Source code for nix_daemon_protocol.drv_output

"""DrvOutput — a derivation output identifier as a canonical wire scalar.

Wire format: plain string like ``sha256:abc123!out``.

**That is the shape with no feature, and it is one of two.**
`WorkerProto::Serialise<DrvOutput>` at `worker-protocol.cc:544` of the master
branch raises when `realisation-with-path-not-hash` is off, and writes a
derivation **path** and an output name when it is on. The hash form does not
exist in that shape at all: a `DrvOutput` there names the derivation that made
the output, and not a hash of it.

`KeyedDrvOutput` in `keyed_drv_output.py` holds the other shape. Issue #14.
"""

from __future__ import annotations

from .wire_scalar import WireScalar




class DrvOutput(WireScalar):
    """DrvOutput on the wire — ``"drvHash!outputName"`` format.

    Uses the same ``from_str``/``to_str`` pattern as ``Signature``
    but with ``!`` as the delimiter instead of ``:``.
    """

    def __new__(
        cls,
        value: str = "",
        *,
        drv_hash: str | None = None,
        output_name: str | None = None,
    ) -> DrvOutput:
        if drv_hash is not None or output_name is not None:
            composed = f"{drv_hash or ''}!{output_name or ''}"
            if value and value != composed:
                raise ValueError("DrvOutput value and drv_hash/output_name disagree")
            value = composed
        return super().__new__(cls, value)

    @classmethod
    def from_str(cls, data: str) -> object:
        parts = data.split("!", 1)
        return {"drv_hash": parts[0], "output_name": parts[1] if len(parts) > 1 else ""}

    @property
    def drv_hash(self) -> str:
        """The derivation hash before the first exclamation mark."""
        return self.partition("!")[0]

    @property
    def output_name(self) -> str:
        """The output name after the first exclamation mark."""
        return self.partition("!")[2]



    def to_str(self) -> str:
        """Compatibility spelling for the canonical string value."""
        return self