versionTuple.py

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# This file is part of dax_apdb.
#
# Developed for the LSST Data Management System.
# This product includes software developed by the LSST Project
# (http://www.lsst.org).
# See the COPYRIGHT file at the top-level directory of this distribution
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#
# This software is dual licensed under the GNU General Public License and also
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#
# This program is free software: you can redistribute it and/or modify
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from __future__ import annotations
 
__all__ = [
    "IncompatibleVersionError",
    "VersionTuple",
]
 
from typing import NamedTuple
 
 
class IncompatibleVersionError(RuntimeError):
    """Exception raised when version numbers are not compatible."""
 
 
class VersionTuple(NamedTuple):
    """Class representing a version number.
 
    Parameters
    ----------
    major, minor, patch : `int`
        Version number components
    """
 
    major: int
    minor: int
    patch: int
 
    @classmethod
    def fromString(cls, versionStr: str) -> VersionTuple:
        """Extract version number from a string.
 
        Parameters
        ----------
        versionStr : `str`
            Version number in string form "X.Y.Z", all components must be
            present.
 
        Returns
        -------
        version : `VersionTuple`
            Parsed version tuple.
 
        Raises
        ------
        ValueError
            Raised if string has an invalid format.
        """
        try:
            version = tuple(int(v) for v in versionStr.split("."))
        except ValueError as exc:
            raise ValueError(f"Invalid version  string '{versionStr}'") from exc
        if len(version) != 3:
            raise ValueError(f"Invalid version  string '{versionStr}', must consist of three numbers")
        return cls(*version)
 
    def checkCompatibility(self, database_version: VersionTuple, update: bool) -> bool:
        """Compare implementation schema version with schema version in
        database.
 
        Parameters
        ----------
        database_version : `VersionTuple`
            Version of the database schema.
        update : `bool`
            If True then read-write access is expected.
 
        Returns
        -------
        compatible : `bool`
            True if schema versions are compatible.
 
        Notes
        -----
        This method implements default rules for checking schema compatibility:
 
            - if major numbers differ, schemas are not compatible;
            - otherwise, if minor versions are different then newer version can
              read schema made by older version, but cannot write into it;
              older version can neither read nor write into newer schema;
            - otherwise, different patch versions are totally compatible.
        """
        if self.major != database_version.major:
            # different major versions are not compatible at all
            return False
        if self.minor != database_version.minor:
            # different minor versions are backward compatible for read
            # access only
            return self.minor > database_version.minor and not update
        # patch difference does not matter
        return True
 
    def __str__(self) -> str:
        """Transform version tuple into a canonical string form."""
        return f"{self.major}.{self.minor}.{self.patch}"