fix(go): unable to set an array of interfaces/enums (#2754)

Contents of array objects were not correctly de-serialized upon receiving
them from the node process: the re-hydratation was not recursive, and
also hit a bug in array re-hydratation when the receiving pointer does
not point to a slice type (i.e: it is an `interface{}`).

The runtime is now correctly re-hydrating recursively through arrays, and
they can be correctly re-hydrated into `interface{}` values.

Fixes #2686



---

By submitting this pull request, I confirm that my contribution is made under the terms of the [Apache 2.0 license].

[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0

gh-pages/content/specification/6-compliance-report.md

@@ -5,7 +5,7 @@
 This section details the current state of each language binding with respect to our standard compliance suite.
 
 
-| number | test                                                                                                                                                             | java (100.00%) | golang (76.07%)                              | Dotnet | Python |
+| number | test                                                                                                                                                             | java (100.00%) | golang (77.78%)                              | Dotnet | Python |
 | ------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------- | -------------------------------------------- | ------ | ------ |
 | 1      | asyncOverrides_overrideCallsSuper                                                                                                                                | 🟢             | [🔴](https://github.com/aws/jsii/issues/2670) | ⭕      | ⭕      |
 | 2      | [arrayReturnedByMethodCanBeRead]("Array created in the kernel can be queried for its elements")                                                                  | 🟢             | 🟢                                           | ⭕      | ⭕      |
@@ -32,8 +32,8 @@ This section details the current state of each language binding with respect to
 | 23     | [reservedKeywordsAreSlugifiedInClassProperties]("TS code that uses reserved words as class property names get slugified so it is usable in the target language") | 🟢             | ⚪                                            | ⭕      | ⭕      |
 | 24     | [objectIdDoesNotGetReallocatedWhenTheConstructorPassesThisOut]("Ensure the JSII kernel can pass 'this' out to JSII remotes from within the constructor")         | 🟢             | 🟢                                           | ⭕      | ⭕      |
 | 25     | [interfaceBuilder]("Seems to be a duplicate of 'propertyOverrides_interfaces'?")                                                                                 | 🟢             | 🟢                                           | ⭕      | ⭕      |
-| 26     | unionTypes                                                                                                                                                       | 🟢             | [🔴](https://github.com/aws/jsii/issues/2686) | ⭕      | ⭕      |
-| 27     | arrays                                                                                                                                                           | 🟢             | [🔴](https://github.com/aws/jsii/issues/2686) | ⭕      | ⭕      |
+| 26     | unionTypes                                                                                                                                                       | 🟢             | 🟢                                           | ⭕      | ⭕      |
+| 27     | arrays                                                                                                                                                           | 🟢             | 🟢                                           | ⭕      | ⭕      |
 | 28     | staticMapInClassCannotBeModified                                                                                                                                 | 🟢             | ⚪                                            | ⭕      | ⭕      |
 | 29     | consts                                                                                                                                                           | 🟢             | 🟢                                           | ⭕      | ⭕      |
 | 30     | pureInterfacesCanBeUsedTransparently_WhenTransitivelyImplementing                                                                                                | 🟢             | 🟢                                           | ⭕      | ⭕      |

packages/@jsii/go-runtime-test/project/compliance_test.go

@@ -1402,25 +1402,23 @@ func (suite *ComplianceSuite) TestUnionTypes() {
 	require.Equal(float64(99), *number.Value())
 
 	// array
-	suite.FailTest("Unable to set an array of interfaces", "https://github.com/aws/jsii/issues/2686")
 	a := []interface{}{123, calclib.NewNumber(jsii.Number(33))}
 	types.SetUnionArrayProperty(&a)
 
 	unionArrayProp := *types.UnionArrayProperty()
 	number, ok = unionArrayProp[1].(calclib.Number)
 	require.True(ok)
-	require.Equal(33, *number.Value())
+	require.Equal(float64(33), *number.Value())
 }
 
 func (suite *ComplianceSuite) TestArrays() {
 	require := suite.Require()
 	sum := calc.NewSum()
 
-	suite.FailTest("Unable to set an array of interfaces", "https://github.com/aws/jsii/issues/2686")
 	sum.SetParts(&[]calclib.NumericValue{calclib.NewNumber(jsii.Number(5)), calclib.NewNumber(jsii.Number(10)), calc.NewMultiply(calclib.NewNumber(jsii.Number(2)), calclib.NewNumber(jsii.Number(3)))})
-	require.Equal(10+5+(2*3), sum.Value())
-	require.Equal(5, *(*sum.Parts())[0].Value())
-	require.Equal(6, *(*sum.Parts())[2].Value())
+	require.Equal(float64(10+5+(2*3)), *sum.Value())
+	require.Equal(float64(5), *(*sum.Parts())[0].Value())
+	require.Equal(float64(6), *(*sum.Parts())[2].Value())
 	require.Equal("(((0 + 5) + 10) + (2 * 3))", *sum.ToString())
 }
 

packages/@jsii/go-runtime/jsii-runtime-go/internal/kernel/conversions.go

@@ -7,6 +7,10 @@ import (
 	"github.com/aws/jsii-runtime-go/internal/api"
 )
 
+var (
+	anyType = reflect.TypeOf((*interface{})(nil)).Elem()
+)
+
 // CastAndSetToPtr accepts a pointer to any type and attempts to cast the value
 // argument to be the same type. Then it sets the value of the pointer element
 // to be the newly cast data. This is used to cast payloads from JSII to
@@ -98,15 +102,21 @@ func (c *Client) castAndSetToPtr(ptr reflect.Value, data reflect.Value) {
 	}
 
 	// arrays
-	if ptr.Kind() == reflect.Slice && data.Kind() == reflect.Slice {
+	if data.Kind() == reflect.Slice {
 		len := data.Len()
-		ptr.Set(reflect.MakeSlice(ptr.Type(), len, len))
+		var slice reflect.Value
+		if ptr.Kind() == reflect.Slice {
+			slice = reflect.MakeSlice(ptr.Type(), len, len)
+		} else {
+			slice = reflect.MakeSlice(reflect.SliceOf(anyType), len, len)
+		}
 
 		// If return type is a slice, recursively cast elements
 		for i := 0; i < len; i++ {
-			c.castAndSetToPtr(ptr.Index(i), data.Index(i))
+			c.castAndSetToPtr(slice.Index(i), data.Index(i))
 		}
 
+		ptr.Set(slice)
 		return
 	}
 
@@ -186,7 +196,7 @@ func (c *Client) CastPtrToRef(dataVal reflect.Value) interface{} {
 	case reflect.Slice:
 		refs := make([]interface{}, dataVal.Len())
 		for i := 0; i < dataVal.Len(); i++ {
-			refs[i] = dataVal.Index(i).Interface()
+			refs[i] = c.CastPtrToRef(dataVal.Index(i))
 		}
 		return refs
 
@@ -307,7 +317,6 @@ func (c *Client) castValToMap(data reflect.Value, mapType reflect.Type) (m refle
 	if mapType.Kind() == reflect.Map && mapType.Key().Kind() != reflect.String {
 		return
 	}
-	anyType := reflect.TypeOf((*interface{})(nil)).Elem()
 	if mapType == anyType {
 		mapType = reflect.TypeOf((map[string]interface{})(nil))
 	}