use tblib to enable pickleable tracebacks

_trio_parallel_workers/__init__.py

@@ -15,6 +15,9 @@
     from pickle import dumps, loads
 
 from outcome import capture, Error
+from tblib.pickling_support import install
+
+install()
 
 MAX_TIMEOUT = 24.0 * 60.0 * 60.0
 ACK = b"\x06"

_trio_parallel_workers/_funcs.py

@@ -92,3 +92,10 @@ def _monkeypatch_max_timeout():
 
 def _no_trio():
     return "trio" not in sys.modules
+
+
+def _chained_exc():
+    try:
+        raise ValueError('test1')
+    except BaseException as e:
+        raise TypeError('test2') from e

newsfragments/323.feature.rst

@@ -0,0 +1,2 @@
+Use ``tblib`` to enable pickling of tracebacks between processes. Mainly, this
+preserves context of exceptions including chained exceptions.

requirements/build.txt

@@ -13,7 +13,7 @@ packaging==21.3
     # via
     #   build
     #   setuptools-scm
-pep517==0.12.0
+pep517==0.13.0
     # via build
 pyparsing==3.0.9
     # via packaging
@@ -30,7 +30,7 @@ wheel==0.37.1
     # via -r requirements\build.in
 
 # The following packages are considered to be unsafe in a requirements file:
-setuptools==63.1.0
+setuptools==65.3.0
     # via
     #   -r requirements\build.in
     #   setuptools-scm

requirements/coverage.txt

@@ -5,7 +5,7 @@
 #
 #    pip-compile-multi
 #
-coverage[toml]==6.4.1
+coverage[toml]==6.4.4
     # via -r requirements\coverage.in
 tomli==2.0.1
     # via coverage

requirements/docs.txt

@@ -10,13 +10,13 @@ alabaster==0.7.12
     # via sphinx
 babel==2.10.3
     # via sphinx
-certifi==2022.6.15
+certifi==2022.9.14
     # via requests
 cffi==1.15.1 ; os_name == "nt" and implementation_name != "pypy"
     # via
     #   -r requirements\install.in
     #   trio
-charset-normalizer==2.1.0
+charset-normalizer==2.1.1
     # via requests
 click==8.1.3
     # via
@@ -44,17 +44,17 @@ markupsafe==2.1.1
     # via jinja2
 packaging==21.3
     # via sphinx
-pygments==2.12.0
+pygments==2.13.0
     # via sphinx
 pyparsing==3.0.9
     # via packaging
-pytz==2022.1
+pytz==2022.2.1
     # via babel
 requests==2.28.1
     # via sphinx
 snowballstemmer==2.2.0
     # via sphinx
-sphinx==5.0.2
+sphinx==5.1.1
     # via
     #   -r requirements\docs.in
     #   sphinx-rtd-theme
@@ -77,11 +77,11 @@ sphinxcontrib-trio==1.1.2
     # via -r requirements\docs.in
 tomli==2.0.1
     # via towncrier
-towncrier==21.9.0
+towncrier==22.8.0
     # via -r requirements\docs.in
-urllib3==1.26.10
+urllib3==1.26.12
     # via requests
 
 # The following packages are considered to be unsafe in a requirements file:
-setuptools==63.1.0
+setuptools==65.3.0
     # via towncrier

requirements/install.in

@@ -2,4 +2,5 @@
 trio >= 0.18.0
 outcome
 attrs >= 17.3.0
-cffi; os_name == 'nt' and implementation_name != 'pypy'
+cffi; os_name == 'nt' and implementation_name != 'pypy'
+tblib

requirements/install.txt

@@ -1,4 +1,4 @@
-# SHA1:bb6e9a7b5d2a35f9ddeec40f11d7bc137ea27c3e
+# SHA1:63e73656a123a857e40bd1da6cce5906958410ed
 #
 # This file is autogenerated by pip-compile-multi
 # To update, run:
@@ -7,7 +7,7 @@
 #
 async-generator==1.10
     # via trio
-attrs==21.4.0
+attrs==22.1.0
     # via
     #   -r requirements\install.in
     #   outcome
@@ -16,17 +16,19 @@ cffi==1.15.1 ; os_name == "nt" and implementation_name != "pypy"
     # via
     #   -r requirements\install.in
     #   trio
-idna==3.3
+idna==3.4
     # via trio
 outcome==1.2.0
     # via
     #   -r requirements\install.in
     #   trio
 pycparser==2.21
     # via cffi
-sniffio==1.2.0
+sniffio==1.3.0
     # via trio
 sortedcontainers==2.4.0
     # via trio
+tblib==1.7.0
+    # via -r requirements\install.in
 trio==0.21.0
     # via -r requirements\install.in

requirements/lint.txt

@@ -5,25 +5,25 @@
 #
 #    pip-compile-multi
 #
-black==22.6.0
+black==22.8.0
     # via -r requirements\lint.in
 click==8.1.3
     # via black
 colorama==0.4.5
     # via click
-flake8==4.0.1
+flake8==5.0.4
     # via -r requirements\lint.in
-mccabe==0.6.1
+mccabe==0.7.0
     # via flake8
 mypy-extensions==0.4.3
     # via black
-pathspec==0.9.0
+pathspec==0.10.1
     # via black
 platformdirs==2.5.2
     # via black
-pycodestyle==2.8.0
+pycodestyle==2.9.1
     # via flake8
-pyflakes==2.4.0
+pyflakes==2.5.0
     # via flake8
 tomli==2.0.1
     # via black

requirements/test.txt

@@ -6,15 +6,13 @@
 #    pip-compile-multi
 #
 -r install.txt
-atomicwrites==1.4.1
-    # via pytest
 cffi==1.15.1 ; os_name == "nt" and implementation_name != "pypy"
     # via
     #   -r requirements\install.in
     #   trio
 colorama==0.4.5
     # via pytest
-coverage[toml]==6.4.1
+coverage[toml]==6.4.4
     # via
     #   -r requirements\test.in
     #   pytest-cov
@@ -28,7 +26,7 @@ py==1.11.0
     # via pytest
 pyparsing==3.0.9
     # via packaging
-pytest==7.1.2
+pytest==7.1.3
     # via
     #   -r requirements\test.in
     #   pytest-cov

setup.cfg

@@ -36,6 +36,7 @@ install_requires =
     outcome
     attrs >= 17.3.0
     cffi; os_name == 'nt' and implementation_name != 'pypy'
+    tblib
 python_requires = >=3.7
 
 [options.extras_require]

trio_parallel/_tests/test_worker.py

@@ -3,11 +3,12 @@
     All workers should pass these tests, regardless of implementation
 """
 import math
+import traceback
 
 import pytest
 import trio
 
-from _trio_parallel_workers._funcs import _null_async_fn
+from _trio_parallel_workers._funcs import _null_async_fn, _chained_exc
 from .._impl import WORKER_MAP
 
 
@@ -68,3 +69,17 @@ async def test_clean_exit_on_shutdown(worker, capfd):
     out, err = capfd.readouterr()
     assert not out
     assert not err
+
+
+async def test_tracebacks(worker):
+    await worker.start()
+    try:
+        (await worker.run_sync(_chained_exc)).unwrap()
+    except TypeError as e:
+        assert str(e) == "test2"
+        text = "".join(traceback.format_exception(type(e), e, e.__traceback__))
+    else:  # pragma: no cover
+        assert False, "an error should be raised"
+
+    assert "raise ValueError(" in text
+    assert "raise TypeError(" in text