Use File.Open overload that overwrites file entirely in DiscoverCommand (#2110)

* Use File.Open overload that overwrites file entirely in DiscoverCommand

Re-enable TagHelper discovery incrementalism test

Fixes #2104

src/Microsoft.AspNetCore.Razor.Tools/DiscoverCommand.cs

@@ -150,7 +150,7 @@ namespace Microsoft.AspNetCore.Razor.Tools
             {
                 Serialize(stream, tagHelpers);
 
-                stream.Position = 0L;
+                stream.Position = 0;
 
                 var newHash = Hash(stream);
                 var existingHash = Hash(outputFilePath);
@@ -158,7 +158,7 @@ namespace Microsoft.AspNetCore.Razor.Tools
                 if (!HashesEqual(newHash, existingHash))
                 {
                     stream.Position = 0;
-                    using (var output = File.OpenWrite(outputFilePath))
+                    using (var output = File.Open(outputFilePath, FileMode.Create))
                     {
                         stream.CopyTo(output);
                     }

test/Microsoft.AspNetCore.Razor.Design.Test/IntegrationTests/Assert.cs

@@ -136,6 +136,23 @@ namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
             }
         }
 
+        public static void FileContentEquals(MSBuildResult result, string filePath, string expected)
+        {
+            if (result == null)
+            {
+                throw new ArgumentNullException(nameof(result));
+            }
+
+            filePath = Path.Combine(result.Project.DirectoryPath, filePath);
+            FileExists(result, filePath);
+
+            var actual = File.ReadAllText(filePath);
+            if (!actual.Equals(expected, StringComparison.Ordinal))
+            {
+                throw new FileContentNotEqualException(result, filePath, expected, actual);
+            }
+        }
+
         public static void FileContainsLine(MSBuildResult result, string filePath, string match)
         {
             if (result == null)
@@ -470,6 +487,36 @@ namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
             }
         }
 
+        private class FileContentNotEqualException : MSBuildXunitException
+        {
+            public FileContentNotEqualException(MSBuildResult result, string filePath, string expected, string actual)
+                : base(result)
+            {
+                FilePath = filePath;
+                Expected = expected;
+                Actual = actual;
+            }
+
+            public string Actual { get; }
+
+            public string FilePath { get; }
+
+            public string Expected { get; }
+
+            protected override string Heading
+            {
+                get
+                {
+                    var builder = new StringBuilder();
+                    builder.AppendFormat("File content of '{0}' did not match the expected content: '{1}'.", FilePath, Expected);
+                    builder.AppendLine();
+                    builder.AppendLine();
+                    builder.AppendLine(Actual);
+                    return builder.ToString();
+                }
+            }
+        }
+
         private class FileMissingException : MSBuildXunitException
         {
             public FileMissingException(MSBuildResult result, string filePath)

test/Microsoft.AspNetCore.Razor.Design.Test/IntegrationTests/BuildIncrementalismTest.cs

@@ -56,5 +56,34 @@ namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
                 }
             }
         }
+
+        [Fact]
+        [InitializeTestProject("SimpleMvc")]
+        public async Task RazorGenerate_RegeneratesTagHelperInputs_IfFileChanges()
+        {
+            // Act - 1
+            var expectedTagHelperCacheContent = @"""Name"":""SimpleMvc.SimpleTagHelper""";
+            var result = await DotnetMSBuild("Build", "/p:RazorCompileOnBuild=true");
+            var file = Path.Combine(Project.DirectoryPath, "SimpleTagHelper.cs");
+            var tagHelperOutputCache = Path.Combine(IntermediateOutputPath, "SimpleMvc.TagHelpers.output.cache");
+            var generatedFile = Path.Combine(RazorIntermediateOutputPath, "Views", "Home", "Index.cs");
+
+            // Assert - 1
+            Assert.BuildPassed(result);
+            Assert.FileContains(result, tagHelperOutputCache, expectedTagHelperCacheContent);
+            var fileThumbPrint = GetThumbPrint(generatedFile);
+
+            // Act - 2
+            // Update the source content and build. We should expect the outputs to be regenerated.
+            ReplaceContent(string.Empty, file);
+            result = await DotnetMSBuild("Build", "/p:RazorCompileOnBuild=true");
+
+            // Assert - 2
+            Assert.BuildPassed(result);
+            Assert.FileContentEquals(result, tagHelperOutputCache, "[]");
+            var newThumbPrint = GetThumbPrint(generatedFile);
+            Assert.NotEqual(fileThumbPrint, newThumbPrint);
+        }
+
     }
 }

test/Microsoft.AspNetCore.Razor.Design.Test/IntegrationTests/MSBuildIntegrationTestBase.cs

@@ -92,6 +92,9 @@ namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
             }
 
             File.WriteAllText(filePath, content, Encoding.UTF8);
+            // Timestamps on xplat are precise only to a second. Update it's last write time by at least 1 second
+            // so we can ensure that MSBuild recognizes the file change. See https://github.com/dotnet/corefx/issues/26024
+            File.SetLastWriteTimeUtc(filePath, File.GetLastWriteTimeUtc(filePath).AddSeconds(1));
         }
 
         /// <summary>

test/Microsoft.AspNetCore.Razor.Design.Test/IntegrationTests/RazorGenerateIntegrationTest.cs

@@ -109,9 +109,6 @@ namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
 
             // Act - 2
             // Update the source content and build. We should expect the outputs to be regenerated.
-            // Timestamps on xplat are precise only to a second. Add a delay so we can ensure that MSBuild recognizes the
-            // file change. See https://github.com/dotnet/corefx/issues/26024
-            await Task.Delay(TimeSpan.FromSeconds(1));
             ReplaceContent("Uodated content", file);
             result = await DotnetMSBuild(RazorGenerateTarget);
 
@@ -189,37 +186,6 @@ namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
             Assert.FileDoesNotExist(result, generatedFile);
         }
 
-        [Fact(Skip = "https://github.com/aspnet/Razor/issues/2104")]
-        [InitializeTestProject("SimpleMvc")]
-        public async Task RazorGenerate_Rebuilds_IfTagHelpersChanged()
-        {
-            // Act - 1
-            var expectedTagHelperCacheContent = @"""Name"":""SimpleMvc.SimpleTagHelper""";
-            var result = await DotnetMSBuild(RazorGenerateTarget);
-            var file = Path.Combine(Project.DirectoryPath, "SimpleTagHelper.cs");
-            var tagHelperOutputCache = Path.Combine(IntermediateOutputPath, "SimpleMvc.TagHelpers.output.cache");
-            var generatedFile = Path.Combine(RazorIntermediateOutputPath, "Views", "Home", "Index.cs");
-
-            // Assert - 1
-            Assert.BuildPassed(result);
-            Assert.FileContains(result, tagHelperOutputCache, expectedTagHelperCacheContent);
-            var fileThumbPrint = GetThumbPrint(generatedFile);
-
-            // Act - 2
-            // Update the source content and build. We should expect the outputs to be regenerated.
-            // Timestamps on xplat are precise only to a second. Add a delay so we can ensure that MSBuild recognizes the
-            // file change. See https://github.com/dotnet/corefx/issues/26024
-            await Task.Delay(TimeSpan.FromSeconds(1));
-            ReplaceContent(string.Empty, file);
-            result = await DotnetMSBuild(RazorGenerateTarget);
-
-            // Assert - 2
-            Assert.BuildPassed(result);
-            Assert.FileDoesNotContain(result, tagHelperOutputCache, expectedTagHelperCacheContent);
-            var newThumbPrint = GetThumbPrint(generatedFile);
-            Assert.NotEqual(fileThumbPrint, newThumbPrint);
-        }
-
         [Fact]
         [InitializeTestProject("SimpleMvc")]
         public async Task RazorGenerate_Noops_WithNoFiles()

test/testapps/SimpleMvc/SimpleTagHelper.cs

@@ -5,4 +5,4 @@ namespace SimpleMvc
     public class SimpleTagHelper : TagHelper
     {
     }
-}
+}