Test empty Immutable collections with {min: false} option (jestjs#4121)

* Test empty Immutable collections with {min: false} option

* Make neutral change to code to see if it helps CI

* Fix 2 prettier lint errors

packages/pretty-format/src/__tests__/immutable.test.js

@@ -22,12 +22,18 @@ const toPrettyPrintTo = expectUtil.getPrettyPrint(
 expect.extend({toPrettyPrintTo});
 
 describe('Immutable.OrderedSet plugin', () => {
-  it('supports an empty set', () => {
+  it('supports an empty collection {min: true}', () => {
     expect(
       Immutable.OrderedSet([]),
     ).toPrettyPrintTo('Immutable.OrderedSet []', {min: true});
   });
 
+  it('supports an empty collection {min: false}', () => {
+    expect(
+      Immutable.OrderedSet([]),
+    ).toPrettyPrintTo('Immutable.OrderedSet [\n]', {min: false});
+  });
+
   it('supports a single string element', () => {
     expect(
       Immutable.OrderedSet(['foo']),
@@ -109,12 +115,18 @@ describe('Immutable.OrderedSet plugin', () => {
 });
 
 describe('Immutable.List plugin', () => {
-  it('supports an empty set', () => {
+  it('supports an empty collection {min: true}', () => {
     expect(Immutable.List([])).toPrettyPrintTo('Immutable.List []', {
       min: true,
     });
   });
 
+  it('supports an empty collection {min: false}', () => {
+    expect(Immutable.List([])).toPrettyPrintTo('Immutable.List [\n]', {
+      min: false,
+    });
+  });
+
   it('supports a single string element', () => {
     expect(Immutable.List(['foo'])).toPrettyPrintTo('Immutable.List ["foo"]', {
       min: true,
@@ -184,12 +196,18 @@ describe('Immutable.List plugin', () => {
 });
 
 describe('Immutable.Stack plugin', () => {
-  it('supports an empty set', () => {
+  it('supports an empty collection {min: true}', () => {
     expect(Immutable.Stack([])).toPrettyPrintTo('Immutable.Stack []', {
       min: true,
     });
   });
 
+  it('supports an empty collection {min: false}', () => {
+    expect(Immutable.Stack([])).toPrettyPrintTo('Immutable.Stack [\n]', {
+      min: false,
+    });
+  });
+
   it('supports a single string element', () => {
     expect(
       Immutable.Stack(['foo']),
@@ -261,10 +279,16 @@ describe('Immutable.Stack plugin', () => {
 });
 
 describe('Immutable.Set plugin', () => {
-  it('supports an empty set', () => {
+  it('supports an empty collection {min: true}', () => {
     expect(Immutable.Set([])).toPrettyPrintTo('Immutable.Set []', {min: true});
   });
 
+  it('supports an empty collection {min: false}', () => {
+    expect(Immutable.Set([])).toPrettyPrintTo('Immutable.Set [\n]', {
+      min: false,
+    });
+  });
+
   it('supports a single string element', () => {
     expect(Immutable.Set(['foo'])).toPrettyPrintTo('Immutable.Set ["foo"]', {
       min: true,
@@ -333,10 +357,16 @@ describe('Immutable.Set plugin', () => {
 });
 
 describe('Immutable.Map plugin', () => {
-  it('supports an empty set', () => {
+  it('supports an empty collection {min: true}', () => {
     expect(Immutable.Map({})).toPrettyPrintTo('Immutable.Map {}', {min: true});
   });
 
+  it('supports an empty collection {min: false}', () => {
+    expect(Immutable.Map({})).toPrettyPrintTo('Immutable.Map {\n}', {
+      min: false,
+    });
+  });
+
   it('supports an object with single key', () => {
     expect(Immutable.Map({a: 1})).toPrettyPrintTo('Immutable.Map {a: 1}', {
       min: true,
@@ -390,12 +420,18 @@ describe('Immutable.Map plugin', () => {
 });
 
 describe('Immutable.OrderedMap plugin', () => {
-  it('supports an empty set', () => {
+  it('supports an empty collection {min: true}', () => {
     expect(
       Immutable.OrderedMap({}),
     ).toPrettyPrintTo('Immutable.OrderedMap {}', {min: true});
   });
 
+  it('supports an empty collection {min: false}', () => {
+    expect(
+      Immutable.OrderedMap({}),
+    ).toPrettyPrintTo('Immutable.OrderedMap {\n}', {min: false});
+  });
+
   it('supports an object with single key', () => {
     expect(
       Immutable.OrderedMap({a: 1}),
@@ -449,7 +485,23 @@ describe('Immutable.OrderedMap plugin', () => {
 });
 
 describe('Immutable.Record plugin', () => {
-  it('supports an empty record', () => {
+  it('supports an empty record {min: true}', () => {
+    const ABRecord = Immutable.Record({}, 'ABRecord');
+
+    expect(new ABRecord()).toPrettyPrintTo('Immutable.ABRecord {}', {
+      min: true,
+    });
+  });
+
+  it('supports an empty record {min: false}', () => {
+    const ABRecord = Immutable.Record({}, 'ABRecord');
+
+    expect(new ABRecord()).toPrettyPrintTo('Immutable.ABRecord {\n}', {
+      min: false,
+    });
+  });
+
+  it('supports a record with descriptive name', () => {
     const ABRecord = Immutable.Record({a: 1, b: 2}, 'ABRecord');
 
     expect(new ABRecord()).toPrettyPrintTo('Immutable.ABRecord {a: 1, b: 2}', {

packages/pretty-format/src/plugins/lib/print_immutable.js

@@ -16,7 +16,7 @@ const SPACE = ' ';
 const addKey = (isMap: boolean, key: any) => (isMap ? key + ': ' : '');
 
 const addFinalEdgeSpacing = (length: number, edgeSpacing: string) =>
-  length > 0 ? edgeSpacing : '';
+  length !== 0 ? edgeSpacing : '';
 
 const printImmutable = (
   val: any,
@@ -51,7 +51,7 @@ const printImmutable = (
   }
 
   result += immutableArray.join(',' + opts.spacing);
-  if (!opts.min && immutableArray.length > 0) {
+  if (!opts.min && immutableArray.length !== 0) {
     result += ',';
   }