feat(go): Runtime interface type casting

Adds an implementation map to all code generated getters and method
invocations to pass to the runtime. This allows the runtime to construct
concrete types when the return type of the function is a go interface.

Adds test for `UpcasingReflectable` which returns
`[]ReflectableEntryIface` type on the `entries` property.

packages/@jsii/go-runtime/jsii-calc-test/main_test.go

@@ -5,6 +5,7 @@ import (
 	"github.com/aws-cdk/jsii/jsii-experimental"
 	"math"
 	"os"
+	"strings"
 	"testing"
 )
 
@@ -54,24 +55,25 @@ func TestCalculator(t *testing.T) {
 	})
 }
 
-// func TestUpcasingReflectable(t *testing.T) {
-// 	delegate := make(map[string]interface{})
-// 	key, val := "key1", "value1"
-// 	delegate[key] = val
-// 	upReflectable := calc.NewUpcasingReflectable(delegate)
-// 	entries := upReflectable.GetEntries()
+func TestUpcasingReflectable(t *testing.T) {
+	delegate := make(map[string]interface{})
+	key, val := "key1", "value1"
+	delegate[key] = val
+	upReflectable := calc.NewUpcasingReflectable(delegate)
+	entries := upReflectable.GetEntries()
 
-// 	if len(entries) != 1 {
-// 		t.Errorf("Entries expected to have length of: 1; Actual: %d", len(entries))
-// 	}
+	if len(entries) != 1 {
+		t.Errorf("Entries expected to have length of: 1; Actual: %d", len(entries))
+	}
 
-// 	entry := entries[0]
+	entry := entries[0]
+	upperKey := strings.ToUpper(key)
+	actualKey, actualVal := entry.GetKey(), entry.GetValue()
+	if actualKey != upperKey {
+		t.Errorf("Expected Key: %s; Received Key: %s", upperKey, actualKey)
+	}
 
-// 	// t.Logf("Pointer entry obj: %s\n", entry)
-// 	// t.Logf("Pointer entry addr: %p\n", entry)
-// 	actualKey, actualVal := entry.GetKey(), entry.GetValue()
-// 	if actualKey != key || actualVal != val {
-// 		t.Errorf("Expected Key: %s; Received Key: %s", key, actualKey)
-// 		t.Errorf("Expected Value: %s; Received Value: %s", val, actualVal)
-// 	}
-// }
+	if actualVal != val {
+		t.Errorf("Expected Value: %s; Received Value: %s", val, actualVal)
+	}
+}

packages/@jsii/go-runtime/jsii-experimental/runtime.go

@@ -8,6 +8,8 @@ import (
 	"regexp"
 )
 
+type implementationMap = map[reflect.Type]reflect.Type
+
 // Load ensures a npm package is loaded in the jsii kernel.
 func Load(name string, version string, tarball []byte) {
 	client := getClient()
@@ -58,7 +60,7 @@ func Create(fqn FQN, args []interface{}, interfaces []FQN, overrides []Override,
 
 // Invoke will call a method on a jsii class instance. The response should be
 // decoded into the expected return type for the method being called.
-func Invoke(obj interface{}, method string, args []interface{}, returns bool, returnsPtr interface{}) {
+func Invoke(obj interface{}, method string, args []interface{}, returns bool, returnsPtr interface{}, implMap implementationMap) {
 	client := getClient()
 
 	// Find reference to class instance in client
@@ -82,11 +84,11 @@ func Invoke(obj interface{}, method string, args []interface{}, returns bool, re
 	}
 
 	if returns {
-		castAndSetToPtr(returnsPtr, res.Result)
+		castAndSetToPtr(returnsPtr, res.Result, implMap)
 	}
 }
 
-func InvokeStatic(fqn FQN, method string, args []interface{}, returns bool, returnsPtr interface{}) {
+func InvokeStatic(fqn FQN, method string, args []interface{}, returns bool, returnsPtr interface{}, implMap implementationMap) {
 	client := getClient()
 
 	res, err := client.sinvoke(staticInvokeRequest{
@@ -101,11 +103,11 @@ func InvokeStatic(fqn FQN, method string, args []interface{}, returns bool, retu
 	}
 
 	if returns {
-		castAndSetToPtr(returnsPtr, res.Result)
+		castAndSetToPtr(returnsPtr, res.Result, implMap)
 	}
 }
 
-func Get(obj interface{}, property string, returnsPtr interface{}) {
+func Get(obj interface{}, property string, returnsPtr interface{}, implMap implementationMap) {
 	client := getClient()
 
 	// Find reference to class instance in client
@@ -127,10 +129,10 @@ func Get(obj interface{}, property string, returnsPtr interface{}) {
 		panic(err)
 	}
 
-	castAndSetToPtr(returnsPtr, res.Value)
+	castAndSetToPtr(returnsPtr, res.Value, implMap)
 }
 
-func StaticGet(fqn FQN, property string, returnsPtr interface{}) {
+func StaticGet(fqn FQN, property string, returnsPtr interface{}, implMap implementationMap) {
 	client := getClient()
 
 	res, err := client.sget(staticGetRequest{
@@ -143,7 +145,7 @@ func StaticGet(fqn FQN, property string, returnsPtr interface{}) {
 		panic(err)
 	}
 
-	castAndSetToPtr(returnsPtr, res.Value)
+	castAndSetToPtr(returnsPtr, res.Value, implMap)
 }
 
 func Set(obj interface{}, property string, value interface{}) {
@@ -211,10 +213,31 @@ func castValToRef(data interface{}) (objref, bool) {
 // argument to be the same type. Then it sets the value of the pointer element
 // to be the newly casted data. This is used to cast payloads from JSII to
 // expected return types for Get and Invoke functions.
-func castAndSetToPtr(ptr interface{}, data interface{}) {
+func castAndSetToPtr(ptr interface{}, data interface{}, implMap implementationMap) {
 	ptrVal := reflect.ValueOf(ptr).Elem()
-	val := reflect.ValueOf(data)
-	ptrVal.Set(val)
+	dataVal := reflect.ValueOf(data)
+
+	ref, isRef := castValToRef(data)
+
+	if ptrVal.Kind() == reflect.Slice && dataVal.Kind() == reflect.Slice {
+		// If return type is a slice, recursively cast elements
+		for i := 0; i < dataVal.Len(); i++ {
+			innerType := ptrVal.Type().Elem()
+			inner := reflect.New(innerType)
+
+			castAndSetToPtr(inner.Interface(), dataVal.Index(i).Interface(), implMap)
+			ptrVal.Set(reflect.Append(ptrVal, inner.Elem()))
+		}
+	} else if isRef {
+		// If return data is JSII object references, add to objects table.
+		concreteType := implMap[ptrVal.Type()]
+		ptrVal.Set(reflect.New(concreteType))
+		client := getClient()
+		client.objects[ptrVal.Interface()] = ref.JsiiInstanceId
+	} else {
+		val := reflect.ValueOf(data)
+		ptrVal.Set(val)
+	}
 }
 
 // Close finalizes the runtime process, signalling the end of the execution to

packages/jsii-pacmak/lib/targets/go/package.ts

@@ -87,6 +87,14 @@ export abstract class Package {
     return findTypeInTree(this, fqn);
   }
 
+  public get importPath(): string {
+    const moduleName = this.root.moduleName;
+    const prefix = moduleName !== '' ? `${moduleName}/` : '';
+    const rootPackageName = this.root.packageName;
+    const suffix = this.filePath !== '' ? `/${this.filePath}` : '';
+    return `${prefix}${rootPackageName}${suffix}`;
+  }
+
   public emit(context: EmitContext): void {
     const { code } = context;
     code.openFile(this.file);
@@ -123,25 +131,36 @@ export abstract class Package {
     );
   }
 
+  protected get usesReflectionPackage(): boolean {
+    return (
+      this.types.some((type) => type.usesReflectionPackage) ||
+      this.submodules.some((sub) => sub.usesReflectionPackage)
+    );
+  }
+
   private emitImports(code: CodeMaker) {
     code.open('import (');
     if (this.usesRuntimePackage) {
       code.line(`${JSII_RT_ALIAS} "${JSII_RT_MODULE_NAME}"`);
     }
 
+    if (this.usesInitPackage) {
+      code.line(
+        `${JSII_INIT_ALIAS} "${this.root.moduleName}/${this.root.packageName}/${JSII_INIT_PACKAGE}"`,
+      );
+    }
+
+    if (this.usesReflectionPackage) {
+      code.line(`"reflect"`);
+    }
+
     for (const packageName of this.dependencyImports) {
       // If the module is the same as the current one being written, don't emit an import statement
       if (packageName !== this.packageName) {
         code.line(`"${packageName}"`);
       }
     }
 
-    if (this.usesInitPackage) {
-      code.line(
-        `${JSII_INIT_ALIAS} "${this.root.moduleName}/${this.root.packageName}/${JSII_INIT_PACKAGE}"`,
-      );
-    }
-
     code.close(')');
     code.line();
   }
@@ -188,6 +207,7 @@ export class RootPackage extends Package {
   public emit(context: EmitContext): void {
     super.emit(context);
     this.emitJsiiPackage(context);
+    // this.emitTypeMapPackage(context);
     this.readme?.emit(context);
   }
 
@@ -245,10 +265,12 @@ export class RootPackage extends Package {
         );
       }
     }
+
     code.close(')');
     code.line();
     code.line('var once sync.Once');
     code.line();
+
     code.line(
       `// ${JSII_INIT_FUNC} performs the necessary work for the enclosing`,
     );
@@ -268,6 +290,7 @@ export class RootPackage extends Package {
     );
     code.close('})');
     code.close('}');
+
     code.closeFile(file);
   }
 }

packages/jsii-pacmak/lib/targets/go/runtime/constants.ts

@@ -8,6 +8,8 @@ export const JSII_INIT_PACKAGE = 'jsii';
 export const JSII_INIT_FUNC = 'Initialize';
 // Alias used for the jsii init
 export const JSII_INIT_ALIAS = '_init_';
+// Type of global implementation map
+export const JSII_IMPL_MAP_TYPE = `map[reflect.Type]reflect.Type`;
 
 // Function to make create request
 export const JSII_CREATE_FUNC = `${JSII_RT_ALIAS}.Create`;

packages/jsii-pacmak/lib/targets/go/runtime/method-call.ts

@@ -1,7 +1,11 @@
 import { CodeMaker } from 'codemaker';
 
 import { GoMethod } from '../types';
-import { JSII_INVOKE_FUNC, JSII_SINVOKE_FUNC } from './constants';
+import {
+  JSII_INVOKE_FUNC,
+  JSII_SINVOKE_FUNC,
+  JSII_IMPL_MAP_TYPE,
+} from './constants';
 import { slugify, emitInitialization } from './util';
 
 export class MethodCall {
@@ -17,6 +21,7 @@ export class MethodCall {
 
   private emitDynamic(code: CodeMaker) {
     code.line(`var ${this.returnVarName} ${this.concreteReturnType}`);
+    code.line(`${this.implMapVar} := make(${JSII_IMPL_MAP_TYPE})`);
     code.open(`${JSII_INVOKE_FUNC}(`);
 
     const returnsArg = this.parent.returnsRef
@@ -28,6 +33,7 @@ export class MethodCall {
     code.line(`${this.argsString},`);
     code.line(`${this.returnsVal ? 'true' : 'false'},`);
     code.line(`${returnsArg},`);
+    code.line(`${this.implMapVar},`);
 
     code.close(`)`);
 
@@ -39,6 +45,7 @@ export class MethodCall {
   private emitStatic(code: CodeMaker) {
     emitInitialization(code);
     code.line(`var ${this.returnVarName} ${this.concreteReturnType}`);
+    code.line(`${this.implMapVar} := make(${JSII_IMPL_MAP_TYPE})`);
 
     code.open(`${JSII_SINVOKE_FUNC}(`);
 
@@ -47,6 +54,7 @@ export class MethodCall {
     code.line(`${this.argsString},`);
     code.line(`${this.returnsVal ? 'true' : 'false'},`);
     code.line(`&${this.returnVarName},`);
+    code.line(`${this.implMapVar},`);
 
     code.close(`)`);
 
@@ -62,6 +70,13 @@ export class MethodCall {
     );
   }
 
+  private get implMapVar(): string {
+    return slugify(
+      'implMap',
+      this.parent.parameters.map((p) => p.name),
+    );
+  }
+
   private get returnsVal(): boolean {
     return Boolean(this.parent.reference && !this.parent.reference.void);
   }

packages/jsii-pacmak/lib/targets/go/runtime/property-access.ts

@@ -6,6 +6,7 @@ import {
   JSII_SET_FUNC,
   JSII_SGET_FUNC,
   JSII_SSET_FUNC,
+  JSII_IMPL_MAP_TYPE,
 } from './constants';
 import { slugify, emitInitialization } from './util';
 
@@ -14,12 +15,24 @@ export class GetProperty {
 
   public emit(code: CodeMaker) {
     const resultVar = slugify('returns', [this.parent.instanceArg]);
+    const implMapVar = slugify('implMap', [this.parent.instanceArg]);
     code.line(`var ${resultVar} ${this.parent.returnType}`);
+    code.line(`${implMapVar} := make(${JSII_IMPL_MAP_TYPE})`);
+
+    const implMap =
+      this.parent.reference?.scopedImplMap(this.parent.parent.pkg) ?? [];
+    if (implMap.length) {
+      const [interfaceName, structName] = implMap;
+      code.line(
+        `${implMapVar}[reflect.TypeOf((*${interfaceName})(nil)).Elem()] = reflect.TypeOf((*${structName})(nil)).Elem()`,
+      );
+    }
 
     code.open(`${JSII_GET_FUNC}(`);
     code.line(`${this.parent.instanceArg},`);
     code.line(`"${this.parent.property.name}",`);
     code.line(`&${resultVar},`);
+    code.line(`${implMapVar},`);
     code.close(`)`);
 
     code.line(`return ${resultVar}`);
@@ -44,12 +57,24 @@ export class StaticGetProperty {
   public emit(code: CodeMaker) {
     emitInitialization(code);
     const resultVar = slugify('returns', []);
+    const implMapVar = slugify('implMap', [this.parent.instanceArg]);
     code.line(`var ${resultVar} ${this.parent.returnType}`);
+    code.line(`${implMapVar} := make(${JSII_IMPL_MAP_TYPE})`);
+
+    const implMap =
+      this.parent.reference?.scopedImplMap(this.parent.parent.pkg) ?? [];
+    if (implMap.length) {
+      const [interfaceName, structName] = implMap;
+      code.line(
+        `${implMapVar}[reflect.TypeOf((*${interfaceName})(nil)).Elem()] = reflect.TypeOf((*${structName})(nil)).Elem()`,
+      );
+    }
 
     code.open(`${JSII_SGET_FUNC}(`);
     code.line(`"${this.parent.parent.fqn}",`);
     code.line(`"${this.parent.property.name}",`);
     code.line(`&${resultVar},`);
+    code.line(`${implMapVar},`);
     code.close(`)`);
 
     code.line(`return ${resultVar}`);

packages/jsii-pacmak/lib/targets/go/types/class.ts

@@ -84,6 +84,13 @@ export class GoClass extends GoStruct {
     );
   }
 
+  public get usesReflectionPackage() {
+    return (
+      this.properties.some((p) => p.usesReflectionPackage) ||
+      this.methods.some((m) => m.usesReflectionPackage)
+    );
+  }
+
   protected emitInterface(context: EmitContext): void {
     const { code } = context;
     code.line('// Class interface'); // FIXME for debugging
@@ -241,6 +248,10 @@ export class ClassMethod extends GoMethod {
   public get instanceArg(): string {
     return this.parent.name.substring(0, 1).toLowerCase();
   }
+
+  public get usesReflectionPackage() {
+    return Boolean(this.reference?.scopedImplMap(this.parent.pkg).length);
+  }
 }
 
 export class StaticMethod extends ClassMethod {