import-checker: refactor sys.path prefix check (issue4129)
This patch refactors the logic in contrib/import-checker.py responsible for
checking the beginnings of the paths in sys.path. In particular, it adds a
variable that defines the set of allowed prefixes.
The primary purpose of this change is to make it easier to add more allowed
prefixes. This will be useful in resolving issue4129, which involves making
the function list_stdlib_modules() work when run from a virtualenv.
import ast
import os
import sys
def dotted_name_of_path(path):
"""Given a relative path to a source file, return its dotted module name.
>>> dotted_name_of_path('mercurial/error.py')
'mercurial.error'
"""
parts = path.split('/')
parts[-1] = parts[-1][:-3] # remove .py
return '.'.join(parts)
def list_stdlib_modules():
"""List the modules present in the stdlib.
>>> mods = set(list_stdlib_modules())
>>> 'BaseHTTPServer' in mods
True
os.path isn't really a module, so it's missing:
>>> 'os.path' in mods
False
sys requires special treatment, because it's baked into the
interpreter, but it should still appear:
>>> 'sys' in mods
True
>>> 'collections' in mods
True
>>> 'cStringIO' in mods
True
"""
for m in sys.builtin_module_names:
yield m
# These modules only exist on windows, but we should always
# consider them stdlib.
for m in ['msvcrt', '_winreg']:
yield m
# These get missed too
for m in 'ctypes', 'email':
yield m
yield 'builtins' # python3 only
stdlib_prefixes = set([sys.prefix, sys.exec_prefix])
for libpath in sys.path:
# We want to walk everything in sys.path that starts with something
# in stdlib_prefixes.
for prefix in stdlib_prefixes:
if libpath.startswith(prefix):
break
else:
continue
if 'site-packages' in libpath:
continue
for top, dirs, files in os.walk(libpath):
for name in files:
if name == '__init__.py':
continue
if not (name.endswith('.py') or name.endswith('.so')):
continue
full_path = os.path.join(top, name)
if 'site-packages' in full_path:
continue
rel_path = full_path[len(libpath) + 1:]
mod = dotted_name_of_path(rel_path)
yield mod
stdlib_modules = set(list_stdlib_modules())
def imported_modules(source, ignore_nested=False):
"""Given the source of a file as a string, yield the names
imported by that file.
Args:
source: The python source to examine as a string.
ignore_nested: If true, import statements that do not start in
column zero will be ignored.
Returns:
A list of module names imported by the given source.
>>> sorted(imported_modules(
... 'import foo ; from baz import bar; import foo.qux'))
['baz.bar', 'foo', 'foo.qux']
>>> sorted(imported_modules(
... '''import foo
... def wat():
... import bar
... ''', ignore_nested=True))
['foo']
"""
for node in ast.walk(ast.parse(source)):
if ignore_nested and getattr(node, 'col_offset', 0) > 0:
continue
if isinstance(node, ast.Import):
for n in node.names:
yield n.name
elif isinstance(node, ast.ImportFrom):
prefix = node.module + '.'
for n in node.names:
yield prefix + n.name
def verify_stdlib_on_own_line(source):
"""Given some python source, verify that stdlib imports are done
in separate statements from relative local module imports.
Observing this limitation is important as it works around an
annoying lib2to3 bug in relative import rewrites:
http://bugs.python.org/issue19510.
>>> list(verify_stdlib_on_own_line('import sys, foo'))
['mixed stdlib and relative imports:\\n foo, sys']
>>> list(verify_stdlib_on_own_line('import sys, os'))
[]
>>> list(verify_stdlib_on_own_line('import foo, bar'))
[]
"""
for node in ast.walk(ast.parse(source)):
if isinstance(node, ast.Import):
from_stdlib = {}
for n in node.names:
from_stdlib[n.name] = n.name in stdlib_modules
num_std = len([x for x in from_stdlib.values() if x])
if num_std not in (len(from_stdlib.values()), 0):
yield ('mixed stdlib and relative imports:\n %s' %
', '.join(sorted(from_stdlib.iterkeys())))
class CircularImport(Exception):
pass
def cyclekey(names):
return tuple(sorted(set(names)))
def check_one_mod(mod, imports, path=None, ignore=None):
if path is None:
path = []
if ignore is None:
ignore = []
path = path + [mod]
for i in sorted(imports.get(mod, [])):
if i not in stdlib_modules:
i = mod.rsplit('.', 1)[0] + '.' + i
if i in path:
firstspot = path.index(i)
cycle = path[firstspot:] + [i]
if cyclekey(cycle) not in ignore:
raise CircularImport(cycle)
continue
check_one_mod(i, imports, path=path, ignore=ignore)
def rotatecycle(cycle):
"""arrange a cycle so that the lexicographically first module listed first
>>> rotatecycle(['foo', 'bar', 'foo'])
['bar', 'foo', 'bar']
"""
lowest = min(cycle)
idx = cycle.index(lowest)
return cycle[idx:] + cycle[1:idx] + [lowest]
def find_cycles(imports):
"""Find cycles in an already-loaded import graph.
>>> imports = {'top.foo': ['bar', 'os.path', 'qux'],
... 'top.bar': ['baz', 'sys'],
... 'top.baz': ['foo'],
... 'top.qux': ['foo']}
>>> print '\\n'.join(sorted(find_cycles(imports)))
top.bar -> top.baz -> top.foo -> top.bar -> top.bar
top.foo -> top.qux -> top.foo -> top.foo
"""
cycles = {}
for mod in sorted(imports.iterkeys()):
try:
check_one_mod(mod, imports, ignore=cycles)
except CircularImport, e:
cycle = e.args[0]
cycles[cyclekey(cycle)] = ' -> '.join(rotatecycle(cycle))
return cycles.values()
def _cycle_sortkey(c):
return len(c), c
def main(argv):
if len(argv) < 2:
print 'Usage: %s file [file] [file] ...'
return 1
used_imports = {}
any_errors = False
for source_path in argv[1:]:
f = open(source_path)
modname = dotted_name_of_path(source_path)
src = f.read()
used_imports[modname] = sorted(
imported_modules(src, ignore_nested=True))
for error in verify_stdlib_on_own_line(src):
any_errors = True
print source_path, error
f.close()
cycles = find_cycles(used_imports)
if cycles:
firstmods = set()
for c in sorted(cycles, key=_cycle_sortkey):
first = c.split()[0]
# As a rough cut, ignore any cycle that starts with the
# same module as some other cycle. Otherwise we see lots
# of cycles that are effectively duplicates.
if first in firstmods:
continue
print 'Import cycle:', c
firstmods.add(first)
any_errors = True
return not any_errors
if __name__ == '__main__':
sys.exit(int(main(sys.argv)))