Enable CA1825: Avoid zero-length array allocations (#13961)

.globalconfig

@@ -286,7 +286,7 @@ dotnet_diagnostic.CA1823.severity = none
 dotnet_diagnostic.CA1824.severity = suggestion
 
 # CA1825: Avoid zero-length array allocations
-dotnet_diagnostic.CA1825.severity = suggestion
+dotnet_diagnostic.CA1825.severity = warning
 
 # CA1826: Do not use Enumerable methods on indexable collections
 dotnet_diagnostic.CA1826.severity = suggestion

docs/dev-process/coding-guidelines.md

@@ -111,9 +111,6 @@ Some general guidelines:
 * Avoid using string interpolations and overloads with implicit parameters such as `Culture` and `StringComparison`.
   Instead, use overloads with more explicit parameters such as `String.Format(IFormatProvider, String, Object[])` and `Equals(String, String, StringComparison)`.
 
-* Avoid creating empty arrays.
-  Instead, reuse the static ones via `Utils.EmptyArray<T>`.
-
 * Avoid unnecessary memory allocation in a loop.
   Move the memory allocation outside the loop if possible.
 

src/Microsoft.PowerShell.Commands.Utility/commands/utility/ImplicitRemotingCommands.cs

@@ -480,7 +480,7 @@ namespace Microsoft.PowerShell.Commands
             }
         }
 
-        private ModuleSpecification[] _moduleSpecifications = new ModuleSpecification[0];
+        private ModuleSpecification[] _moduleSpecifications = Array.Empty<ModuleSpecification>();
         internal bool IsFullyQualifiedModuleSpecified = false;
 
         private bool _commandParameterSpecified; // initialized to default value in the constructor

src/Microsoft.PowerShell.Commands.Utility/commands/utility/MatchString.cs

@@ -366,7 +366,7 @@ namespace Microsoft.PowerShell.Commands
         /// <summary>
         /// Gets or sets a list of all Regex matches on the matching line.
         /// </summary>
-        public Match[] Matches { get; set; } = new Match[] { };
+        public Match[] Matches { get; set; } = Array.Empty<Match>();
 
         /// <summary>
         /// Create a deep copy of this MatchInfo instance.
@@ -1897,8 +1897,8 @@ namespace Microsoft.PowerShell.Commands
                     if (matchInfo.Context != null)
                     {
                         matchResult = matchInfo.Clone();
-                        matchResult.Context.DisplayPreContext = new string[] { };
-                        matchResult.Context.DisplayPostContext = new string[] { };
+                        matchResult.Context.DisplayPreContext = Array.Empty<string>();
+                        matchResult.Context.DisplayPostContext = Array.Empty<string>();
                     }
                     else
                     {
@@ -1924,7 +1924,7 @@ namespace Microsoft.PowerShell.Commands
 
                 // Matches should be an empty list, rather than null,
                 // in the cases of notMatch and simpleMatch.
-                matchResult.Matches = matches ?? new Match[] { };
+                matchResult.Matches = matches ?? Array.Empty<Match>();
 
                 return true;
             }

src/Microsoft.PowerShell.Commands.Utility/commands/utility/New-Object.cs

@@ -207,7 +207,7 @@ namespace Microsoft.PowerShell.Commands
                     ConstructorInfo ci = type.GetConstructor(Type.EmptyTypes);
                     if (ci != null && ci.IsPublic)
                     {
-                        _newObject = CallConstructor(type, new ConstructorInfo[] { ci }, new object[] { });
+                        _newObject = CallConstructor(type, new ConstructorInfo[] { ci }, Array.Empty<object>());
                         if (_newObject != null && Property != null)
                         {
                             // The method invocation is disabled for "Hashtable to Object conversion" (Win8:649519), but we need to keep it enabled for New-Object for compatibility to PSv2

src/System.Management.Automation/engine/EventManager.cs

@@ -599,7 +599,7 @@ namespace System.Management.Automation
                     if (_engineEventSubscribers.TryGetValue(PSEngineEvent.OnIdle, out subscribers) && subscribers.Count > 0)
                     {
                         // We send out on-idle event and keep enabling the timer only if there still are subscribers to the on-idle event
-                        GenerateEvent(PSEngineEvent.OnIdle, null, new object[] { }, null, false, false);
+                        GenerateEvent(PSEngineEvent.OnIdle, null, Array.Empty<object>(), null, false, false);
                         EnableTimer();
                     }
                     else

src/System.Management.Automation/engine/LanguagePrimitives.cs

@@ -384,7 +384,7 @@ namespace System.Management.Automation
 
                 emitter.Emit(OpCodes.Ldarg_0);
                 emitter.Emit(OpCodes.Castclass, _enumerableType);
-                MethodInfo methodInfo = _enumerableType.GetMethod("GetEnumerator", new Type[] { });
+                MethodInfo methodInfo = _enumerableType.GetMethod("GetEnumerator", Array.Empty<Type>());
                 emitter.Emit(OpCodes.Callvirt, methodInfo);
                 emitter.Emit(OpCodes.Ret);
             }

src/System.Management.Automation/engine/Modules/ModuleCmdletBase.cs

@@ -6882,7 +6882,7 @@ namespace Microsoft.PowerShell.Commands
                     iss.Bind(Context, updateOnly: true, module, options.NoClobber, options.Local, setLocation: false);
 
                     // Scan all of the types in the assembly to register JobSourceAdapters.
-                    IEnumerable<Type> allTypes = new Type[] { };
+                    IEnumerable<Type> allTypes = Array.Empty<Type>();
                     if (assembly != null)
                     {
                         allTypes = assembly.ExportedTypes;

src/System.Management.Automation/engine/ParameterBinderBase.cs

@@ -1559,7 +1559,7 @@ namespace System.Management.Automation
                                 toType,
                                 0,
                                 null,
-                                new object[] { },
+                                Array.Empty<object>(),
                                 System.Globalization.CultureInfo.InvariantCulture);
                         if (collectionTypeInformation.ParameterCollectionType == ParameterCollectionType.IList)
                             resultAsIList = (IList)resultCollection;

src/System.Management.Automation/engine/PseudoParameters.cs

@@ -236,6 +236,6 @@ namespace System.Management.Automation
         /// </summary>
         public object Data { get; set; }
 
-        internal static readonly RuntimeDefinedParameter[] EmptyParameterArray = new RuntimeDefinedParameter[0];
+        internal static readonly RuntimeDefinedParameter[] EmptyParameterArray = Array.Empty<RuntimeDefinedParameter>();
     }
 }

src/System.Management.Automation/engine/hostifaces/LocalConnection.cs

@@ -851,7 +851,7 @@ namespace System.Management.Automation.Runspaces
 
             // Generate the shutdown event
             if (Events != null)
-                Events.GenerateEvent(PSEngineEvent.Exiting, null, new object[] { }, null, true, false);
+                Events.GenerateEvent(PSEngineEvent.Exiting, null, Array.Empty<object>(), null, true, false);
 
             // Stop all running pipelines
             // Note:Do not perform the Cancel in lock. Reason is

src/System.Management.Automation/engine/remoting/host/RemoteHostMethodInfo.cs

@@ -144,35 +144,35 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHost),
                         "get_Name",
                         typeof(string),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.GetVersion:
                     return new RemoteHostMethodInfo(
                         typeof(PSHost),
                         "get_Version",
                         typeof(Version),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.GetInstanceId:
                     return new RemoteHostMethodInfo(
                         typeof(PSHost),
                         "get_InstanceId",
                         typeof(Guid),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.GetCurrentCulture:
                     return new RemoteHostMethodInfo(
                         typeof(PSHost),
                         "get_CurrentCulture",
                         typeof(System.Globalization.CultureInfo),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.GetCurrentUICulture:
                     return new RemoteHostMethodInfo(
                         typeof(PSHost),
                         "get_CurrentUICulture",
                         typeof(System.Globalization.CultureInfo),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 // Host methods.
 
@@ -188,28 +188,28 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHost),
                         "EnterNestedPrompt",
                         typeof(void),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.ExitNestedPrompt:
                     return new RemoteHostMethodInfo(
                         typeof(PSHost),
                         "ExitNestedPrompt",
                         typeof(void),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.NotifyBeginApplication:
                     return new RemoteHostMethodInfo(
                         typeof(PSHost),
                         "NotifyBeginApplication",
                         typeof(void),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.NotifyEndApplication:
                     return new RemoteHostMethodInfo(
                         typeof(PSHost),
                         "NotifyEndApplication",
                         typeof(void),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 // Host UI methods.
 
@@ -218,14 +218,14 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostUserInterface),
                         "ReadLine",
                         typeof(string),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.ReadLineAsSecureString:
                     return new RemoteHostMethodInfo(
                         typeof(PSHostUserInterface),
                         "ReadLineAsSecureString",
                         typeof(System.Security.SecureString),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.Write1:
                     return new RemoteHostMethodInfo(
@@ -246,7 +246,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostUserInterface),
                         "WriteLine",
                         typeof(void),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.WriteLine2:
                     return new RemoteHostMethodInfo(
@@ -339,7 +339,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_ForegroundColor",
                         typeof(ConsoleColor),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetForegroundColor:
                     return new RemoteHostMethodInfo(
@@ -353,7 +353,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_BackgroundColor",
                         typeof(ConsoleColor),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetBackgroundColor:
                     return new RemoteHostMethodInfo(
@@ -367,7 +367,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_CursorPosition",
                         typeof(Coordinates),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetCursorPosition:
                     return new RemoteHostMethodInfo(
@@ -381,7 +381,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_WindowPosition",
                         typeof(Coordinates),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetWindowPosition:
                     return new RemoteHostMethodInfo(
@@ -395,7 +395,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_CursorSize",
                         typeof(int),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetCursorSize:
                     return new RemoteHostMethodInfo(
@@ -409,7 +409,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_BufferSize",
                         typeof(Size),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetBufferSize:
                     return new RemoteHostMethodInfo(
@@ -423,7 +423,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_WindowSize",
                         typeof(Size),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetWindowSize:
                     return new RemoteHostMethodInfo(
@@ -437,7 +437,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_WindowTitle",
                         typeof(string),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetWindowTitle:
                     return new RemoteHostMethodInfo(
@@ -453,21 +453,21 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "get_MaxWindowSize",
                         typeof(Size),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.GetMaxPhysicalWindowSize:
                     return new RemoteHostMethodInfo(
                         typeof(PSHostRawUserInterface),
                         "get_MaxPhysicalWindowSize",
                         typeof(Size),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.GetKeyAvailable:
                     return new RemoteHostMethodInfo(
                         typeof(PSHostRawUserInterface),
                         "get_KeyAvailable",
                         typeof(bool),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 // Host raw UI methods.
 
@@ -483,7 +483,7 @@ namespace System.Management.Automation.Remoting
                         typeof(PSHostRawUserInterface),
                         "FlushInputBuffer",
                         typeof(void),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.SetBufferContents1:
                     return new RemoteHostMethodInfo(
@@ -527,7 +527,7 @@ namespace System.Management.Automation.Remoting
                         typeof(IHostSupportsInteractiveSession),
                         "PopRunspace",
                         typeof(void),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 // IHostSupportsInteractiveSession properties.
 
@@ -536,14 +536,14 @@ namespace System.Management.Automation.Remoting
                         typeof(IHostSupportsInteractiveSession),
                         "get_IsRunspacePushed",
                         typeof(bool),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 case RemoteHostMethodId.GetRunspace:
                     return new RemoteHostMethodInfo(
                         typeof(IHostSupportsInteractiveSession),
                         "get_Runspace",
                         typeof(System.Management.Automation.Runspaces.Runspace),
-                        new Type[] { });
+                        Array.Empty<Type>());
 
                 default:
                     Dbg.Assert(false, "All RemoteHostMethodId's should be handled. This code should not be reached.");

src/System.Management.Automation/engine/runtime/Operations/ArrayOps.cs

@@ -52,7 +52,10 @@ namespace System.Management.Automation
 
             if (times == 0 || array.Length == 0)
             {
-                return new T[0]; // don't use Utils.EmptyArray, always return a new array
+#pragma warning disable CA1825 // Avoid zero-length array allocations
+                // Don't use Array.Empty<T>(); always return a new instance.
+                return new T[0];
+#pragma warning restore CA1825 // Avoid zero-length array allocations
             }
 
             var context = LocalPipeline.GetExecutionContextFromTLS();

src/System.Management.Automation/engine/runtime/Operations/MiscOps.cs

@@ -3228,7 +3228,10 @@ namespace System.Management.Automation
 
             if (originalList.Count == 0)
             {
-                return new object[0]; // don't use Utils.EmptyArray, always return a new array
+#pragma warning disable CA1825 // Avoid zero-length array allocations
+                // Don't use Array.Empty<object>(); always return a new instance.
+                return new object[0];
+#pragma warning restore CA1825 // Avoid zero-length array allocations
             }
 
             return ArrayOps.Multiply(originalList.ToArray(), times);

src/System.Management.Automation/namespaces/RegistryProvider.cs

@@ -3814,7 +3814,7 @@ namespace Microsoft.PowerShell.Commands
                             value,
                             typeof(byte[]),
                             CultureInfo.CurrentCulture)
-                        : new byte[] { };
+                        : Array.Empty<byte>();
                     break;
 
                 case RegistryValueKind.DWord:
@@ -3851,7 +3851,7 @@ namespace Microsoft.PowerShell.Commands
                             value,
                             typeof(string[]),
                             CultureInfo.CurrentCulture)
-                        : new string[] { };
+                        : Array.Empty<string>();
                     break;
 
                 case RegistryValueKind.QWord:

src/System.Management.Automation/utils/GraphicalHostReflectionWrapper.cs

@@ -128,12 +128,12 @@ namespace System.Management.Automation.Internal
             ConstructorInfo constructor = returnValue._graphicalHostHelperType.GetConstructor(
                 BindingFlags.NonPublic | BindingFlags.Instance,
                 null,
-                new Type[] { },
+                Array.Empty<Type>(),
                 null);
 
             if (constructor != null)
             {
-                returnValue._graphicalHostHelperObject = constructor.Invoke(new object[] { });
+                returnValue._graphicalHostHelperObject = constructor.Invoke(Array.Empty<object>());
                 Diagnostics.Assert(returnValue._graphicalHostHelperObject != null, "the constructor does not throw anything");
             }
 
@@ -187,7 +187,7 @@ namespace System.Management.Automation.Internal
             Diagnostics.Assert(_graphicalHostHelperObject != null, "there should be a constructor in order to get an instance property value");
             PropertyInfo property = _graphicalHostHelperType.GetProperty(propertyName, BindingFlags.NonPublic | BindingFlags.Instance);
             Diagnostics.Assert(property != null, "property " + propertyName + " exists in graphicalHostHelperType is verified by caller");
-            return property.GetValue(_graphicalHostHelperObject, new object[] { });
+            return property.GetValue(_graphicalHostHelperObject, Array.Empty<object>());
         }
 
         /// <summary>
@@ -199,7 +199,7 @@ namespace System.Management.Automation.Internal
         {
             PropertyInfo property = _graphicalHostHelperType.GetProperty(propertyName, BindingFlags.NonPublic | BindingFlags.Static);
             Diagnostics.Assert(property != null, "property " + propertyName + " exists in graphicalHostHelperType is verified by caller");
-            return property.GetValue(null, new object[] { });
+            return property.GetValue(null, Array.Empty<object>());
         }
 
         /// <summary>

test/xUnit/csharp/test_CommandLineParser.cs

@@ -19,7 +19,7 @@ namespace PSTests.Parallel
         {
             var cpp = new CommandLineParameterParser();
 
-            cpp.Parse(new string[0]);
+            cpp.Parse(System.Array.Empty<string>());
 
             Assert.False(cpp.AbortStartup);
             Assert.Empty(cpp.Args);
@@ -60,9 +60,9 @@ namespace PSTests.Parallel
         {
             var cpp = new CommandLineParameterParser();
 
-            cpp.Parse(new string[0]);
+            cpp.Parse(System.Array.Empty<string>());
 
-            Assert.Throws<System.InvalidOperationException>(() => cpp.Parse(new string[0]));
+            Assert.Throws<System.InvalidOperationException>(() => cpp.Parse(System.Array.Empty<string>()));
         }
 
         [Theory]