[andrewabestGH-87] Added new convention to enforce that a given proje…

…ct doesn't include project references to (any) other projects

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

@@ -219,5 +219,27 @@ public void MustBeIncludedInSetOfAssemblies_Failure()
             // TODO: Use result.Should().AllSatisfy() once we've updated to fluentassertions 6.5.0+
             result.Select(x => x.IsSatisfied).Distinct().Single().Should().BeFalse();
         }
+
+        [Test]
+        public void MustNotIncludeProjectReferences_Success()
+        {
+            var result = TheAssembly
+                .WithNameMatching("TestProjectTwo")
+                .MustConformTo(Convention.MustNotIncludeProjectReferences);
+
+            // Note: TestProjectTwo doesn't import any other projects (at time of writing)
+            result.IsSatisfied.Should().BeTrue();
+        }
+
+        [Test]
+        public void MustNotIncludeProjectReferences_Failure()
+        {
+            var result = TheAssembly
+                .WithNameMatching("Conventional.Tests")
+                .MustConformTo(Convention.MustNotIncludeProjectReferences); // Note: Conventional.Tests of course includes a reference to Conventional
+
+            result.IsSatisfied.Should().BeFalse();
+            result.Failures.Single().Should().StartWith("Conventional.Tests includes reference to project");
+        }
     }
 }

src/Core/Conventional/Convention.Assembly.cs

@@ -81,5 +81,12 @@ public static MustBeIncludedInSetOfAssembliesConventionSpecification MustBeInclu
         {
             return new MustBeIncludedInSetOfAssembliesConventionSpecification(assemblies, setName);
         }
+
+        /// <summary>
+        /// Disallows this assembly (project) from referencing other projects
+        /// </summary>
+        /// <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 MustNotIncludeProjectReferencesConventionSpecification MustNotIncludeProjectReferences =>
+            new MustNotIncludeProjectReferencesConventionSpecification();
     }
 }

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

@@ -0,0 +1,39 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Xml.Linq;
+using System.Xml.XPath;
+
+namespace Conventional.Conventions.Assemblies
+{
+    public class MustNotIncludeProjectReferencesConventionSpecification : AssemblyConventionSpecification
+    {
+        protected override ConventionResult IsSatisfiedBy(string assemblyName, XDocument projectDocument)
+        {
+            var projectReferences = GetProjectReferences(projectDocument).ToArray();
+
+            if (projectReferences.Any())
+            {
+                return ConventionResult.NotSatisfied(assemblyName, string.Format(FailureMessage, assemblyName, projectReferences.First()));
+            }
+
+            return ConventionResult.Satisfied(assemblyName);
+        }
+
+        protected override ConventionResult IsSatisfiedByLegacyCsprojFormat(string assemblyName, XDocument projectDocument)
+        {
+            return IsSatisfiedBy(assemblyName, projectDocument);
+        }
+
+        private IEnumerable<string> GetProjectReferences(XDocument projectDocument)
+        {
+            // Note: The Project element (and descendants) are namespaced in legacy csproj files, so our XPath ignores the
+            // Note: namespace by considering the local element name only. Once we no-longer need to support legacy csproj
+            // Note: files, the XPath can be simplified to /Project/ItemGroup/ProjectReference
+            return projectDocument.XPathSelectElements("/*[local-name() = 'Project']/*[local-name() = 'ItemGroup']/*[local-name() = 'ProjectReference']")
+                .Select(referenceElement => referenceElement.Attribute("Include")?.Value)
+                .Where(value => value != null);
+        }
+
+        protected override string FailureMessage => "{0} includes reference to project {1}";
+    }
+}