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