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except MemoryError: clearcache() return [] def checkcache(filename=None): """Discard cache entries that are out of date.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