Fix zip method yielded type

CHANGELOG.md

@@ -23,6 +23,7 @@ All notable changes to this project will be documented in this file.
 - The `switch` output now produces error logs when messages do not pass at least one case with `strict_mode` enabled, previously these rejected messages were potentially re-processed in a loop without any logs depending on the config. An inaccuracy to the documentation has also been fixed in order to clarify behaviour when strict mode is not enabled.
 - The `log` processor `fields_mapping` field should no longer reject metadata queries using `@` syntax.
 - Fixed an issue where heavily utilised streams with nested resource based outputs could lock-up when performing heavy resource mutating traffic on the streams mode REST API.
+- The Bloblang `zip` method no longer produces values that yield an "Unknown data type".
 
 ## 4.20.0 - 2023-08-22
 

internal/impl/pure/bloblang_objects.go

@@ -127,7 +127,7 @@ If a key within a nested path does not exist then it is ignored.`).
 				if len(i) != len(argSlices[0]) {
 					return nil, sizeError
 				}
-				resSlice := make([][]any, 0, len(i))
+				resSlice := make([]any, 0, len(i))
 				for offset, value := range i {
 					zipValue := make([]any, 0, len(argSlices)+1)
 					zipValue = append(zipValue, value)

internal/impl/pure/bloblang_objects_test.go

@@ -97,10 +97,10 @@ func TestZipMethod(t *testing.T) {
 				},
 			},
 			output: map[string]any{
-				"foo": [][]any{
-					{"a", 1, []any{"x"}},
-					{"b", 2, []any{"y"}},
-					{"c", 3, []any{"z"}},
+				"foo": []any{
+					[]any{"a", 1, []any{"x"}},
+					[]any{"b", 2, []any{"y"}},
+					[]any{"c", 3, []any{"z"}},
 				},
 			},
 		},