Suppress verbose tracebacks by default, show only with -vv by Copilot · Pull Request #852 · NOAA-GFDL/fre-cli

Copilot · 2026-04-09T14:40:01Z

Describe your changes

Unhandled exceptions currently dump full Python stack traces, burying the actual error message in noise. This installs a custom sys.excepthook in the fre() entry point that shows only the error type and message at default/-v verbosity, with a hint to use -vv for the full traceback.

Before (default):

clone of FMSpid exited with status 128
Traceback (most recent call last):
  File "...", line 8, in <module>
    sys.exit(fre())
  ... (20+ lines of click internals) ...
subprocess.CalledProcessError: Command '...' returned non-zero exit status 128.

After (default):

CalledProcessError: Command '...' returned non-zero exit status 128.
(use 'fre -vv ...' for the full traceback)

After (fre -vv): full traceback, same as current behavior.

Changes:

fre/fre.py: Set sys.excepthook to a brief formatter when log_level > DEBUG. Updated -v help text.
fre/tests/test_fre_cli.py: Three subprocess-based tests covering default, -v, and -vv traceback behavior.
docs/tools.rst: Document traceback suppression under the -v[v] flag.

Issue ticket number and link (if applicable)

Checklist before requesting a review

I ran my code
I tried to make my code readable
I tried to comment my code
I wrote a new test, if applicable
I wrote new instructions/documentation, if applicable
I ran pytest and inspected it's output
I ran pylint and attempted to implement some of it's feedback
No print statements; all user-facing info uses logging module

Install a custom sys.excepthook in the fre() entry point that suppresses Python tracebacks at default and -v verbosity levels. At -vv (DEBUG), the full traceback is shown. At lower levels, only the exception type and message are printed, along with a hint to use 'fre -vv ...' for more detail. Closes #793 Agent-Logs-Url: https://github.com/NOAA-GFDL/fre-cli/sessions/d594a572-8566-467b-9a96-4b233d712582 Co-authored-by: ilaflott <6273252+ilaflott@users.noreply.github.com>

Agent-Logs-Url: https://github.com/NOAA-GFDL/fre-cli/sessions/d594a572-8566-467b-9a96-4b233d712582 Co-authored-by: ilaflott <6273252+ilaflott@users.noreply.github.com>

codecov · 2026-04-14T20:43:41Z

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.32%. Comparing base (4d4ac66) to head (dbb88b5).

Files with missing lines	Patch %	Lines
fre/fre.py	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #852      +/-   ##
==========================================
- Coverage   84.35%   84.32%   -0.03%     
==========================================
  Files          71       71              
  Lines        4997     5003       +6     
==========================================
+ Hits         4215     4219       +4     
- Misses        782      784       +2

Flag	Coverage Δ
unittests	`84.32% <66.66%> (-0.03%)`	⬇️

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Files with missing lines	Coverage Δ
fre/fre.py	`94.44% <66.66%> (-5.56%)`	⬇️

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singhd789 · 2026-05-06T19:19:05Z

@ilaflott is this ready for review? Seems like it could be pretty helpful in generating easier-to-look at output!

ilaflott · 2026-05-06T19:24:40Z

untested and i haven't checked copilot's output very closely

Copilot

Pull request overview

This PR changes the fre CLI’s default behavior for unexpected/unhandled exceptions to reduce noisy stack traces, showing a brief ExceptionType: message output by default (and with -v), while preserving full tracebacks when users opt into -vv (debug verbosity).

Changes:

Add a custom sys.excepthook in the fre click group entrypoint to suppress tracebacks unless debug logging is enabled.
Add subprocess-based tests to validate default, -v, and -vv traceback behavior.
Document the new traceback behavior under the -v[v] flag in the tools documentation.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
`fre/fre.py`	Installs a brief `sys.excepthook` when not in debug verbosity; updates `-v` help text to mention traceback behavior.
`fre/tests/test_fre_cli.py`	Adds subprocess tests to exercise real interpreter-level exception printing and verify suppression vs full tracebacks.
`docs/tools.rst`	Documents that default / `-v` suppress tracebacks and `-vv` shows full tracebacks.

+    # install custom exception hook to suppress tracebacks unless -vv is used
+    if log_level > logging.DEBUG:
+        def _brief_excepthook(exc_type, exc_value, exc_tb):
+            click.echo(f"{exc_type.__name__}: {exc_value}", err=True)
+            click.echo("(use 'fre -vv ...' for the full traceback)", err=True)
+        sys.excepthook = _brief_excepthook


    fre_logger.debug('click entry-point function call done.')
+
+    # install custom exception hook to suppress tracebacks unless -vv is used
+    if log_level > logging.DEBUG:
+        def _brief_excepthook(exc_type, exc_value, exc_tb):
+            click.echo(f"{exc_type.__name__}: {exc_value}", err=True)
+            click.echo("(use 'fre -vv ...' for the full traceback)", err=True)
+        sys.excepthook = _brief_excepthook


 @click.option( '-v', '--verbose', default = 0, required = False, count = True, type = int,
               help = "Increment logging verbosity from default (logging.WARNING) to logging.INFO. " + \
-                      "use -vv for logging.DEBUG. will be overridden by -q/--quiet" )
+                      "use -vv for logging.DEBUG and to show full tracebacks on errors. " + \
+                      "will be overridden by -q/--quiet" )


+def test_traceback_suppressed_by_default():
+    '''fre run function - default verbosity should suppress traceback'''
+    result = _run_fre_subprocess(["fre", "run", "function"])
+    assert result.returncode != 0
+    assert "NotImplementedError" in result.stderr
+    assert "Traceback" not in result.stderr
+    assert "fre -vv" in result.stderr
+
+def test_traceback_suppressed_with_single_v():
+    '''fre -v run function - single -v should still suppress traceback'''
+    result = _run_fre_subprocess(["fre", "-v", "run", "function"])
+    assert result.returncode != 0
+    assert "NotImplementedError" in result.stderr
+    assert "Traceback" not in result.stderr
+    assert "fre -vv" in result.stderr
+
+def test_traceback_shown_with_vv():
+    '''fre -vv run function - double -v should show full traceback'''
+    result = _run_fre_subprocess(["fre", "-vv", "run", "function"])
+    assert result.returncode != 0
+    assert "NotImplementedError" in result.stderr
+    assert "Traceback" in result.stderr
+    assert "fre -vv" not in result.stderr


Initial plan

abe33ca

Copilot AI assigned Copilot and ilaflott Apr 9, 2026

Copilot started work on behalf of ilaflott April 9, 2026 15:06 View session

Copilot AI linked an issue Apr 9, 2026 that may be closed by this pull request

Cleaner Error messages #849

Open

Copilot AI and others added 2 commits April 9, 2026 15:11

Fix em dashes in test docstrings per code review

cf83c57

Agent-Logs-Url: https://github.com/NOAA-GFDL/fre-cli/sessions/d594a572-8566-467b-9a96-4b233d712582 Co-authored-by: ilaflott <6273252+ilaflott@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Refactor error messages for clarity~~ Suppress verbose tracebacks by default, show only with -vv Apr 9, 2026

Copilot finished work on behalf of ilaflott April 9, 2026 15:17

Copilot AI requested a review from ilaflott April 9, 2026 15:17

ilaflott unassigned ilaflott and Copilot Apr 14, 2026

ilaflott requested review from uramirez8707 and removed request for ilaflott April 14, 2026 20:25

ilaflott assigned uramirez8707 Apr 14, 2026

Merge branch 'main' into copilot/cleaner-error-messages

dbb88b5

ilaflott requested a review from Copilot May 6, 2026 19:24

singhd789 self-requested a review May 6, 2026 19:25

Copilot started reviewing on behalf of ilaflott May 6, 2026 19:25 View session

Copilot AI reviewed May 6, 2026

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Suppress verbose tracebacks by default, show only with -vv#852

Suppress verbose tracebacks by default, show only with -vv#852
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Copilot AI commented Apr 9, 2026 •

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