Report error if ProjectAssetsFile is not set, and update tests

Author: dsplaisted

src/Tasks/Microsoft.NET.Build.Tasks/CheckForTargetInAssetsFile.cs

@@ -11,7 +11,6 @@ namespace Microsoft.NET.Build.Tasks
 {
     public class CheckForTargetInAssetsFile : TaskBase
     {
-        [Required]
         public string AssetsFilePath { get; set; }
 
         [Required]

src/Tasks/Microsoft.NET.Build.Tasks/FilterResolvedFiles.cs

@@ -19,7 +19,6 @@ public class FilterResolvedFiles : TaskBase
         private readonly List<ITaskItem> _assembliesToPublish = new List<ITaskItem>();
         private readonly List<ITaskItem> _packagesResolved = new List<ITaskItem>();
 
-        [Required]
         public string AssetsFilePath { get; set; }
 
         [Required]

src/Tasks/Microsoft.NET.Build.Tasks/GenerateDepsFile.cs

@@ -23,7 +23,6 @@ public class GenerateDepsFile : TaskBase
         [Required]
         public string ProjectPath { get; set; }
 
-        [Required]
         public string AssetsFilePath { get; set; }
 
         [Required]

src/Tasks/Microsoft.NET.Build.Tasks/GenerateRuntimeConfigurationFiles.cs

@@ -21,7 +21,6 @@ namespace Microsoft.NET.Build.Tasks
     /// </summary>
     public class GenerateRuntimeConfigurationFiles : TaskBase
     {
-        [Required]
         public string AssetsFilePath { get; set; }
 
         [Required]

src/Tasks/Microsoft.NET.Build.Tasks/LoadAssetsFile.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.NET.Build.Tasks
+{
+    public sealed class LoadAssetsFile : TaskBase
+    {
+        /// <summary>
+        /// The assets file to process
+        /// </summary>
+        public string ProjectAssetsFile
+        {
+            get; set;
+        }
+
+        protected override void ExecuteCore()
+        {
+            var lockFile = new LockFileCache(BuildEngine4).GetLockFile(ProjectAssetsFile);
+        }
+    }
+}

src/Tasks/Microsoft.NET.Build.Tasks/LockFileCache.cs

@@ -20,6 +20,10 @@ public LockFileCache(IBuildEngine4 buildEngine)
 
         public LockFile GetLockFile(string path)
         {
+            if (string.IsNullOrEmpty(path))
+            {
+                throw new BuildErrorException(Strings.AssetsFileNotSet);
+            }
             if (!Path.IsPathRooted(path))
             {
                 throw new BuildErrorException(Strings.AssetsFilePathNotRooted, path);

src/Tasks/Microsoft.NET.Build.Tasks/ReportAssetsLogMessages.cs

@@ -30,7 +30,6 @@ public sealed class ReportAssetsLogMessages : TaskBase
         /// <summary>
         /// The assets file to process
         /// </summary>
-        [Required]
         public string ProjectAssetsFile
         {
             get; set;

src/Tasks/Microsoft.NET.Build.Tasks/ResolvePackageAssets.cs

@@ -13,7 +13,6 @@ namespace Microsoft.NET.Build.Tasks
 {
     public class ResolvePackageAssets : TaskBase
     {
-        [Required]
         public string ProjectAssetsFile { get; set; }
 
         [Required]

src/Tasks/Microsoft.NET.Build.Tasks/ResolvePackageDependencies.cs

@@ -93,7 +93,6 @@ public string ProjectPath
         /// <summary>
         /// The assets file to process
         /// </summary>
-        [Required]
         public string ProjectAssetsFile
         {
             get; set;

src/Tasks/Microsoft.NET.Build.Tasks/ResolvePublishAssemblies.cs

@@ -20,7 +20,6 @@ public class ResolvePublishAssemblies : TaskBase
         [Required]
         public string ProjectPath { get; set; }
 
-        [Required]
         public string AssetsFilePath { get; set; }
 
         [Required]