Treat String.Empty as "", fixes #32

Suchiman · Jun 1, 2018 · d457b80 · d457b80
1 parent 7caa191
commit d457b80
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Showing 2 changed files with 59 additions and 4 deletions.
diff --git a/SerilogAnalyzer/SerilogAnalyzer.Test/AnalyzerTests.cs b/SerilogAnalyzer/SerilogAnalyzer.Test/AnalyzerTests.cs
@@ -660,6 +660,53 @@ public static void Test()
             VerifyCSharpDiagnostic(src, expected);
         }
 
+        [TestMethod]
+        public void TestStringEmptyIsConstantMessageTemplate()
+        {
+            string src = @"
+    using Serilog;
+    using System;
+
+    class TypeName
+    {
+        public static void Test()
+        {
+            Log.Error(String.Empty);
+            Log.Error(string.Empty);
+        }
+    }";
+
+            VerifyCSharpDiagnostic(src);
+        }
+
+        [TestMethod]
+        public void TestStringEmptyWithTooManyArguments()
+        {
+            string src = @"
+    using Serilog;
+    using System;
+
+    class TypeName
+    {
+        public static void Test()
+        {
+            Log.Error(String.Empty, ""Hello"");
+        }
+    }";
+
+            var expected = new DiagnosticResult
+            {
+                Id = "Serilog003",
+                Message = String.Format("Error while binding properties: {0}", "There is no property that corresponds to this argument"),
+                Severity = DiagnosticSeverity.Error,
+                Locations = new[]
+                {
+                    new DiagnosticResultLocation("Test0.cs", 9, 37, 7)
+                }
+            };
+            VerifyCSharpDiagnostic(src, expected);
+        }
+
         [TestMethod]
         public void TestDiagnosticLengthWithEscapes()
         {

diff --git a/SerilogAnalyzer/SerilogAnalyzer/DiagnosticAnalyzer.cs b/SerilogAnalyzer/SerilogAnalyzer/DiagnosticAnalyzer.cs
@@ -146,15 +146,23 @@ private static void AnalyzeSymbol(SyntaxNodeAnalysisContext context)
                     {
                         // can we at least get a computed constant value for it?
                         var constantValue = context.SemanticModel.GetConstantValue(argument.Expression, context.CancellationToken);
-                        if (!constantValue.HasValue || !(constantValue.Value is string))
+                        if (!constantValue.HasValue || !(constantValue.Value is string constString))
                         {
-                            context.ReportDiagnostic(Diagnostic.Create(ConstantMessageTemplateRule, argument.Expression.GetLocation(), argument.Expression.ToString()));
-                            continue;
+                            INamedTypeSymbol StringType() => context.SemanticModel.Compilation.GetTypeByMetadataName("System.String");
+                            if (context.SemanticModel.GetSymbolInfo(argument.Expression, context.CancellationToken).Symbol is IFieldSymbol field && field.Name == "Empty" && field.Type == StringType())
+                            {
+                                constString = "";
+                            }
+                            else
+                            {
+                                context.ReportDiagnostic(Diagnostic.Create(ConstantMessageTemplateRule, argument.Expression.GetLocation(), argument.Expression.ToString()));
+                                continue;
+                            }
                         }
 
                         // we can't map positions back from the computed string into the real positions
                         exactPositions = false;
-                        messageTemplate = constantValue.Value as string;
+                        messageTemplate = constString;
                     }
 
                     literalSpan = argument.Expression.GetLocation().SourceSpan;