src/python/jw/pkg/lib/App.py

@@ -36,6 +36,11 @@ if TYPE_CHECKING:
     from typing import TypeVar
     T = TypeVar('T')
 
+class _SubCommand(NamedTuple):
+
+    cmd: AbstractCmd
+    parser: ArgumentParser
+
 def _get_current_event_loop() -> asyncio.AbstractEventLoop | None:
     """Return the current event loop of this thread, or None if there is
     none, without creating one implicitly or emitting a deprecation
@@ -47,10 +52,63 @@ def _get_current_event_loop() -> asyncio.AbstractEventLoop | None:
         except (RuntimeError, DeprecationWarning):
             return None
 
-class _SubCommand(NamedTuple):
+def _build_option_map(parser: ArgumentParser) -> dict[str, int | str | None]:
+    """Map each option string to its nargs, so the invoked-path walk can tell
+    which options consume the following token (a value) and which are bare
+    flags."""
+    opt_map: dict[str, int | str | None] = {}
+    for action in parser._actions:  # noqa: SLF001
+        for opt in getattr(action, 'option_strings', ()):
+            opt_map[opt] = action.nargs
+    return opt_map
 
-    cmd: AbstractCmd
+def _find_invoked_subcommand(
-    parser: ArgumentParser
+    opt_map: dict[str, int | str | None],
+    names: set[str],
+    argv: list[str],
+    pos: int,
+) -> tuple[str | None, int]:
+    """Find the invoked subcommand name in argv starting at pos.
+
+    Walk the argv, skipping options and the tokens they consume (using
+    opt_map), and return the first positional token that is a subcommand
+    name, along with the position just past it. Return (None, pos) if no
+    subcommand name is present at or after pos.
+    """
+    n = len(argv)
+    i = pos
+    while i < n:
+        tok = argv[i]
+        if tok.startswith('-') and len(tok) > 1:
+            if '=' in tok:
+                # --opt=value: the value is inline, consume the token only.
+                i += 1
+            elif tok in opt_map and opt_map[tok] != 0:
+                nargs = opt_map[tok]
+                if nargs in ('+', '*') or (isinstance(nargs, int) and nargs > 1):
+                    # -- Multi-value option: consume the following non-option,
+                    # non-subcommand tokens (its values).
+                    j = i + 1
+                    while (j < n and not argv[j].startswith('-')
+                           and argv[j] not in names):
+                        j += 1
+                    i = j
+                elif i + 1 < n and not argv[i + 1].startswith('-'):
+                    # -- One value: consume the following token.
+                    i += 2
+                else:
+                    i += 1
+            else:
+                # -- Flag or unknown option: consume the token only.
+                i += 1
+            continue
+        if tok in names:
+            return tok, i + 1
+        # -- A positional token that is not a subcommand name: the invoked
+        # path ends here.
+        return None, i
+    # -- Ran off the end of the argv consuming option values: no subcommand.
+    return None, i
 
 class App:  # export
 
@@ -185,6 +243,7 @@ class App:  # export
             cmds: Collection[AbstractCmd],
             all: bool,
             top_level: bool,
+            pos: int,
         ) -> None:
             if not cmds:
                 return
@@ -223,15 +282,24 @@ class App:  # export
                             sc.cmd.children,
                             all = all,
                             top_level = False,
+                            pos = pos,
                         )
                 return
-            # -- Re-parse the command line to find the invoked subcommand.
+            # -- Find the invoked subcommand by walking the argv. The
-            # This works because every level below uses dest = 'command',
+            # subcommand names at this level are known (the commands are
-            # so each pass descends one level further into the command
+            # materialized), so the invoked path is found by matching tokens
-            # tree.
+            # against those names and skipping the options (and their
-            args, _ = self.__parser.parse_known_args(argv)
+            # values) that precede them. Walking the tokens never parses the
-            cmd_name = getattr(args, 'command', None)
+            # tail against a half-built parser, so a deeper option cannot
-            if cmd_name in scs:
+            # collide with a same-named option of a shallower level the way
+            # a discovery re-parse would.
+            cmd_name, new_pos = _find_invoked_subcommand(
+                _build_option_map(parser),
+                set(scs.keys()),
+                argv_list,
+                pos,
+            )
+            if cmd_name is not None and cmd_name in scs:
                 sc = scs[cmd_name]
                 add_cmds_to_parser(
                     sc.cmd,
@@ -239,11 +307,16 @@ class App:  # export
                     sc.cmd.children,
                     all = all,
                     top_level = False,
+                    pos = new_pos,
                 )
 
         cmdline = sys.argv if argv is None else argv
         if argv is None:
             argv = sys.argv[1:]
+        # -- The argv the invoked-path walk (below) operates on. A separate
+        # binding so the nested closure sees a plain list[str], not the
+        # optional parameter type.
+        argv_list: list[str] = argv
         add_all_parsers = (
             '-h' in argv or '--help' in argv or '_ARGCOMPLETE' in os.environ
         )
@@ -279,6 +352,7 @@ class App:  # export
                 self.__cmds,
                 all = add_all_parsers,
                 top_level = False,
+                pos = 0,
             )
         else:
             add_cmds_to_parser(
@@ -287,6 +361,7 @@ class App:  # export
                 self.__root.children,
                 all = add_all_parsers,
                 top_level = True,
+                pos = 0,
             )
 
         # -- Add help only now, wouldn't want to have parse_known_args() exit

src/python/jw/pkg/lib/Cmd.py

@@ -25,6 +25,12 @@ class AbstractCmd(abc.ABC):
         self.__children: list[Cmd] = []
         self.__child_classes: list[type[Cmd]] = []
         self.__parser: ArgumentParser | None = None
+        # -- Subcommands registered via load_subcommands() are not built
+        # immediately; the module search path and name filter are stored here
+        # and the subcommands are materialized on first access to `children`
+        # (see __materialize_pending_subcommands()). This keeps a simple run
+        # from instantiating the whole command tree.
+        self.__pending_subcommands: tuple[list[str], str] | None = None
 
     def set_parent(self, parent: Any | Cmd) -> None:
         self.__parent = parent
@@ -61,12 +67,25 @@ class AbstractCmd(abc.ABC):
                 parent = parent.__parent
         return self.__app
 
+    def __materialize_pending_subcommands(self) -> None:
+        # -- Build the subcommands that load_subcommands() registered
+        # lazily, if any. Called on first access to `children` (and
+        # `child_classes`) so that only the parts of the tree a run actually
+        # descends into are ever instantiated.
+        if self.__pending_subcommands is None:
+            return
+        modules, name_filter = self.__pending_subcommands
+        self.__pending_subcommands = None
+        self.add_subcommands(LoadTypes(modules, type_name_filter = name_filter))
+
     @property
     def children(self) -> tuple[Cmd, ...]:
+        self.__materialize_pending_subcommands()
         return tuple(self.__children)
 
     @property
     def child_classes(self) -> tuple[type[Cmd], ...]:
+        self.__materialize_pending_subcommands()
         return tuple(self.__child_classes)
 
     @property
@@ -127,7 +146,11 @@ class AbstractCmd(abc.ABC):
             modules = [type(self).__module__.replace('Cmd', '').lower()]
         elif isinstance(modules, str):
             modules = [modules]
-        self.add_subcommands(LoadTypes(modules, type_name_filter = name_filter))
+        # -- Defer the actual subcommand construction: store the search path
+        # and filter, and materialize on first access to `children`. Building
+        # them here (in __init__) would instantiate the entire tree up front,
+        # even for a run that only descends into a single branch.
+        self.__pending_subcommands = (modules, name_filter)
 
     # -- Interface to derived classes