e9519d207e
Use context manager interface (with statement) to atomically update source files. This ensures that all files are properly closed and the temporary file is removed even in case of errors. Task-number: QTBUG-83488 Pick-to: 6.2 Change-Id: I18cd96f1d03e467dea6212f6576a41e65f414ce1 Reviewed-by: Edward Welbourne <edward.welbourne@qt.io> Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
207 lines
7.5 KiB
Python
207 lines
7.5 KiB
Python
#############################################################################
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##
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## Copyright (C) 2020 The Qt Company Ltd.
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## Contact: https://www.qt.io/licensing/
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##
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## This file is part of the test suite of the Qt Toolkit.
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##
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## $QT_BEGIN_LICENSE:GPL-EXCEPT$
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## Commercial License Usage
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## Licensees holding valid commercial Qt licenses may use this file in
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## accordance with the commercial license agreement provided with the
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## Software or, alternatively, in accordance with the terms contained in
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## a written agreement between you and The Qt Company. For licensing terms
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## and conditions see https://www.qt.io/terms-conditions. For further
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## information use the contact form at https://www.qt.io/contact-us.
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##
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## GNU General Public License Usage
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## Alternatively, this file may be used under the terms of the GNU
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## General Public License version 3 as published by the Free Software
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## Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
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## included in the packaging of this file. Please review the following
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## information to ensure the GNU General Public License requirements will
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## be met: https://www.gnu.org/licenses/gpl-3.0.html.
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##
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## $QT_END_LICENSE$
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##
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#############################################################################
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"""Utilities shared among the CLDR extraction tools.
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Functions:
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unicode2hex() -- converts unicode text to UCS-2 in hex form.
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wrap_list() -- map list to comma-separated string, 20 entries per line.
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Classes:
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Error -- A shared error class.
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Transcriber -- edit a file by writing a temporary file, then renaming.
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SourceFileEditor -- adds standard prelude and tail handling to Transcriber.
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"""
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from contextlib import ExitStack, contextmanager
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from pathlib import Path
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from tempfile import NamedTemporaryFile
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class Error (Exception):
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def __init__(self, msg, *args):
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super().__init__(msg, *args)
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self.message = msg
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def __str__(self):
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return self.message
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def unicode2hex(s):
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lst = []
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for x in s:
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v = ord(x)
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if v > 0xFFFF:
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# make a surrogate pair
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# copied from qchar.h
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high = (v >> 10) + 0xd7c0
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low = (v % 0x400 + 0xdc00)
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lst.append(hex(high))
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lst.append(hex(low))
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else:
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lst.append(hex(v))
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return lst
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def wrap_list(lst):
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def split(lst, size):
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while lst:
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head, lst = lst[:size], lst[size:]
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yield head
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return ",\n".join(", ".join(x) for x in split(lst, 20))
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@contextmanager
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def AtomicRenameTemporaryFile(originalLocation: Path, *, prefix: str, dir: Path):
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"""Context manager for safe file update via a temporary file.
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Accepts path to the file to be updated. Yields a temporary file to the user
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code, open for writing.
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On success closes the temporary file and moves its content to the original
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location. On error, removes temporary file, without disturbing the original.
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"""
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tempFile = NamedTemporaryFile('w', prefix=prefix, dir=dir, delete=False)
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try:
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yield tempFile
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tempFile.close()
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# Move the modified file to the original location
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Path(tempFile.name).rename(originalLocation)
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except Exception:
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# delete the temporary file in case of error
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tempFile.close()
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Path(tempFile.name).unlink()
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raise
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class Transcriber:
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"""Context manager base-class to manage source file rewrites.
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Derived classes need to implement transcribing of the content, with
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whatever modifications they may want. Members reader and writer
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are exposed; use writer.write() to output to the new file; use
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reader.readline() or iterate reader to read the original.
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This class is intended to be used as context manager only (inside a
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`with` statement).
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Reimplement onEnter() to write any preamble the file may have,
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onExit() to write any tail. The body of the with statement takes
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care of anything in between, using methods provided by derived classes.
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The data is written to a temporary file first. The temporary file data
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is then moved to the original location if there were no errors. Otherwise
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the temporary file is removed and the original is left unchanged.
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"""
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def __init__(self, path: Path, temp_dir: Path):
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self.path = path
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self.tempDir = temp_dir
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def onEnter(self) -> None:
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"""
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Called before transferring control to user code.
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This function can be overridden in derived classes to perform actions
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before transferring control to the user code.
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The default implementation does nothing.
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"""
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pass
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def onExit(self) -> None:
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"""
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Called after return from user code.
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This function can be overridden in derived classes to perform actions
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after successful return from user code.
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The default implementation does nothing.
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"""
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pass
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def __enter__(self):
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with ExitStack() as resources:
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# Create a temp file to write the new data into
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self.writer = resources.enter_context(
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AtomicRenameTemporaryFile(self.path, prefix=self.path.name, dir=self.tempDir))
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# Open the old file
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self.reader = resources.enter_context(open(self.path))
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self.onEnter()
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# Prevent resources from being closed on normal return from this
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# method and make them available inside __exit__():
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self.__resources = resources.pop_all()
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return self
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def __exit__(self, exc_type, exc_value, traceback):
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if exc_type is None:
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with self.__resources:
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self.onExit()
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else:
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self.__resources.__exit__(exc_type, exc_value, traceback)
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return False
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class SourceFileEditor (Transcriber):
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"""Transcriber with transcription of code around a gnerated block.
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We have a common pattern of source files with a generated part
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embedded in a context that's not touched by the regeneration
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scripts. The generated part is, in each case, marked with a common
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pair of start and end markers. We transcribe the old file to a new
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temporary file; on success, we then remove the original and move
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the new version to replace it.
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This class takes care of transcribing the parts before and after
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the generated content; on entering the context, an instance will
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copy the preamble up to the start marker; on exit from the context
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it will skip over the original's generated content and resume
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transcribing with the end marker.
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This class is only intended to be used as a context manager:
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see Transcriber. Derived classes implement suitable methods for use in
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the body of the with statement, using self.writer to rewrite the part
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of the file between the start and end markers.
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"""
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GENERATED_BLOCK_START = '// GENERATED PART STARTS HERE'
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GENERATED_BLOCK_END = '// GENERATED PART ENDS HERE'
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def onEnter(self) -> None:
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# Copy over the first non-generated section to the new file
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for line in self.reader:
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self.writer.write(line)
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if line.strip() == self.GENERATED_BLOCK_START:
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break
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def onExit(self) -> None:
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# Skip through the old generated data in the old file
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for line in self.reader:
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if line.strip() == self.GENERATED_BLOCK_END:
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self.writer.write(line)
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break
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# Transcribe the remainder:
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for line in self.reader:
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self.writer.write(line)
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