[ProjectModel] Optimize allocations on evaluation

Avoid enumerator boxing and avoid allocating a string for all the property imports

3 files changed, 30 insertions, 9 deletions

diff --git a/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.Extensions/ImportSearchPathExtensionNode.cs b/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.Extensions/ImportSearchPathExtensionNode.cs
index 7835f1cc35..bb3875187d 100644
--- a/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.Extensions/ImportSearchPathExtensionNode.cs
+++ b/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.Extensions/ImportSearchPathExtensionNode.cs
@@ -36,6 +36,15 @@ namespace MonoDevelop.Projects.Extensions
 		[NodeAttribute ("property")]
 		public string Property { get; set; }
 
+		string msbuildProperty;
+		internal string MSBuildProperty {
+			get {
+				if (msbuildProperty == null)
+					msbuildProperty = "$(" + Property + ")";
+				return msbuildProperty;
+			}
+		}
+
 		string path;
 
 		public new string Path {
diff --git a/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/DefaultMSBuildEngine.cs b/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/DefaultMSBuildEngine.cs
index 90adb3c67b..031bd2492f 100644
--- a/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/DefaultMSBuildEngine.cs
+++ b/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/DefaultMSBuildEngine.cs
@@ -1042,12 +1042,12 @@ namespace MonoDevelop.Projects.MSBuild
 			return CreateEvaluatedItem (context, project, project.Project, item, context.EvaluateString (item.Include));
 		}
 
-		IEnumerable<ProjectInfo> GetImportedProjects (ProjectInfo project, MSBuildImport import)
+		IReadOnlyList<ProjectInfo> GetImportedProjects (ProjectInfo project, MSBuildImport import)
 		{
 			List<ProjectInfo> prefProjects;
 			if (project.ImportedProjects.TryGetValue (import, out prefProjects))
 				return prefProjects;
-			return Enumerable.Empty<ProjectInfo> ();
+			return Array.Empty<ProjectInfo> ();
 		}
 
 		void AddImportedProject (ProjectInfo project, MSBuildImport import, ProjectInfo imported)
@@ -1068,10 +1068,12 @@ namespace MonoDevelop.Projects.MSBuild
 
 		void Evaluate (ProjectInfo project, MSBuildEvaluationContext context, MSBuildImport import, bool evalItems)
 		{
-			if (evalItems) {
-				// Properties have already been evaluated
-				// Don't evaluate properties, only items and other elements
-				foreach (var p in GetImportedProjects (project, import)) {
+			if (evalItems) {

+				// Properties have already been evaluated

+				// Don't evaluate properties, only items and other elements

+				var importedProjects = GetImportedProjects (project, import);

+				for (int i = 0; i < importedProjects.Count; ++i) {
+					var p = importedProjects [i];
 					
 					EvaluateProject (p, new MSBuildEvaluationContext (context), true);
 
@@ -1115,9 +1117,19 @@ namespace MonoDevelop.Projects.MSBuild
 			// In that case, look in fallback search paths
 
 			if (keepSearching) {
-				foreach (var prop in context.GetProjectImportSearchPaths ()) {
-					if (import.Project.IndexOf ("$(" + prop.Property + ")", StringComparison.OrdinalIgnoreCase) == -1)
+				// Short-circuit if we don't have an import that is done via a property.
+				int propertyStart = import.Project.IndexOf ("$(", StringComparison.Ordinal);
+				if (propertyStart == -1)
+					return;
+				
+				var importSearchPaths = context.GetProjectImportSearchPaths ();
+				for (int i = 0; i < importSearchPaths.Count; ++i) {
+					var prop = importSearchPaths [i];
+
+					// Start searching from where the property was found.
+					if (import.Project.IndexOf (prop.MSBuildProperty, propertyStart, StringComparison.OrdinalIgnoreCase) == -1)
 						continue;
+
 					files = GetImportFiles (project, context, import, prop.Property, prop.Path, out resolvedSdksPath, out keepSearching);
 					if (files != null) {
 						foreach (var f in files)
diff --git a/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/MSBuildEvaluationContext.cs b/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/MSBuildEvaluationContext.cs
index 7afbf74a5e..0f37e215f9 100644
--- a/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/MSBuildEvaluationContext.cs
+++ b/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/MSBuildEvaluationContext.cs
@@ -227,7 +227,7 @@ namespace MonoDevelop.Projects.MSBuild
 			get { return project; }
 		}
 
-		public IEnumerable<ImportSearchPathExtensionNode> GetProjectImportSearchPaths ()
+		public IReadOnlyList<ImportSearchPathExtensionNode> GetProjectImportSearchPaths ()
 		{
 			if (parentContext != null)
 				return parentContext.GetProjectImportSearchPaths ();