Repository: facebookresearch/hydra

Issue:
[Bug] failure while sanitiainzg exception stack trace in some cases
In some scenarios, one of the insepected frames in the stack trace does not have a module, resulting in a failure to print the underlying error.

The following looks like it's resolving it:

```diff
++ hydra/_internal/utils.py
@@ -248,6 +248,8 @@
                 while end is not None:
                     frame = end.tb_frame
                     mdl = inspect.getmodule(frame)
+                    if mdl is None:
+                        break
-                     assert mdl is not None
```


Discussion:

Resolving patch:
diff --git a/hydra/_internal/utils.py b/hydra/_internal/utils.py
--- a/hydra/_internal/utils.py
+++ b/hydra/_internal/utils.py
@@ -7,7 +7,7 @@
 from dataclasses import dataclass
 from os.path import dirname, join, normpath, realpath
 from traceback import print_exc, print_exception
-from types import FrameType
+from types import FrameType, TracebackType
 from typing import Any, Callable, List, Optional, Sequence, Tuple, Union
 
 from omegaconf.errors import OmegaConfBaseException
@@ -213,75 +213,85 @@ def run_and_report(func: Any) -> Any:
         if _is_env_set("HYDRA_FULL_ERROR") or is_under_debugger():
             raise ex
         else:
-            if isinstance(ex, CompactHydraException):
-                sys.stderr.write(str(ex) + os.linesep)
-                if isinstance(ex.__cause__, OmegaConfBaseException):
-                    sys.stderr.write(str(ex.__cause__) + os.linesep)
-            else:
-                # Custom printing that strips the Hydra related stack frames from the top
-                # And any omegaconf frames from the bottom.
-                # It is possible to add additional libraries to sanitize from the bottom later,
-                # maybe even make it configurable.
-
-                tb: Any = ex.__traceback__
-                search_max = 10
-                # strip Hydra frames from start of stack
-                # will strip until it hits run_job()
-                while search_max > 0:
-                    if tb is None:
-                        break
-                    frame = tb.tb_frame
-                    tb = tb.tb_next
-                    search_max = search_max - 1
-                    if inspect.getframeinfo(frame).function == "run_job":
-                        break
-
-                if search_max == 0 or tb is None:
-                    # could not detect run_job, probably a runtime exception before we got there.
-                    # do not sanitize the stack trace.
-                    print_exc()
-                    sys.exit(1)
-
-                # strip OmegaConf frames from bottom of stack
-                end = tb
-                num_frames = 0
-                while end is not None:
-                    frame = end.tb_frame
-                    mdl = inspect.getmodule(frame)
-                    assert mdl is not None
-                    name = mdl.__name__
-                    if name.startswith("omegaconf."):
-                        break
-                    end = end.tb_next
-                    num_frames = num_frames + 1
-
-                @dataclass
-                class FakeTracebackType:
-                    tb_next: Any = None  # Optional["FakeTracebackType"]
-                    tb_frame: Optional[FrameType] = None
-                    tb_lasti: Optional[int] = None
-                    tb_lineno: Optional[int] = None
-
-                iter_tb = tb
-                final_tb = FakeTracebackType()
-                cur = final_tb
-                added = 0
-                while True:
-                    cur.tb_lasti = iter_tb.tb_lasti
-                    cur.tb_lineno = iter_tb.tb_lineno
-                    cur.tb_frame = iter_tb.tb_frame
-
-                    if added == num_frames - 1:
-                        break
-                    added = added + 1
-                    cur.tb_next = FakeTracebackType()
-                    cur = cur.tb_next
-                    iter_tb = iter_tb.tb_next
-
-                print_exception(etype=None, value=ex, tb=final_tb)  # type: ignore
-            sys.stderr.write(
-                "\nSet the environment variable HYDRA_FULL_ERROR=1 for a complete stack trace.\n"
-            )
+            try:
+                if isinstance(ex, CompactHydraException):
+                    sys.stderr.write(str(ex) + os.linesep)
+                    if isinstance(ex.__cause__, OmegaConfBaseException):
+                        sys.stderr.write(str(ex.__cause__) + os.linesep)
+                else:
+                    # Custom printing that strips the Hydra related stack frames from the top
+                    # And any omegaconf frames from the bottom.
+                    # It is possible to add additional libraries to sanitize from the bottom later,
+                    # maybe even make it configurable.
+
+                    tb = ex.__traceback__
+                    search_max = 10
+                    # strip Hydra frames from start of stack
+                    # will strip until it hits run_job()
+                    while search_max > 0:
+                        if tb is None:
+                            break
+                        frame = tb.tb_frame
+                        tb = tb.tb_next
+                        search_max = search_max - 1
+                        if inspect.getframeinfo(frame).function == "run_job":
+                            break
+
+                    if search_max == 0 or tb is None:
+                        # could not detect run_job, probably a runtime exception before we got there.
+                        # do not sanitize the stack trace.
+                        print_exc()
+                        sys.exit(1)
+
+                    # strip OmegaConf frames from bottom of stack
+                    end: Optional[TracebackType] = tb
+                    num_frames = 0
+                    while end is not None:
+                        frame = end.tb_frame
+                        mdl = inspect.getmodule(frame)
+                        assert mdl is not None
+                        name = mdl.__name__
+                        if name.startswith("omegaconf."):
+                            break
+                        end = end.tb_next
+                        num_frames = num_frames + 1
+
+                    @dataclass
+                    class FakeTracebackType:
+                        tb_next: Any = None  # Optional["FakeTracebackType"]
+                        tb_frame: Optional[FrameType] = None
+                        tb_lasti: Optional[int] = None
+                        tb_lineno: Optional[int] = None
+
+                    iter_tb = tb
+                    final_tb = FakeTracebackType()
+                    cur = final_tb
+                    added = 0
+                    while True:
+                        cur.tb_lasti = iter_tb.tb_lasti
+                        cur.tb_lineno = iter_tb.tb_lineno
+                        cur.tb_frame = iter_tb.tb_frame
+
+                        if added == num_frames - 1:
+                            break
+                        added = added + 1
+                        cur.tb_next = FakeTracebackType()
+                        cur = cur.tb_next
+                        assert iter_tb.tb_next is not None
+                        iter_tb = iter_tb.tb_next
+
+                    print_exception(etype=None, value=ex, tb=final_tb)  # type: ignore
+                sys.stderr.write(
+                    "\nSet the environment variable HYDRA_FULL_ERROR=1 for a complete stack trace.\n"
+                )
+            except Exception as ex2:
+                sys.stderr.write(
+                    "An error occurred during Hydra's exception formatting:"
+                    + os.linesep
+                    + repr(ex2)
+                    + os.linesep
+                )
+                raise ex
         sys.exit(1)
 
 


Test patch:
diff --git a/tests/test_utils.py b/tests/test_utils.py
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,17 +1,22 @@
 # Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
+import io
 import os
 import re
 from pathlib import Path
+from textwrap import dedent
 from typing import Any, Optional
+from unittest.mock import patch
 
 from omegaconf import DictConfig, OmegaConf
 from pytest import mark, param, raises, warns
 
 from hydra import utils
 from hydra._internal.deprecation_warning import deprecation_warning
+from hydra._internal.utils import run_and_report
 from hydra.conf import HydraConf, RuntimeConf
 from hydra.core.hydra_config import HydraConfig
 from hydra.errors import HydraDeprecationError
+from hydra.test_utils.test_utils import assert_regex_match
 
 
 def test_get_original_cwd(hydra_restore_singletons: Any) -> None:
@@ -85,3 +90,152 @@ def test_deprecation_warning(
     else:
         with warns(UserWarning, match=re.escape(msg)):
             deprecation_warning(msg)
+
+
+class TestRunAndReport:
+    """
+    Test the `hydra._internal.utils.run_and_report` function.
+
+    def run_and_report(func: Any) -> Any: ...
+
+    This class defines several test methods:
+      test_success:
+          a simple test case where `run_and_report(func)` succeeds.
+      test_failure:
+          test when `func` raises an exception, and `run_and_report(func)`
+          prints a nicely-formatted error message
+      test_simplified_traceback_failure:
+          test when printing a nicely-formatted error message fails, so
+          `run_and_report` falls back to re-raising the exception from `func`.
+    """
+
+    class DemoFunctions:
+        """
+        The methods of this `DemoFunctions` class are passed to
+        `run_and_report` as the func argument.
+        """
+
+        @staticmethod
+        def success_func() -> Any:
+            return 123
+
+        @staticmethod
+        def simple_error() -> None:
+            assert False, "simple_err_msg"
+
+        @staticmethod
+        def run_job_wrapper() -> None:
+            """
+            Trigger special logic in `run_and_report` that looks for a function
+            called "run_job" in the stack and strips away the leading stack
+            frames.
+            """
+
+            def run_job() -> None:
+                def nested_error() -> None:
+                    assert False, "nested_err"
+
+                nested_error()
+
+            run_job()
+
+        @staticmethod
+        def omegaconf_job_wrapper() -> None:
+            """
+            Trigger special logic in `run_and_report` that looks for the
+            `omegaconf` module in the stack and strips away the bottom stack
+            frames.
+            """
+
+            def run_job() -> None:
+                def job_calling_omconf() -> None:
+                    from omegaconf import OmegaConf
+
+                    # The below causes an exception:
+                    OmegaConf.resolve(123)  # type: ignore
+
+                job_calling_omconf()
+
+            run_job()
+
+    def test_success(self) -> None:
+        assert run_and_report(self.DemoFunctions.success_func) == 123
+
+    @mark.parametrize(
+        "demo_func, expected_traceback_regex",
+        [
+            param(
+                DemoFunctions.simple_error,
+                dedent(
+                    r"""
+                    Traceback \(most recent call last\):$
+                      File "[^"]+", line \d+, in run_and_report$
+                        return func\(\)$
+                      File "[^"]+", line \d+, in simple_error$
+                        assert False, "simple_err_msg"$
+                    AssertionError: simple_err_msg$
+                    assert False$
+                    """
+                ),
+                id="simple_failure_full_traceback",
+            ),
+            param(
+                DemoFunctions.run_job_wrapper,
+                dedent(
+                    r"""
+                    Traceback \(most recent call last\):$
+                      File "[^"]+", line \d+, in nested_error$
+                        assert False, "nested_err"$
+                    AssertionError: nested_err$
+                    assert False$
+                    Set the environment variable HYDRA_FULL_ERROR=1 for a complete stack trace\.$
+                    """
+                ),
+                id="strip_run_job_from_top_of_stack",
+            ),
+            param(
+                DemoFunctions.omegaconf_job_wrapper,
+                dedent(
+                    r"""
+                    Traceback \(most recent call last\):$
+                      File "[^"]+", line \d+, in job_calling_omconf$
+                        OmegaConf.resolve\(123\)  # type: ignore$
+                    ValueError: Invalid config type \(int\), expected an OmegaConf Container$
+                    Set the environment variable HYDRA_FULL_ERROR=1 for a complete stack trace\.$
+                    """
+                ),
+                id="strip_omegaconf_from_bottom_of_stack",
+            ),
+        ],
+    )
+    def test_failure(self, demo_func: Any, expected_traceback_regex: str) -> None:
+        mock_stderr = io.StringIO()
+        with raises(SystemExit, match="1"), patch("sys.stderr", new=mock_stderr):
+            run_and_report(demo_func)
+        mock_stderr.seek(0)
+        stderr_output = mock_stderr.read()
+        assert_regex_match(expected_traceback_regex, stderr_output)
+
+    def test_simplified_traceback_failure(self) -> None:
+        """
+        Test that a warning is printed and the original exception is re-raised
+        when an exception occurs during the simplified traceback logic.
+        """
+        demo_func = self.DemoFunctions.run_job_wrapper
+        expected_traceback_regex = dedent(
+            r"""
+            An error occurred during Hydra's exception formatting:$
+            AssertionError\(.*\)$
+            """
+        )
+        mock_stderr = io.StringIO()
+        with raises(AssertionError, match="nested_err"), patch(
+            "sys.stderr", new=mock_stderr
+        ):
+            # patch `inspect.getmodule` so that an exception will occur in the
+            # simplified traceback logic:
+            with patch("inspect.getmodule", new=lambda *args: None):
+                run_and_report(demo_func)
+        mock_stderr.seek(0)
+        stderr_output = mock_stderr.read()
+        assert_regex_match(expected_traceback_regex, stderr_output)