Add analyzer and fixer for redundant DataField tag arguments (#5134)

* Add analyzer and fixer for redundant DataField tag arguments

* Share Tag autogeneration logic

Robust.Analyzers/DataDefinitionAnalyzer.cs

@@ -6,6 +6,7 @@ using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Robust.Roslyn.Shared;
+using Robust.Shared.Serialization.Manager.Definition;
 
 namespace Robust.Analyzers;
 
@@ -56,8 +57,18 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
         "Make sure to add a setter."
     );
 
+    private static readonly DiagnosticDescriptor DataFieldRedundantTagRule = new(
+        Diagnostics.IdDataFieldRedundantTag,
+        "Data field has redundant tag specified",
+        "Data field {0} in data definition {1} has an explicitly set tag that matches autogenerated tag",
+        "Usage",
+        DiagnosticSeverity.Info,
+        true,
+        "Make sure to remove the tag string from the data field attribute."
+    );
     public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(
-        DataDefinitionPartialRule, NestedDataDefinitionPartialRule, DataFieldWritableRule, DataFieldPropertyWritableRule
+        DataDefinitionPartialRule, NestedDataDefinitionPartialRule, DataFieldWritableRule, DataFieldPropertyWritableRule,
+        DataFieldRedundantTagRule
     );
 
     public override void Initialize(AnalysisContext context)
@@ -125,6 +136,11 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
             {
                 context.ReportDiagnostic(Diagnostic.Create(DataFieldWritableRule, context.Node.GetLocation(), fieldSymbol.Name, type.Name));
             }
+
+            if (HasRedundantTag(fieldSymbol))
+            {
+                context.ReportDiagnostic(Diagnostic.Create(DataFieldRedundantTagRule, context.Node.GetLocation(), fieldSymbol.Name, type.Name));
+            }
         }
     }
 
@@ -149,6 +165,11 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
         {
             context.ReportDiagnostic(Diagnostic.Create(DataFieldPropertyWritableRule, context.Node.GetLocation(), propertySymbol.Name, type.Name));
         }
+
+        if (HasRedundantTag(propertySymbol))
+        {
+            context.ReportDiagnostic(Diagnostic.Create(DataFieldRedundantTagRule, context.Node.GetLocation(), propertySymbol.Name, type.Name));
+        }
     }
 
     private static bool IsReadOnlyDataField(ITypeSymbol type, ISymbol field)
@@ -248,6 +269,29 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
         return false;
     }
 
+    private static bool HasRedundantTag(ISymbol symbol)
+    {
+        if (!IsDataField(symbol, out var _, out var attribute))
+            return false;
+
+        // No args, no problem
+        if (attribute.ConstructorArguments.Length == 0)
+            return false;
+
+        // If a tag is explicitly specified, it will be the first argument...
+        var tagArgument = attribute.ConstructorArguments[0];
+        // ...but the first arg could also something else, since tag is optional
+        // so we make sure that it's a string
+        if (tagArgument.Value is not string explicitName)
+            return false;
+
+        // Get the name that sourcegen would provide
+        var automaticName = DataDefinitionUtility.AutoGenerateTag(symbol.Name);
+
+        // If the explicit name matches the sourcegen name, we have a redundancy
+        return explicitName == automaticName;
+    }
+
     private static bool IsImplicitDataDefinition(ITypeSymbol type)
     {
         if (HasAttribute(type, ImplicitDataDefinitionNamespace))

Robust.Analyzers/DataDefinitionFixer.cs

@@ -1,8 +1,5 @@
 #nullable enable
 using System.Collections.Immutable;
-using System.Linq;
-using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CodeActions;
 using Microsoft.CodeAnalysis.CodeFixes;
@@ -16,8 +13,11 @@ namespace Robust.Analyzers;
 [ExportCodeFixProvider(LanguageNames.CSharp)]
 public sealed class DefinitionFixer : CodeFixProvider
 {
+    private const string DataFieldAttributeName = "DataField";
+
     public override ImmutableArray<string> FixableDiagnosticIds => ImmutableArray.Create(
-        IdDataDefinitionPartial, IdNestedDataDefinitionPartial, IdDataFieldWritable, IdDataFieldPropertyWritable
+        IdDataDefinitionPartial, IdNestedDataDefinitionPartial, IdDataFieldWritable, IdDataFieldPropertyWritable,
+        IdDataFieldRedundantTag
     );
 
     public override Task RegisterCodeFixesAsync(CodeFixContext context)
@@ -34,6 +34,8 @@ public sealed class DefinitionFixer : CodeFixProvider
                     return RegisterDataFieldFix(context, diagnostic);
                 case IdDataFieldPropertyWritable:
                     return RegisterDataFieldPropertyFix(context, diagnostic);
+                case IdDataFieldRedundantTag:
+                    return RegisterRedundantTagFix(context, diagnostic);
             }
         }
 
@@ -72,6 +74,68 @@ public sealed class DefinitionFixer : CodeFixProvider
         return document.WithSyntaxRoot(root);
     }
 
+    private static async Task RegisterRedundantTagFix(CodeFixContext context, Diagnostic diagnostic)
+    {
+        var root = await context.Document.GetSyntaxRootAsync(context.CancellationToken);
+        var span = diagnostic.Location.SourceSpan;
+        var token = root?.FindToken(span.Start).Parent?.AncestorsAndSelf().OfType<MemberDeclarationSyntax>().First();
+
+        if (token == null)
+            return;
+
+        // Find the DataField attribute
+        AttributeSyntax? dataFieldAttribute = null;
+        foreach (var attributeList in token.AttributeLists)
+        {
+            foreach (var attribute in attributeList.Attributes)
+            {
+                if (attribute.Name.ToString() == DataFieldAttributeName)
+                {
+                    dataFieldAttribute = attribute;
+                    break;
+                }
+            }
+            if (dataFieldAttribute != null)
+                break;
+        }
+
+        if (dataFieldAttribute == null)
+            return;
+
+        context.RegisterCodeFix(CodeAction.Create(
+            "Remove explicitly set tag",
+            c => RemoveRedundantTag(context.Document, dataFieldAttribute, c),
+            "Remove explicitly set tag"
+        ), diagnostic);
+    }
+
+    private static async Task<Document> RemoveRedundantTag(Document document, AttributeSyntax syntax, CancellationToken cancellation)
+    {
+        var root = (CompilationUnitSyntax?) await document.GetSyntaxRootAsync(cancellation);
+
+        if (syntax.ArgumentList == null)
+            return document;
+
+        AttributeSyntax? newSyntax;
+        if (syntax.ArgumentList.Arguments.Count == 1)
+        {
+            // If this is the only argument, delete the ArgumentList so we don't leave empty parentheses
+            newSyntax = syntax.RemoveNode(syntax.ArgumentList, SyntaxRemoveOptions.KeepNoTrivia);
+        }
+        else
+        {
+            // Remove the first argument, which is the tag
+            var newArgs = syntax.ArgumentList.Arguments.RemoveAt(0);
+            var newArgList = syntax.ArgumentList.WithArguments(newArgs);
+            // Construct a new attribute with the tag removed
+            newSyntax = syntax.WithArgumentList(newArgList);
+        }
+
+        root = root!.ReplaceNode(syntax, newSyntax!);
+
+        return document.WithSyntaxRoot(root);
+    }
+
     private static async Task RegisterDataFieldFix(CodeFixContext context, Diagnostic diagnostic)
     {
         var root = await context.Document.GetSyntaxRootAsync(context.CancellationToken);

Robust.Analyzers/Robust.Analyzers.csproj

@@ -16,6 +16,11 @@
     <Compile Include="..\Robust.Shared\Analyzers\PreferGenericVariantAttribute.cs" LinkBase="Implementations" />
   </ItemGroup>
 
+  <ItemGroup>
+    <!-- Needed for DataDefinitionAnalyzer. -->
+    <Compile Include="..\Robust.Shared\Serialization\Manager\Definition\DataDefinitionUtility.cs" LinkBase="Implementations" />
+  </ItemGroup>
+
   <Import Project="../Robust.Roslyn.Shared/Robust.Roslyn.Shared.props" />
 
   <PropertyGroup>

Robust.Roslyn.Shared/Diagnostics.cs

@@ -30,6 +30,7 @@ public static class Diagnostics
     public const string IdComponentPauseWrongTypeAttribute = "RA0024";
     public const string IdDependencyFieldAssigned = "RA0025";
     public const string IdUncachedRegex = "RA0026";
+    public const string IdDataFieldRedundantTag = "RA0027";
 
     public static SuppressionDescriptor MeansImplicitAssignment =>
         new SuppressionDescriptor("RADC1000", "CS0649", "Marked as implicitly assigned.");

Robust.Shared/Serialization/Manager/Definition/DataDefinition.cs

@@ -65,8 +65,7 @@ namespace Robust.Shared.Serialization.Manager.Definition
                     continue;
                 }
 
-                var name = field.FieldInfo.Name.AsSpan();
-                attribute.Tag = $"{char.ToLowerInvariant(name[0])}{name[1..]}";
+                attribute.Tag = DataDefinitionUtility.AutoGenerateTag(field.FieldInfo.Name);
             }
 
             var dataFields = fieldDefs

Robust.Shared/Serialization/Manager/Definition/DataDefinitionUtility.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace Robust.Shared.Serialization.Manager.Definition;
+
+public class DataDefinitionUtility
+{
+    public static string AutoGenerateTag(string name)
+    {
+        var span = name.AsSpan();
+        return $"{char.ToLowerInvariant(span[0])}{span.Slice(1).ToString()}";
+    }
+}