protohcl: allow attribute syntax for all map fields (#19108)

internal/protohcl/decoder.go

@@ -173,22 +173,22 @@ func (bd bodyDecoder) schema(desc protoreflect.MessageDescriptor) (*hcl.BodySche
 		f := fields.Get(i)
 
 		kind := f.Kind()
-		// maps are special and whether they use block or attribute syntax depends
+		// maps are special and whether they can use block syntax depends on the value type
-		// on the value type
 		if f.IsMap() {
 			valueDesc := f.MapValue()
 			valueKind := valueDesc.Kind()
 
 			wktHint := wellKnownTypeSchemaHint(valueDesc)
 
-			// Message types should generally be encoded as blocks unless its a special Well Known Type
+			// Maps with values that are Messages can generally be decoded using the block syntax.
-			// that should use attribute encoding
+			// The exception are some of the Well-Known-Types that appear as scalar values with
+			// either string or numeric encoding but get parsed into message types. It is still
+			// fine to also decode these from the attribute syntax.
 			if valueKind == protoreflect.MessageKind && wktHint != wellKnownAttribute {
 				schema.Blocks = append(schema.Blocks, hcl.BlockHeaderSchema{
 					Type:       bd.namer.NameField(f),
 					LabelNames: []string{"key"},
 				})
-				continue
 			}
 
 			// non-message types or Well Known Message types that need attribute encoding

internal/protohcl/unmarshal_test.go

@@ -109,6 +109,56 @@ func TestNestedAndCollections(t *testing.T) {
 	require.Equal(t, out.IntList[1], int32(2))
 }
 
+func TestNestedAndCollections_AttributeSyntax(t *testing.T) {
+	hcl := `
+		primitives {
+			uint32_val = 42
+		}
+		
+		primitives_map = {
+			"foo" = {
+			   uint32_val = 42
+			}
+		}
+		
+		protocol_map = {
+			"foo" = "PROTOCOL_TCP"
+		}
+		
+		primitives_list = [
+			{
+				uint32_val = 42
+			},
+			{
+				uint32_val = 56
+			}
+		] 
+		
+		int_list = [
+			1,
+			2
+		]
+	
+	`
+
+	var out testproto.NestedAndCollections
+
+	err := Unmarshal([]byte(hcl), &out)
+	require.NoError(t, err)
+
+	require.NotNil(t, out.Primitives)
+	require.Equal(t, out.Primitives.Uint32Val, uint32(42))
+	require.NotNil(t, out.PrimitivesMap)
+	require.Equal(t, out.PrimitivesMap["foo"].Uint32Val, uint32(42))
+	require.NotNil(t, out.ProtocolMap)
+	require.Equal(t, out.ProtocolMap["foo"], testproto.Protocol_PROTOCOL_TCP)
+	require.Len(t, out.PrimitivesList, 2)
+	require.Equal(t, out.PrimitivesList[0].Uint32Val, uint32(42))
+	require.Equal(t, out.PrimitivesList[1].Uint32Val, uint32(56))
+	require.Len(t, out.IntList, 2)
+	require.Equal(t, out.IntList[1], int32(2))
+}
+
 func TestPrimitiveWrappers(t *testing.T) {
 	hcl := `
 		double_val = 1.234