James R. Barlow
84f5fe9ee0
Split ocrmypdf.subprocess/__init__.py into three private submodules by concern (_run, _version, _check) and reduce __init__ to re-exports. Introduce ocrmypdf._exec._probe.ToolProbe to centralize the version()/ available() pattern each tool module was reimplementing, so the "is this tool installed and suitable?" question is cleanly distinct from the pure, picklable functions that do the work. Also replace the ghostscript module-import log.addFilter() side effect with an idempotent _ensure_log_filter_installed() called at the top of each work function, so the DuplicateFilter is present in subprocess workers without relying on import-time ordering. Public API of ocrmypdf.subprocess is unchanged.
73 lines
2.6 KiB
Python
73 lines
2.6 KiB
Python
# SPDX-FileCopyrightText: 2026 James R. Barlow
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# SPDX-License-Identifier: MPL-2.0
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"""Probe helper for external executables.
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Each ``ocrmypdf._exec.<tool>`` module describes its external program with a
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module-level :class:`ToolProbe` and delegates ``version()`` / ``available()``
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to it. This separates the "is the tool installed and suitable?" question
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(probing) from the "run the tool" question (execution). Work functions stay
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as pure module-level functions so they are trivially picklable for use in
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subprocess workers.
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"""
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from __future__ import annotations
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from collections.abc import Mapping
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from dataclasses import dataclass
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from packaging.version import Version
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from ocrmypdf.exceptions import MissingDependencyError
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from ocrmypdf.subprocess import get_version
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@dataclass(frozen=True)
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class ToolProbe:
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"""Describes how to detect an external executable and its version.
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Attributes:
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program: The program name as it appears on PATH (or a full path).
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version_arg: The argument that elicits a version string.
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version_regex: A regex with a capturing group that extracts the
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version from the program's output.
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version_cls: A :class:`packaging.version.Version` subclass, used for
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tools with non-standard version strings (e.g. Tesseract).
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env: Optional environment overrides applied when probing the version.
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also_catch: Additional exception types that should be treated as
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"not available" by :meth:`available`. :class:`OSError` is useful
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for tools like verapdf whose launcher may fail with non-standard
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errors when the JVM is missing.
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"""
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program: str
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version_arg: str = '--version'
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version_regex: str = r'(\d+(\.\d+)*)'
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version_cls: type[Version] = Version
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env: Mapping[str, str] | None = None
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also_catch: tuple[type[BaseException], ...] = ()
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def version(self) -> Version:
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"""Return the installed version of the program.
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Raises:
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MissingDependencyError: if the program cannot be found or its
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version string cannot be parsed.
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"""
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raw = get_version(
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self.program,
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version_arg=self.version_arg,
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regex=self.version_regex,
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env=self.env,
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)
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return self.version_cls(raw)
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def available(self) -> bool:
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"""Return whether a usable version of the program is installed."""
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try:
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self.version()
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except MissingDependencyError:
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return False
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except self.also_catch:
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return False
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return True
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