Make toContain more strict with the received type (#10119)

CHANGELOG.md

@@ -16,6 +16,7 @@
 
 - `[babel-plugin-jest-hoist]` Add `__dirname` and `__filename` to whitelisted globals ([#10903](https://github.com/facebook/jest/pull/10903))
 - `[expect]` [**BREAKING**] Revise `expect.not.objectContaining()` to be the inverse of `expect.objectContaining()`, as documented. ([#10708](https://github.com/facebook/jest/pull/10708))
+- `[expect]` [**BREAKING**] Make `toContain` more strict with the received type ([#10119](https://github.com/facebook/jest/pull/10119))
 - `[jest-circus]` Fixed the issue of beforeAll & afterAll hooks getting executed even if it is inside a skipped `describe` block [#10451](https://github.com/facebook/jest/issues/10451)
 - `[jest-circus]` Fix `testLocation` on Windows when using `test.each` ([#10871](https://github.com/facebook/jest/pull/10871))
 - `[jest-console]` `console.dir` now respects the second argument correctly ([#10638](https://github.com/facebook/jest/pull/10638))

packages/expect/src/__tests__/__snapshots__/matchers.test.js.snap

@@ -1958,6 +1958,37 @@ exports[`.toContain(), .toContainEqual() error cases 1`] = `
 Received has value: <r>null</>
 `;
 
+exports[`.toContain(), .toContainEqual() error cases 2`] = `
+<d>expect(</><r>-0</><d>).</>toContain<d>(</><g>0</><d>) // indexOf</>
+
+<b>Matcher error</>: <g>expected</> value must be a string if <r>received</> value is a string
+
+Expected has type:  number
+Expected has value: <g>-0</>
+Received has type:  string
+Received has value: <r>"-0"</>
+`;
+
+exports[`.toContain(), .toContainEqual() error cases 3`] = `
+<d>expect(</><r>null</><d>).</>toContain<d>(</><g>null</><d>) // indexOf</>
+
+<b>Matcher error</>: <g>expected</> value must be a string if <r>received</> value is a string
+
+Expected has value: <g>null</>
+Received has type:  string
+Received has value: <r>"null"</>
+`;
+
+exports[`.toContain(), .toContainEqual() error cases 4`] = `
+<d>expect(</><r>undefined</><d>).</>toContain<d>(</><g>undefined</><d>) // indexOf</>
+
+<b>Matcher error</>: <g>expected</> value must be a string if <r>received</> value is a string
+
+Expected has value: <g>undefined</>
+Received has type:  string
+Received has value: <r>"undefined"</>
+`;
+
 exports[`.toContain(), .toContainEqual() error cases for toContainEqual 1`] = `
 <d>expect(</><r>received</><d>).</>toContainEqual<d>(</><g>expected</><d>) // deep equality</>
 

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

@@ -1463,6 +1463,13 @@ describe('.toContain(), .toContainEqual()', () => {
 
   test('error cases', () => {
     expect(() => jestExpect(null).toContain(1)).toThrowErrorMatchingSnapshot();
+    expect(() => jestExpect('-0').toContain(-0)).toThrowErrorMatchingSnapshot();
+    expect(() =>
+      jestExpect('null').toContain(null),
+    ).toThrowErrorMatchingSnapshot();
+    expect(() =>
+      jestExpect('undefined').toContain(undefined),
+    ).toThrowErrorMatchingSnapshot();
   });
 
   [

packages/expect/src/matchers.ts

@@ -474,6 +474,35 @@ const matchers: MatchersObject = {
     }
 
     if (typeof received === 'string') {
+      const wrongTypeErrorMessage = `${EXPECTED_COLOR(
+        'expected',
+      )} value must be a string if ${RECEIVED_COLOR(
+        'received',
+      )} value is a string`;
+
+      if (expected == null) {
+        throw new Error(
+          matcherErrorMessage(
+            matcherHint(matcherName, received, String(expected), options),
+            wrongTypeErrorMessage,
+            printWithType('Expected', expected, printExpected) +
+              '\n' +
+              printWithType('Received', received, printReceived),
+          ),
+        );
+      }
+      if (typeof expected === 'number') {
+        throw new Error(
+          matcherErrorMessage(
+            matcherHint(matcherName, received, String(expected), options),
+            wrongTypeErrorMessage,
+            printWithType('Expected', expected, printExpected) +
+              '\n' +
+              printWithType('Received', received, printReceived),
+          ),
+        );
+      }
+
       const index = received.indexOf(String(expected));
       const pass = index !== -1;