support string_with_interpolation as an object key (#232)

Author: kkozik-amplify

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 
 - More robust escaping for special characters. Thanks, @eranor ([#224](https://github.com/amplify-education/python-hcl2/pull/224))
+- Issue parsing interpolation string as an object key ([#232](https://github.com/amplify-education/python-hcl2/pull/232))
 
 ## \[7.2.0\] - 2025-04-24
 

hcl2/hcl2.lark

@@ -77,7 +77,7 @@ EQ : /[ \t]*=(?!=|>)/
 tuple : "[" (new_line_or_comment* expression new_line_or_comment* ",")* (new_line_or_comment* expression)? new_line_or_comment* "]"
 object : "{" new_line_or_comment? (new_line_or_comment* (object_elem | (object_elem COMMA)) new_line_or_comment*)* "}"
 object_elem : object_elem_key ( EQ | COLON ) expression
-object_elem_key : float_lit | int_lit | identifier | STRING_LIT | object_elem_key_dot_accessor | object_elem_key_expression
+object_elem_key : float_lit | int_lit | identifier | STRING_LIT | object_elem_key_dot_accessor | object_elem_key_expression | string_with_interpolation
 object_elem_key_expression : LPAR expression RPAR
 object_elem_key_dot_accessor : identifier (DOT identifier)+
 

hcl2/transformer.py

@@ -102,10 +102,12 @@ def object_elem(self, args: List) -> Dict:
         # This returns a dict with a single key/value pair to make it easier to merge these
         # into a bigger dict that is returned by the "object" function
 
-        key = self.strip_quotes(str(args[0].children[0]))
-        value = args[2]
+        key = str(args[0].children[0])
+        if not re.match(r".*?(\${).*}.*", key):
+            # do not strip quotes of a interpolation string
+            key = self.strip_quotes(key)
 
-        value = self.to_string_dollar(value)
+        value = self.to_string_dollar(args[2])
         return {key: value}
 
     def object_elem_key_dot_accessor(self, args: List) -> str:

test/helpers/terraform-config-json/variables.json

@@ -48,7 +48,8 @@
       "bar": {
         "baz": 1,
         "${(var.account)}": 2,
-        "${(format(\"key_prefix_%s\", local.foo))}": 3
+        "${(format(\"key_prefix_%s\", local.foo))}": 3,
+        "\"prefix_${var.account}:${var.user}_suffix\"": "interpolation"
       },
       "tuple": ["${local.foo}"],
       "empty_tuple": []

test/helpers/terraform-config/variables.tf

@@ -10,6 +10,7 @@ locals {
     baz : 1
     (var.account) : 2
     (format("key_prefix_%s", local.foo)) : 3
+    "prefix_${var.account}:${var.user}_suffix":"interpolation",
   }
   tuple = [local.foo]
   empty_tuple = []