Fix environment variable leak for unused formatters (#338)

* Add tests against environment pollution

* Delay `rpy2` import until the formatter is requested

jupyterlab_code_formatter/formatters.py

@@ -9,15 +9,11 @@
 from functools import wraps
 from typing import List, Type
 
-try:
-    import rpy2
-    import rpy2.robjects
-except ImportError:
-    pass
 if sys.version_info >= (3, 9):
     from functools import cache
 else:
     from functools import lru_cache
+
     cache = lru_cache(maxsize=None)
 
 from packaging import version
@@ -357,56 +353,55 @@ def format_code(self, code: str, notebook: bool, **options) -> str:
             return isort.code(code=code, **options)
 
 
-class FormatRFormatter(BaseFormatter):
-    label = "Apply FormatR Formatter"
-    package_name = "formatR"
+class RFormatter(BaseFormatter):
+    @property
+    @abc.abstractmethod
+    def package_name(self) -> str:
+        pass
 
     @property
     def importable(self) -> bool:
-        try:
-            import rpy2.robjects.packages as rpackages
+        package_location = subprocess.run(
+            ["Rscript", "-e", f"cat(system.file(package='{self.package_name}'))"],
+            capture_output=True,
+            text=True,
+        )
+        return package_location != ""
 
-            rpackages.importr(self.package_name, robject_translations={".env": "env"})
 
-            return True
-        except Exception:
-            return False
+class FormatRFormatter(RFormatter):
+    label = "Apply FormatR Formatter"
+    package_name = "formatR"
 
     @handle_line_ending_and_magic
     def format_code(self, code: str, notebook: bool, **options) -> str:
         import rpy2.robjects.packages as rpackages
+        from rpy2.robjects import conversion, default_converter
 
-        format_r = rpackages.importr(self.package_name, robject_translations={".env": "env"})
-        formatted_code = format_r.tidy_source(text=code, output=False, **options)
-        return "\n".join(formatted_code[0])
+        with conversion.localconverter(default_converter):
+            format_r = rpackages.importr(self.package_name, robject_translations={".env": "env"})
+            formatted_code = format_r.tidy_source(text=code, output=False, **options)
+            return "\n".join(formatted_code[0])
 
 
-class StylerFormatter(BaseFormatter):
+class StylerFormatter(RFormatter):
     label = "Apply Styler Formatter"
     package_name = "styler"
 
-    @property
-    def importable(self) -> bool:
-        try:
-            import rpy2.robjects.packages as rpackages
-
-            rpackages.importr(self.package_name)
-
-            return True
-        except Exception:
-            return False
-
     @handle_line_ending_and_magic
     def format_code(self, code: str, notebook: bool, **options) -> str:
         import rpy2.robjects.packages as rpackages
+        from rpy2.robjects import conversion, default_converter
 
-        styler_r = rpackages.importr(self.package_name)
-        formatted_code = styler_r.style_text(code, **self._transform_options(styler_r, options))
-        return "\n".join(formatted_code)
+        with conversion.localconverter(default_converter):
+            styler_r = rpackages.importr(self.package_name)
+            formatted_code = styler_r.style_text(code, **self._transform_options(styler_r, options))
+            return "\n".join(formatted_code)
 
     @staticmethod
     def _transform_options(styler_r, options):
         transformed_options = copy.deepcopy(options)
+        import rpy2.robjects
 
         if "math_token_spacing" in transformed_options:
             if isinstance(options["math_token_spacing"], dict):

jupyterlab_code_formatter/tests/test_formatters.py

@@ -0,0 +1,38 @@
+import json
+import os
+import sys
+from subprocess import run
+from unittest import mock
+
+import pytest
+
+from jupyterlab_code_formatter.formatters import SERVER_FORMATTERS
+
+
+def test_env_pollution_on_import():
+    # should not pollute environment on import
+    code = "; ".join(
+        [
+            "from jupyterlab_code_formatter import formatters",
+            "import json",
+            "import os",
+            "assert formatters",
+            "print(json.dumps(os.environ.copy()))",
+        ]
+    )
+    result = run([sys.executable, "-c", f"{code}"], capture_output=True, text=True, check=True, env={})
+    environ = json.loads(result.stdout)
+    assert set(environ.keys()) - {"LC_CTYPE"} == set()
+
+
+@pytest.mark.parametrize("name", SERVER_FORMATTERS)
+def test_env_pollution_on_importable_check(name):
+    formatter = SERVER_FORMATTERS[name]
+    # should not pollute environment on `importable` check
+    with mock.patch.dict(os.environ, {}, clear=True):
+        # invoke the property getter
+        is_importable = formatter.importable
+        # the environment should have no extra keys
+        assert set(os.environ.keys()) == set()
+        if not is_importable:
+            pytest.skip(f"{name} formatter was not importable, the test may yield false negatives")