mirror of
https://github.com/python/cpython
synced 2024-09-05 08:17:45 +00:00
183 lines
5.6 KiB
Python
183 lines
5.6 KiB
Python
"""Cache lines from Python source files.
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This is intended to read lines from modules imported -- hence if a filename
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is not found, it will look down the module search path for a file by
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that name.
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"""
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import functools
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import sys
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import os
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import tokenize
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__all__ = ["getline", "clearcache", "checkcache", "lazycache"]
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# The cache. Maps filenames to either a thunk which will provide source code,
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# or a tuple (size, mtime, lines, fullname) once loaded.
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cache = {}
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def clearcache():
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"""Clear the cache entirely."""
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cache.clear()
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def getline(filename, lineno, module_globals=None):
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"""Get a line for a Python source file from the cache.
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Update the cache if it doesn't contain an entry for this file already."""
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lines = getlines(filename, module_globals)
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if 1 <= lineno <= len(lines):
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return lines[lineno - 1]
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return ''
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def getlines(filename, module_globals=None):
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"""Get the lines for a Python source file from the cache.
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Update the cache if it doesn't contain an entry for this file already."""
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if filename in cache:
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entry = cache[filename]
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if len(entry) != 1:
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return cache[filename][2]
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try:
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return updatecache(filename, module_globals)
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except MemoryError:
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clearcache()
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return []
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def checkcache(filename=None):
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"""Discard cache entries that are out of date.
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(This is not checked upon each call!)"""
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if filename is None:
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filenames = list(cache.keys())
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elif filename in cache:
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filenames = [filename]
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else:
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return
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for filename in filenames:
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entry = cache[filename]
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if len(entry) == 1:
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# lazy cache entry, leave it lazy.
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continue
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size, mtime, lines, fullname = entry
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if mtime is None:
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continue # no-op for files loaded via a __loader__
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try:
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stat = os.stat(fullname)
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except OSError:
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cache.pop(filename, None)
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continue
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if size != stat.st_size or mtime != stat.st_mtime:
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cache.pop(filename, None)
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def updatecache(filename, module_globals=None):
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"""Update a cache entry and return its list of lines.
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If something's wrong, print a message, discard the cache entry,
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and return an empty list."""
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if filename in cache:
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if len(cache[filename]) != 1:
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cache.pop(filename, None)
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if not filename or (filename.startswith('<') and filename.endswith('>')):
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return []
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fullname = filename
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try:
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stat = os.stat(fullname)
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except OSError:
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basename = filename
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# Realise a lazy loader based lookup if there is one
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# otherwise try to lookup right now.
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if lazycache(filename, module_globals):
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try:
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data = cache[filename][0]()
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except (ImportError, OSError):
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pass
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else:
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if data is None:
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# No luck, the PEP302 loader cannot find the source
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# for this module.
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return []
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cache[filename] = (
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len(data),
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None,
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[line + '\n' for line in data.splitlines()],
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fullname
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)
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return cache[filename][2]
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# Try looking through the module search path, which is only useful
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# when handling a relative filename.
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if os.path.isabs(filename):
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return []
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for dirname in sys.path:
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try:
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fullname = os.path.join(dirname, basename)
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except (TypeError, AttributeError):
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# Not sufficiently string-like to do anything useful with.
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continue
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try:
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stat = os.stat(fullname)
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break
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except OSError:
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pass
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else:
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return []
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try:
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with tokenize.open(fullname) as fp:
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lines = fp.readlines()
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except (OSError, UnicodeDecodeError, SyntaxError):
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return []
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if lines and not lines[-1].endswith('\n'):
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lines[-1] += '\n'
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size, mtime = stat.st_size, stat.st_mtime
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cache[filename] = size, mtime, lines, fullname
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return lines
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def lazycache(filename, module_globals):
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"""Seed the cache for filename with module_globals.
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The module loader will be asked for the source only when getlines is
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called, not immediately.
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If there is an entry in the cache already, it is not altered.
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:return: True if a lazy load is registered in the cache,
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otherwise False. To register such a load a module loader with a
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get_source method must be found, the filename must be a cacheable
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filename, and the filename must not be already cached.
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"""
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if filename in cache:
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if len(cache[filename]) == 1:
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return True
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else:
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return False
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if not filename or (filename.startswith('<') and filename.endswith('>')):
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return False
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# Try for a __loader__, if available
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if module_globals and '__name__' in module_globals:
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name = module_globals['__name__']
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if (loader := module_globals.get('__loader__')) is None:
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if spec := module_globals.get('__spec__'):
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try:
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loader = spec.loader
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except AttributeError:
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pass
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get_source = getattr(loader, 'get_source', None)
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if name and get_source:
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get_lines = functools.partial(get_source, name)
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cache[filename] = (get_lines,)
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return True
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return False
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