Update `._entry` actor status log

Log-report the different types of actor exit conditions including cancel
via KBI, error or normal return with varying levels depending on case.

Also, start proto-ing out this weird ascii-syntax idea for describing
conc system states and implement the first bit in a `nest_from_op()`
log-message fmter that joins and indents an obj `repr()` with
a tree-like `'>)\n|_'` header.

tractor/_entry.py

@@ -20,7 +20,8 @@ Sub-process entry points.
 """
 from __future__ import annotations
 from functools import partial
-# import textwrap
+import os
+import textwrap
 from typing import (
     Any,
     TYPE_CHECKING,
@@ -58,7 +59,7 @@ def _mp_main(
 
 ) -> None:
     '''
-    The routine called *after fork* which invokes a fresh ``trio.run``
+    The routine called *after fork* which invokes a fresh `trio.run()`
 
     '''
     actor._forkserver_info = forkserver_info
@@ -96,6 +97,107 @@ def _mp_main(
         log.info(f"Subactor {actor.uid} terminated")
 
 
+# TODO: move this func to some kinda `.devx._conc_lang.py` eventually
+# as we work out our multi-domain state-flow-syntax!
+def nest_from_op(
+    input_op: str,
+    #
+    # ?TODO? an idea for a syntax to the state of concurrent systems
+    # as a "3-domain" (execution, scope, storage) model and using
+    # a minimal ascii/utf-8 operator-set.
+    #
+    # try not to take any of this seriously yet XD
+    #
+    # > is a "play operator" indicating (CPU bound)
+    #   exec/work/ops required at the "lowest level computing"
+    #
+    # execution primititves (tasks, threads, actors..) denote their
+    # lifetime with '(' and ')' since parentheses normally are used
+    # in many langs to denote function calls.
+    #
+    # starting = (
+    # >(  opening/starting; beginning of the thread-of-exec (toe?)
+    # (>  opened/started,  (finished spawning toe)
+    # |_<Task: blah blah..>  repr of toe, in py these look like <objs>
+    #
+    # >) closing/exiting/stopping,
+    # )> closed/exited/stopped,
+    # |_<Task: blah blah..>
+    #   [OR <), )< ?? ]
+    #
+    # ending = )
+    # >c) cancelling to close/exit
+    # c)> cancelled (caused close), OR?
+    #  |_<Actor: ..>
+    #   OR maybe "<c)" which better indicates the cancel being
+    #   "delivered/returned" / returned" to LHS?
+    #
+    # >x)  erroring to eventuall exit
+    # x)>  errored and terminated
+    #  |_<Actor: ...>
+    #
+    # scopes: supers/nurseries, IPC-ctxs, sessions, perms, etc.
+    # >{  opening
+    # {>  opened
+    # }>  closed
+    # >}  closing
+    #
+    # storage: like queues, shm-buffers, files, etc..
+    # >[  opening
+    # [>  opened
+    #  |_<FileObj: ..>
+    #
+    # >]  closing
+    # ]>  closed
+
+    # IPC ops: channels, transports, msging
+    # =>  req msg
+    # <=  resp msg
+    # <=> 2-way streaming (of msgs)
+    # <-  recv 1 msg
+    # ->  send 1 msg
+    #
+    # TODO: still not sure on R/L-HS approach..?
+    # =>(  send-req to exec start (task, actor, thread..)
+    # (<=  recv-req to ^
+    #
+    # (<=  recv-req ^
+    # <=(  recv-resp opened remote exec primitive
+    # <=)  recv-resp closed
+    #
+    # )<=c req to stop due to cancel
+    # c=>) req to stop due to cancel
+    #
+    # =>{  recv-req to open
+    # <={  send-status that it closed
+
+    tree_str: str,
+
+    # NOTE: so move back-from-the-left of the `input_op` by
+    # this amount.
+    back_from_op: int = 0,
+) -> str:
+    '''
+    Depth-increment the input (presumably hierarchy/supervision)
+    input "tree string" below the provided `input_op` execution
+    operator, so injecting a `"\n|_{input_op}\n"`and indenting the
+    `tree_str` to nest content aligned with the ops last char.
+
+    '''
+    return (
+        f'{input_op}\n'
+        +
+        textwrap.indent(
+            tree_str,
+            prefix=(
+                len(input_op)
+                -
+                (back_from_op + 1)
+            ) * ' ',
+        )
+    )
+
+
 def _trio_main(
     actor: Actor,
     *,
@@ -107,7 +209,6 @@ def _trio_main(
     Entry point for a `trio_run_in_process` subactor.
 
     '''
-    # __tracebackhide__: bool = True
     _debug.hide_runtime_frames()
 
     _state._current_actor = actor
@@ -119,7 +220,6 @@ def _trio_main(
 
     if actor.loglevel is not None:
         get_console_log(actor.loglevel)
-        import os
         actor_info: str = (
             f'|_{actor}\n'
             f'  uid: {actor.uid}\n'
@@ -128,13 +228,23 @@ def _trio_main(
             f'  loglevel: {actor.loglevel}\n'
         )
         log.info(
-            'Started new trio subactor:\n'
+            'Starting new `trio` subactor:\n'
             +
-            '>\n'  # like a "started/play"-icon from super perspective
+            nest_from_op(
-            +
+                input_op='>(',  # see syntax ideas above
-            actor_info,
+                tree_str=actor_info,
+                back_from_op=1,
+            )
+        )
+    logmeth = log.info
+    exit_status: str = (
+        'Subactor exited\n'
+        +
+        nest_from_op(
+            input_op=')>',  # like a "closed-to-play"-icon from super perspective
+            tree_str=actor_info,
+        )
     )
-
     try:
         if infect_asyncio:
             actor._infected_aio = True
@@ -143,16 +253,28 @@ def _trio_main(
             trio.run(trio_main)
 
     except KeyboardInterrupt:
-        log.cancel(
+        logmeth = log.cancel
-            'Actor received KBI\n'
+        exit_status: str = (
+            'Actor received KBI (aka an OS-cancel)\n'
             +
-            actor_info
+            nest_from_op(
+                input_op='c)>',  # closed due to cancel (see above)
+                tree_str=actor_info,
             )
+        )
+    except BaseException as err:
+        logmeth = log.error
+        exit_status: str = (
+            'Main actor task crashed during exit?\n'
+            +
+            nest_from_op(
+                input_op='x)>',  # closed by error
+                tree_str=actor_info,
+            )
+        )
+        # NOTE since we raise a tb will already be shown on the
+        # console, thus we do NOT use `.exception()` above.
+        raise err
+
     finally:
-        log.info(
+        logmeth(exit_status)
-            'Subactor terminated\n'
-            +
-            'x\n'  # like a "crossed-out/killed" from super perspective
-            +
-            actor_info
-        )