fix: preserve double curly braces in python code [#215]

snakefmt/parser/parser.py

@@ -1,3 +1,4 @@
+import sys
 import tokenize
 from abc import ABC, abstractmethod
 from typing import NamedTuple, Optional
@@ -324,3 +325,12 @@ def get_next_queriable(self, snakefile: TokenIterator) -> Status:
             if not pythonable and token.type != tokenize.COMMENT:
                 pythonable = True
             buffer += token.string
+            if (
+                token is not None
+                and sys.version_info >= (3, 12)
+                and token.type == tokenize.FSTRING_MIDDLE
+            ):
+                if token.string.endswith("}"):
+                    buffer += "}"
+                elif token.string.endswith("{"):
+                    buffer += "{"

tests/test_formatter.py

@@ -858,6 +858,19 @@ def test_f_string_with_double_braces_in_input(self):
         formatter = setup_formatter(snakecode)
         assert formatter.get_formatted() == snakecode
 
+    def test_f_string_with_double_braces_in_python_code(self):
+        """https://github.com/snakemake/snakefmt/issues/215"""
+        """def get_test_regions(wildcards):
+    benchmark = config["variant-calls"][wildcards.callset]["benchmark"]
+    return f"resources/regions/{benchmark}/test-regions.cov-{{cov}}.bed"""
+        snakecode = (
+            "def get_test_regions(wildcards):\n"
+            f'{TAB * 1}benchmark = config["variant-calls"][wildcards.callset]["benchmark"]\n'  # noqa: E501
+            f'{TAB * 1}return f"resources/regions/{{benchmark}}/test-regions.cov-{{{{cov}}}}.bed"\n'  # noqa: E501
+        )
+        formatter = setup_formatter(snakecode)
+        assert formatter.get_formatted() == snakecode
+
 
 class TestReformatting_SMK_BREAK:
     """