dotnet/runtime · error · NotImplementedError

{coreclr_args.mode}

Error message

{coreclr_args.mode}

What it means

Raised as a defensive fallback in superpmi.py's main() dispatch when coreclr_args.mode does not match any of the implemented modes (collect, replay, asmdiffs, tpdiff, metricdiff, upload, upload-private, download, list-collections, merge-mch, summarize). It signals that a mode value reached the dispatch chain at src/coreclr/scripts/superpmi.py:6126 without a matching elif handler.

Source

Thrown at src/coreclr/scripts/superpmi.py:6126

        elapsed_time = end_time - begin_time

        logging.debug("Finish time: %s", end_time.strftime("%H:%M:%S"))
        logging.debug("Elapsed time: %s", elapsed_time)

    elif coreclr_args.mode == "list-collections":
        if coreclr_args.local:
            list_collections_local_command(coreclr_args)
        else:
            list_collections_command(coreclr_args)

    elif coreclr_args.mode == "merge-mch":
        success = merge_mch(coreclr_args)

    elif coreclr_args.mode == "summarize":
        summarize_json_summaries(coreclr_args)

    else:
        raise NotImplementedError(coreclr_args.mode)

    return 0 if success else 1

################################################################################
# __main__
################################################################################

if __name__ == "__main__":
    args = parser.parse_args()
    sys.exit(main(args))

View on GitHub (pinned to 60108ba66e)

Solutions

1. Run `python superpmi.py --help` to list valid subcommands and use the exact name.
2. Check for typos or stray whitespace in the mode argument.
3. Grep the checked-out superpmi.py for `coreclr_args.mode ==` to confirm the mode is implemented in this version.
4. If you are adding a new mode, add a matching elif branch in both dispatch blocks (setup near line 5333 and run near line 5918).

Example fix

// before
python superpmi.py collcet -core_root ...
// after
python superpmi.py collect -core_root ...

valid_modes = {'collect', 'replay', 'asmdiffs', 'tpdiff', 'metricdiff',
                  'upload', 'upload-private', 'download', 'list-collections',
                  'merge-mch', 'summarize'}
if coreclr_args.mode not in valid_modes:
    parser.error(f"Unknown mode '{coreclr_args.mode}'. Valid: {sorted(valid_modes)}")

When it happens

Trigger: Passing an unrecognized or misspelled --mode/subcommand to superpmi.py, or invoking main() with a mode string that exists in the argument parser but has no corresponding elif branch in the run-dispatch block.

Common situations: Typos in the mode name (e.g. 'collcet'), using a mode name from a different/newer checkout than the one running, or programmatic calls that set coreclr_args.mode to an unhandled value.

Related errors

• Unknown OS.
• Invalid arch.
• Pass only one tiering option.
• Collection 'smoke_tests' is only available for 'nativeaot' c
• Cannot find System.Private.CoreLib.dll at {corelib_src}

AI-assisted analysis of dotnet/runtime@60108ba66e (2026-08-10). Data as JSON: /api/errors/2ff4869c4835395a. Report an issue: GitHub.