def fluent_astify_message()

in python/moz/l10n/formats/fluent/serialize.py [0:0]

• 43 lines of code
• 18 McCabe index (conditional complexity)

def fluent_astify_message(message: str | Message) -> ftl.Pattern:
    """
    Transform a message into a corresponding Fluent AST pattern.

    Function names are upper-cased, and expressions using the `message` function
    are mapped to message and term references.
    """

    if isinstance(message, str):
        return ftl.Pattern([ftl.TextElement(message)])
    if not isinstance(message, (PatternMessage, SelectMessage)):
        raise ValueError(f"Unsupported message: {message}")
    if isinstance(message, PatternMessage):
        return flat_pattern(message.declarations, message.pattern)

    # It gets a bit complicated for SelectMessage. We'll be modifying this list,
    # building select expressions for each selector starting from the last one
    # until this list has only one entry `[[], pattern]`.
    #
    # We rely on the variants being in order, so that a variant with N keys
    # will be next to all other variants for which the first N-1 keys are equal.
    variants = [
        (list(keys), flat_pattern(message.declarations, value))
        for keys, value in message.variants.items()
    ]

    other = fallback_name(message)
    keys0 = variants[0][0]
    while keys0:
        selector = value(message.declarations, message.selectors[len(keys0) - 1])
        if (
            isinstance(selector, ftl.FunctionReference)
            and selector.id.name == "NUMBER"
            and selector.arguments.positional
            and isinstance(selector.arguments.positional[0], ftl.VariableReference)
            and not selector.arguments.named
        ):
            selector = selector.arguments.positional[0]
        base_keys = []
        sel_exp = None
        i = 0
        while i < len(variants):
            keys, pattern = variants[i]
            key = keys.pop()  # Ultimately modifies keys0
            ftl_variant = ftl.Variant(
                variant_key(key, other), pattern, isinstance(key, CatchallKey)
            )
            if sel_exp and keys == base_keys:
                sel_exp.variants.append(ftl_variant)
                variants.pop(i)
            else:
                base_keys = keys
                sel_exp = ftl.SelectExpression(selector.clone(), [ftl_variant])
                variants[i] = (keys, ftl.Pattern([ftl.Placeable(sel_exp)]))
                i += 1
    if len(variants) != 1:
        raise ValueError(f"Error resolving select message variants (n={len(variants)})")
    return variants[0][1]