18 files changed, 311 insertions, 62 deletions

diff --git a/src/api/wix/WixToolset.Extensibility/BaseLibrarianExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseLibrarianExtension.cs
index cbc9e4ba..ff5edae3 100644
--- a/src/api/wix/WixToolset.Extensibility/BaseLibrarianExtension.cs
+++ b/src/api/wix/WixToolset.Extensibility/BaseLibrarianExtension.cs
@@ -48,8 +48,8 @@ namespace WixToolset.Extensibility
         /// <summary>
         /// Called at the end of combining.
         /// </summary>
-        /// <param name="library">Combined library intermediate.</param>
-        public virtual void PostCombine(Intermediate library)
+        /// <param name="result">Combined library result.</param>
+        public virtual void PostCombine(ILibraryResult result)
         {
         }
 
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ILibraryResult.cs b/src/api/wix/WixToolset.Extensibility/Data/ILibraryResult.cs
new file mode 100644
index 00000000..6974e265
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ILibraryResult.cs
@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Result of a library combine operation.
+    /// </summary>
+    public interface ILibraryResult
+    {
+        /// <summary>
+        /// Collection of files tracked when binding files into the library.
+        /// </summary>
+        IReadOnlyCollection<ITrackedFile> TrackedFiles { get; set; }
+
+        /// <summary>
+        /// Output of librarian.
+        /// </summary>
+        Intermediate Library { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/ILibrarianExtension.cs b/src/api/wix/WixToolset.Extensibility/ILibrarianExtension.cs
index d9b04cd2..d25da5e4 100644
--- a/src/api/wix/WixToolset.Extensibility/ILibrarianExtension.cs
+++ b/src/api/wix/WixToolset.Extensibility/ILibrarianExtension.cs
@@ -5,13 +5,30 @@ namespace WixToolset.Extensibility
     using WixToolset.Data;
     using WixToolset.Extensibility.Data;
 
-#pragma warning disable 1591 // TODO: add documentation
+    /// <summary>
+    /// Interface all librarian extensions implement.
+    /// </summary>
     public interface ILibrarianExtension
     {
+        /// <summary>
+        /// Called at the beginning of combining.
+        /// </summary>
+        /// <param name="context">Librarian context.</param>
         void PreCombine(ILibraryContext context);
 
+        /// <summary>
+        /// Resolves a path to a file path on disk.
+        /// </summary>
+        /// <param name="sourceLineNumber">Source line number for the path to resolve.</param>
+        /// <param name="symbolDefinition">Symbol related to the path to resolve.</param>
+        /// <param name="path">Path to resolve.</param>
+        /// <returns>Optional resolved file result.</returns>
         IResolveFileResult ResolveFile(SourceLineNumber sourceLineNumber, IntermediateSymbolDefinition symbolDefinition, string path);
 
-        void PostCombine(Intermediate library);
+        /// <summary>
+        /// Called at the end of combining.
+        /// </summary>
+        /// <param name="result">Combined library result.</param>
+        void PostCombine(ILibraryResult result);
     }
 }
diff --git a/src/test/wix/TestData/WixprojModuleCsprojWinFormsNetFx/WixprojModuleCsprojWinFormsNetFx.wixproj b/src/test/wix/TestData/WixprojModuleCsprojWinFormsNetFx/WixprojModuleCsprojWinFormsNetFx.wixproj
index 07e42b08..6009460c 100644
--- a/src/test/wix/TestData/WixprojModuleCsprojWinFormsNetFx/WixprojModuleCsprojWinFormsNetFx.wixproj
+++ b/src/test/wix/TestData/WixprojModuleCsprojWinFormsNetFx/WixprojModuleCsprojWinFormsNetFx.wixproj
@@ -1,19 +1,11 @@
 <!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+
  <Project Sdk='WixToolset.Sdk'> 
-<!--<Project>
-  <Import Sdk="WixToolset.Sdk" Project='D:\src\wix4\build\wix\Debug\netcoreapp3.1\Sdk\Sdk.props' />-->
   <PropertyGroup>
     <OutputType>Module</OutputType>
   </PropertyGroup>
 
-  <!--<PropertyGroup>
-    <WixBinDir>D:\src\wix4\build\wix\Debug\publish\WixToolset.Sdk\tools\net461\x86\</WixBinDir>
-    <WixBinDir64>D:\src\wix4\build\wix\Debug\publish\WixToolset.Sdk\tools\net461\x64\</WixBinDir64>
-  </PropertyGroup>-->
-
   <ItemGroup>
     <ProjectReference Include="..\CsprojWindowsFormsNetFx\CsprojWindowsFormsNetFx.csproj" />
   </ItemGroup>
-
-  <!--<Import Sdk="WixToolset.Sdk" Project='D:\src\wix4\build\wix\Debug\netcoreapp3.1\Sdk\Sdk.targets' />-->
 </Project>
diff --git a/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/Package.ja-jp.wxl b/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/Package.ja-jp.wxl
index 52e1871e..0f902c8d 100644
--- a/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/Package.ja-jp.wxl
+++ b/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/Package.ja-jp.wxl
@@ -5,7 +5,7 @@ This file contains the declaration of all the localizable strings.
 -->
 <WixLocalization xmlns="http://wixtoolset.org/schemas/v4/wxl" Culture="ja-JP">
 
-  <String Id="PackageName">WixprojPackageVcxprojWindowsApp, eh?</String>
+  <String Id="PackageName">WixprojPackageVcxprojWindowsApp-jp</String>
   <String Id="FeatureTitle">The First Feature in my Prooooduct, eh?</String>
 
 </WixLocalization>
diff --git a/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/Package.wxs b/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/Package.wxs
index fe849608..508d4721 100644
--- a/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/Package.wxs
+++ b/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/Package.wxs
@@ -1,5 +1,7 @@
-<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs">
+<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs"
+     xmlns:ui="http://wixtoolset.org/schemas/v4/wxs/ui">
   <Package Name='!(loc.PackageName)' Manufacturer='WiX Toolset' Version='0.0.1' UpgradeCode='41a2c17e-1976-465b-bcde-eae03516ca68'>
+    <SoftwareTag Regid='wixtoolset.org' InstallDirectory='ApplicationFolder' />
 
     <StandardDirectory Id='ProgramFiles6432Folder'>
       <Directory Id='ApplicationFolder' Name='Test App'>
@@ -16,5 +18,7 @@
 
       <MergeRef Id='WinFormsModule' />
     </Feature>
+
+    <ui:WixUI Id="WixUI_Minimal" />
   </Package>
 </Wix>
diff --git a/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/WixprojPackageVcxprojWindowsApp.wixproj b/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/WixprojPackageVcxprojWindowsApp.wixproj
index 7dc26a2d..bbd39870 100644
--- a/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/WixprojPackageVcxprojWindowsApp.wixproj
+++ b/src/test/wix/TestData/WixprojPackageVcxprojWindowsApp/WixprojPackageVcxprojWindowsApp.wixproj
@@ -5,5 +5,7 @@
     <ProjectReference Include="..\VcxprojWindowsApp\VcxprojWindowsApp.vcxproj" />
     <ProjectReference Include="..\WixprojLibraryVcxprojDll\WixprojLibraryVcxprojDll.wixproj" />
     <ProjectReference Include="..\WixprojModuleCsprojWinFormsNetFx\WixprojModuleCsprojWinFormsNetFx.wixproj" />
+
+    <PackageReference Include="Wixtoolset.UI.wixext" Version="4.0.0-preview.1-build.205" />
   </ItemGroup>
 </Project>
diff --git a/src/test/wix/WixE2E/WixE2EFixture.cs b/src/test/wix/WixE2E/WixE2EFixture.cs
index 89762f72..b1c6b2de 100644
--- a/src/test/wix/WixE2E/WixE2EFixture.cs
+++ b/src/test/wix/WixE2E/WixE2EFixture.cs
@@ -2,7 +2,12 @@
 
 namespace WixE2E
 {
+    using System;
     using System.IO;
+    using System.Linq;
+    using System.Security.Cryptography;
+    using System.Text;
+    using System.Threading;
     using WixBuildTools.TestSupport;
     using Xunit;
 
@@ -52,6 +57,93 @@ namespace WixE2E
             result.AssertSuccess();
         }
 
+        [Fact]
+        public void CanIncrementalBuildPackageWithNativeWindowsAppWithNoEdits()
+        {
+            var projectDirectory = TestData.Get("TestData", "WixprojPackageVcxprojWindowsApp");
+            var projectPath = Path.Combine(projectDirectory, "WixprojPackageVcxprojWindowsApp.wixproj");
+            var projectBinPath = Path.Combine(projectDirectory, "bin");
+
+            CleanEverything();
+
+            var result = RestoreAndBuild(projectPath);
+            result.AssertSuccess();
+
+            var firstBuiltFiles = Directory.GetFiles(projectBinPath, "*.*", SearchOption.AllDirectories).ToArray();
+            var firstHashes = firstBuiltFiles.Select(s => $"{s.Substring(projectBinPath.Length).TrimStart('\\')} with hash: {GetFileHash(s)}").ToArray();
+
+            // This should be an incremental build and not do any work.
+            //
+            result = RestoreAndBuild(projectPath);
+            result.AssertSuccess();
+
+            var secondBuiltFiles = Directory.GetFiles(projectBinPath, "*.*", SearchOption.AllDirectories).ToArray();
+            var secondHashes = secondBuiltFiles.Select(s => $"{s.Substring(projectBinPath.Length).TrimStart('\\')} with hash: {GetFileHash(s)}").ToArray();
+
+            WixAssert.CompareLineByLine(firstHashes, secondHashes);
+        }
+
+        [Fact]
+        public void CanIncrementalBuildPackageWithNativeWindowsAppWithEdits()
+        {
+            var projectDirectory = TestData.Get("TestData", "WixprojPackageVcxprojWindowsApp");
+            var projectPath = Path.Combine(projectDirectory, "WixprojPackageVcxprojWindowsApp.wixproj");
+            var projectBinPath = Path.Combine(projectDirectory, "bin");
+
+            CleanEverything();
+
+            var result = RestoreAndBuild(projectPath);
+            result.AssertSuccess();
+
+            var firstBuiltFiles = Directory.GetFiles(projectBinPath, "*.*", SearchOption.AllDirectories).ToArray();
+            var firstRelativePaths = firstBuiltFiles.Select(s => $"{s.Substring(projectBinPath.Length).TrimStart('\\')}").ToArray();
+            var firstHashes = firstBuiltFiles.Select(s => $"{s.Substring(projectBinPath.Length).TrimStart('\\')} with hash: {GetFileHash(s)}").ToArray();
+
+            var packageWxsPath = Path.Combine(projectDirectory, "Package.wxs");
+            File.SetLastWriteTime(packageWxsPath, DateTime.Now);
+
+            // This should be an incremental build that does work because a file was updated.
+            //
+            result = RestoreAndBuild(projectPath);
+            result.AssertSuccess();
+
+            var secondBuiltFiles = Directory.GetFiles(projectBinPath, "*.*", SearchOption.AllDirectories).ToArray();
+            var secondRelativePaths = secondBuiltFiles.Select(s => $"{s.Substring(projectBinPath.Length).TrimStart('\\')}").ToArray();
+            var secondHashes = secondBuiltFiles.Select(s => $"{s.Substring(projectBinPath.Length).TrimStart('\\')} with hash: {GetFileHash(s)}").ToArray();
+
+            WixAssert.CompareLineByLine(firstRelativePaths, secondRelativePaths);
+            Assert.NotEqual(firstHashes, secondHashes);
+        }
+
+        [Fact(Skip = "Investigate if .NET Core WebApplications can be incrementally built")]
+        public void CanIncrementalBuildPackageWithNetCoreWebAppWithoutEdits()
+        {
+            var projectDirectory = TestData.Get("TestData", "WixprojPackageCsprojWebApplicationNetCore");
+            var projectPath = Path.Combine(projectDirectory, "WixprojPackageCsprojWebApplicationNetCore.wixproj");
+            var projectBinPath = Path.Combine(projectDirectory, "bin");
+
+            CleanEverything();
+
+            var result = RestoreAndBuild(projectPath);
+            result.AssertSuccess();
+
+            var firstBuiltFiles = Directory.GetFiles(projectBinPath, "*.*", SearchOption.AllDirectories).ToArray();
+            var firstHashes = firstBuiltFiles.Select(s => $"{s.Substring(projectBinPath.Length).TrimStart('\\')} with hash: {GetFileHash(s)}").ToArray();
+
+            //var packageWxsPath = Path.Combine(projectDirectory, "Package.wxs");
+            //File.SetLastWriteTime(packageWxsPath, DateTime.Now);
+
+            // This should be an incremental build that does work because a file was updated.
+            //
+            result = RestoreAndBuild(projectPath);
+            result.AssertSuccess();
+
+            var secondBuiltFiles = Directory.GetFiles(projectBinPath, "*.*", SearchOption.AllDirectories).ToArray();
+            var secondHashes = secondBuiltFiles.Select(s => $"{s.Substring(projectBinPath.Length).TrimStart('\\')} with hash: {GetFileHash(s)}").ToArray();
+
+            WixAssert.CompareLineByLine(firstHashes, secondHashes);
+        }
+
         private static void CleanEverything()
         {
             var rootFolder = TestData.Get("TestData");
@@ -71,6 +163,23 @@ namespace WixE2E
             }
         }
 
+        private static string GetFileHash(string path)
+        {
+            using (var sha2 = SHA256.Create())
+            {
+                var bytes = File.ReadAllBytes(path);
+                var hashBytes = sha2.ComputeHash(bytes);
+
+                var sb = new StringBuilder();
+                foreach (var hash in hashBytes)
+                {
+                    sb.AppendFormat("{0:X}", hash);
+                }
+
+                return sb.ToString();
+            }
+        }
+
         private static MsbuildRunnerResult RestoreAndBuild(string projectPath, bool x64 = true)
         {
             return MsbuildRunner.Execute(projectPath, new[] { "-Restore", "-v:m", "-bl" }, x64);
diff --git a/src/wix/WixToolset.Core.WindowsInstaller/Bind/BindDatabaseCommand.cs b/src/wix/WixToolset.Core.WindowsInstaller/Bind/BindDatabaseCommand.cs
index ab471702..c3dbcfce 100644
--- a/src/wix/WixToolset.Core.WindowsInstaller/Bind/BindDatabaseCommand.cs
+++ b/src/wix/WixToolset.Core.WindowsInstaller/Bind/BindDatabaseCommand.cs
@@ -244,6 +244,7 @@ namespace WixToolset.Core.WindowsInstaller.Bind
                     command.Execute();
 
                     fileFacades.AddRange(command.MergeModulesFileFacades);
+                    trackedFiles.AddRange(command.TrackedFiles);
                 }
             }
 
@@ -260,8 +261,10 @@ namespace WixToolset.Core.WindowsInstaller.Bind
 
                 if (softwareTags.Any())
                 {
-                    var command = new ProcessPackageSoftwareTagsCommand(section, softwareTags, this.IntermediateFolder);
+                    var command = new ProcessPackageSoftwareTagsCommand(section, this.WindowsInstallerBackendHelper, softwareTags, this.IntermediateFolder);
                     command.Execute();
+
+                    trackedFiles.AddRange(command.TrackedFiles);
                 }
             }
 
@@ -483,8 +486,10 @@ namespace WixToolset.Core.WindowsInstaller.Bind
             {
                 this.Messaging.Write(VerboseMessages.MergingModules());
 
-                var command = new MergeModulesCommand(this.Messaging, fileFacades, section, suppressedTableNames, this.OutputPath, this.IntermediateFolder);
+                var command = new MergeModulesCommand(this.Messaging, this.WindowsInstallerBackendHelper, fileFacades, section, suppressedTableNames, this.OutputPath, this.IntermediateFolder);
                 command.Execute();
+
+                trackedFiles.AddRange(command.TrackedFiles);
             }
 
             if (this.Messaging.EncounteredError)
@@ -508,8 +513,8 @@ namespace WixToolset.Core.WindowsInstaller.Bind
                 trackedFiles.AddRange(command.TrackedFiles);
             }
 
-            // TODO: this is not sufficient to collect all Input files (for example, it misses Binary and Icon tables).
-            trackedFiles.AddRange(fileFacades.Select(f => this.WindowsInstallerBackendHelper.TrackFile(f.SourcePath, TrackedFileType.Input, f.SourceLineNumber)));
+            var trackedInputFiles = this.TrackInputFiles(data, trackedFiles);
+            trackedFiles.AddRange(trackedInputFiles);
 
             var result = this.ServiceProvider.GetService<IBindResult>();
             result.FileTransfers = fileTransfers;
@@ -613,5 +618,26 @@ namespace WixToolset.Core.WindowsInstaller.Bind
 
             return layout;
         }
+
+        private IEnumerable<ITrackedFile> TrackInputFiles(WindowsInstallerData data, List<ITrackedFile> trackedFiles)
+        {
+            var trackedInputFiles = new List<ITrackedFile>();
+            var intermediateAndTemporaryPaths = new HashSet<string>(trackedFiles.Where(t => t.Type == TrackedFileType.Intermediate || t.Type == TrackedFileType.Temporary).Select(t => t.Path), StringComparer.OrdinalIgnoreCase);
+
+            foreach (var row in data.Tables.SelectMany(t => t.Rows))
+            {
+                foreach (var field in row.Fields.Where(f => f.Column.Type == ColumnType.Object))
+                {
+                    var path = field.AsString();
+
+                    if (!intermediateAndTemporaryPaths.Contains(path))
+                    {
+                        trackedInputFiles.Add(this.WindowsInstallerBackendHelper.TrackFile(path, TrackedFileType.Input, row.SourceLineNumbers));
+                    }
+                }
+            }
+
+            return trackedInputFiles;
+        }
     }
 }
diff --git a/src/wix/WixToolset.Core.WindowsInstaller/Bind/ExtractMergeModuleFilesCommand.cs b/src/wix/WixToolset.Core.WindowsInstaller/Bind/ExtractMergeModuleFilesCommand.cs
index aac4dd4f..06168727 100644
--- a/src/wix/WixToolset.Core.WindowsInstaller/Bind/ExtractMergeModuleFilesCommand.cs
+++ b/src/wix/WixToolset.Core.WindowsInstaller/Bind/ExtractMergeModuleFilesCommand.cs
@@ -49,9 +49,12 @@ namespace WixToolset.Core.WindowsInstaller.Bind
 
         public IEnumerable<IFileFacade> MergeModulesFileFacades { get; private set; }
 
+        public IReadOnlyList<ITrackedFile> TrackedFiles { get; private set; }
+
         public void Execute()
         {
             var mergeModulesFileFacades = new List<IFileFacade>();
+            var trackedFiles = new List<ITrackedFile>();
 
             var merge = MsmInterop.GetMsmMerge();
 
@@ -66,21 +69,23 @@ namespace WixToolset.Core.WindowsInstaller.Bind
 
             foreach (var wixMergeRow in this.WixMergeSymbols)
             {
-                var containsFiles = this.CreateFacadesForMergeModuleFiles(wixMergeRow, mergeModulesFileFacades, indexedFileFacades);
+                var modulesTrackedFiles = this.CreateFacadesForMergeModuleFiles(wixMergeRow, mergeModulesFileFacades, indexedFileFacades);
 
                 // If the module has files and creating layout
-                if (containsFiles && !this.SuppressLayout)
+                if (modulesTrackedFiles.Count > 0 && !this.SuppressLayout)
                 {
                     this.ExtractFilesFromMergeModule(merge, wixMergeRow);
+                    trackedFiles.AddRange(modulesTrackedFiles);
                 }
             }
 
             this.MergeModulesFileFacades = mergeModulesFileFacades;
+            this.TrackedFiles = trackedFiles;
         }
 
-        private bool CreateFacadesForMergeModuleFiles(WixMergeSymbol wixMergeRow, List<IFileFacade> mergeModulesFileFacades, Dictionary<string, IFileFacade> indexedFileFacades)
+        private IReadOnlyCollection<ITrackedFile> CreateFacadesForMergeModuleFiles(WixMergeSymbol wixMergeRow, List<IFileFacade> mergeModulesFileFacades, Dictionary<string, IFileFacade> indexedFileFacades)
         {
-            var containsFiles = false;
+            var trackedFiles = new List<ITrackedFile>();
 
             try
             {
@@ -125,12 +130,13 @@ namespace WixToolset.Core.WindowsInstaller.Bind
                                 {
                                     mergeModulesFileFacades.Add(mergeModuleFileFacade);
 
-                                    // Keep updating the indexes as new rows are added.
+                                    // Keep updating the indexes as new facades are added.
                                     indexedFileFacades.Add(mergeModuleFileFacade.Id, mergeModuleFileFacade);
                                     uniqueModuleFileIdentifiers.Add(mergeModuleFileFacade.Id, mergeModuleFileFacade);
-                                }
 
-                                containsFiles = true;
+                                    // Track where file will be extracted.
+                                    trackedFiles.Add(this.BackendHelper.TrackFile(mergeModuleFileFacade.SourcePath, TrackedFileType.Intermediate, mergeModuleFileFacade.SourceLineNumber));
+                                }
                             }
                         }
                     }
@@ -164,7 +170,7 @@ namespace WixToolset.Core.WindowsInstaller.Bind
                 throw new WixException(ErrorMessages.CannotOpenMergeModule(wixMergeRow.SourceLineNumbers, wixMergeRow.Id.Id, wixMergeRow.SourceFile));
             }
 
-            return containsFiles;
+            return trackedFiles;
         }
 
         private void ExtractFilesFromMergeModule(IMsmMerge2 merge, WixMergeSymbol wixMergeRow)
diff --git a/src/wix/WixToolset.Core.WindowsInstaller/Bind/MergeModulesCommand.cs b/src/wix/WixToolset.Core.WindowsInstaller/Bind/MergeModulesCommand.cs
index 6446692e..96b7866c 100644
--- a/src/wix/WixToolset.Core.WindowsInstaller/Bind/MergeModulesCommand.cs
+++ b/src/wix/WixToolset.Core.WindowsInstaller/Bind/MergeModulesCommand.cs
@@ -22,9 +22,10 @@ namespace WixToolset.Core.WindowsInstaller.Bind
     /// </summary>
     internal class MergeModulesCommand
     {
-        public MergeModulesCommand(IMessaging messaging, IEnumerable<IFileFacade> fileFacades, IntermediateSection section, IEnumerable<string> suppressedTableNames, string outputPath, string intermediateFolder)
+        public MergeModulesCommand(IMessaging messaging, IBackendHelper backendHelper, IEnumerable<IFileFacade> fileFacades, IntermediateSection section, IEnumerable<string> suppressedTableNames, string outputPath, string intermediateFolder)
         {
             this.Messaging = messaging;
+            this.BackendHelper = backendHelper;
             this.FileFacades = fileFacades;
             this.Section = section;
             this.SuppressedTableNames = suppressedTableNames ?? Array.Empty<string>();
@@ -34,6 +35,8 @@ namespace WixToolset.Core.WindowsInstaller.Bind
 
         private IMessaging Messaging { get; }
 
+        private IBackendHelper BackendHelper { get; }
+
         private IEnumerable<IFileFacade> FileFacades { get; }
 
         private IntermediateSection Section { get; }
@@ -44,8 +47,12 @@ namespace WixToolset.Core.WindowsInstaller.Bind
 
         private string IntermediateFolder { get; }
 
+        public IReadOnlyList<ITrackedFile> TrackedFiles { get; private set; }
+
         public void Execute()
         {
+            var trackedFiles = new List<ITrackedFile>();
+
             var wixMergeSymbols = this.Section.Symbols.OfType<WixMergeSymbol>().ToList();
             if (!wixMergeSymbols.Any())
             {
@@ -93,6 +100,8 @@ namespace WixToolset.Core.WindowsInstaller.Bind
                         merge.OpenModule(wixMergeRow.SourceFile, mergeLanguage);
                         moduleOpen = true;
 
+                        trackedFiles.Add(this.BackendHelper.TrackFile(wixMergeRow.SourceFile, TrackedFileType.Input, wixMergeRow.SourceLineNumbers));
+
                         // If there is merge configuration data, create a callback object to contain it all.
                         ConfigurationCallback callback = null;
                         if (!String.IsNullOrEmpty(wixMergeRow.ConfigurationData))
@@ -326,6 +335,8 @@ namespace WixToolset.Core.WindowsInstaller.Bind
 
                 db.Commit();
             }
+
+            this.TrackedFiles = trackedFiles;
         }
     }
 }
diff --git a/src/wix/WixToolset.Core.WindowsInstaller/Bind/ProcessPackageSoftwareTagsCommand.cs b/src/wix/WixToolset.Core.WindowsInstaller/Bind/ProcessPackageSoftwareTagsCommand.cs
index 9a068603..68e11790 100644
--- a/src/wix/WixToolset.Core.WindowsInstaller/Bind/ProcessPackageSoftwareTagsCommand.cs
+++ b/src/wix/WixToolset.Core.WindowsInstaller/Bind/ProcessPackageSoftwareTagsCommand.cs
@@ -9,12 +9,15 @@ namespace WixToolset.Core.WindowsInstaller.Bind
     using System.Xml;
     using WixToolset.Data;
     using WixToolset.Data.Symbols;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
 
     internal class ProcessPackageSoftwareTagsCommand
     {
-        public ProcessPackageSoftwareTagsCommand(IntermediateSection section, IEnumerable<WixProductTagSymbol> softwareTags, string intermediateFolder)
+        public ProcessPackageSoftwareTagsCommand(IntermediateSection section, IBackendHelper backendHelper, IEnumerable<WixProductTagSymbol> softwareTags, string intermediateFolder)
         {
             this.Section = section;
+            this.BackendHelper = backendHelper;
             this.SoftwareTags = softwareTags;
             this.IntermediateFolder = intermediateFolder;
         }
@@ -23,10 +26,16 @@ namespace WixToolset.Core.WindowsInstaller.Bind
 
         private IntermediateSection Section { get; }
 
+        private IBackendHelper BackendHelper { get; }
+
         private IEnumerable<WixProductTagSymbol> SoftwareTags { get; }
 
+        public IReadOnlyCollection<ITrackedFile> TrackedFiles { get; private set; }
+
         public void Execute()
         {
+            var trackedFiles = new List<ITrackedFile>();
+
             string productName = null;
             string productVersion = null;
             string manufacturer = null;
@@ -70,6 +79,8 @@ namespace WixToolset.Core.WindowsInstaller.Bind
                     // Write the tag file.
                     fileSymbol.Source = new IntermediateFieldPathValue { Path = Path.Combine(workingFolder, fileSymbol.Name) };
 
+                    trackedFiles.Add(this.BackendHelper.TrackFile(fileSymbol.Source.Path, TrackedFileType.Intermediate, tagRow.SourceLineNumbers));
+
                     using (var fs = new FileStream(fileSymbol.Source.Path, FileMode.Create))
                     {
                         CreateTagFile(fs, uniqueId, productName, productVersion, tagRow.Regid, manufacturer, persistentId);
@@ -86,6 +97,8 @@ namespace WixToolset.Core.WindowsInstaller.Bind
                     });
                 }
             }
+
+            this.TrackedFiles = trackedFiles;
         }
 
         private static string NormalizeGuid(string guidString)
diff --git a/src/wix/WixToolset.Core/Bind/ExtractEmbeddedFilesCommand.cs b/src/wix/WixToolset.Core/Bind/ExtractEmbeddedFilesCommand.cs
index ec2d8896..5d984d53 100644
--- a/src/wix/WixToolset.Core/Bind/ExtractEmbeddedFilesCommand.cs
+++ b/src/wix/WixToolset.Core/Bind/ExtractEmbeddedFilesCommand.cs
@@ -31,6 +31,7 @@ namespace WixToolset.Core.Bind
             foreach (var expectedEmbeddedFileByUri in group)
             {
                 var baseUri = expectedEmbeddedFileByUri.Key;
+                trackedFiles.Add(this.BackendHelper.TrackFile(baseUri.LocalPath, TrackedFileType.Input));
 
                 using (var wixout = WixOutput.Read(baseUri))
                 {
@@ -41,7 +42,7 @@ namespace WixToolset.Core.Bind
                         if (uniqueIds.Add(embeddedFile.EmbeddedFileId))
                         {
                             wixout.ExtractEmbeddedFile(embeddedFile.EmbeddedFileId, embeddedFile.OutputPath);
-                            trackedFiles.Add(this.BackendHelper.TrackFile(embeddedFile.OutputPath, TrackedFileType.Temporary));
+                            trackedFiles.Add(this.BackendHelper.TrackFile(embeddedFile.OutputPath, TrackedFileType.Intermediate));
                         }
                     }
                 }
diff --git a/src/wix/WixToolset.Core/CommandLine/BuildCommand.cs b/src/wix/WixToolset.Core/CommandLine/BuildCommand.cs
index d289b557..67d2876d 100644
--- a/src/wix/WixToolset.Core/CommandLine/BuildCommand.cs
+++ b/src/wix/WixToolset.Core/CommandLine/BuildCommand.cs
@@ -132,12 +132,7 @@ namespace WixToolset.Core.CommandLine
             {
                 using (new IntermediateFieldContext("wix.lib"))
                 {
-                    var wixlib = this.LibraryPhase(wixobjs, wxls, this.commandLine.BindFiles, this.commandLine.BindPaths, cancellationToken);
-
-                    if (!this.Messaging.EncounteredError)
-                    {
-                        wixlib.Save(this.OutputFile);
-                    }
+                    this.LibraryPhase(wixobjs, wxls, this.commandLine.BindFiles, this.commandLine.BindPaths, cancellationToken);
                 }
             }
             else
@@ -260,7 +255,7 @@ namespace WixToolset.Core.CommandLine
             return intermediates;
         }
 
-        private Intermediate LibraryPhase(IReadOnlyCollection<Intermediate> intermediates, IReadOnlyCollection<Localization> localizations, bool bindFiles, IReadOnlyCollection<IBindPath> bindPaths, CancellationToken cancellationToken)
+        private void LibraryPhase(IReadOnlyCollection<Intermediate> intermediates, IReadOnlyCollection<Localization> localizations, bool bindFiles, IReadOnlyCollection<IBindPath> bindPaths, CancellationToken cancellationToken)
         {
             var context = this.ServiceProvider.GetService<ILibraryContext>();
             context.BindFiles = bindFiles;
@@ -270,18 +265,22 @@ namespace WixToolset.Core.CommandLine
             context.Intermediates = intermediates;
             context.CancellationToken = cancellationToken;
 
-            Intermediate library = null;
             try
             {
                 var librarian = this.ServiceProvider.GetService<ILibrarian>();
-                library = librarian.Combine(context);
+                var result = librarian.Combine(context);
+
+                if (!this.Messaging.EncounteredError)
+                {
+                    result.Library.Save(this.OutputFile);
+
+                    this.LayoutFiles(this.IntermediateFolder, result.TrackedFiles, null, cancellationToken);
+                }
             }
             catch (WixException e)
             {
                 this.Messaging.Write(e.Error);
             }
-
-            return library;
         }
 
         private Intermediate LinkPhase(IEnumerable<Intermediate> intermediates, IEnumerable<string> libraryFiles, ISymbolDefinitionCreator creator, CancellationToken cancellationToken)
@@ -365,19 +364,7 @@ namespace WixToolset.Core.CommandLine
                     return;
                 }
 
-                {
-                    var context = this.ServiceProvider.GetService<ILayoutContext>();
-                    context.Extensions = this.ExtensionManager.GetServices<ILayoutExtension>();
-                    context.TrackedFiles = bindResult.TrackedFiles;
-                    context.FileTransfers = bindResult.FileTransfers;
-                    context.IntermediateFolder = intermediateFolder;
-                    context.TrackingFile = this.TrackingFile;
-                    context.ResetAcls = this.commandLine.ResetAcls;
-                    context.CancellationToken = cancellationToken;
-
-                    var layout = this.ServiceProvider.GetService<ILayoutCreator>();
-                    layout.Layout(context);
-                }
+                this.LayoutFiles(intermediateFolder, bindResult.TrackedFiles, bindResult.FileTransfers, cancellationToken);
             }
             finally
             {
@@ -385,6 +372,21 @@ namespace WixToolset.Core.CommandLine
             }
         }
 
+        private void LayoutFiles(string intermediateFolder, IReadOnlyCollection<ITrackedFile> trackedFiles, IReadOnlyCollection<IFileTransfer> fileTransfers, CancellationToken cancellationToken)
+        {
+            var context = this.ServiceProvider.GetService<ILayoutContext>();
+            context.Extensions = this.ExtensionManager.GetServices<ILayoutExtension>();
+            context.TrackedFiles = trackedFiles;
+            context.FileTransfers = fileTransfers;
+            context.IntermediateFolder = intermediateFolder;
+            context.TrackingFile = this.TrackingFile;
+            context.ResetAcls = this.commandLine.ResetAcls;
+            context.CancellationToken = cancellationToken;
+
+            var layout = this.ServiceProvider.GetService<ILayoutCreator>();
+            layout.Layout(context);
+        }
+
         private IEnumerable<Intermediate> LoadLibraries(IEnumerable<string> libraryFiles, ISymbolDefinitionCreator creator)
         {
             try
diff --git a/src/wix/WixToolset.Core/ILibrarian.cs b/src/wix/WixToolset.Core/ILibrarian.cs
index 0fcedea5..8f57ca67 100644
--- a/src/wix/WixToolset.Core/ILibrarian.cs
+++ b/src/wix/WixToolset.Core/ILibrarian.cs
@@ -5,9 +5,16 @@ namespace WixToolset.Core
     using WixToolset.Data;
     using WixToolset.Extensibility.Data;
 
-#pragma warning disable 1591 // TODO: add documentation
+    /// <summary>
+    /// Create libraries from input intermediates.
+    /// </summary>
     public interface ILibrarian
     {
-        Intermediate Combine(ILibraryContext context);
+        /// <summary>
+        /// Combine intermediates into a single result.
+        /// </summary>
+        /// <param name="context">Library context.</param>
+        /// <returns>Library result.</returns>
+        ILibraryResult Combine(ILibraryContext context);
     }
 }
diff --git a/src/wix/WixToolset.Core/Librarian.cs b/src/wix/WixToolset.Core/Librarian.cs
index 1dd1b44d..2762fb33 100644
--- a/src/wix/WixToolset.Core/Librarian.cs
+++ b/src/wix/WixToolset.Core/Librarian.cs
@@ -21,17 +21,20 @@ namespace WixToolset.Core
             this.ServiceProvider = serviceProvider;
 
             this.Messaging = this.ServiceProvider.GetService<IMessaging>();
+            this.LayoutServices = this.ServiceProvider.GetService<ILayoutServices>();
         }
 
         private IServiceProvider ServiceProvider { get; }
 
         private IMessaging Messaging { get; }
 
+        private ILayoutServices LayoutServices { get; }
+
         /// <summary>
         /// Create a library by combining several intermediates (objects).
         /// </summary>
-        /// <returns>Returns the new library.</returns>
-        public Intermediate Combine(ILibraryContext context)
+        /// <returns>Returns tracked input files and the new library.</returns>
+        public ILibraryResult Combine(ILibraryContext context)
         {
             if (String.IsNullOrEmpty(context.LibraryId))
             {
@@ -43,7 +46,9 @@ namespace WixToolset.Core
                 extension.PreCombine(context);
             }
 
+            ILibraryResult result = this.ServiceProvider.GetService<ILibraryResult>();
             Intermediate library = null;
+            IReadOnlyCollection<ITrackedFile> trackedFiles = null;
             try
             {
                 var sections = context.Intermediates.SelectMany(i => i.Sections).ToList();
@@ -56,7 +61,7 @@ namespace WixToolset.Core
                     return null;
                 }
 
-                this.ResolveFilePathsToEmbed(context, sections);
+                trackedFiles = this.ResolveFilePathsToEmbed(context, sections);
 
                 foreach (var section in sections)
                 {
@@ -71,17 +76,22 @@ namespace WixToolset.Core
             }
             finally
             {
+                result.Library = library;
+                result.TrackedFiles = trackedFiles;
+
                 foreach (var extension in context.Extensions)
                 {
-                    extension.PostCombine(library);
+                    extension.PostCombine(result);
                 }
             }
 
-            return this.Messaging.EncounteredError ? null : library;
+            return result;
         }
 
-        private void ResolveFilePathsToEmbed(ILibraryContext context, IEnumerable<IntermediateSection> sections)
+        private IReadOnlyCollection<ITrackedFile> ResolveFilePathsToEmbed(ILibraryContext context, IEnumerable<IntermediateSection> sections)
         {
+            var trackedFiles = new List<ITrackedFile>();
+
             // Resolve paths to files that are to be embedded in the library.
             if (context.BindFiles)
             {
@@ -105,6 +115,8 @@ namespace WixToolset.Core
                             {
                                 // File was successfully resolved so track the embedded index as the embedded file index.
                                 field.Set(new IntermediateFieldPathValue { Embed = true, Path = file });
+
+                                trackedFiles.Add(this.LayoutServices.TrackFile(file, TrackedFileType.Input, symbol.SourceLineNumbers));
                             }
                             else
                             {
@@ -114,6 +126,8 @@ namespace WixToolset.Core
                     }
                 }
             }
+
+            return trackedFiles;
         }
 
         private void Validate(Intermediate library)
diff --git a/src/wix/WixToolset.Core/LibraryResult.cs b/src/wix/WixToolset.Core/LibraryResult.cs
new file mode 100644
index 00000000..80db2c3a
--- /dev/null
+++ b/src/wix/WixToolset.Core/LibraryResult.cs
@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Core
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using WixToolset.Data;
+    using WixToolset.Extensibility;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    internal class LibraryResult : ILibraryResult
+    {
+        public IReadOnlyCollection<ITrackedFile> TrackedFiles { get; set; }
+
+        public Intermediate Library { get; set; }
+    }
+}
diff --git a/src/wix/WixToolset.Core/WixToolsetServiceProvider.cs b/src/wix/WixToolset.Core/WixToolsetServiceProvider.cs
index 7bbd4075..06dbdfae 100644
--- a/src/wix/WixToolset.Core/WixToolsetServiceProvider.cs
+++ b/src/wix/WixToolset.Core/WixToolsetServiceProvider.cs
@@ -35,6 +35,7 @@ namespace WixToolset.Core
             this.AddService<IPreprocessContext>((provider, singletons) => new PreprocessContext(provider));
             this.AddService<ICompileContext>((provider, singletons) => new CompileContext(provider));
             this.AddService<ILibraryContext>((provider, singletons) => new LibraryContext(provider));
+            this.AddService<ILibraryResult>((provider, singletons) => new LibraryResult());
             this.AddService<ILinkContext>((provider, singletons) => new LinkContext(provider));
             this.AddService<IResolveContext>((provider, singletons) => new ResolveContext(provider));
             this.AddService<IBindContext>((provider, singletons) => new BindContext(provider));