[GH-87] Added convention to enforce a project file treats a given com…

…piler warning as an error

src/Core/Conventional.Tests/Conventional/Conventions/Assemblies/AssemblyConventionSpecificationTests.cs

@@ -336,5 +336,61 @@ public void MustSetPropertyValue_NoValues_Failure()
             result.IsSatisfied.Should().BeFalse();
             result.Failures.Single().Should().Be("SdkClassLibrary1 should have property ThisPropertyShouldNeverEverExist with value x");
         }
+
+        [Theory]
+        [TestCase("CS0162")]
+        [TestCase("CS4014")]
+        public void MustTreatWarningAsError_MultipleWarnings_Success(string warning)
+        {
+            var result = TheAssembly
+                .WithNameMatching("TestProjectTwo")
+                .MustConformTo(Convention.MustTreatWarningAsError(warning));
+
+            result.IsSatisfied.Should().BeTrue();
+        }
+
+        [Test]
+        public void MustTreatWarningAsError_SingleWarning_Success()
+        {
+            var result = TheAssembly
+                .WithNameMatching("SdkClassLibrary1")
+                .MustConformTo(Convention.MustTreatWarningAsError("CS0162"));
+
+            result.IsSatisfied.Should().BeTrue();
+        }
+
+        [Test]
+        public void MustTreatWarningAsError_MultipleWarnings_Failure()
+        {
+            var result = TheAssembly
+                .WithNameMatching("TestProjectTwo")
+                .MustConformTo(Convention.MustTreatWarningAsError("XX9999"));
+
+            result.IsSatisfied.Should().BeFalse();
+            result.Failures.Single().Should().Be("Assembly TestProjectTwo should treat warning XX9999 as an error but does not");
+        }
+
+        [Test]
+        public void MustTreatWarningAsError_SingleWarnings_Failure()
+        {
+            var result = TheAssembly
+                .WithNameMatching("SdkClassLibrary1")
+                .MustConformTo(Convention.MustTreatWarningAsError("XX9999"));
+
+            result.IsSatisfied.Should().BeFalse();
+            result.Failures.Single().Should().Be("Assembly SdkClassLibrary1 should treat warning XX9999 as an error but does not");
+        }
+
+        [Test]
+        public void MustTreatWarningAsError_NoWarnings_Failure()
+        {
+            var result = TheAssembly
+                .WithNameMatching("TestSolution.TestProject")
+                .MustConformTo(Convention.MustTreatWarningAsError("CS0162"));
+
+            // TestSolution.TestProject does not set the WarningsAsErrors property, at time of writing
+            result.IsSatisfied.Should().BeFalse();
+            result.Failures.Single().Should().Be("Assembly TestSolution.TestProject should treat warning CS0162 as an error but does not");
+        }
     }
 }

src/Core/Conventional/Convention.Assembly.cs

@@ -121,5 +121,15 @@ public static MustSetPropertyValueAssemblyConventionSpecification MustSetPropert
         {
             return new MustSetPropertyValueAssemblyConventionSpecification(propertyName, value);
         }
+
+        /// <summary>
+        /// Require this project to treat the specified compiler warning as an error
+        /// </summary>
+        /// <param name="warning">The warning code to treat as fatal (e.g. CS0162)</param>
+        /// <remarks>This convention is unaware of shared build prop files (Directory.Build.Props + Directory.Build.Targets) - see https://github.com/andrewabest/Conventional/issues/88</remarks>
+        public static MustTreatWarningAsErrorAssemblyConventionSpecification MustTreatWarningAsError(string warning)
+        {
+            return new MustTreatWarningAsErrorAssemblyConventionSpecification(warning);
+        }
     }
 }

src/Core/Conventional/Conventions/Assemblies/MustTreatWarningAsErrorAssemblyConventionSpecification.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Linq;
+using System.Xml.Linq;
+using System.Xml.XPath;
+
+namespace Conventional.Conventions.Assemblies
+{
+    public class MustTreatWarningAsErrorAssemblyConventionSpecification : AssemblyConventionSpecification
+    {
+        private readonly string _warning;
+
+        public MustTreatWarningAsErrorAssemblyConventionSpecification(string warning)
+        {
+            _warning = warning;
+        }
+
+        protected override ConventionResult IsSatisfiedByLegacyCsprojFormat(string assemblyName, XDocument projectDocument)
+        {
+            return IsSatisfiedBy(assemblyName, projectDocument);
+        }
+
+        protected override ConventionResult IsSatisfiedBy(string assemblyName, XDocument projectDocument)
+        {
+            // The Project element (and descendants) are namespaced in legacy csproj files, so our XPath ignores the
+            // namespace by considering the local element name only. Once we no-longer need to support legacy csproj
+            // files, the XPath can be simplified to /Project/ItemGroup/ProjectReference
+            var warningsAsErrors = projectDocument.XPathSelectElements("/*[local-name() = 'Project']/*[local-name() = 'PropertyGroup']/*[local-name() = 'WarningsAsErrors']")
+                .SingleOrDefault()
+                ?.Value ?? "";
+
+            var warnings = warningsAsErrors.Split(new[] {' ', ','}, StringSplitOptions.RemoveEmptyEntries);
+            if (!warnings.Contains(_warning))
+            {
+                return ConventionResult.NotSatisfied(assemblyName, string.Format(FailureMessage, assemblyName, _warning));
+            }
+
+            return ConventionResult.Satisfied(assemblyName);
+        }
+
+        protected override string FailureMessage => "Assembly {0} should treat warning {1} as an error but does not";
+    }
+}

src/Core/TestSolution/TestProjectTwo/TestProjectTwo.csproj

@@ -11,6 +11,7 @@
     <AssemblyName>TestProjectTwo</AssemblyName>
     <TargetFrameworkVersion>v4.5.1</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
+    <WarningsAsErrors>CS0162,CS4014</WarningsAsErrors>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>

src/Core/TestSolution/TestSolution.TestProject/SdkClassLibrary1/SdkClassLibrary1.csproj

@@ -9,6 +9,10 @@
     <PropertyGroup>
         <TargetFramework>netstandard2.1</TargetFramework>
     </PropertyGroup>
+
+    <PropertyGroup>
+        <WarningsAsErrors>CS0162</WarningsAsErrors>
+    </PropertyGroup>
 
     <ItemGroup>
       <PackageReference Include="coverlet.collector" Version="6.0.0">