chore: enforce no negated first condition

.eslintrc.cjs

@@ -591,6 +591,7 @@ module.exports = {
     'wrap-regex': 'off',
     yoda: 'off',
 
+    'unicorn/no-negated-condition': 'error',
     'unicorn/prefer-includes': 'error',
     'unicorn/template-indent': 'error',
   },

docs/ExpectAPI.md

@@ -1186,10 +1186,10 @@ function areVolumesEqual(a, b) {
 
   if (isAVolume && isBVolume) {
     return a.equals(b);
-  } else if (isAVolume !== isBVolume) {
-    return false;
-  } else {
+  } else if (isAVolume === isBVolume) {
     return undefined;
+  } else {
+    return false;
   }
 }
 
@@ -1243,10 +1243,10 @@ function areVolumesEqual(a: unknown, b: unknown): boolean | undefined {
 
   if (isAVolume && isBVolume) {
     return a.equals(b);
-  } else if (isAVolume !== isBVolume) {
-    return false;
-  } else {
+  } else if (isAVolume === isBVolume) {
     return undefined;
+  } else {
+    return false;
   }
 }
 
@@ -1297,10 +1297,10 @@ function areAuthorEqual(a, b) {
   if (isAAuthor && isBAuthor) {
     // Authors are equal if they have the same name
     return a.name === b.name;
-  } else if (isAAuthor !== isBAuthor) {
-    return false;
-  } else {
+  } else if (isAAuthor === isBAuthor) {
     return undefined;
+  } else {
+    return false;
   }
 }
 
@@ -1315,10 +1315,10 @@ function areBooksEqual(a, b, customTesters) {
     return (
       a.name === b.name && this.equals(a.authors, b.authors, customTesters)
     );
-  } else if (isABook !== isBBook) {
-    return false;
-  } else {
+  } else if (isABook === isBBook) {
     return undefined;
+  } else {
+    return false;
   }
 }
 

e2e/custom-matcher-stack-trace/__tests__/sync.test.js

@@ -10,13 +10,13 @@
 function toCustomMatch(callback, expectation) {
   const actual = callback();
 
-  if (actual !== expectation) {
+  if (actual === expectation) {
+    return {pass: true};
+  } else {
     return {
       message: () => `Expected "${expectation}" but got "${actual}"`,
       pass: false,
     };
-  } else {
-    return {pass: true};
   }
 }
 

e2e/custom-reporters/reporters/TestCaseStartReporter.js

@@ -14,7 +14,7 @@
 class TestCaseStartReporter {
   onTestCaseStart(test, testCaseStartInfo) {
     const mode =
-      testCaseStartInfo.mode != null ? testCaseStartInfo.mode : 'undefined';
+      testCaseStartInfo.mode == null ? 'undefined' : testCaseStartInfo.mode;
     console.log(
       `onTestCaseStart: ${testCaseStartInfo.title}, ` +
         `mode: ${mode}, ` +

packages/create-jest/src/runCreate.ts

@@ -131,9 +131,9 @@ export async function runCreate(rootDir = process.cwd()): Promise<void> {
 
   // Determine Jest config path
   const jestConfigPath =
-    existingJestConfigExt != null
-      ? getConfigFilename(existingJestConfigExt)
-      : path.join(rootDir, getConfigFilename(jestConfigFileExt));
+    existingJestConfigExt == null
+      ? path.join(rootDir, getConfigFilename(jestConfigFileExt))
+      : getConfigFilename(existingJestConfigExt);
 
   const shouldModifyScripts = results.scripts;
 

packages/expect/src/__tests__/customEqualityTesters.test.ts

@@ -50,10 +50,10 @@ const areVolumesEqual: Tester = (
 
   if (isAVolume && isBVolume) {
     return a.equals(b);
-  } else if (isAVolume !== isBVolume) {
-    return false;
-  } else {
+  } else if (isAVolume === isBVolume) {
     return undefined;
+  } else {
+    return false;
   }
 };
 

packages/expect/src/__tests__/customEqualityTestersRecursive.test.ts

@@ -45,10 +45,10 @@ const areAuthorsEqual: Tester = (a: unknown, b: unknown) => {
 
   if (isAAuthor && isBAuthor) {
     return a.name === b.name;
-  } else if (isAAuthor !== isBAuthor) {
-    return false;
-  } else {
+  } else if (isAAuthor === isBAuthor) {
     return undefined;
+  } else {
+    return false;
   }
 };
 
@@ -64,10 +64,10 @@ const areBooksEqual: Tester = function (
     return (
       a.name === b.name && this.equals(a.authors, b.authors, customTesters)
     );
-  } else if (isABook !== isBBook) {
-    return false;
-  } else {
+  } else if (isABook === isBBook) {
     return undefined;
+  } else {
+    return false;
   }
 };
 

packages/expect/src/matchers.ts

@@ -120,11 +120,11 @@ const matchers: MatchersObject = {
             // eslint-disable-next-line prefer-template
             matcherHint(matcherName, undefined, undefined, options) +
             '\n\n' +
-            (deepEqualityName !== null
-              ? `${DIM_COLOR(
+            (deepEqualityName === null
+              ? ''
+              : `${DIM_COLOR(
                   `If it should pass with deep equality, replace "${matcherName}" with "${deepEqualityName}"`,
-                )}\n\n`
-              : '') +
+                )}\n\n`) +
             printDiffOrStringify(
               expected,
               received,
@@ -330,12 +330,12 @@ const matchers: MatchersObject = {
             ? `\nReceived value has no prototype\nReceived value: ${printReceived(
                 received,
               )}`
-            : typeof received.constructor !== 'function'
-            ? `\nReceived value: ${printReceived(received)}`
-            : printReceivedConstructorName(
+            : typeof received.constructor === 'function'
+            ? printReceivedConstructorName(
                 'Received constructor',
                 received.constructor,
-              ));
+              )
+            : `\nReceived value: ${printReceived(received)}`);
 
     return {message, pass};
   },
@@ -628,9 +628,9 @@ const matchers: MatchersObject = {
           matcherHint(matcherName, undefined, undefined, options) +
           '\n\n' +
           `Expected: not ${printExpected(expected)}\n` +
-          (stringify(expected) !== stringify(received)
-            ? `Received:     ${printReceived(received)}`
-            : '')
+          (stringify(expected) === stringify(received)
+            ? ''
+            : `Received:     ${printReceived(received)}`)
       : () =>
           // eslint-disable-next-line prefer-template
           matcherHint(matcherName, undefined, undefined, options) +
@@ -777,9 +777,9 @@ const matchers: MatchersObject = {
           (hasValue
             ? `Expected path: ${printExpected(expectedPath)}\n\n` +
               `Expected value: not ${printExpected(expectedValue)}${
-                stringify(expectedValue) !== stringify(receivedValue)
-                  ? `\nReceived value:     ${printReceived(receivedValue)}`
-                  : ''
+                stringify(expectedValue) === stringify(receivedValue)
+                  ? ''
+                  : `\nReceived value:     ${printReceived(receivedValue)}`
               }`
             : `Expected path: not ${printExpected(expectedPath)}\n\n` +
               `Received value: ${printReceived(receivedValue)}`)
@@ -926,9 +926,9 @@ const matchers: MatchersObject = {
           matcherHint(matcherName, undefined, undefined, options) +
           '\n\n' +
           `Expected: not ${printExpected(expected)}` +
-          (stringify(expected) !== stringify(received)
-            ? `\nReceived:     ${printReceived(received)}`
-            : '')
+          (stringify(expected) === stringify(received)
+            ? ''
+            : `\nReceived:     ${printReceived(received)}`)
       : () =>
           // eslint-disable-next-line prefer-template
           matcherHint(matcherName, undefined, undefined, options) +
@@ -965,9 +965,9 @@ const matchers: MatchersObject = {
           matcherHint(matcherName, undefined, undefined, options) +
           '\n\n' +
           `Expected: not ${printExpected(expected)}\n` +
-          (stringify(expected) !== stringify(received)
-            ? `Received:     ${printReceived(received)}`
-            : '')
+          (stringify(expected) === stringify(received)
+            ? ''
+            : `Received:     ${printReceived(received)}`)
       : () =>
           // eslint-disable-next-line prefer-template
           matcherHint(matcherName, undefined, undefined, options) +

packages/expect/src/print.ts

@@ -125,12 +125,12 @@ const printConstructorName = (
   isNot: boolean,
   isExpected: boolean,
 ): string =>
-  typeof constructor.name !== 'string'
-    ? `${label} name is not a string`
-    : constructor.name.length === 0
-    ? `${label} name is an empty string`
-    : `${label}: ${!isNot ? '' : isExpected ? 'not ' : '    '}${
-        isExpected
-          ? EXPECTED_COLOR(constructor.name)
-          : RECEIVED_COLOR(constructor.name)
-      }`;
+  typeof constructor.name === 'string'
+    ? constructor.name.length === 0
+      ? `${label} name is an empty string`
+      : `${label}: ${isNot ? (isExpected ? 'not ' : '    ') : ''}${
+          isExpected
+            ? EXPECTED_COLOR(constructor.name)
+            : RECEIVED_COLOR(constructor.name)
+        }`
+    : `${label} name is not a string`;

packages/expect/src/spyMatchers.ts

@@ -82,9 +82,9 @@ const printNumberOfReturns = (
   countCalls: number,
 ): string =>
   `\nNumber of returns: ${printReceived(countReturns)}${
-    countCalls !== countReturns
-      ? `\nNumber of calls:   ${printReceived(countCalls)}`
-      : ''
+    countCalls === countReturns
+      ? ''
+      : `\nNumber of calls:   ${printReceived(countCalls)}`
   }`;
 
 type PrintLabel = (string: string, isExpectedCall: boolean) => string;
@@ -439,22 +439,22 @@ const createToReturnMatcher = (
               return lines;
             }, [])
             .join('\n') +
-          (received.mock.calls.length !== count
-            ? `\n\nReceived number of calls:   ${printReceived(
+          (received.mock.calls.length === count
+            ? ''
+            : `\n\nReceived number of calls:   ${printReceived(
                 received.mock.calls.length,
-              )}`
-            : '')
+              )}`)
       : () =>
           // eslint-disable-next-line prefer-template
           matcherHint(matcherName, receivedName, expectedArgument, options) +
           '\n\n' +
           `Expected number of returns: >= ${printExpected(1)}\n` +
           `Received number of returns:    ${printReceived(count)}` +
-          (received.mock.calls.length !== count
-            ? `\nReceived number of calls:      ${printReceived(
+          (received.mock.calls.length === count
+            ? ''
+            : `\nReceived number of calls:      ${printReceived(
                 received.mock.calls.length,
-              )}`
-            : '');
+              )}`);
 
     return {message, pass};
   };
@@ -523,22 +523,22 @@ const createToReturnTimesMatcher = (
           matcherHint(matcherName, receivedName, expectedArgument, options) +
           '\n\n' +
           `Expected number of returns: not ${printExpected(expected)}` +
-          (received.mock.calls.length !== count
-            ? `\n\nReceived number of calls:       ${printReceived(
+          (received.mock.calls.length === count
+            ? ''
+            : `\n\nReceived number of calls:       ${printReceived(
                 received.mock.calls.length,
-              )}`
-            : '')
+              )}`)
       : () =>
           // eslint-disable-next-line prefer-template
           matcherHint(matcherName, receivedName, expectedArgument, options) +
           '\n\n' +
           `Expected number of returns: ${printExpected(expected)}\n` +
           `Received number of returns: ${printReceived(count)}` +
-          (received.mock.calls.length !== count
-            ? `\nReceived number of calls:   ${printReceived(
+          (received.mock.calls.length === count
+            ? ''
+            : `\nReceived number of calls:   ${printReceived(
                 received.mock.calls.length,
-              )}`
-            : '');
+              )}`);
 
     return {message, pass};
   };

packages/expect/src/toThrowMatchers.ts

@@ -88,7 +88,13 @@ export const createMatcher = (
     if (fromPromise && isError(received)) {
       thrown = getThrown(received);
     } else {
-      if (typeof received !== 'function') {
+      if (typeof received === 'function') {
+        try {
+          received();
+        } catch (e) {
+          thrown = getThrown(e);
+        }
+      } else {
         if (!fromPromise) {
           const placeholder = expected === undefined ? '' : 'expected';
           throw new Error(
@@ -99,12 +105,6 @@ export const createMatcher = (
             ),
           );
         }
-      } else {
-        try {
-          received();
-        } catch (e) {
-          thrown = getThrown(e);
-        }
       }
     }
 
@@ -227,7 +227,7 @@ const toThrowExpectedObject = (
 ): SyncExpectationResult => {
   const expectedMessageAndCause = createMessageAndCause(expected);
   const thrownMessageAndCause =
-    thrown !== null ? createMessageAndCause(thrown.value) : null;
+    thrown === null ? null : createMessageAndCause(thrown.value);
   const pass =
     thrown !== null &&
     thrown.message === expected.message &&

packages/jest-circus/src/formatNodeAssertErrors.ts

@@ -50,14 +50,14 @@ const formatNodeAssertErrors = (
 
         if (originalError == null) {
           error = asyncError;
-        } else if (!originalError.stack) {
+        } else if (originalError.stack) {
+          error = originalError;
+        } else {
           error = asyncError;
 
           error.message = originalError.message
             ? originalError.message
             : `thrown: ${prettyFormat(originalError, {maxDepth: 3})}`;
-        } else {
-          error = originalError;
         }
       } else {
         error = errors;

packages/jest-circus/src/legacy-code-todo-rewrite/jestAdapter.ts

@@ -128,7 +128,7 @@ const _addSnapshotData = (
   results.snapshot.matched = snapshotState.matched;
   results.snapshot.unmatched = snapshotState.unmatched;
   results.snapshot.updated = snapshotState.updated;
-  results.snapshot.unchecked = !status.deleted ? uncheckedCount : 0;
+  results.snapshot.unchecked = status.deleted ? 0 : uncheckedCount;
   // Copy the array to prevent memory leaks
   results.snapshot.uncheckedKeys = Array.from(uncheckedKeys);
 };