Do not warn when invoking APIs that has SupportedOSPlatformGuard attribute

src/NetAnalyzers/Core/Microsoft.NetCore.Analyzers/InteropServices/PlatformCompatibilityAnalyzer.cs

@@ -1407,14 +1407,18 @@ void CheckOperationAttributes(ISymbol symbol, bool checkParents)
                             platformSpecificOperations.TryAdd(new KeyValuePair<IOperation, ISymbol>(operation, symbol), (notSuppressedAttributes, callSiteAttributes.Platforms));
                         }
                     }
-                    else if (TryCopyAttributesNotSuppressedByMsBuild(operationAttributes.Platforms!, msBuildPlatforms, out var copiedAttributes))
+                    else if (!OperationHasOnlyAssemblyAttributesAndCalledFromSameAssembly(operationAttributes, symbol, containingSymbol) &&
+                             TryCopyAttributesNotSuppressedByMsBuild(operationAttributes.Platforms!, msBuildPlatforms, out var copiedAttributes))
                     {
                         platformSpecificOperations.TryAdd(new KeyValuePair<IOperation, ISymbol>(operation, symbol), (copiedAttributes, null));
                     }
                 }
             }
         }
 
+        private static bool OperationHasOnlyAssemblyAttributesAndCalledFromSameAssembly(PlatformAttributes operationAttributes, ISymbol symbol, ISymbol containingSymbol) =>
+            operationAttributes.IsAssemblyAttribute && containingSymbol.ContainingAssembly == symbol.ContainingAssembly;
+
         private static bool UsedInCreatingNotSupportedException(IArgumentOperation operation, ITypeSymbol? notSupportedExceptionType)
         {
             if (operation.Parent is IObjectCreationOperation creation &&
@@ -1799,11 +1803,7 @@ static void MergePlatformAttributes(ImmutableArray<AttributeData> immediateAttri
 
                     if (attribute.AttributeClass.Name is SupportedOSPlatformGuardAttribute or UnsupportedOSPlatformGuardAttribute)
                     {
-                        if (!parentAttributes.IsAssemblyAttribute)
-                        {
-                            parentAttributes = new PlatformAttributes();
-                        }
-
+                        parentAttributes = new PlatformAttributes(); // The API is for guard, clear parent attributes
                         return;
                     }
 

src/NetAnalyzers/RulesMissingDocumentation.md

@@ -2,7 +2,5 @@
 
 Rule ID | Missing Help Link | Title |
 --------|-------------------|-------|
-CA1871 | <https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1871> | Do not pass a nullable struct to 'ArgumentNullException.ThrowIfNull' |
 CA2022 | <https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca2022> | Avoid inexact read with 'Stream.Read' |
-CA2264 | <https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca2264> | Do not pass a non-nullable value to 'ArgumentNullException.ThrowIfNull' |
 CA2265 | <https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca2265> | Do not compare Span\<T> to 'null' or 'default' |

src/NetAnalyzers/UnitTests/Microsoft.NetCore.Analyzers/InteropServices/PlatformCompatibilityAnalyzerTests.GuardedCallsTests.cs

@@ -2,6 +2,7 @@
 
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Testing;
 using Test.Utilities;
 using Xunit;
 
@@ -1216,6 +1217,76 @@ static void M1()
             await VerifyAnalyzerCSAsync(csSource);
         }
 
+        [Fact]
+        public async Task CallGuardFromPlatformSpecificAssembly()
+        {
+            string csDependencyCode = @"
+public class Library
+{
+    [System.Runtime.Versioning.SupportedOSPlatformGuard(""windows"")]
+    [System.Runtime.Versioning.SupportedOSPlatformGuard(""linux"")]
+    public static bool IsSupported => false;
+
+    public static void AMethod() { }
+}";
+            csDependencyCode = @$"[assembly: System.Runtime.Versioning.SupportedOSPlatform(""windows"")]
+                                  [assembly: System.Runtime.Versioning.SupportedOSPlatform(""linux"")]
+                                  {csDependencyCode}";
+
+            string csCurrentAssemblyCode = @"
+using System;
+
+public class Program
+{
+    public void ProgramMethod()
+    {
+        [|Library.AMethod()|]; // Not guarded, warns
+        if (Library.IsSupported)
+        {
+             Library.AMethod();
+        }
+    }
+}";
+            var test = SetupDependencyAndTestCSWithOneSourceFile(csCurrentAssemblyCode, csDependencyCode);
+            test.TestState.AnalyzerConfigFiles.Add(("/.editorconfig", $@"root = true
+
+[*]
+build_property.TargetFramework = net5
+"));
+            await test.RunAsync();
+        }
+
+        private static VerifyCS.Test SetupDependencyAndTestCSWithOneSourceFile(string csInput, string csDependencyCode)
+        {
+            return new VerifyCS.Test
+            {
+                ReferenceAssemblies = ReferenceAssemblies.Net.Net80,
+                LanguageVersion = CodeAnalysis.CSharp.LanguageVersion.CSharp10,
+                MarkupOptions = MarkupOptions.UseFirstDescriptor,
+                TestState =
+                {
+                    Sources =
+                    {
+                        csInput
+                    },
+                    AdditionalProjects =
+                    {
+                        ["PreviewAssembly"] =
+                        {
+                            Sources =
+                            {
+                                ("/PreviewAssembly/AssemblyInfo.g.cs", csDependencyCode)
+                            },
+                        },
+                    },
+                    AdditionalProjectReferences =
+                    {
+                        "PreviewAssembly",
+                    },
+                },
+            };
+        }
+
         [Fact]
         public async Task GuardedWith_RuntimeInformation_IsOSPlatform_SimpleIfElseAsync()
         {
@@ -4181,7 +4252,7 @@ public async Task GuardCallingCachedValue_CallSiteHasAssemblyAttributeAsync()
 [assembly: SupportedOSPlatform(""ios10.0"")]
 class Test
 {
-    static bool s_isiOS11OrNewer => false;
+    static bool s_isiOS11OrNewer = false;
 
     [SupportedOSPlatformGuard(""ios11.0"")]
     private bool IsIos11Supported() => s_isiOS11OrNewer; // should not warn