analyze the catch statement (#1158)

src/Neo.SmartContract.Analyzer/AnalyzerReleases.Unshipped.md

@@ -23,3 +23,4 @@ NC4020 | Naming | Warning | SmartContractMethodNamingAnalyzerUnderline
 NC4021 | Usage | Warning | SupportedStandardsAnalyzer
 NC4022 | Usage | Warning | BigIntegerUsingUsageAnalyzer
 NC4023 | Usage | Error | StaticFieldInitializationAnalyzer
+NC4024 | Usage | Error | MultipleCatchBlockAnalyzer

src/Neo.SmartContract.Analyzer/MultipleCatchBlockAnalyzer.cs

@@ -0,0 +1,48 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+using System.Collections.Immutable;
+
+namespace Neo.SmartContract.Analyzer
+{
+    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public class MultipleCatchBlockAnalyzer : DiagnosticAnalyzer
+    {
+        public const string DiagnosticId = "NC4024";
+
+        private static readonly LocalizableString Title = "Multiple catch blocks are not allowed in Neo smart contracts";
+        private static readonly LocalizableString MessageFormat = "Neo smart contracts only support a single catch block: {0}";
+        private static readonly LocalizableString Description = "Neo smart contracts are limited to one catch block per try statement.";
+        private const string Category = "Usage";
+
+        private static readonly DiagnosticDescriptor Rule = new DiagnosticDescriptor(
+            DiagnosticId,
+            Title,
+            MessageFormat,
+            Category,
+            DiagnosticSeverity.Error,
+            isEnabledByDefault: true,
+            description: Description);
+
+        public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(Rule);
+
+        public override void Initialize(AnalysisContext context)
+        {
+            context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+            context.EnableConcurrentExecution();
+            context.RegisterSyntaxNodeAction(AnalyzeTryStatement, SyntaxKind.TryStatement);
+        }
+
+        private static void AnalyzeTryStatement(SyntaxNodeAnalysisContext context)
+        {
+            var tryStatement = (TryStatementSyntax)context.Node;
+
+            if (tryStatement.Catches.Count > 1)
+            {
+                var diagnostic = Diagnostic.Create(Rule, tryStatement.GetLocation(), tryStatement.Catches.Count);
+                context.ReportDiagnostic(diagnostic);
+            }
+        }
+    }
+}

src/Neo.SmartContract.Analyzer/Readme.md

@@ -26,6 +26,7 @@ This repository contains a set of Roslyn analyzers and code fix providers for Ne
 - [SupportedStandardsAnalyzer.cs](NeoContractAnalyzer/SupportedStandardsAnalyzer.cs): This analyzer checks for correct implementation of supported standards in smart contracts.
 - [BigIntegerUsingUsageAnalyzer.cs](NeoContractAnalyzer/BigIntegerUsingUsageAnalyzer.cs): This analyzer warns about incorrect usage of BigInteger in using statements.
 - [StaticFieldInitializationAnalyzer.cs](NeoContractAnalyzer/StaticFieldInitializationAnalyzer.cs): This analyzer checks for proper initialization of static fields in smart contracts.
+- [MultipleCatchBlockAnalyzer.cs](NeoContractAnalyzer/MultipleCatchBlockAnalyzer.cs): This analyzer checks for multiple catch blocks in try statements.
 
 ## How to Use
 
@@ -41,4 +42,4 @@ Contributions to improve existing analyzers or add new ones are welcome. Please
 
 ## License
 
-This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.
+This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.

tests/Neo.SmartContract.Analyzer.UnitTests/MultipleCatchBlockAnalyzerUnitTest.cs

@@ -0,0 +1,43 @@
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Verifier = Microsoft.CodeAnalysis.CSharp.Testing.XUnit.AnalyzerVerifier<Neo.SmartContract.Analyzer.MultipleCatchBlockAnalyzer>;
+
+namespace Neo.SmartContract.Analyzer.UnitTests
+{
+    [TestClass]
+    public class MultipleCatchBlockAnalyzerUnitTest
+    {
+        [TestMethod]
+        public async Task MultipleCatchBlockAnalyzer_DetectMultipleCatchBlocks()
+        {
+            const string sourceCode = """
+                                      using System;
+
+                                      public class TestClass
+                                      {
+                                          public void TestMethod()
+                                          {
+                                              try
+                                              {
+                                                  // Some code that might throw an exception
+                                              }
+                                              catch (FormatException ex)
+                                              {
+                                                  // Handle general exception
+                                              }
+                                              catch (Exception ex)
+                                              {
+                                                  // Handle specific exception
+                                              }
+                                          }
+                                      }
+                                      """;
+
+            var expected = Verifier.Diagnostic(MultipleCatchBlockAnalyzer.DiagnosticId)
+                .WithSpan(7, 9, 18, 10)
+                .WithArguments("2");
+
+            await Verifier.VerifyAnalyzerAsync(sourceCode, expected);
+        }
+    }
+}