[Dependency] source generator part 2

RELEASE-NOTES.md

@@ -46,6 +46,8 @@ END TEMPLATE-->
 - `IParsable`, `ISpanParsable`, and `IUtf8SpanParsable` are now allowed by the sandbox.
 - Added `MarkupNode.IsPlainText` helper property.
 - Added an analyzer to detect and warn about `[Dependency]` fields with nullable types. These have never done anything special and are programming error.
+- Added a `[Dependency]` source generator. This should reduce runtime codegen overhead amount and reduce reflection use.
+  - Existing code using dependency fields should be updated to be `partial` and not use `readonly`. Analyzers and code fixers exist for this. It is not yet an error, but will become one in the future.
 
 ### Bugfixes
 

Robust.Analyzers.Tests/HasDependenciesAnalyzerTest.cs

@@ -0,0 +1,107 @@
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CSharp.Testing;
+using Microsoft.CodeAnalysis.Testing;
+using NUnit.Framework;
+using VerifyCS =
+    Microsoft.CodeAnalysis.CSharp.Testing.CSharpAnalyzerVerifier<Robust.Analyzers.HasDependenciesAnalyzer, Microsoft.CodeAnalysis.Testing.DefaultVerifier>;
+
+namespace Robust.Analyzers.Tests;
+
+[Parallelizable(ParallelScope.All | ParallelScope.Fixtures)]
+[TestFixture]
+public sealed class HasDependenciesAnalyzerTest
+{
+    private static Task Verifier(string code, params DiagnosticResult[] expected)
+    {
+        var test = new CSharpAnalyzerTest<HasDependenciesAnalyzer, DefaultVerifier>()
+        {
+            TestState =
+            {
+                Sources = { code }
+            },
+        };
+
+        TestHelper.AddEmbeddedSources(test.TestState, "Robust.Shared.IoC.DependencyAttribute.cs");
+
+        // ExpectedDiagnostics cannot be set, so we need to AddRange here...
+        test.TestState.ExpectedDiagnostics.AddRange(expected);
+
+        return test.RunAsync();
+    }
+
+    [Test]
+    public async Task ReadOnlyFieldTest()
+    {
+        const string code = """
+            using Robust.Shared.IoC;
+
+            public sealed partial class Foo
+            {
+                [Dependency] private readonly string _x;
+                [Dependency] private string _y;
+            }
+            """;
+
+        await Verifier(code,
+            // /0/Test0.cs(5,26): warning RA0049: Field '_x' is a [Dependency] but is readonly. This will be an error in the future.
+            VerifyCS.Diagnostic(HasDependenciesAnalyzer.DiagnosticReadOnly).WithSpan(5, 26, 5, 34).WithArguments("_x")
+        );
+    }
+
+    [Test]
+    public async Task NotPartialTest()
+    {
+        const string code = """
+            using Robust.Shared.IoC;
+
+            public sealed class Foo
+            {
+                [Dependency] private string _y;
+            }
+            """;
+
+        await Verifier(code,
+            // /0/Test0.cs(3,15): warning RA0048: Type 'Foo' has [Dependency] fields but is not partial. This will be required in the future.
+            VerifyCS.Diagnostic(HasDependenciesAnalyzer.DiagnosticNotPartial).WithSpan(3, 15, 3, 20).WithArguments("Foo")
+        );
+    }
+
+    [Test]
+    public async Task NotPartialNestedTest()
+    {
+        const string code = """
+            using Robust.Shared.IoC;
+
+            public sealed class Foo
+            {
+                public sealed partial class Bar
+                {
+                    [Dependency] private string _y;
+                }
+            }
+            """;
+
+        await Verifier(code,
+            // /0/Test0.cs(5,27): warning RA0049: Type 'Foo.Bar' has [Dependency] fields but is nested in a non-partial type. This will be illegal in the future.
+            VerifyCS.Diagnostic(HasDependenciesAnalyzer.DiagnosticNotPartialParent).WithSpan(5, 27, 5, 32).WithArguments("Foo.Bar")
+        );
+    }
+
+    [Test]
+    public async Task NotPropertyField()
+    {
+        const string code = """
+            using Robust.Shared.IoC;
+
+            public sealed partial class Bar
+            {
+                [field: Dependency] private string _y { get; } = "A";
+            }
+            """;
+
+        await Verifier(code,
+            // /0/Test0.cs(5,5): warning RA0051: Property '_y' has a backing field marked with [Dependency]. This will be an error in the future.
+            VerifyCS.Diagnostic(HasDependenciesAnalyzer.DiagnosticPropertyField).WithSpan(5, 5, 5, 58).WithArguments("_y")
+        );
+    }
+}