Change CronExpression equality operators to accept null operands (#87)

Co-authored-by: Pierre-Henri SCHOFFIT <[email protected]>

Author: Nechepso

src/Cronos/CronExpression.cs

@@ -406,12 +406,12 @@ public override int GetHashCode()
         /// <summary>
         /// Implements the operator ==.
         /// </summary>
-        public static bool operator ==(CronExpression left, CronExpression right) => Equals(left, right);
+        public static bool operator ==(CronExpression? left, CronExpression? right) => Equals(left, right);
 
         /// <summary>
         /// Implements the operator !=.
         /// </summary>
-        public static bool operator !=(CronExpression left, CronExpression right) => !Equals(left, right);
+        public static bool operator !=(CronExpression? left, CronExpression? right) => !Equals(left, right);
 
         private DateTimeOffset? GetOccurrenceConsideringTimeZone(DateTimeOffset fromUtc, TimeZoneInfo zone, bool inclusive)
         {

tests/Cronos.Tests/CronExpressionFacts.cs

@@ -517,7 +517,7 @@ public void TryParse_ReturnsTrue_WhenAbleToParseTheGivenExpression_WithCorrectCr
             var result = CronExpression.TryParse("* * * * *", out var cron);
 
             Assert.True(result);
-            Assert.Equal(Today.AddMinutes(1), cron.GetNextOccurrence(Today));
+            Assert.Equal(Today.AddMinutes(1), cron!.GetNextOccurrence(Today));
         }
 
         [Fact]
@@ -542,7 +542,7 @@ public void TryParse_WithSecondsSpecified_ReturnsTrue_AndGivesSecondBasedCronExp
             var result = CronExpression.TryParse("* * * * * *", CronFormat.IncludeSeconds, out var cron);
 
             Assert.True(result);
-            Assert.Equal(Today.AddSeconds(1), cron.GetNextOccurrence(Today));
+            Assert.Equal(Today.AddSeconds(1), cron!.GetNextOccurrence(Today));
         }
 
         [Theory]
@@ -2785,6 +2785,7 @@ public void Equals_ReturnsFalse_WhenOtherIsNull()
 
             Assert.False(cronExpression.Equals(null));
             Assert.False(cronExpression == null);
+            Assert.True(cronExpression != null);
         }
 
         [Theory]

tests/Directory.Build.props

@@ -2,6 +2,8 @@
     <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props', '$(MSBuildThisFileDirectory)../'))" />
     <PropertyGroup>
         <SignAssembly>true</SignAssembly><!-- InernalsVisibleTo requires test assemblies to be signed too -->
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
     </PropertyGroup>
 
     <ItemGroup>