Run Flynt to convert str.format to f-strings (#464)

* chore: Convert old style str.format to f strings

Ran `flynt`: https://github.com/ikamensh/flynt against nox
to automatically convert `"{}".format` style strings to the
newer `f"{}"` style strings.

* Fix Lint failure by running black

* Improve readibility of some converted strings

* Run Flynt string conversion against tests/

* Change remaining str.format calls to f-strings

nox/_decorators.py

@@ -68,7 +68,7 @@ def copy(self, name: Optional[str] = None) -> "Func":
 class Call(Func):
     def __init__(self, func: Func, param_spec: "Param") -> None:
         call_spec = param_spec.call_spec
-        session_signature = "({})".format(param_spec)
+        session_signature = f"({param_spec})"
 
         # Determine the Python interpreter for the session using either @session
         # or @parametrize. For backwards compatibility, we only use a "python"

nox/_option_set.py

@@ -85,7 +85,7 @@ def __init__(
         default: Union[Any, Callable[[], Any]] = None,
         hidden: bool = False,
         completer: Optional[Callable[..., List[str]]] = None,
-        **kwargs: Any
+        **kwargs: Any,
     ) -> None:
         self.name = name
         self.flags = flags
@@ -156,27 +156,25 @@ def make_flag_pair(
     name: str,
     enable_flags: Union[Tuple[str, str], Tuple[str]],
     disable_flags: Tuple[str],
-    **kwargs: Any
+    **kwargs: Any,
 ) -> Tuple[Option, Option]:
     """Returns two options - one to enable a behavior and another to disable it.
 
     The positive option is considered to be available to the noxfile, as
     there isn't much point in doing flag pairs without it.
     """
-    disable_name = "no_{}".format(name)
+    disable_name = f"no_{name}"
 
     kwargs["action"] = "store_true"
     enable_option = Option(
         name,
         *enable_flags,
         noxfile=True,
         merge_func=functools.partial(flag_pair_merge_func, name, disable_name),
-        **kwargs
+        **kwargs,
     )
 
-    kwargs["help"] = "Disables {} if it is enabled in the Noxfile.".format(
-        enable_flags[-1]
-    )
+    kwargs["help"] = f"Disables {enable_flags[-1]} if it is enabled in the Noxfile."
     disable_option = Option(disable_name, *disable_flags, **kwargs)
 
     return enable_option, disable_option
@@ -285,7 +283,7 @@ def namespace(self, **kwargs: Any) -> argparse.Namespace:
         # used in tests.
         for key, value in kwargs.items():
             if key not in args:
-                raise KeyError("{} is not an option.".format(key))
+                raise KeyError(f"{key} is not an option.")
             args[key] = value
 
         return argparse.Namespace(**args)

nox/_options.py

@@ -197,14 +197,14 @@ def _posargs_finalizer(
     if "--" not in posargs:
         unexpected_posargs = posargs
         raise _option_set.ArgumentError(
-            None, "Unknown argument(s) '{}'.".format(" ".join(unexpected_posargs))
+            None, f"Unknown argument(s) '{' '.join(unexpected_posargs)}'."
         )
 
     dash_index = posargs.index("--")
     if dash_index != 0:
         unexpected_posargs = posargs[0:dash_index]
         raise _option_set.ArgumentError(
-            None, "Unknown argument(s) '{}'.".format(" ".join(unexpected_posargs))
+            None, f"Unknown argument(s) '{' '.join(unexpected_posargs)}'."
         )
 
     return posargs[dash_index + 1 :]

nox/_parametrize.py

@@ -32,7 +32,7 @@ def __init__(
         self,
         *args: Any,
         arg_names: Optional[Sequence[str]] = None,
-        id: Optional[str] = None
+        id: Optional[str] = None,
     ) -> None:
         self.args = tuple(args)
         self.id = id
@@ -51,7 +51,7 @@ def __str__(self) -> str:
             return self.id
         else:
             call_spec = self.call_spec
-            args = ["{}={}".format(k, repr(call_spec[k])) for k in call_spec.keys()]
+            args = [f"{k}={call_spec[k]!r}" for k in call_spec.keys()]
             return ", ".join(args)
 
     __repr__ = __str__

nox/command.py

@@ -50,8 +50,8 @@ def which(program: str, paths: Optional[List[str]]) -> str:
     if full_path:
         return full_path.strpath
 
-    logger.error("Program {} not found.".format(program))
-    raise CommandFailed("Program {} not found".format(program))
+    logger.error(f"Program {program} not found.")
+    raise CommandFailed(f"Program {program} not found")
 
 
 def _clean_env(env: Optional[dict]) -> Optional[dict]:
@@ -76,15 +76,15 @@ def run(
     success_codes: Optional[Iterable[int]] = None,
     log: bool = True,
     external: Union[Literal["error"], bool] = False,
-    **popen_kws: Any
+    **popen_kws: Any,
 ) -> Union[str, bool]:
     """Run a command-line program."""
 
     if success_codes is None:
         success_codes = [0]
 
     cmd, args = args[0], args[1:]
-    full_cmd = "{} {}".format(cmd, " ".join(args))
+    full_cmd = f"{cmd} {' '.join(args)}"
 
     cmd_path = which(cmd, paths)
 
@@ -97,18 +97,14 @@ def run(
         if is_external_tool:
             if external == "error":
                 logger.error(
-                    "Error: {} is not installed into the virtualenv, it is located at {}. "
-                    "Pass external=True into run() to explicitly allow this.".format(
-                        cmd, cmd_path
-                    )
+                    f"Error: {cmd} is not installed into the virtualenv, it is located at {cmd_path}. "
+                    "Pass external=True into run() to explicitly allow this."
                 )
                 raise CommandFailed("External program disallowed.")
             elif external is False:
                 logger.warning(
-                    "Warning: {} is not installed into the virtualenv, it is located at {}. This might cause issues! "
-                    "Pass external=True into run() to silence this message.".format(
-                        cmd, cmd_path
-                    )
+                    f"Warning: {cmd} is not installed into the virtualenv, it is located at {cmd_path}. This might cause issues! "
+                    "Pass external=True into run() to silence this message."
                 )
 
     env = _clean_env(env)
@@ -119,16 +115,15 @@ def run(
         )
 
         if return_code not in success_codes:
+            suffix = ":" if silent else ""
             logger.error(
-                "Command {} failed with exit code {}{}".format(
-                    full_cmd, return_code, ":" if silent else ""
-                )
+                f"Command {full_cmd} failed with exit code {return_code}{suffix}"
             )
 
             if silent:
                 sys.stderr.write(output)
 
-            raise CommandFailed("Returned code {}".format(return_code))
+            raise CommandFailed(f"Returned code {return_code}")
 
         if output:
             logger.output(output)

nox/manifest.py

@@ -162,7 +162,7 @@ def filter_by_name(self, specified_sessions: Iterable[str]) -> None:
             if _normalize_arg(session_name) not in all_sessions
         ]
         if missing_sessions:
-            raise KeyError("Sessions not found: {}".format(", ".join(missing_sessions)))
+            raise KeyError(f"Sessions not found: {', '.join(missing_sessions)}")
 
     def filter_by_python_interpreter(self, specified_pythons: Sequence[str]) -> None:
         """Filter sessions in the queue based on the user-specified
@@ -247,7 +247,7 @@ def make_session(
             if not multi:
                 long_names.append(name)
             if func.python:
-                long_names.append("{}-{}".format(name, func.python))
+                long_names.append(f"{name}-{func.python}")
 
             return [SessionRunner(name, long_names, func, self._config, self)]
 
@@ -258,13 +258,11 @@ def make_session(
         for call in calls:
             long_names = []
             if not multi:
-                long_names.append("{}{}".format(name, call.session_signature))
+                long_names.append(f"{name}{call.session_signature}")
             if func.python:
-                long_names.append(
-                    "{}-{}{}".format(name, func.python, call.session_signature)
-                )
+                long_names.append(f"{name}-{func.python}{call.session_signature}")
                 # Ensure that specifying session-python will run all parameterizations.
-                long_names.append("{}-{}".format(name, func.python))
+                long_names.append(f"{name}-{func.python}")
 
             sessions.append(SessionRunner(name, long_names, call, self._config, self))
 
@@ -318,7 +316,7 @@ def notify(
                 return True
 
         # The session was not found in the list of sessions.
-        raise ValueError("Session {} not found.".format(session))
+        raise ValueError(f"Session {session} not found.")
 
 
 class KeywordLocals(collections.abc.Mapping):

nox/sessions.py

@@ -63,9 +63,9 @@ def _normalize_path(envdir: str, path: Union[str, bytes]) -> str:
             logger.warning("The virtualenv name was hashed to avoid being too long.")
         else:
             logger.error(
-                "The virtualenv path {} is too long and will cause issues on "
+                f"The virtualenv path {full_path} is too long and will cause issues on "
                 "some environments. Use the --envdir path to modify where "
-                "nox stores virtualenvs.".format(full_path)
+                "nox stores virtualenvs."
             )
 
     return full_path
@@ -79,7 +79,7 @@ def _dblquote_pkg_install_arg(pkg_req_str: str) -> str:
         # sanity check: we need an even number of double-quotes
         if pkg_req_str.count('"') % 2 != 0:
             raise ValueError(
-                "ill-formated argument with odd number of quotes: %s" % pkg_req_str
+                f"ill-formated argument with odd number of quotes: {pkg_req_str}"
             )
 
         if "<" in pkg_req_str or ">" in pkg_req_str:
@@ -89,10 +89,8 @@ def _dblquote_pkg_install_arg(pkg_req_str: str) -> str:
             else:
                 # need to double-quote string
                 if '"' in pkg_req_str:
-                    raise ValueError(
-                        "Cannot escape requirement string: %s" % pkg_req_str
-                    )
-                return '"%s"' % pkg_req_str
+                    raise ValueError(f"Cannot escape requirement string: {pkg_req_str}")
+                return f'"{pkg_req_str}"'
         else:
             # no dangerous char: no need to double-quote string
             return pkg_req_str
@@ -193,7 +191,7 @@ def interactive(self) -> bool:
 
     def chdir(self, dir: Union[str, os.PathLike]) -> None:
         """Change the current working directory."""
-        self.log("cd {}".format(dir))
+        self.log(f"cd {dir}")
         os.chdir(dir)
 
     cd = chdir
@@ -203,11 +201,11 @@ def _run_func(
         self, func: Callable, args: Iterable[Any], kwargs: Mapping[str, Any]
     ) -> Any:
         """Legacy support for running a function through :func`run`."""
-        self.log("{}(args={!r}, kwargs={!r})".format(func, args, kwargs))
+        self.log(f"{func}(args={args!r}, kwargs={kwargs!r})")
         try:
             return func(*args, **kwargs)
         except Exception as e:
-            logger.exception("Function {!r} raised {!r}.".format(func, e))
+            logger.exception(f"Function {func!r} raised {e!r}.")
             raise nox.command.CommandFailed()
 
     def run(
@@ -263,7 +261,7 @@ def run(
             raise ValueError("At least one argument required to run().")
 
         if self._runner.global_config.install_only:
-            logger.info("Skipping {} run, as --install-only is set.".format(args[0]))
+            logger.info(f"Skipping {args[0]} run, as --install-only is set.")
             return None
 
         return self._run(*args, env=env, **kwargs)
@@ -410,7 +408,7 @@ def conda_install(
             *prefix_args,
             *args,
             external="error",
-            **kwargs
+            **kwargs,
         )
 
     def install(self, *args: str, **kwargs: Any) -> None:
@@ -534,7 +532,7 @@ def description(self) -> Optional[str]:
 
     def __str__(self) -> str:
         sigs = ", ".join(self.signatures)
-        return "Session(name={}, signatures={})".format(self.name, sigs)
+        return f"Session(name={self.name}, signatures={sigs})"
 
     @property
     def friendly_name(self) -> str:
@@ -583,15 +581,13 @@ def _create_venv(self) -> None:
             )
         else:
             raise ValueError(
-                "Expected venv_backend one of ('virtualenv', 'conda', 'venv'), but got '{}'.".format(
-                    backend
-                )
+                f"Expected venv_backend one of ('virtualenv', 'conda', 'venv'), but got '{backend}'."
             )
 
         self.venv.create()
 
     def execute(self) -> "Result":
-        logger.warning("Running session {}".format(self.friendly_name))
+        logger.warning(f"Running session {self.friendly_name}")
 
         try:
             # By default, nox should quietly change to the directory where
@@ -624,13 +620,11 @@ def execute(self) -> "Result":
             return Result(self, Status.FAILED)
 
         except KeyboardInterrupt:
-            logger.error("Session {} interrupted.".format(self.friendly_name))
+            logger.error(f"Session {self.friendly_name} interrupted.")
             raise
 
         except Exception as exc:
-            logger.exception(
-                "Session {} raised exception {!r}".format(self.friendly_name, exc)
-            )
+            logger.exception(f"Session {self.friendly_name} raised exception {exc!r}")
             return Result(self, Status.FAILED)
 
 
@@ -669,7 +663,7 @@ def imperfect(self) -> str:
             return "was successful"
         status = self.status.name.lower()
         if self.reason:
-            return "{}: {}".format(status, self.reason)
+            return f"{status}: {self.reason}"
         else:
             return status