Add GetImportItems to RazorTemplateEngine

Fixes #1109

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Microsoft.AspNetCore.Razor.Evolution
 {
@@ -189,17 +190,14 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
             var result = new List<RazorSourceDocument>();
 
-            var importsFileName = Options.ImportsFileName;
+
-            if (!string.IsNullOrEmpty(importsFileName))
+            var importProjectItems = GetImportItems(projectItem);
+            foreach (var importItem in importProjectItems)
             {
-                var importProjectItems = Project.FindHierarchicalItems(projectItem.Path, importsFileName);
+                if (importItem.Exists)
-                foreach (var importItem in importProjectItems)
                 {
-                    if (importItem.Exists)
+                    // We want items in descending order. FindHierarchicalItems returns items in ascending order.
-                    {
+                    result.Insert(0, RazorSourceDocument.ReadFrom(importItem));
-                        // We want items in descending order. FindHierarchicalItems returns items in ascending order.
-                        result.Insert(0, RazorSourceDocument.ReadFrom(importItem));
-                    }
                 }
             }
 
@@ -210,5 +208,41 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
             return result;
         }
+
+        /// <summary>
+        /// Gets the sequence of imports with the name specified by <see cref="RazorTemplateEngineOptions.ImportsFileName" />
+        /// that apply to <paramref name="path"/>.
+        /// </summary>
+        /// <param name="path">The path to look up import items for.</param>
+        /// <returns>A sequence of <see cref="RazorProjectItem"/> instances that apply to the
+        /// <paramref name="path"/>.</returns>
+        public IEnumerable<RazorProjectItem> GetImportItems(string path)
+        {
+            if (string.IsNullOrEmpty(path))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(path));
+            }
+
+            var projectItem = Project.GetItem(path);
+            return GetImportItems(projectItem);
+        }
+
+        /// <summary>
+        /// Gets the sequence of imports with the name specified by <see cref="RazorTemplateEngineOptions.ImportsFileName" />
+        /// that apply to <paramref name="projectItem"/>.
+        /// </summary>
+        /// <param name="projectItem">The <see cref="RazorProjectItem"/> to look up import items for.</param>
+        /// <returns>A sequence of <see cref="RazorProjectItem"/> instances that apply to the
+        /// <paramref name="projectItem"/>.</returns>
+        public virtual IEnumerable<RazorProjectItem> GetImportItems(RazorProjectItem projectItem)
+        {
+            var importsFileName = Options.ImportsFileName;
+            if (!string.IsNullOrEmpty(importsFileName))
+            {
+                return Project.FindHierarchicalItems(projectItem.Path, importsFileName);
+            }
+
+            return Enumerable.Empty<RazorProjectItem>();
+        }
     }
 }

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.IO;
+using System.Linq;
 using Microsoft.AspNetCore.Testing;
 using Xunit;
 
@@ -215,5 +216,52 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             Assert.Collection(codeDocument.Imports,
                 import => Assert.Same(defaultImport, import));
         }
+
+        [Fact]
+        public void GetImportItems_WithPath_ReturnsAllImportsForFile()
+        {
+            // Arrange
+            var expected = new[] { "/Views/Home/MyImport.cshtml", "/Views/MyImport.cshtml", "/MyImport.cshtml" };
+            var project = new TestRazorProject();
+            var razorEngine = RazorEngine.Create();
+            var templateEngine = new RazorTemplateEngine(razorEngine, project)
+            {
+                Options =
+                {
+                    ImportsFileName = "MyImport.cshtml"
+                }
+            };
+
+            // Act
+            var imports = templateEngine.GetImportItems("/Views/Home/Index.cshtml");
+
+            // Assert
+            var paths = imports.Select(i => i.Path);
+            Assert.Equal(expected, paths);
+        }
+
+        [Fact]
+        public void GetImportItems_WithItem_ReturnsAllImportsForFile()
+        {
+            // Arrange
+            var expected = new[] { "/Views/Home/MyImport.cshtml", "/Views/MyImport.cshtml", "/MyImport.cshtml" };
+            var projectItem = new TestRazorProjectItem("/Views/Home/Index.cshtml");
+            var project = new TestRazorProject(new[] { projectItem });
+            var razorEngine = RazorEngine.Create();
+            var templateEngine = new RazorTemplateEngine(razorEngine, project)
+            {
+                Options =
+                {
+                    ImportsFileName = "MyImport.cshtml"
+                }
+            };
+
+            // Act
+            var imports = templateEngine.GetImportItems(projectItem);
+
+            // Assert
+            var paths = imports.Select(i => i.Path);
+            Assert.Equal(expected, paths);
+        }
     }
 }