Add support for _Imports.razor (dotnet/aspnetcore-tooling#354)

* Added support _Imports.razor

* Feedback
\n\nCommit migrated from 14704054f2

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentImportProjectFeature.cs

@@ -11,8 +11,6 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
 {
     internal class ComponentImportProjectFeature : IImportProjectFeature
     {
-        private const string ImportsFileName = "_ViewImports.cshtml";
-
         private static readonly char[] PathSeparators = new char[]{ '/', '\\' };
 
         // Using explicit newlines here to avoid fooling our baseline tests
@@ -74,7 +72,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
         public IEnumerable<RazorProjectItem> GetHierarchicalImports(RazorProject project, RazorProjectItem projectItem)
         {
             // We want items in descending order. FindHierarchicalItems returns items in ascending order.
-            return project.FindHierarchicalItems(projectItem.FilePath, ImportsFileName).Reverse();
+            return project.FindHierarchicalItems(projectItem.FilePath, ComponentMetadata.ImportsFileName).Reverse();
         }
 
         private class VirtualProjectItem : RazorProjectItem
@@ -99,6 +97,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
 
             public override bool Exists => true;
 
+            public override string FileKind => FileKinds.ComponentImport;
+
             public override Stream Read() => new MemoryStream(_bytes);
         }
     }

src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentMetadata.cs

@@ -11,6 +11,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
         // use our own metadata entry to denote non-Component tag helpers.
         public static readonly string SpecialKindKey = "Components.IsSpecialKind";
 
+        public static readonly string ImportsFileName = "_Imports.razor";
+
         public static class Bind
         {
             public static readonly string RuntimeName = "Components.None";

src/Razor/Microsoft.AspNetCore.Razor.Language/src/FileKinds.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.IO;
+using Microsoft.AspNetCore.Razor.Language.Components;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
@@ -10,12 +11,20 @@ namespace Microsoft.AspNetCore.Razor.Language
     {
         public static readonly string Component = "component";
 
+        public static readonly string ComponentImport = "componentImport";
+
         public static readonly string Legacy = "mvc";
 
         public static bool IsComponent(string fileKind)
         {
             // fileKind might be null.
-            return string.Equals(fileKind, FileKinds.Component, StringComparison.OrdinalIgnoreCase);
+            return string.Equals(fileKind, FileKinds.Component, StringComparison.OrdinalIgnoreCase) || IsComponentImport(fileKind);
+        }
+
+        public static bool IsComponentImport(string fileKind)
+        {
+            // fileKind might be null.
+            return string.Equals(fileKind, FileKinds.ComponentImport, StringComparison.OrdinalIgnoreCase);
         }
 
         public static string GetFileKindFromFilePath(string filePath)
@@ -25,7 +34,11 @@ namespace Microsoft.AspNetCore.Razor.Language
                 throw new ArgumentNullException(nameof(filePath));
             }
 
-            if (string.Equals(".razor", Path.GetExtension(filePath), StringComparison.OrdinalIgnoreCase))
+            if (string.Equals(ComponentMetadata.ImportsFileName, Path.GetFileName(filePath), StringComparison.Ordinal))
+            {
+                return FileKinds.ComponentImport;
+            }
+            else if (string.Equals(".razor", Path.GetExtension(filePath), StringComparison.OrdinalIgnoreCase))
             {
                 return FileKinds.Component;
             }