chore: enable ruff flake8-comprehensions (C4) rules and fix violations

Enable the C4 (flake8-comprehensions) rule set in ruff and fix all
existing violations:

- C401: Use set comprehension instead of set(generator)
- C408: Use tuple literal () instead of tuple()
- C417: Use generator expression / list comprehension instead of map(lambda)

Addresses #4227

Assisted-by: Claude Opus 4.6

Author: yosofbadr

codegen/opentelemetry-codegen-json/src/opentelemetry/codegen/json/generator.py

@@ -386,10 +386,10 @@ def _collect_imports(self, proto_file: str) -> Set[str]:
         Returns:
             Set of import statement strings
         """
-        return set(
+        return {
             "import " + self._get_module_path(dep_file)
             for dep_file in self._file_dependencies.get(proto_file, [])
-        )
+        }
 
     def _generate_enums_for_file(
         self,

exporter/opentelemetry-exporter-otlp-proto-grpc/src/opentelemetry/exporter/otlp/proto/grpc/exporter.py

@@ -328,7 +328,7 @@ def __init__(
         elif isinstance(self._headers, dict):
             self._headers = tuple(self._headers.items())
         if self._headers is None:
-            self._headers = tuple()
+            self._headers = ()
 
         if channel_options:
             # merge the default channel options with the one passed as parameter

opentelemetry-sdk/src/opentelemetry/sdk/util/__init__.py

@@ -34,12 +34,8 @@ def get_dict_as_key(labels):
     """Converts a dict to be used as a unique key"""
     return tuple(
         sorted(
-            map(
-                lambda kv: (
-                    (kv[0], tuple(kv[1])) if isinstance(kv[1], list) else kv
-                ),
-                labels.items(),
-            )
+            (kv[0], tuple(kv[1])) if isinstance(kv[1], list) else kv
+            for kv in labels.items()
         )
     )
 

pyproject.toml

@@ -81,6 +81,7 @@ select = [
   "F",   # pyflakes
   "E",   # pycodestyle errors
   "W",   # pycodestyle warnings
+  "C4",  # flake8-comprehensions
   "PLC", # pylint convention
   "PLE", # pylint error
   "Q",   # flake8-quotes

shim/opentelemetry-opentracing-shim/tests/testbed/testcase.py

@@ -43,4 +43,4 @@ def assertIsNotChildOf(self, spanA, spanB):
         self.assertNotEqual(ctxA.span_id, ctxB.span_id)
 
     def assertNamesEqual(self, spans, names):
-        self.assertEqual(list(map(lambda x: x.name, spans)), names)
+        self.assertEqual([x.name for x in spans], names)