Add support for base path in FindHiearchicalItems

Required for https://github.com/aspnet/Mvc/issues/5915

src/Microsoft.AspNetCore.Razor.Evolution/RazorProject.cs

@@ -39,8 +39,27 @@ namespace Microsoft.AspNetCore.Razor.Evolution
         /// e.g.
         /// /Views/Home/View.cshtml -> [ /Views/Home/FileName.cshtml, /Views/FileName.cshtml, /FileName.cshtml ]
         /// </remarks>
-        public virtual IEnumerable<RazorProjectItem> FindHierarchicalItems(string path, string fileName)
+        public IEnumerable<RazorProjectItem> FindHierarchicalItems(string path, string fileName)
         {
+            return FindHierarchicalItems(basePath: "/", path: path, fileName: fileName);
+        }
+
+        /// <summary>
+        /// Gets the sequence of files named <paramref name="fileName"/> that are applicable to the specified path.
+        /// </summary>
+        /// <param name="basePath">The base path.</param>
+        /// <param name="path">The path of a project item.</param>
+        /// <param name="fileName">The file name to seek.</param>
+        /// <returns>A sequence of applicable <see cref="RazorProjectItem"/> instances.</returns>
+        /// <remarks>
+        /// This method returns paths starting from the directory of <paramref name="path"/> and
+        /// traverses to the <paramref name="basePath"/>.
+        /// e.g.
+        /// (/Views, /Views/Home/View.cshtml) -> [ /Views/Home/FileName.cshtml, /Views/FileName.cshtml ]
+        /// </remarks>
+        public virtual IEnumerable<RazorProjectItem> FindHierarchicalItems(string basePath, string path, string fileName)
+        {
+            EnsureValidPath(basePath);
             EnsureValidPath(path);
             if (string.IsNullOrEmpty(fileName))
             {
@@ -53,6 +72,11 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 yield break;
             }
 
+            if (!path.StartsWith(basePath, StringComparison.OrdinalIgnoreCase))
+            {
+                yield break;
+            }
+
             StringBuilder builder;
             var fileNameIndex = path.LastIndexOf('/');
             var length = path.Length;
@@ -69,8 +93,9 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 builder = new StringBuilder(path);
             }
 
+            var maxDepth = 255;
             var index = length;
-            while (index > 0 && (index = path.LastIndexOf('/', index - 1)) != -1)
+            while (maxDepth-- > 0 && index > basePath.Length && (index = path.LastIndexOf('/', index - 1)) != -1)
             {
                 builder.Length = index + 1;
                 builder.Append(fileName);

test/Microsoft.AspNetCore.Razor.Evolution.Test/RazorProjectTest.cs

@@ -188,6 +188,127 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 });
         }
 
+        [Theory]
+        [InlineData("/Areas")]
+        [InlineData("/Areas/")]
+        public void FindHierarchicalItems_WithBasePath(string basePath)
+        {
+            // Arrange
+            var path = "/Areas/MyArea/Views/Home/Test.cshtml";
+            var items = new Dictionary<string, RazorProjectItem>
+            {
+                { "/Areas/MyArea/File.cshtml", CreateProjectItem("/Areas/MyArea/File.cshtml") },
+                { "/File.cshtml", CreateProjectItem("/File.cshtml") },
+            };
+            var project = new TestRazorProject(items);
+
+            // Act
+            var result = project.FindHierarchicalItems(basePath, path, "File.cshtml");
+
+            // Assert
+            Assert.Collection(
+                result,
+                item =>
+                {
+                    Assert.Equal("/Areas/MyArea/Views/Home/File.cshtml", item.Path);
+                    Assert.False(item.Exists);
+                },
+                item =>
+                {
+                    Assert.Equal("/Areas/MyArea/Views/File.cshtml", item.Path);
+                    Assert.False(item.Exists);
+                },
+                item =>
+                {
+                    Assert.Equal("/Areas/MyArea/File.cshtml", item.Path);
+                    Assert.True(item.Exists);
+                },
+                item =>
+                {
+                    Assert.Equal("/Areas/File.cshtml", item.Path);
+                    Assert.False(item.Exists);
+                });
+        }
+
+        [Theory]
+        [InlineData("/Areas/MyArea/Views")]
+        [InlineData("/Areas/MyArea/Views/")]
+        public void FindHierarchicalItems_WithNestedBasePath(string basePath)
+        {
+            // Arrange
+            var path = "/Areas/MyArea/Views/Home/Test.cshtml";
+            var items = new Dictionary<string, RazorProjectItem>
+            {
+                { "/Areas/MyArea/File.cshtml", CreateProjectItem("/Areas/MyArea/File.cshtml") },
+                { "/File.cshtml", CreateProjectItem("/File.cshtml") },
+            };
+            var project = new TestRazorProject(items);
+
+            // Act
+            var result = project.FindHierarchicalItems(basePath, path, "File.cshtml");
+
+            // Assert
+            Assert.Collection(
+                result,
+                item =>
+                {
+                    Assert.Equal("/Areas/MyArea/Views/Home/File.cshtml", item.Path);
+                    Assert.False(item.Exists);
+                },
+                item =>
+                {
+                    Assert.Equal("/Areas/MyArea/Views/File.cshtml", item.Path);
+                    Assert.False(item.Exists);
+                });
+        }
+
+        [Theory]
+        [InlineData("/Areas/MyArea/Views/Home")]
+        [InlineData("/Areas/MyArea/Views/Home/")]
+        public void FindHierarchicalItems_WithFileAtBasePath(string basePath)
+        {
+            // Arrange
+            var path = "/Areas/MyArea/Views/Home/Test.cshtml";
+            var items = new Dictionary<string, RazorProjectItem>
+            {
+                { "/Areas/MyArea/File.cshtml", CreateProjectItem("/Areas/MyArea/File.cshtml") },
+                { "/File.cshtml", CreateProjectItem("/File.cshtml") },
+            };
+            var project = new TestRazorProject(items);
+
+            // Act
+            var result = project.FindHierarchicalItems(basePath, path, "File.cshtml");
+
+            // Assert
+            Assert.Collection(
+                result,
+                item =>
+                {
+                    Assert.Equal("/Areas/MyArea/Views/Home/File.cshtml", item.Path);
+                    Assert.False(item.Exists);
+                });
+        }
+
+        [Fact]
+        public void FindHierarchicalItems_ReturnsEmptySequenceIfPathIsNotASubPathOfBasePath()
+        {
+            // Arrange
+            var basePath = "/Pages";
+            var path = "/Areas/MyArea/Views/Home/Test.cshtml";
+            var items = new Dictionary<string, RazorProjectItem>
+            {
+                { "/Areas/MyArea/File.cshtml", CreateProjectItem("/Areas/MyArea/File.cshtml") },
+                { "/File.cshtml", CreateProjectItem("/File.cshtml") },
+            };
+            var project = new TestRazorProject(items);
+
+            // Act
+            var result = project.FindHierarchicalItems(basePath, path, "File.cshtml");
+
+            // Assert
+            Assert.Empty(result);
+        }
+
         private RazorProjectItem CreateProjectItem(string path)
         {
             var projectItem = new Mock<RazorProjectItem>();