Merge pull request #145 from mono/fix-load-system-text-json

Fix loading System.Text.Json in ALC

Mono.TextTemplating.Tests/AssemblyLoadContextTests.cs

@@ -31,6 +31,21 @@ protected override void VerifyFinalState ((SnapshotSet<string> assembliesInDefau
 
 		state.allContexts.AssertUnchanged ();
 	}
+
+	/// Issue #143: System.Text.Json is a framework assembly on .NET Core 3.0 and does not need to be specified by absolute path
+	[Fact]
+	public async Task LoadSystemTextJson ()
+	{
+		string template = "<#@ assembly name=\"System.Text.Json\" #><#=System.Text.Json.JsonValueKind.Array.ToString()#>";
+
+		var gen = new TemplateGenerator ();
+		(_, string content, _) = await gen.ProcessTemplateAsync (null, template, null);
+
+		CompilerError firstError = gen.Errors.OfType<CompilerError> ().FirstOrDefault ();
+		Assert.Null (firstError);
+
+		Assert.Equal ("Array", content);
+	}
 }
 
 #endif

Mono.TextTemplating/Mono.TextTemplating/TemplateAssemblyLoadContext.cs

@@ -3,6 +3,7 @@
 
 #if FEATURE_ASSEMBLY_LOAD_CONTEXT
 
+using System;
 using System.CodeDom.Compiler;
 using System.IO;
 using System.Reflection;
@@ -52,9 +53,20 @@ protected override Assembly Load (AssemblyName assemblyName)
 				return hostAssembly;
 			}
 
-			foreach (var asmFile in templateAssemblyFiles) {
-				if (assemblyName.Name == Path.GetFileNameWithoutExtension (asmFile)) {
-					return LoadFromAssemblyPath (asmFile);
+			for (int i = 0; i < templateAssemblyFiles.Length; i++) {
+				var asmFile = templateAssemblyFiles[i];
+				if (asmFile is null) {
+					continue;
+				}
+				if (MemoryExtensions.Equals (assemblyName.Name, Path.GetFileNameWithoutExtension (asmFile.AsSpan()), StringComparison.OrdinalIgnoreCase)) {
+					// if the file doesn't exist, fall through to host.ResolveAssemblyReference
+					if (File.Exists (asmFile)) {
+						return LoadFromAssemblyPath (asmFile);
+					} else {
+						// null out the missing file so we don't check it exists again
+						templateAssemblyFiles[i] = null;
+						break;
+					}
 				}
 			}