Add support for interpolating env vars into task arg default values

README.rst

@@ -641,8 +641,25 @@ Task argument options
 Named arguments support the following configuration options:
 
 - **default** : Union[str, int, float, bool]
-   The value to use if the argument is not provided. This option has no effect if the
-   required option is set to true.
+   The value to use if the argument is not provided. This option has no significance if
+   the required option is set to true.
+
+   For string values, environment variables can be referenced using the usual templating
+   syntax as in the following example.
+
+   .. code-block:: toml
+
+    [[tool.poe.tasks.deploy.args]]
+    name    = "region"
+    help    = "The region to deploy to"
+    default = "${AWS_REGION}"
+
+   This can be combined with setting an env values on the task with the default
+   specifier to get the following precendence of values for the arg:
+
+   1. the value passed on the command line
+   2. the value of the variable set on the environment
+   3. the default value for the environment variable configured on the task
 
 - **help** : str
    A short description of the argument to include in the documentation of the task.

poethepoet/task/args.py

@@ -12,6 +12,8 @@
     Union,
 )
 
+from ..env.manager import EnvVarsManager
+
 if TYPE_CHECKING:
     from ..config import PoeConfig
 
@@ -39,9 +41,10 @@
 class PoeTaskArgs:
     _args: Tuple[ArgParams, ...]
 
-    def __init__(self, args_def: ArgsDef, task_name: str):
+    def __init__(self, args_def: ArgsDef, task_name: str, env: EnvVarsManager):
         self._args = self._normalize_args_def(args_def)
         self._task_name = task_name
+        self._env = env
 
     @classmethod
     def _normalize_args_def(cls, args_def: ArgsDef) -> Tuple[ArgParams, ...]:
@@ -244,6 +247,9 @@ def build_parser(self) -> argparse.ArgumentParser:
 
     def _get_argument_params(self, arg: ArgParams):
         default = arg.get("default")
+        if isinstance(default, str):
+            default = self._env.fill_template(default)
+
         result = {
             "default": default,
             "help": arg.get("help", ""),

poethepoet/task/base.py

@@ -8,7 +8,6 @@
     Dict,
     Iterator,
     List,
-    Mapping,
     Optional,
     Sequence,
     Tuple,
@@ -54,6 +53,7 @@ class PoeTask(metaclass=MetaPoeTask):
     name: str
     content: TaskContent
     options: Dict[str, Any]
+    named_args: Optional[Dict[str, str]] = None
 
     __options__: Dict[str, Union[Type, Tuple[Type, ...]]] = {}
     __content_type__: Type = str
@@ -94,7 +94,6 @@ def __init__(
         self._config = config
         self._is_windows = sys.platform == "win32"
         self.invocation = invocation
-        self.named_args = self._parse_named_args(invocation[1:])
 
     @classmethod
     def from_config(
@@ -202,18 +201,23 @@ def resolve_task_type(
 
         return None
 
-    def _parse_named_args(self, extra_args: Sequence[str]) -> Optional[Dict[str, str]]:
+    def _parse_named_args(
+        self, extra_args: Sequence[str], env: EnvVarsManager
+    ) -> Optional[Dict[str, str]]:
         args_def = self.options.get("args")
         if args_def:
-            return PoeTaskArgs(args_def, self.name).parse(extra_args)
+            return PoeTaskArgs(args_def, self.name, env).parse(extra_args)
         return None
 
-    @property
-    def has_named_args(self):
-        return bool(self.named_args)
+    # @property
+    # def has_named_args(self):
+    #     return bool(self.named_args)
 
-    def get_named_arg_values(self) -> Mapping[str, str]:
-        result = {}
+    def get_named_arg_values(self, env: EnvVarsManager) -> Dict[str, str]:
+        result: Dict[str, str] = {}
+
+        if self.named_args is None:
+            self.named_args = self._parse_named_args(self.invocation[1:], env)
 
         if not self.named_args:
             return {}
@@ -279,7 +283,7 @@ def _get_upstream_invocations(self, context: "RunContext"):
             env = context.get_task_env(
                 None, self.options.get("envfile"), self.options.get("env")
             )
-            env.update(self.get_named_arg_values())
+            env.update(self.get_named_arg_values(env))
 
             self.__upstream_invocations = {
                 "deps": [

poethepoet/task/cmd.py

@@ -32,9 +32,10 @@ def _handle_run(
         extra_args: Sequence[str],
         env: EnvVarsManager,
     ) -> int:
-        env.update(self.get_named_arg_values())
+        named_arg_values = self.get_named_arg_values(env)
+        env.update(named_arg_values)
 
-        if self.has_named_args:
+        if named_arg_values:
             # If named arguments are defined then it doesn't make sense to pass extra
             # args to the command, because they've already been parsed
             cmd = self._resolve_args(context, env)

poethepoet/task/sequence.py

@@ -69,9 +69,10 @@ def _handle_run(
         extra_args: Sequence[str],
         env: EnvVarsManager,
     ) -> int:
-        env.update(self.get_named_arg_values())
+        named_arg_values = self.get_named_arg_values(env)
+        env.update(named_arg_values)
 
-        if not self.has_named_args and any(arg.strip() for arg in extra_args):
+        if not named_arg_values and any(arg.strip() for arg in extra_args):
             raise PoeException(f"Sequence task {self.name!r} does not accept arguments")
 
         if len(self.subtasks) > 1:

poethepoet/task/shell.py

@@ -38,9 +38,10 @@ def _handle_run(
         extra_args: Sequence[str],
         env: EnvVarsManager,
     ) -> int:
-        env.update(self.get_named_arg_values())
+        named_arg_values = self.get_named_arg_values(env)
+        env.update(named_arg_values)
 
-        if not self.has_named_args and any(arg.strip() for arg in extra_args):
+        if not named_arg_values and any(arg.strip() for arg in extra_args):
             raise PoeException(f"Shell task {self.name!r} does not accept arguments")
 
         interpreter_cmd = self.resolve_interpreter_cmd()

tests/fixtures/scripts_project/pyproject.toml

@@ -77,10 +77,11 @@ greet = "pkg:greet"
 
   [tool.poe.tasks.greet-strict]
   script = "pkg:greet(greeting, user=name)"
-  help = "All arguments are required"
+  help   = "All arguments are required"
+  env    = { DOES = "does", STUFF = "matter" }
 
     [tool.poe.tasks.greet-strict.args.greeting]
-    default = "doesn't matter"
+    default = "${DOES}n't ${STUFF}"
     required = true
     help = "this one is required"
 
@@ -90,11 +91,12 @@ greet = "pkg:greet"
 
   [tool.poe.tasks.greet-positional]
   script = "pkg:greet(greeting, user=username, upper=uppercase)"
+  env.DEFAULT_GREETING.default = "yo"
 
     [[tool.poe.tasks.greet-positional.args]]
     name = "greeting"
     positional = true
-    default = "yo"
+    default = "${DEFAULT_GREETING}"
     help = "this one is required"
 
     [[tool.poe.tasks.greet-positional.args]]