Add `TransportClosed.from_src_exc()`

Such that re-wrapping/raising from a low-level `trio` resource error is
simpler and includes the `.src_exc` in the `__repr__()` and
`.message/.args` rendered at higher layers (like from `Channel` and
`._rpc` machinery).

Impl deats,
- mainly leverages packing in a new cls-method `.repr_src_exc() -> str:`
  repr of the underlying error before an optional `body: str` all as
  handled by the previously augmented `.pformat()`'s delegation to
  `pformat_exc()`.
- change `.src_exc` to be a property around a renamed `._src_exc`.

But wait, why?
- use it inside `MsgpackTransport.send()` to rewrap any
  `trio.BrokenResourceError`s so we always see the underlying
  `trio`-src-exc just like in the `.recv()._iter_packets()` handlers.

tractor/_exceptions.py

@@ -948,7 +948,8 @@ class TransportClosed(Exception):
         self._loglevel: str = loglevel
         super().__init__(message)
 
-        self.src_exc = src_exc
+        self._src_exc = src_exc
+        # set the cause manually if not already set by python
         if (
             src_exc is not None
             and
@@ -960,9 +961,18 @@ class TransportClosed(Exception):
         # the exc in its `TransportClosed` handler block.
         self._raise_on_report = raise_on_report
 
+    @property
+    def src_exc(self) -> Exception:
+        return (
+            self.__cause__
+            or
+            self._src_exc
+        )
+
     def report_n_maybe_raise(
         self,
         message: str|None = None,
+        hide_tb: bool = True,
 
     ) -> None:
         '''
@@ -970,9 +980,10 @@ class TransportClosed(Exception):
         for this error.
 
         '''
+        __tracebackhide__: bool = hide_tb
         message: str = message or self.message
         # when a cause is set, slap it onto the log emission.
-        if cause := self.__cause__:
+        if cause := self.src_exc:
             cause_tb_str: str = ''.join(
                 traceback.format_tb(cause.__traceback__)
             )
@@ -991,26 +1002,76 @@ class TransportClosed(Exception):
         if self._raise_on_report:
             raise self from cause
 
+    @classmethod
+    def repr_src_exc(
+        self,
+        src_exc: Exception|None = None,
+    ) -> str:
+
+        if src_exc is None:
+            return '<unknown>'
+
+        src_msg: tuple[str] = src_exc.args
+        src_exc_repr: str = (
+            f'{type(src_exc).__name__}[ {src_msg} ]'
+        )
+        return src_exc_repr
+
     def pformat(self) -> str:
         from tractor.devx.pformat import (
             pformat_exc,
         )
-        src_err: Exception|None = self.src_exc or '<unknown>'
-        src_msg: tuple[str] = src_err.args
-        src_exc_repr: str = (
-            f'{type(src_err).__name__}[ {src_msg} ]'
-        )
         return pformat_exc(
             exc=self,
-            # message=self.message,  # implicit!
-            body=(
-                f' |_src_exc: {src_exc_repr}\n'
-            ),
         )
 
     # delegate to `str`-ified pformat
     __repr__ = pformat
 
+    @classmethod
+    def from_src_exc(
+        cls,
+        src_exc: (
+            Exception|
+            trio.ClosedResource|
+            trio.BrokenResourceError
+        ),
+        message: str,
+        body: str = '',
+        **init_kws,
+    ) -> TransportClosed:
+        '''
+        Convenience constructor for creation from an underlying
+        `trio`-sourced async-resource/chan/stream error.
+
+        Embeds the original `src_exc`'s repr within the
+        `Exception.args` via a first-line-in-`.message`-put-in-header
+        pre-processing and allows inserting additional content beyond
+        the main message via a `body: str`.
+
+        '''
+        repr_src_exc: str = cls.repr_src_exc(
+            src_exc,
+        )
+        next_line: str = f'  src_exc: {repr_src_exc}\n'
+        if body:
+            body: str = textwrap.indent(
+                body,
+                prefix=' '*2,
+            )
+
+        return TransportClosed(
+            message=(
+                message
+                +
+                next_line
+                +
+                body
+            ),
+            src_exc=src_exc,
+            **init_kws,
+        )
+
 
 class NoResult(RuntimeError):
     "No final result is expected for this actor"

tractor/ipc/_transport.py

@@ -367,7 +367,7 @@ class MsgpackTransport(MsgTransport):
         msg: msgtypes.MsgType,
 
         strict_types: bool = True,
-        hide_tb: bool = False,
+        hide_tb: bool = True,
 
     ) -> None:
         '''
@@ -430,8 +430,9 @@ class MsgpackTransport(MsgTransport):
                 return await self.stream.send_all(size + bytes_data)
             except (
                 trio.BrokenResourceError,
-            ) as trans_err:
+            ) as bre:
-                loglevel = 'transport'
+                trans_err = bre
+                tpt_name: str = f'{type(self).__name__!r}'
                 match trans_err:
                     case trio.BrokenResourceError() if (
                         '[Errno 32] Broken pipe' in trans_err.args[0]
@@ -442,21 +443,22 @@ class MsgpackTransport(MsgTransport):
                         #    as it pertains to rando pings from the
                         #    `.discovery` subsys and protos.
                     ):
-                        raise TransportClosed(
+                        raise TransportClosed.from_src_exc(
                             message=(
-                                f'IPC transport already closed by peer\n'
+                                f'{tpt_name} already closed by peer\n'
-                                f'x)> {type(trans_err)}\n'
-                                f' |_{self}\n'
                             ),
-                            loglevel=loglevel,
+                            body=f'{self}\n',
-                        ) from trans_err
+                            src_exc=trans_err,
+                            raise_on_report=True,
+                            loglevel='transport',
+                        ) from bre
 
                     # unless the disconnect condition falls under "a
                     # normal operation breakage" we usualy console warn
                     # about it.
                     case _:
                         log.exception(
-                            'Transport layer failed for {self.transport!r} ?\n'
+                            '{tpt_name} layer failed pre-send ??\n'
                         )
                         raise trans_err
 
@@ -501,11 +503,11 @@ class MsgpackTransport(MsgTransport):
     def pformat(self) -> str:
         return (
             f'<{type(self).__name__}(\n'
-            f' |_task: {self._task}\n'
-            f'\n'
             f' |_peers: 2\n'
             f'   laddr: {self._laddr}\n'
             f'   raddr: {self._raddr}\n'
+            # f'\n'
+            f' |_task: {self._task}\n'
             f')>\n'
         )