Raise diagnostics when not exposing expression bodies members

src/EntityFrameworkCore.Projections.Generator/AnalyzerReleases.Shipped.md

@@ -0,0 +1,3 @@
+; Shipped analyzer releases
+; https://github.com/dotnet/roslyn-analyzers/blob/master/src/Microsoft.CodeAnalysis.Analyzers/ReleaseTrackingAnalyzers.Help.md
+

src/EntityFrameworkCore.Projections.Generator/AnalyzerReleases.Unshipped.md

@@ -0,0 +1,5 @@
+### New Rules
+
+Rule ID | Category | Severity | Notes
+--------|----------|----------|--------------------
+EFP0001 |  Design  |  Error   | ST0001_AnalyzerName

src/EntityFrameworkCore.Projections.Generator/Diagnostics.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+
+namespace EntityFrameworkCore.Projections.Generator
+{
+    public static class Diagnostics
+    {
+        public static readonly DiagnosticDescriptor RequiresExpressionBodyDefinition = new(
+            id: "EFP0001",
+            title: "Method or property should expose an expression body definition",
+            messageFormat: "Method or property '{0}' should expose an expression body definition.",
+            category: "Design",
+            DiagnosticSeverity.Error,
+            isEnabledByDefault: true);
+
+    }
+}

src/EntityFrameworkCore.Projections.Generator/ProjectableInterpreter.cs

@@ -84,6 +84,13 @@ namespace EntityFrameworkCore.Projections.Generator
 
             if (memberDeclarationSyntax is MethodDeclarationSyntax methodDeclarationSyntax)
             {
+                if (methodDeclarationSyntax.ExpressionBody is null)
+                {
+                    var diagnostic = Diagnostic.Create(Diagnostics.RequiresExpressionBodyDefinition, methodDeclarationSyntax.GetLocation(), memberSymbol.Name);
+                    context.ReportDiagnostic(diagnostic);
+                    return null;
+                }
+
                 descriptor.ReturnTypeName = methodDeclarationSyntax.ReturnType.ToString();
                 descriptor.Body = expressionSyntaxRewriter.Visit(methodDeclarationSyntax.ExpressionBody.Expression);
                 foreach (var additionalParameter in ((ParameterListSyntax)parameterSyntaxRewriter.Visit(methodDeclarationSyntax.ParameterList)).Parameters)
@@ -93,6 +100,13 @@ namespace EntityFrameworkCore.Projections.Generator
             }
             else if (memberDeclarationSyntax is PropertyDeclarationSyntax propertyDeclarationSyntax)
             {
+                if (propertyDeclarationSyntax.ExpressionBody is null)
+                {
+                    var diagnostic = Diagnostic.Create(Diagnostics.RequiresExpressionBodyDefinition, propertyDeclarationSyntax.GetLocation(), memberSymbol.Name);
+                    context.ReportDiagnostic(diagnostic);
+                    return null;
+                }
+
                 descriptor.ReturnTypeName = propertyDeclarationSyntax.Type.ToString();
                 descriptor.Body = expressionSyntaxRewriter.Visit(propertyDeclarationSyntax.ExpressionBody.Expression);
             }

tests/EntityFrameworkCore.Projections.Generator.Tests/ProjectionExpressionGeneratorTests.cs

@@ -340,6 +340,49 @@ namespace Foo {
             return Verifier.Verify(result.GeneratedTrees[0].ToString());
         }
 
+        [Fact]
+        public void BlockBodiedMember_RaisesDiagnostics()
+        {
+            var compilation = CreateCompilation(@"
+using System;
+using EntityFrameworkCore.Projections;
+namespace Foo {
+    class C {
+        [Projectable]
+        public int Foo 
+        {
+            get => 1;
+        }
+    }
+}
+");
+
+            var result = RunGenerator(compilation);
+
+            Assert.Single(result.Diagnostics);
+        }
+
+        [Fact]
+        public void BlockBodiedMethod_RaisesDiagnostics()
+        {
+            var compilation = CreateCompilation(@"
+using System;
+using EntityFrameworkCore.Projections;
+namespace Foo {
+    class C {
+        [Projectable]
+        public int Foo() 
+        {
+            return 1;
+        }
+    }
+}
+");
+
+            var result = RunGenerator(compilation);
+
+            Assert.Single(result.Diagnostics);
+        }
 
         #region Helpers