What causes "Unknown type {value.__class__.__name__} for {key}" in nodejs/node?

Replace the offending value with a string or int — e.g. use '1'/'0' or 1/0 instead of True/False, and a string for floats.

nodejs/node · error · TypeError

Unknown type {value.class.name} for {key}

Error message

Unknown type {value.__class__.__name__} for {key}

What it means

When ProcessVariablesAndConditionsInDict recurses over the_dict's keys, it handles dict, list, str, and int values; anything else (e.g. a bool, float, None, tuple) reaches the final elif and raises this TypeError naming the class and the key. GYP build dicts are JSON-like and only support those four value types.

Source

Thrown at tools/gyp/pylib/gyp/input.py:1398

    for key, value in the_dict.items():
        # Skip "variables" and string values, which were already processed if
        # present.
        if key == "variables" or isinstance(value, str):
            continue
        if isinstance(value, dict):
            # Pass a copy of the variables dict so that subdicts can't influence
            # parents.
            ProcessVariablesAndConditionsInDict(
                value, phase, variables, build_file, key
            )
        elif isinstance(value, list):
            # The list itself can't influence the variables dict, and
            # ProcessVariablesAndConditionsInList will make copies of the variables
            # dict if it needs to pass it to something that can influence it.  No
            # copy is necessary here.
            ProcessVariablesAndConditionsInList(value, phase, variables, build_file)
        elif not isinstance(value, int):
            raise TypeError("Unknown type " + value.__class__.__name__ + " for " + key)


def ProcessVariablesAndConditionsInList(the_list, phase, variables, build_file):
    # Iterate using an index so that new values can be assigned into the_list.
    index = 0
    while index < len(the_list):
        item = the_list[index]
        if isinstance(item, dict):
            # Make a copy of the variables dict so that it won't influence anything
            # outside of its own scope.
            ProcessVariablesAndConditionsInDict(item, phase, variables, build_file)
        elif isinstance(item, list):
            ProcessVariablesAndConditionsInList(item, phase, variables, build_file)
        elif isinstance(item, str):
            expanded = ExpandVariables(item, phase, variables, build_file)
            if type(expanded) in (str, int):
                the_list[index] = expanded
            elif isinstance(expanded, list):

View on GitHub (pinned to 1b2de5e052)

Solutions

Replace the offending value with a string or int — e.g. use '1'/'0' or 1/0 instead of True/False, and a string for floats.
Remove the key if it is not meaningful to GYP.
Audit the programmatic caller or .gypi include that produced the value.

Example fix

// before
'enable_feature': True,
// after
'enable_feature': 1,  // or '1'

Defensive patterns

Strategy: type-guard

Validate before calling

for key, value in the_dict.items():
    assert isinstance(value, (dict, list, str, int)), \
        f'Value for {key!r} has unsupported type {type(value).__name__}'

Type guard

def is_supported_gyp_value(value) -> bool:
    return isinstance(value, (dict, list, str, int)) and not isinstance(value, bool)

Prevention

GYP has no native boolean — use '1'/'0' or 1/0.
Avoid None/null values in .gyp and .gypi files.
Lint programmatic gyp callers to emit only dict/list/str/int.

When it happens

Trigger: A .gyp file (or a programmatic gyp caller) places a bool, float, None, or tuple as a dict value; JSON config injection that yields null/true/false where GYP expects a string/int; hand-edit introducing a Python-only literal.

Common situations: Writing 'something': None or 'flag': True in a .gyp file (GYP has no native boolean — use '1'/'0'); floating-point versions; a templating layer injecting JSON nulls.

Related errors

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/b9a97905a95bfa30. Report an issue: GitHub.