support jest-diffing numbers and booleans

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Features
 
 - `[jest-runtime]` Add `jest.isolateModules` for scoped module initialization ([#6701](https://github.com/facebook/jest/pull/6701))
+- `[jest-diff]` [**BREAKING**] Support diffing numbers and booleans instead of returning null for different ones (TODO link)
 - `[jest-cli]` [**BREAKING**] Only set error process error codes when they are non-zero ([#7363](https://github.com/facebook/jest/pull/7363))
 - `[jest-config]` [**BREAKING**] Deprecate `setupTestFrameworkScriptFile` in favor of new `setupFilesAfterEnv` ([#7119](https://github.com/facebook/jest/pull/7119))
 - `[jest-worker]` [**BREAKING**] Add functionality to call a `setup` method in the worker before the first call and a `teardown` method when ending the farm ([#7014](https://github.com/facebook/jest/pull/7014))

packages/expect/src/matchers.js

@@ -66,7 +66,10 @@ const matchers: MatchersObject = {
             (receivedType === 'object' || expectedType === 'array') &&
             equals(received, expected, [iterableEquality]);
           const oneline = isOneline(expected, received);
-          const diffString = diff(expected, received, {expand: this.expand});
+          const diffString = diff(expected, received, {
+            expand: this.expand,
+            omitTrivial: true,
+          });
 
           return (
             matcherHint('.toBe', undefined, undefined, {
@@ -391,7 +394,10 @@ const matchers: MatchersObject = {
           `Expected: ${printExpected(expected)}\n` +
           `Received: ${printReceived(received)}`
       : () => {
-          const diffString = diff(expected, received, {expand: this.expand});
+          const diffString = diff(expected, received, {
+            expand: this.expand,
+            omitTrivial: true,
+          });
 
           return (
             matcherHint('.toEqual', undefined, undefined, {
@@ -523,7 +529,10 @@ const matchers: MatchersObject = {
       : () => {
           const diffString =
             valuePassed && hasEndProp
-              ? diff(value, result.value, {expand: this.expand})
+              ? diff(value, result.value, {
+                  expand: this.expand,
+                  omitTrivial: true,
+                })
               : '';
           return (
             matcherHint('.toHaveProperty', 'object', 'path', {
@@ -648,6 +657,7 @@ const matchers: MatchersObject = {
             getObjectSubset(receivedObject, expectedObject),
             {
               expand: this.expand,
+              omitTrivial: true,
             },
           );
           return (
@@ -683,6 +693,7 @@ const matchers: MatchersObject = {
       : () => {
           const diffString = diff(expected, received, {
             expand: this.expand,
+            omitTrivial: true,
           });
           return hint + (diffString ? `\n\nDifference:\n\n${diffString}` : '');
         };

packages/expect/src/spyMatchers.js

@@ -566,7 +566,7 @@ const formatMismatchedArgs = (expected, received) => {
   for (let i = 0; i < length; i++) {
     if (!equals(expected[i], received[i], [iterableEquality])) {
       const oneline = isOneline(expected[i], received[i]);
-      const diffString = diff(expected[i], received[i]);
+      const diffString = diff(expected[i], received[i], {omitTrivial: true});
       printedArgs.push(
         `  ${printExpected(expected[i])}\n` +
           `as argument ${i + 1}, but it was called with\n` +

packages/jest-circus/src/formatNodeAssertErrors.js

@@ -66,7 +66,12 @@ const formatNodeAssertErrors = (event: Event, state: State) => {
           error = errors;
         }
         return error.code === 'ERR_ASSERTION'
-          ? {message: assertionErrorMessage(error, {expand: state.expand})}
+          ? {
+              message: assertionErrorMessage(error, {
+                expand: state.expand,
+                omitTrivial: true,
+              }),
+            }
           : errors;
       });
     }

packages/jest-diff/src/__tests__/diff.test.js

@@ -48,9 +48,12 @@ describe('no visual difference', () => {
     [[], []],
     [[1, 2], [1, 2]],
     [11, 11],
+    [NaN, NaN],
+    [Number.NaN, NaN],
     [() => {}, () => {}],
     [null, null],
     [undefined, undefined],
+    [false, false],
     [{a: 1}, {a: 1}],
     [{a: {b: 5}}, {a: {b: 5}}],
   ].forEach(values => {
@@ -178,13 +181,25 @@ describe('objects', () => {
 });
 
 test('numbers', () => {
-  const result = diff(123, 234);
-  expect(result).toBe(null);
+  expect(stripped(1, 2)).toEqual(expect.stringContaining('- 1\n+ 2'));
+});
+
+test('-0 and 0', () => {
+  expect(stripped(-0, 0)).toEqual(expect.stringContaining('- -0\n+ 0'));
+});
+
+test('numbers with omitTrivial', () => {
+  expect(diff(1, 2, {omitTrivial: true})).toBeNull();
 });
 
 test('booleans', () => {
-  const result = diff(true, false);
-  expect(result).toBe(null);
+  expect(stripped(false, true)).toEqual(
+    expect.stringContaining('- false\n+ true'),
+  );
+});
+
+test('booleans with omitTrivial', () => {
+  expect(diff(false, true, {omitTrivial: true})).toBeNull();
 });
 
 describe('multiline string non-snapshot', () => {

packages/jest-diff/src/diffStrings.js

@@ -18,6 +18,10 @@ export type DiffOptions = {|
   bAnnotation?: string,
   expand?: boolean,
   contextLines?: number,
+  // Return null instead of diffing numbers or booleans.
+  // Jest uses this because the matchers already print a short failure reason,
+  // so the diff output would be redundant for those types.
+  omitTrivial?: boolean,
 |};
 
 type Original = {|

packages/jest-diff/src/index.js

@@ -87,9 +87,10 @@ function diff(a: any, b: any, options: ?DiffOptions): ?string {
   switch (aType) {
     case 'string':
       return diffStrings(a, b, options);
-    case 'number':
     case 'boolean':
-      return null;
+      return compareBooleans(a, b, options);
+    case 'number':
+      return compareNumbers(a, b, options);
     case 'map':
       return compareObjects(sortMap(a), sortMap(b), options);
     case 'set':
@@ -99,6 +100,24 @@ function diff(a: any, b: any, options: ?DiffOptions): ?string {
   }
 }
 
+function compareBooleans(a: boolean, b: boolean, options: ?DiffOptions) {
+  if (options && options.omitTrivial) {
+    return null;
+  }
+
+  return diffStrings(String(a), String(b), options);
+}
+
+function compareNumbers(a: number, b: number, options: ?DiffOptions) {
+  if (options && options.omitTrivial) {
+    return null;
+  }
+
+  const aStr = Object.is(a, -0) ? '-0' : String(a);
+  const bStr = Object.is(b, -0) ? '-0' : String(b);
+  return diffStrings(aStr, bStr, options);
+}
+
 function sortMap(map) {
   return new Map(Array.from(map.entries()).sort());
 }

packages/jest-jasmine2/src/jasmine/Env.js

@@ -578,7 +578,10 @@ export default function(j$) {
 
       if (error instanceof AssertionError) {
         checkIsError = false;
-        message = assertionErrorMessage(error, {expand: j$.Spec.expand});
+        message = assertionErrorMessage(error, {
+          expand: j$.Spec.expand,
+          omitTrivial: true,
+        });
       } else {
         const check = isError(error);
 

packages/jest-jasmine2/src/jasmine/Spec.js

@@ -153,7 +153,10 @@ Spec.prototype.onException = function onException(error) {
   }
 
   if (error instanceof AssertionError) {
-    error = assertionErrorMessage(error, {expand: this.expand});
+    error = assertionErrorMessage(error, {
+      expand: this.expand,
+      omitTrivial: true,
+    });
   }
 
   this.addExpectationResult(

packages/jest-snapshot/src/index.js

@@ -186,6 +186,7 @@ const _toMatchSnapshot = ({
       aAnnotation: 'Snapshot',
       bAnnotation: 'Received',
       expand: snapshotState.expand,
+      omitTrivial: true,
     });
 
     report = () =>

packages/pretty-format/src/__tests__/getPrettyPrint.js

@@ -38,6 +38,7 @@ const getPrettyPrint = (plugins: Plugins) =>
       : () => {
           const diffString = diff(expected, prettyFormatted, {
             expand: this.expand,
+            omitTrivial: true,
           });
           return (
             this.utils.matcherHint('.toBe') +