[dotnet/program-gen] Fixes list initializer for plain lists in resource properties

changelog/pending/20230731--programgen-dotnet--fixes-list-initializer-for-plain-lists-in-resource-properties.yaml

@@ -0,0 +1,4 @@
+changes:
+- type: fix
+  scope: programgen/dotnet
+  description: Fixes list initializer for plain lists in resource properties

pkg/codegen/dotnet/gen_program.go

@@ -73,6 +73,15 @@ type generator struct {
 	// Program generation options
 	generateOptions GenerateProgramOptions
 	isComponent     bool
+	// when creating a list of items, we need to know the type of the list
+	// if is it a plain list, then `new()` should be used because we are creating List<T>
+	// however if we have InputList<T> or anything else, we use `new[]` because InputList<T> can be implicitly casted
+	// from an array
+	listInitializer string
+}
+
+func (g *generator) resetListInitializer() {
+	g.listInitializer = "new[]"
 }
 
 const (
@@ -126,6 +135,7 @@ func GenerateProgramWithOptions(
 		functionArgs:    functionArgs,
 		functionInvokes: map[string]*schema.Function{},
 		generateOptions: options,
+		listInitializer: "new[]",
 	}
 
 	g.Formatter = format.NewFormatter(g)
@@ -164,6 +174,7 @@ func GenerateProgramWithOptions(
 			functionInvokes: map[string]*schema.Function{},
 			generateOptions: options,
 			isComponent:     true,
+			listInitializer: "new[]",
 		}
 
 		componentGenerator.Formatter = format.NewFormatter(componentGenerator)
@@ -1205,6 +1216,19 @@ func AnnotateComponentInputs(component *pcl.Component) {
 	}
 }
 
+func isPlainResourceProperty(r *pcl.Resource, name string) bool {
+	if r.Schema == nil {
+		return false
+	}
+
+	for _, property := range r.Schema.InputProperties {
+		if property.Name == name {
+			return property.Plain
+		}
+	}
+	return false
+}
+
 // genResource handles the generation of instantiations of non-builtin resources.
 func (g *generator) genResource(w io.Writer, r *pcl.Resource) {
 	qualifiedMemberName := g.resourceTypeName(r)
@@ -1247,7 +1271,12 @@ func (g *generator) genResource(w io.Writer, r *pcl.Resource) {
 			g.Indented(func() {
 				for _, attr := range r.Inputs {
 					g.Fgenf(w, "%s%s =", g.Indent, propertyName(attr.Name))
+					if isPlainResourceProperty(r, attr.Name) {
+						g.listInitializer = "new()"
+					}
+
 					g.Fgenf(w, " %.v,\n", attr.Value)
+					g.resetListInitializer()
 				}
 			})
 			g.Fgenf(w, "%s}%s)", g.Indent, g.genResourceOptions(r.Options, "CustomResourceOptions"))

pkg/codegen/dotnet/gen_program_expressions.go

@@ -1032,14 +1032,14 @@ func (g *generator) isListOfDifferentTypes(expr *model.TupleConsExpression) bool
 func (g *generator) GenTupleConsExpression(w io.Writer, expr *model.TupleConsExpression) {
 	switch len(expr.Expressions) {
 	case 0:
-		g.Fgen(w, "new[] {}")
+		g.Fgenf(w, "%s {}", g.listInitializer)
 	default:
 		if !g.isListOfDifferentTypes(expr) {
-			// only generate this when we don't have a list of union types
-			// list of a union is mapped to InputList<object>
+			// only generate a list initializer when we don't have a list of union types
+			// because list of a union is mapped to InputList<object>
 			// which means new[] will not work because type-inference won't
-			// know the type of the array before hand
-			g.Fgen(w, "new[]")
+			// know the type of the array beforehand
+			g.Fgenf(w, "%s", g.listInitializer)
 		}
 
 		g.Fgenf(w, "\n%s{", g.Indent)

pkg/codegen/testing/test/program_driver.go

@@ -361,6 +361,11 @@ var PulumiPulumiProgramTests = []ProgramTest{
 		Description: "Tests that interpolated string keys are supported in maps. ",
 		Skip:        allProgLanguages.Except("nodejs").Except("python"),
 	},
+	{
+		Directory:   "csharp-plain-lists",
+		Description: "Tests that plain lists are supported in C#",
+		Skip:        allProgLanguages.Except("dotnet"),
+	},
 	{
 		Directory:   "csharp-typed-for-expressions",
 		Description: "Testing for expressions with typed target expressions in csharp",

pkg/codegen/testing/test/testdata/csharp-plain-lists-pp/csharp-plain-lists.pp

@@ -0,0 +1,6 @@
+resource vpc "awsx:ec2:Vpc" {
+    subnetSpecs = [
+        { type = "Public", cidrMask = 22 },
+        { type = "Private", cidrMask = 20 }
+    ]
+}

pkg/codegen/testing/test/testdata/csharp-plain-lists-pp/dotnet/csharp-plain-lists.cs

@@ -0,0 +1,26 @@
+using System.Collections.Generic;
+using System.Linq;
+using Pulumi;
+using Awsx = Pulumi.Awsx;
+
+return await Deployment.RunAsync(() => 
+{
+    var vpc = new Awsx.Ec2.Vpc("vpc", new()
+    {
+        SubnetSpecs = new()
+        {
+            new Awsx.Ec2.Inputs.SubnetSpecArgs
+            {
+                Type = Awsx.Ec2.SubnetType.Public,
+                CidrMask = 22,
+            },
+            new Awsx.Ec2.Inputs.SubnetSpecArgs
+            {
+                Type = Awsx.Ec2.SubnetType.Private,
+                CidrMask = 20,
+            },
+        },
+    });
+
+});
+