Fix automock for numeric function names (jestjs#7653)

CHANGELOG.md

@@ -53,6 +53,7 @@
 
 ### Fixes
 
+- `[jest-mock]` Fix automock for numeric function names ([#7653](https://github.com/facebook/jest/pull/7653))
 - `[jest-config]` Ensure `existsSync` is only called with a string parameter ([#7607](https://github.com/facebook/jest/pull/7607))
 - `[expect]` `toStrictEqual` considers sparseness of arrays. ([#7591](https://github.com/facebook/jest/pull/7591))
 - `[jest-cli]` Fix empty coverage data for untested files ([#7388](https://github.com/facebook/jest/pull/7388))

packages/jest-mock/src/__tests__/jest_mock.test.js

@@ -70,29 +70,20 @@ describe('moduleMocker', () => {
       expect(mock.name).toBe('foo');
     });
 
-    it('escapes illegal characters in function name property', () => {
+    it('fixes illegal function name properties', () => {
       function getMockFnWithOriginalName(name) {
         const fn = () => {};
         Object.defineProperty(fn, 'name', {value: name});
 
         return moduleMocker.generateFromMetadata(moduleMocker.getMetadata(fn));
       }
 
-      expect(
-        getMockFnWithOriginalName('foo-bar').name === 'foo$bar',
-      ).toBeTruthy();
-      expect(
-        getMockFnWithOriginalName('foo-bar-2').name === 'foo$bar$2',
-      ).toBeTruthy();
-      expect(
-        getMockFnWithOriginalName('foo-bar-3').name === 'foo$bar$3',
-      ).toBeTruthy();
-      expect(
-        getMockFnWithOriginalName('foo/bar').name === 'foo$bar',
-      ).toBeTruthy();
-      expect(
-        getMockFnWithOriginalName('foo𠮷bar').name === 'foo𠮷bar',
-      ).toBeTruthy();
+      expect(getMockFnWithOriginalName('1').name).toBe('$1');
+      expect(getMockFnWithOriginalName('foo-bar').name).toBe('foo$bar');
+      expect(getMockFnWithOriginalName('foo-bar-2').name).toBe('foo$bar$2');
+      expect(getMockFnWithOriginalName('foo-bar-3').name).toBe('foo$bar$3');
+      expect(getMockFnWithOriginalName('foo/bar').name).toBe('foo$bar');
+      expect(getMockFnWithOriginalName('foo𠮷bar').name).toBe('foo𠮷bar');
     });
 
     it('special cases the mockConstructor name', () => {
@@ -348,6 +339,18 @@ describe('moduleMocker', () => {
       ).not.toThrow();
     });
 
+    it('mocks functions with numeric names', () => {
+      const obj = {
+        1: () => {},
+      };
+
+      const objMock = moduleMocker.generateFromMetadata(
+        moduleMocker.getMetadata(obj),
+      );
+
+      expect(typeof objMock[1]).toBe('function');
+    });
+
     describe('mocked functions', () => {
       it('tracks calls to mocks', () => {
         const fn = moduleMocker.fn();

packages/jest-mock/src/index.js

@@ -623,9 +623,13 @@ class ModuleMockerClass {
       return mockConstructor;
     }
 
-    // It's a syntax error to define functions with a reserved keyword
-    // as name.
-    if (RESERVED_KEYWORDS[name]) {
+    if (
+      // It's a syntax error to define functions with a reserved keyword
+      // as name.
+      RESERVED_KEYWORDS[name] ||
+      // It's also a syntax error to define functions with a name that starts with a number
+      /^\d/.test(name)
+    ) {
       name = '$' + name;
     }