AVRO-4331: [csharp] Fix unreachable code in generated Get()/Put()

lang/csharp/src/apache/main/CodeGen/CodeGen.cs

@@ -563,7 +563,7 @@ protected virtual void processInterface(Protocol protocol)
 
             if (protocol.Messages.Count > 0)
             {
-                builder.AppendLine("switch(messageName)");
+                builder.AppendLine("\t\t\tswitch(messageName)");
                 builder.Append("\t\t\t{");
 
                 foreach (var a in protocol.Messages)
@@ -580,11 +580,11 @@ protected virtual void processInterface(Protocol protocol)
                 }
 
                 builder.Append("\t\t\t}");
-            }
 
-            var cseGet = new CodeSnippetExpression(builder.ToString());
+                var cssRequest = new CodeSnippetStatement(builder.ToString());
+                requestMethod.Statements.Add(cssRequest);
+            }
 
-            requestMethod.Statements.Add(cseGet);
             ctd.Members.Add(requestMethod);
 
             AddMethods(protocol, false, ctd);
@@ -770,7 +770,7 @@ protected virtual CodeTypeDeclaration processRecord(Schema schema)
             cmmGet.Attributes = MemberAttributes.Public;
             cmmGet.ReturnType = new CodeTypeReference("System.Object");
             cmmGet.Parameters.Add(new CodeParameterDeclarationExpression(typeof(int), "fieldPos"));
-            StringBuilder getFieldStmt = new StringBuilder("switch (fieldPos)")
+            StringBuilder getFieldStmt = new StringBuilder("\t\t\tswitch (fieldPos)")
                 .AppendLine().AppendLine("\t\t\t{");
 
             // declare Put() to be used by the Reader classes
@@ -780,7 +780,7 @@ protected virtual CodeTypeDeclaration processRecord(Schema schema)
             cmmPut.ReturnType = new CodeTypeReference(typeof(void));
             cmmPut.Parameters.Add(new CodeParameterDeclarationExpression(typeof(int), "fieldPos"));
             cmmPut.Parameters.Add(new CodeParameterDeclarationExpression("System.Object", "fieldValue"));
-            var putFieldStmt = new StringBuilder("switch (fieldPos)")
+            var putFieldStmt = new StringBuilder("\t\t\tswitch (fieldPos)")
                 .AppendLine().AppendLine("\t\t\t{");
 
             if (isError)
@@ -874,15 +874,15 @@ protected virtual CodeTypeDeclaration processRecord(Schema schema)
             // end switch block for Get()
             getFieldStmt.AppendLine("\t\t\tdefault: throw new global::Avro.AvroRuntimeException(\"Bad index \" + fieldPos + \" in Get()\");")
                 .Append("\t\t\t}");
-            var cseGet = new CodeSnippetExpression(getFieldStmt.ToString());
-            cmmGet.Statements.Add(cseGet);
+            var cssGet = new CodeSnippetStatement(getFieldStmt.ToString());
+            cmmGet.Statements.Add(cssGet);
             ctd.Members.Add(cmmGet);
 
             // end switch block for Put()
             putFieldStmt.AppendLine("\t\t\tdefault: throw new global::Avro.AvroRuntimeException(\"Bad index \" + fieldPos + \" in Put()\");")
                 .Append("\t\t\t}");
-            var csePut = new CodeSnippetExpression(putFieldStmt.ToString());
-            cmmPut.Statements.Add(csePut);
+            var cssPut = new CodeSnippetStatement(putFieldStmt.ToString());
+            cmmPut.Statements.Add(cssPut);
             ctd.Members.Add(cmmPut);
 
             string nspace = recordSchema.Namespace;

lang/csharp/src/apache/test/CodGen/CodeGenTest.cs

@@ -110,6 +110,80 @@ public void GetTypesShouldReturnTypes()
                 Assert.That(Regex.Matches(planetEnumCode, "public enum PlanetEnum").Count, Is.EqualTo(1));
             }
 
+            [Test]
+            public void RecordGetAndPutSwitchesShouldNotEmitUnreachableStatement()
+            {
+                AddSchema(@"
+{
+  ""name"": ""Sample"",
+  ""namespace"": ""Avro.Test.CodeGen.UnreachableCodeRegression"",
+  ""type"": ""record"",
+  ""fields"": [
+    { ""name"": ""value"", ""type"": ""string"" }
+  ]
+}
+");
+                GenerateCode();
+                var types = GetTypes();
+                bool hasSampleCode = types.TryGetValue("Sample", out string sampleCode);
+                Assert.That(hasSampleCode);
+
+                // The exhaustive switch in Get()/Put() must not be followed by a stray ";" -
+                // that empty statement is unreachable (every case returns or throws) and
+                // trips IDE-only unreachable-code analysis (e.g. ReSharper) even though Roslyn
+                // does not flag it.
+                Assert.That(Regex.IsMatch(sampleCode, @"\}\s*;\s*\}\s*public virtual void Put"), Is.False);
+                Assert.That(Regex.IsMatch(sampleCode, @"in Put\(\)""\);\s*\}\s*;"), Is.False);
+
+                // CodeDom writes CodeSnippetStatement at column 0, so the snippet carries its own indent.
+                Assert.That(Regex.Matches(sampleCode, @"(?m)^\t\t\tswitch \(fieldPos\)\r?$").Count, Is.EqualTo(2));
+                Assert.That(Regex.Matches(sampleCode, @"(?m)^\s*switch \(fieldPos\)").Count, Is.EqualTo(2));
+            }
+
+            [Test]
+            public void ProtocolRequestSwitchShouldBeIndentedAndNotFollowedByEmptyStatement()
+            {
+                AddProtocol(@"
+{
+  ""protocol"": ""Greeter"",
+  ""namespace"": ""Avro.Test.CodeGen.ProtocolSwitchRegression"",
+  ""types"": [],
+  ""messages"": {
+    ""hello"": {
+      ""request"": [ { ""name"": ""greeting"", ""type"": ""string"" } ],
+      ""response"": ""string""
+    }
+  }
+}
+");
+                GenerateCode();
+                var types = GetTypes();
+                bool hasGreeterCode = types.TryGetValue("Greeter", out string greeterCode);
+                Assert.That(hasGreeterCode);
+
+                Assert.That(Regex.Matches(greeterCode, @"(?m)^\t\t\tswitch\(messageName\)\r?$").Count, Is.EqualTo(1));
+                Assert.That(Regex.IsMatch(greeterCode, @"break;\s*\}\s*;"), Is.False);
+            }
+
+            [Test]
+            public void ProtocolWithoutMessagesShouldGenerateEmptyRequestBody()
+            {
+                AddProtocol(@"
+{
+  ""protocol"": ""Silent"",
+  ""namespace"": ""Avro.Test.CodeGen.EmptyProtocolRegression"",
+  ""types"": [],
+  ""messages"": {}
+}
+");
+                GenerateCode();
+                var types = GetTypes();
+                bool hasSilentCode = types.TryGetValue("Silent", out string silentCode);
+                Assert.That(hasSilentCode);
+
+                Assert.That(Regex.IsMatch(silentCode, @"object callback\)\s*\{\s*\}"), Is.True);
+            }
+
             [Test]
             public void EnumWithKeywordSymbolsShouldHavePrefixedSymbols()
             {