Add model for differentiating design time and runtime parsing.

- If needed, a phase/feature can always retrieve the syntax tree to lookup whether the parse tree was made in a "design time" fashion.
- Future DesignTime / Runtime specific bits will be added to their corresponding `AddRuntimeDefaults`/`AddDesignTimeDefaults` methods.

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

@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.AspNetCore.Razor.Evolution
+{
+    internal class DefaultRazorDesignTimeCSharpLoweringPhase : RazorEnginePhaseBase, IRazorCSharpLoweringPhase
+    {
+        protected override void ExecuteCore(RazorCodeDocument codeDocument)
+        {
+            var irDocument = codeDocument.GetIRDocument();
+            ThrowForMissingDependency(irDocument);
+
+            var syntaxTree = codeDocument.GetSyntaxTree();
+            ThrowForMissingDependency(syntaxTree);
+
+            // Render design time CSharp
+        }
+    }
+}

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

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 
 namespace Microsoft.AspNetCore.Razor.Evolution
@@ -17,6 +18,8 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
         public IList<IRazorEnginePhase> Phases { get; }
 
+        public bool DesignTime { get; set; }
+
         public RazorEngine Build()
         {
             var features = new IRazorEngineFeature[Features.Count];

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

@@ -11,7 +11,7 @@ using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution
 {
-    internal class DefaultRazorCSharpLoweringPhase : RazorEnginePhaseBase, IRazorCSharpLoweringPhase
+    internal class DefaultRazorRuntimeCSharpLoweringPhase : RazorEnginePhaseBase, IRazorCSharpLoweringPhase
     {
         protected override void ExecuteCore(RazorCodeDocument codeDocument)
         {

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

@@ -11,6 +11,8 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
         IList<IRazorEnginePhase> Phases { get; }
 
+        bool DesignTime { get; set; }
+
         RazorEngine Build();
     }
 }

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

@@ -17,6 +17,24 @@ namespace Microsoft.AspNetCore.Razor.Evolution
         {
             var builder = new DefaultRazorEngineBuilder();
             AddDefaults(builder);
+            AddRuntimeDefaults(builder);
+            configure?.Invoke(builder);
+            return builder.Build();
+        }
+
+        public static RazorEngine CreateDesignTime()
+        {
+            return CreateDesignTime(configure: null);
+        }
+
+        public static RazorEngine CreateDesignTime(Action<IRazorEngineBuilder> configure)
+        {
+            var builder = new DefaultRazorEngineBuilder()
+            {
+                DesignTime = true,
+            };
+            AddDefaults(builder);
+            AddDesignTimeDefaults(builder);
             configure?.Invoke(builder);
             return builder.Build();
         }
@@ -34,7 +52,6 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             builder.Phases.Add(new DefaultRazorSyntaxTreePhase());
             builder.Phases.Add(new DefaultRazorIRLoweringPhase());
             builder.Phases.Add(new DefaultRazorIRPhase());
-            builder.Phases.Add(new DefaultRazorCSharpLoweringPhase());
 
             // Syntax Tree passes
             builder.Features.Add(new DefaultDirectiveSyntaxTreePass());
@@ -45,10 +62,34 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             builder.Features.Add(new DefaultDirectiveIRPass());
         }
 
+        internal static void AddRuntimeDefaults(IRazorEngineBuilder builder)
+        {
+            builder.Phases.Add(new DefaultRazorRuntimeCSharpLoweringPhase());
+        }
+
+        internal static void AddDesignTimeDefaults(IRazorEngineBuilder builder)
+        {
+            builder.Phases.Add(new DefaultRazorDesignTimeCSharpLoweringPhase());
+
+            builder.Features.Add(new ConfigureDesignTimeOptions());
+        }
+
         public abstract IReadOnlyList<IRazorEngineFeature> Features { get; }
 
         public abstract IReadOnlyList<IRazorEnginePhase> Phases { get; }
 
         public abstract void Process(RazorCodeDocument document);
+
+        internal class ConfigureDesignTimeOptions : IRazorConfigureParserFeature
+        {
+            public RazorEngine Engine { get; set; }
+
+            public int Order { get; set; }
+
+            public void Configure(RazorParserOptions options)
+            {
+                options.DesignTimeMode = true;
+            }
+        }
     }
 }

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

@@ -8,13 +8,13 @@ using Xunit;
 
 namespace Microsoft.AspNetCore.Razor.Evolution
 {
-    public class DefaultRazorCSharpLoweringPhaseTest
+    public class DefaultRazorRuntimeCSharpLoweringPhaseTest
     {
         [Fact]
         public void Execute_ThrowsForMissingDependency()
         {
             // Arrange
-            var phase = new DefaultRazorCSharpLoweringPhase();
+            var phase = new DefaultRazorRuntimeCSharpLoweringPhase();
 
             var engine = RazorEngine.CreateEmpty(b => b.Phases.Add(phase));
 
@@ -23,7 +23,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             // Act & Assert
             ExceptionAssert.Throws<InvalidOperationException>(
                 () => phase.Execute(codeDocument),
-                $"The '{nameof(DefaultRazorCSharpLoweringPhase)}' phase requires a '{nameof(DocumentIRNode)}' " +
+                $"The '{nameof(DefaultRazorRuntimeCSharpLoweringPhase)}' phase requires a '{nameof(DocumentIRNode)}' " +
                 $"provided by the '{nameof(RazorCodeDocument)}'.");
         }
     }

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

@@ -11,7 +11,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
     public class RazorEngineTest
     {
         [Fact]
-        public void Create_NoArg_CreatesDefaultEngine()
+        public void Create_NoArg_CreatesDefaultRuntimeEngine()
         {
             // Arrange
             // Act
@@ -19,12 +19,25 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
             // Assert
             Assert.IsType<DefaultRazorEngine>(engine);
-            AssertDefaultFeatures(engine.Features);
+            AssertDefaultRuntimeFeatures(engine.Features);
-            AssertDefaultPhases(engine.Phases);
+            AssertDefaultRuntimePhases(engine.Phases);
         }
 
         [Fact]
-        public void Create_Null_CreatesDefaultEngine()
+        public void CreateDesignTime_NoArg_CreatesDefaultDesignTimeEngine()
+        {
+            // Arrange
+            // Act
+            var engine = RazorEngine.CreateDesignTime();
+
+            // Assert
+            Assert.IsType<DefaultRazorEngine>(engine);
+            AssertDefaultDesignTimeFeatures(engine.Features);
+            AssertDefaultDesignTimePhases(engine.Phases);
+        }
+
+        [Fact]
+        public void Create_Null_CreatesDefaultRuntimeEngine()
         {
             // Arrange
             // Act
@@ -32,8 +45,21 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
             // Assert
             Assert.IsType<DefaultRazorEngine>(engine);
-            AssertDefaultFeatures(engine.Features);
+            AssertDefaultRuntimeFeatures(engine.Features);
-            AssertDefaultPhases(engine.Phases);
+            AssertDefaultRuntimePhases(engine.Phases);
+        }
+
+        [Fact]
+        public void CreateDesignTime_Null_CreatesDefaultDesignTimeEngine()
+        {
+            // Arrange
+            // Act
+            var engine = RazorEngine.CreateDesignTime(configure: null);
+
+            // Assert
+            Assert.IsType<DefaultRazorEngine>(engine);
+            AssertDefaultDesignTimeFeatures(engine.Features);
+            AssertDefaultDesignTimePhases(engine.Phases);
         }
 
         [Fact]
@@ -71,7 +97,42 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 p => Assert.Same(phases[1], p));
         }
 
-        private static void AssertDefaultFeatures(IEnumerable<IRazorEngineFeature> features)
+        [Fact]
+        public void CreateDesignTime_Lambda_AddsFeaturesAndPhases()
+        {
+            // Arrange
+            IRazorEngineFeature[] features = null;
+            IRazorEnginePhase[] phases = null;
+
+            // Act
+            var engine = RazorEngine.CreateDesignTime(builder =>
+            {
+                builder.Features.Clear();
+                builder.Phases.Clear();
+
+                builder.Features.Add(Mock.Of<IRazorEngineFeature>());
+                builder.Features.Add(Mock.Of<IRazorEngineFeature>());
+
+                builder.Phases.Add(Mock.Of<IRazorEnginePhase>());
+                builder.Phases.Add(Mock.Of<IRazorEnginePhase>());
+
+                features = builder.Features.ToArray();
+                phases = builder.Phases.ToArray();
+            });
+
+            // Assert
+            Assert.Collection(
+                engine.Features,
+                f => Assert.Same(features[0], f),
+                f => Assert.Same(features[1], f));
+
+            Assert.Collection(
+                engine.Phases,
+                p => Assert.Same(phases[0], p),
+                p => Assert.Same(phases[1], p));
+        }
+
+        private static void AssertDefaultRuntimeFeatures(IEnumerable<IRazorEngineFeature> features)
         {
             Assert.Collection(
                 features,
@@ -81,7 +142,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 feature => Assert.IsType<DefaultDirectiveIRPass>(feature));
         }
 
-        private static void AssertDefaultPhases(IReadOnlyList<IRazorEnginePhase> phases)
+        private static void AssertDefaultRuntimePhases(IReadOnlyList<IRazorEnginePhase> phases)
         {
             Assert.Collection(
                 phases,
@@ -89,7 +150,29 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 phase => Assert.IsType<DefaultRazorSyntaxTreePhase>(phase),
                 phase => Assert.IsType<DefaultRazorIRLoweringPhase>(phase),
                 phase => Assert.IsType<DefaultRazorIRPhase>(phase),
-                phase => Assert.IsType<DefaultRazorCSharpLoweringPhase>(phase));
+                phase => Assert.IsType<DefaultRazorRuntimeCSharpLoweringPhase>(phase));
+        }
+
+        private static void AssertDefaultDesignTimeFeatures(IEnumerable<IRazorEngineFeature> features)
+        {
+            Assert.Collection(
+                features,
+                feature => Assert.IsType<DefaultDirectiveSyntaxTreePass>(feature),
+                feature => Assert.IsType<TagHelperBinderSyntaxTreePass>(feature),
+                feature => Assert.IsType<HtmlNodeOptimizationPass>(feature),
+                feature => Assert.IsType<DefaultDirectiveIRPass>(feature),
+                feature => Assert.IsType<RazorEngine.ConfigureDesignTimeOptions>(feature));
+        }
+
+        private static void AssertDefaultDesignTimePhases(IReadOnlyList<IRazorEnginePhase> phases)
+        {
+            Assert.Collection(
+                phases,
+                phase => Assert.IsType<DefaultRazorParsingPhase>(phase),
+                phase => Assert.IsType<DefaultRazorSyntaxTreePhase>(phase),
+                phase => Assert.IsType<DefaultRazorIRLoweringPhase>(phase),
+                phase => Assert.IsType<DefaultRazorIRPhase>(phase),
+                phase => Assert.IsType<DefaultRazorDesignTimeCSharpLoweringPhase>(phase));
         }
     }
 }