Add type coercion assignment

Update generated code

changelog/pending/20221114--sdk-go--allow-sane-conversions-for-as-map-and-as-array-conversions.yaml

@@ -0,0 +1,4 @@
+changes:
+  - type: feat
+    scope: sdk/go
+    description: Allow sane conversions for `As*Map*` and `As*Array*` conversions.

sdk/go/pulumi/generate/main.go

@@ -213,6 +213,7 @@ func makeBuiltins(primitives []*builtin) []*builtin {
 	// Augment primitives with array and map types.
 	var builtins []*builtin
 	for _, p := range primitives {
+		p.Strategy = "primitive"
 		name := ""
 		if p.Name != "Input" {
 			builtins = append(builtins, p)
@@ -242,9 +243,6 @@ func makeBuiltins(primitives []*builtin) []*builtin {
 
 			InnerElementType: p.Type,
 		}
-		if p.Type != "interface{}" {
-			arrType.Strategy = "array-contravariance"
-		}
 		builtins = append(builtins, arrType)
 		mapType := &builtin{
 			Name:          name + "Map",

sdk/go/pulumi/generate/templates/types_builtins.go.template

@@ -19,7 +19,6 @@ package pulumi
 
 import (
 	"context"
-	"fmt"
 	"reflect"
 )
 
@@ -207,36 +206,26 @@ func getResolvedValue(input Input) (reflect.Value, bool) {
 }
 
 {{range .Builtins}}
-{{ if eq .Strategy "array-contravariance" }}
+{{ if eq .Strategy "primitive" }}
 // As{{.Name}}Output asserts that the type of the AnyOutput's underlying interface{} value is
-// {{.ElementType}} or []interface{} and returns a `{{.Name}}Output` with that value.
-// As{{.Name}}Output panics if the value was not the expected type or a compatible array.
+// {{.ElementType}} and returns a `{{.Name}}Output` with that value. As{{.Name}}Output panics if the value
+// was not the expected type.
 func (a AnyOutput) As{{.Name}}Output() {{.Name}}Output {
-	return a.ApplyT(func(i interface{}) ({{.ElementType}}, error) {
-		if array, ok := i.([]interface{}); ok {
-			if len(array) == 0 {
-				return nil, nil
-			}
-			out := make([]{{.InnerElementType}}, len(array))
-			for i, v := range array {
-				value, ok := v.({{.InnerElementType}})
-				if !ok {
-					return nil, fmt.Errorf("[%d]: expected value of type {{.InnerElementType}}, got %T", i, v)
-				}
-				out[i] = value
-			}
-			return out, nil
-		}
-		return i.({{.ElementType}}), nil
+	return a.ApplyT(func(i interface{}) {{.ElementType}} {
+		return i.({{.ElementType}})
 	}).({{.Name}}Output)
 }
 {{else}}
 // As{{.Name}}Output asserts that the type of the AnyOutput's underlying interface{} value is
-// {{.ElementType}} and returns a `{{.Name}}Output` with that value. As{{.Name}}Output panics if the value
-// was not the expected type.
+// {{.ElementType}} or a compatible type and returns a `{{.Name}}Output` with that value.
+// As{{.Name}}Output panics if the value was not the expected type or a compatible type.
 func (a AnyOutput) As{{.Name}}Output() {{.Name}}Output {
-	return a.ApplyT(func(i interface{}) {{.ElementType}} {
-		return i.({{.ElementType}})
+	return a.ApplyT(func(i interface{}) ({{.ElementType}}, error) {
+        v, err := coerceTypeConversion(i, reflect.TypeOf((*{{.ElementType}})(nil)).Elem())
+        if err != nil {
+           return nil, err
+        }
+        return v.({{.ElementType}}), nil
 	}).({{.Name}}Output)
 }
 {{end}}

sdk/go/pulumi/types.go

@@ -1,4 +1,4 @@
-// Copyright 2016-2020, Pulumi Corporation.
+// Copyright 2016-2022, Pulumi Corporation.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -1248,3 +1248,64 @@ func init() {
 	RegisterOutputType(ResourceOutput{})
 	RegisterOutputType(ResourceArrayOutput{})
 }
+
+// coerceTypeConversion assigns src to dst, performing deep type coercion as necessary.
+func coerceTypeConversion(src interface{}, dst reflect.Type) (interface{}, error) {
+	makeError := func(src, dst reflect.Value) error {
+		return fmt.Errorf("expected value of type %s, not %s", dst.Type(), src.Type())
+	}
+	var coerce func(reflect.Value, reflect.Value) error
+	coerce = func(src, dst reflect.Value) error {
+		if src.Type().Kind() == reflect.Interface && !src.IsNil() {
+			src = src.Elem()
+		}
+		if src.Type().AssignableTo(dst.Type()) {
+			dst.Set(src)
+			return nil
+		}
+		switch dst.Type().Kind() {
+		case reflect.Map:
+			if src.Kind() != reflect.Map {
+				return makeError(src, dst)
+			}
+
+			dst.Set(reflect.MakeMapWithSize(dst.Type(), src.Len()))
+
+			for iter := src.MapRange(); iter.Next(); {
+				dstKey := reflect.New(dst.Type().Key()).Elem()
+				dstVal := reflect.New(dst.Type().Elem()).Elem()
+				if err := coerce(iter.Key(), dstKey); err != nil {
+					return fmt.Errorf("invalid key: %w", err)
+				}
+				if err := coerce(iter.Value(), dstVal); err != nil {
+					return fmt.Errorf("[%#v]: %w", dstKey.Interface(), err)
+				}
+				dst.SetMapIndex(dstKey, dstVal)
+			}
+
+			return nil
+		case reflect.Slice:
+			if src.Kind() != reflect.Slice {
+				return makeError(src, dst)
+			}
+			dst.Set(reflect.MakeSlice(dst.Type(), src.Len(), src.Cap()))
+			for i := 0; i < src.Len(); i++ {
+				dstVal := reflect.New(dst.Type().Elem()).Elem()
+				if err := coerce(src.Index(i), dstVal); err != nil {
+					return fmt.Errorf("[%d]: %w", i, err)
+				}
+				dst.Index(i).Set(dstVal)
+			}
+			return nil
+		default:
+			return makeError(src, dst)
+		}
+	}
+
+	srcV, dstV := reflect.ValueOf(src), reflect.New(dst).Elem()
+
+	if err := coerce(srcV, dstV); err != nil {
+		return nil, err
+	}
+	return dstV.Interface(), nil
+}