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Drop nulls

drop_nulls

Drop-nulls strategy — remove empty values recursively.

DropNullsStrategy

Bases: SmeltStrategy

Recursively remove None, empty strings, empty lists, and empty dicts.

Source code in packages/axm-smelt/src/axm_smelt/strategies/drop_nulls.py
Python
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class DropNullsStrategy(SmeltStrategy):
    """Recursively remove None, empty strings, empty lists, and empty dicts."""

    @property
    def name(self) -> str:
        """Strategy identifier used in the registry."""
        return "drop_nulls"

    @property
    def category(self) -> str:
        """Strategy category (``structural``)."""
        return "structural"

    def apply(self, ctx: SmeltContext) -> SmeltContext:
        """Remove empty values from JSON data.

        Uses ``ctx.parsed`` when available to skip
        ``json.loads``. Propagates the cleaned object as
        ``parsed`` on the returned context.
        """
        parsed = ctx.parsed
        if parsed is not None:
            cleaned = _clean(parsed)
            result = json.dumps(
                cleaned, sort_keys=True, separators=(",", ":"), ensure_ascii=False
            )
            return SmeltContext(text=result, format=ctx.format, parsed=cleaned)

        text = ctx.text
        stripped = text.strip()
        if not stripped:
            return ctx

        if stripped[0] in ("{", "["):
            try:
                data = json.loads(stripped)
                cleaned = _clean(data)
                result = json.dumps(
                    cleaned, sort_keys=True, separators=(",", ":"), ensure_ascii=False
                )
                return SmeltContext(text=result, format=ctx.format, parsed=cleaned)
            except (json.JSONDecodeError, ValueError):
                pass

        return ctx
category property

Strategy category (structural).

name property

Strategy identifier used in the registry.

apply(ctx)

Remove empty values from JSON data.

Uses ctx.parsed when available to skip json.loads. Propagates the cleaned object as parsed on the returned context.

Source code in packages/axm-smelt/src/axm_smelt/strategies/drop_nulls.py
Python
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def apply(self, ctx: SmeltContext) -> SmeltContext:
    """Remove empty values from JSON data.

    Uses ``ctx.parsed`` when available to skip
    ``json.loads``. Propagates the cleaned object as
    ``parsed`` on the returned context.
    """
    parsed = ctx.parsed
    if parsed is not None:
        cleaned = _clean(parsed)
        result = json.dumps(
            cleaned, sort_keys=True, separators=(",", ":"), ensure_ascii=False
        )
        return SmeltContext(text=result, format=ctx.format, parsed=cleaned)

    text = ctx.text
    stripped = text.strip()
    if not stripped:
        return ctx

    if stripped[0] in ("{", "["):
        try:
            data = json.loads(stripped)
            cleaned = _clean(data)
            result = json.dumps(
                cleaned, sort_keys=True, separators=(",", ":"), ensure_ascii=False
            )
            return SmeltContext(text=result, format=ctx.format, parsed=cleaned)
        except (json.JSONDecodeError, ValueError):
            pass

    return ctx