fix(golang): Prevent duplicate enum output (#2447)

internal/codegen/golang/gen.go

@@ -318,10 +318,9 @@ func filterUnusedStructs(enums []Enum, structs []Struct, queries []Query) ([]Enu
 
 	keepEnums := make([]Enum, 0, len(enums))
 	for _, enum := range enums {
-		if _, ok := keepTypes[enum.Name]; ok {
-			keepEnums = append(keepEnums, enum)
-		}
-		if _, ok := keepTypes["Null"+enum.Name]; ok {
+		_, keep := keepTypes[enum.Name]
+		_, keepNull := keepTypes["Null"+enum.Name]
+		if keep || keepNull {
 			keepEnums = append(keepEnums, enum)
 		}
 	}

internal/endtoend/testdata/omit_unused_structs/postgresql/stdlib/query.sql

@@ -2,7 +2,7 @@
 SELECT * FROM query_return_full_table;
 
 -- name: query_param_enum_table :one
-SELECT id FROM query_param_enum_table WHERE value = $1;
+SELECT * FROM query_param_enum_table WHERE value = $1;
 
 -- name: query_param_struct_enum_table :one
 SELECT id FROM query_param_struct_enum_table WHERE id = $1 AND value = $2;

internal/endtoend/testdata/omit_unused_structs/postgresql/stdlib/schema.sql

@@ -23,6 +23,7 @@ CREATE TYPE query_param_enum_table_enum AS ENUM (
 );
 CREATE TABLE query_param_enum_table (
     id      INTEGER PRIMARY KEY,
+    other   query_param_enum_table_enum NOT NULL,
     value   query_param_enum_table_enum
 );