reflex-dev/reflex · error · ValueError

Only one default import is allowed.

Error message

Only one default import is allowed.

What it means

compile_import_statement validates an ImportTag set and raises ValueError when two or more fields in a single import statement are marked as default imports. An ES module import can have only one default binding (e.g. import Def, { named } from 'mod'), so multiple defaults are ambiguous.

Source

Thrown at reflex/compiler/utils.py:70

    Args:
        fields: The set of fields to import from the library.

    Returns:
        The libraries for default and rest.
        default: default library. When install "import def from library".
        rest: rest of libraries. When install "import {rest1, rest2} from library"

    Raises:
        ValueError: If there is more than one default import.
    """
    # ignore the ImportVar fields with render=False during compilation
    fields_set = {field for field in fields if field.render}

    # Check for default imports.
    defaults = {field for field in fields_set if field.is_default}
    if len(defaults) >= 2:
        msg = "Only one default import is allowed."
        raise ValueError(msg)

    # Get the default import, and the specific imports.
    default = next(iter({field.name for field in defaults}), "")
    rest = {field.name for field in fields_set - defaults}

    return default, sorted(rest)


def validate_imports(import_dict: ParsedImportDict):
    """Verify that the same Tag is not used in multiple import.

    Args:
        import_dict: The dict of imports to validate

    Raises:
        ValueError: if a conflict on "tag/alias" is detected for an import.
    """
    used_tags = {}

View on GitHub (pinned to 45b8ed5ab7)

Solutions

1. Ensure only one field per module uses the default import; convert extras to named imports
2. Audit custom component code that builds import dicts manually and deduplicate default tags
3. After upgrading Reflex, regenerate or update import declarations to the current API (rxImportVar / ImportTag usage)

Example fix

# before
imports = {"react": [ImportVar(tag="default", is_default=True), ImportVar(tag="other", is_default=True)]}
# after
imports = {"react": [ImportVar(tag="default", is_default=True), ImportVar(tag="other")]}

defaults = [f for f in fields if f.is_default]
assert len(defaults) <= 1, "only one default import per module"

When it happens

Trigger: Passing multiple fields with is_default=True for the same module when building an import statement, e.g. via custom components or libraries constructing ImportVar/ImportTag lists with several defaults; merging imports that each carry their own default tag for the same package.

Common situations: Custom component libraries or code generators emitting two default ImportVars for one module; Reflex version changes altering how default imports are declared (older field-based API vs newer ImportTag API) after an upgrade.

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AI-assisted analysis of reflex-dev/reflex@45b8ed5ab7 (2026-08-28). Data as JSON: /api/errors/7aa0487057caa438. Report an issue: GitHub.