 
-  asymmetricMatch(other: string) {
-    if (!isA('String', other)) {
-      throw new Error('Actual is not a string');
-    }
-
-    const result = other.includes(this.sample);
+  asymmetricMatch(other: any) {
+    const result = isA('String', other) && other.includes(this.sample);
 
     return this.inverse ? !result : result;
   }
@@ -248,12 +244,8 @@ class StringMatching extends AsymmetricMatcher {
     this.inverse = inverse;
   }
 
-  asymmetricMatch(other: string) {
-    if (!isA('String', other)) {
-      throw new Error('Actual is not a string');
-    }
-
-    const result = this.sample.test(other);
+  asymmetricMatch(other: any) {
+    const result = isA('String', other) && this.sample.test(other);
 
     return this.inverse ? !result : result;
   }