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|
"""
Main module.
Implement the central Checker class.
Also, it models the Bindings and Scopes.
"""
import doctest
import os
import sys
PY2 = sys.version_info < (3, 0)
PY32 = sys.version_info < (3, 3) # Python 2.5 to 3.2
PY33 = sys.version_info < (3, 4) # Python 2.5 to 3.3
builtin_vars = dir(__import__('__builtin__' if PY2 else 'builtins'))
try:
import ast
except ImportError: # Python 2.5
import _ast as ast
if 'decorator_list' not in ast.ClassDef._fields:
# Patch the missing attribute 'decorator_list'
ast.ClassDef.decorator_list = ()
ast.FunctionDef.decorator_list = property(lambda s: s.decorators)
from pyflakes import messages
if PY2:
def getNodeType(node_class):
# workaround str.upper() which is locale-dependent
return str(unicode(node_class.__name__).upper())
else:
def getNodeType(node_class):
return node_class.__name__.upper()
# Python >= 3.3 uses ast.Try instead of (ast.TryExcept + ast.TryFinally)
if PY32:
def getAlternatives(n):
if isinstance(n, (ast.If, ast.TryFinally)):
return [n.body]
if isinstance(n, ast.TryExcept):
return [n.body + n.orelse] + [[hdl] for hdl in n.handlers]
else:
def getAlternatives(n):
if isinstance(n, ast.If):
return [n.body]
if isinstance(n, ast.Try):
return [n.body + n.orelse] + [[hdl] for hdl in n.handlers]
class _FieldsOrder(dict):
"""Fix order of AST node fields."""
def _get_fields(self, node_class):
# handle iter before target, and generators before element
fields = node_class._fields
if 'iter' in fields:
key_first = 'iter'.find
elif 'generators' in fields:
key_first = 'generators'.find
else:
key_first = 'value'.find
return tuple(sorted(fields, key=key_first, reverse=True))
def __missing__(self, node_class):
self[node_class] = fields = self._get_fields(node_class)
return fields
def iter_child_nodes(node, omit=None, _fields_order=_FieldsOrder()):
"""
Yield all direct child nodes of *node*, that is, all fields that
are nodes and all items of fields that are lists of nodes.
"""
for name in _fields_order[node.__class__]:
if name == omit:
continue
field = getattr(node, name, None)
if isinstance(field, ast.AST):
yield field
elif isinstance(field, list):
for item in field:
yield item
class Binding(object):
"""
Represents the binding of a value to a name.
The checker uses this to keep track of which names have been bound and
which names have not. See L{Assignment} for a special type of binding that
is checked with stricter rules.
@ivar used: pair of (L{Scope}, line-number) indicating the scope and
line number that this binding was last used
"""
def __init__(self, name, source):
self.name = name
self.source = source
self.used = False
def __str__(self):
return self.name
def __repr__(self):
return '<%s object %r from line %r at 0x%x>' % (self.__class__.__name__,
self.name,
self.source.lineno,
id(self))
def redefines(self, other):
return isinstance(other, Definition) and self.name == other.name
class Definition(Binding):
"""
A binding that defines a function or a class.
"""
class Importation(Definition):
"""
A binding created by an import statement.
@ivar fullName: The complete name given to the import statement,
possibly including multiple dotted components.
@type fullName: C{str}
"""
def __init__(self, name, source):
self.fullName = name
self.redefined = []
name = name.split('.')[0]
super(Importation, self).__init__(name, source)
def redefines(self, other):
if isinstance(other, Importation):
return self.fullName == other.fullName
return isinstance(other, Definition) and self.name == other.name
class Argument(Binding):
"""
Represents binding a name as an argument.
"""
class Assignment(Binding):
"""
Represents binding a name with an explicit assignment.
The checker will raise warnings for any Assignment that isn't used. Also,
the checker does not consider assignments in tuple/list unpacking to be
Assignments, rather it treats them as simple Bindings.
"""
class FunctionDefinition(Definition):
pass
class ClassDefinition(Definition):
pass
class ExportBinding(Binding):
"""
A binding created by an C{__all__} assignment. If the names in the list
can be determined statically, they will be treated as names for export and
additional checking applied to them.
The only C{__all__} assignment that can be recognized is one which takes
the value of a literal list containing literal strings. For example::
__all__ = ["foo", "bar"]
Names which are imported and not otherwise used but appear in the value of
C{__all__} will not have an unused import warning reported for them.
"""
def __init__(self, name, source, scope):
if '__all__' in scope and isinstance(source, ast.AugAssign):
self.names = list(scope['__all__'].names)
else:
self.names = []
if isinstance(source.value, (ast.List, ast.Tuple)):
for node in source.value.elts:
if isinstance(node, ast.Str):
self.names.append(node.s)
super(ExportBinding, self).__init__(name, source)
class Scope(dict):
importStarred = False # set to True when import * is found
def __repr__(self):
scope_cls = self.__class__.__name__
return '<%s at 0x%x %s>' % (scope_cls, id(self), dict.__repr__(self))
class ClassScope(Scope):
pass
class FunctionScope(Scope):
"""
I represent a name scope for a function.
@ivar globals: Names declared 'global' in this function.
"""
usesLocals = False
alwaysUsed = set(['__tracebackhide__',
'__traceback_info__', '__traceback_supplement__'])
def __init__(self):
super(FunctionScope, self).__init__()
# Simplify: manage the special locals as globals
self.globals = self.alwaysUsed.copy()
self.returnValue = None # First non-empty return
self.isGenerator = False # Detect a generator
def unusedAssignments(self):
"""
Return a generator for the assignments which have not been used.
"""
for name, binding in self.items():
if (not binding.used and name not in self.globals
and not self.usesLocals
and isinstance(binding, Assignment)):
yield name, binding
class GeneratorScope(Scope):
pass
class ModuleScope(Scope):
pass
# Globally defined names which are not attributes of the builtins module, or
# are only present on some platforms.
_MAGIC_GLOBALS = ['__file__', '__builtins__', 'WindowsError']
def getNodeName(node):
# Returns node.id, or node.name, or None
if hasattr(node, 'id'): # One of the many nodes with an id
return node.id
if hasattr(node, 'name'): # a ExceptHandler node
return node.name
class Checker(object):
"""
I check the cleanliness and sanity of Python code.
@ivar _deferredFunctions: Tracking list used by L{deferFunction}. Elements
of the list are two-tuples. The first element is the callable passed
to L{deferFunction}. The second element is a copy of the scope stack
at the time L{deferFunction} was called.
@ivar _deferredAssignments: Similar to C{_deferredFunctions}, but for
callables which are deferred assignment checks.
"""
nodeDepth = 0
offset = None
traceTree = False
builtIns = set(builtin_vars).union(_MAGIC_GLOBALS)
_customBuiltIns = os.environ.get('PYFLAKES_BUILTINS')
if _customBuiltIns:
builtIns.update(_customBuiltIns.split(','))
del _customBuiltIns
def __init__(self, tree, filename='(none)', builtins=None,
withDoctest='PYFLAKES_DOCTEST' in os.environ):
self._nodeHandlers = {}
self._deferredFunctions = []
self._deferredAssignments = []
self.deadScopes = []
self.messages = []
self.filename = filename
if builtins:
self.builtIns = self.builtIns.union(builtins)
self.withDoctest = withDoctest
self.scopeStack = [ModuleScope()]
self.exceptHandlers = [()]
self.futuresAllowed = True
self.root = tree
self.handleChildren(tree)
self.runDeferred(self._deferredFunctions)
# Set _deferredFunctions to None so that deferFunction will fail
# noisily if called after we've run through the deferred functions.
self._deferredFunctions = None
self.runDeferred(self._deferredAssignments)
# Set _deferredAssignments to None so that deferAssignment will fail
# noisily if called after we've run through the deferred assignments.
self._deferredAssignments = None
del self.scopeStack[1:]
self.popScope()
self.checkDeadScopes()
def deferFunction(self, callable):
"""
Schedule a function handler to be called just before completion.
This is used for handling function bodies, which must be deferred
because code later in the file might modify the global scope. When
`callable` is called, the scope at the time this is called will be
restored, however it will contain any new bindings added to it.
"""
self._deferredFunctions.append((callable, self.scopeStack[:], self.offset))
def deferAssignment(self, callable):
"""
Schedule an assignment handler to be called just after deferred
function handlers.
"""
self._deferredAssignments.append((callable, self.scopeStack[:], self.offset))
def runDeferred(self, deferred):
"""
Run the callables in C{deferred} using their associated scope stack.
"""
for handler, scope, offset in deferred:
self.scopeStack = scope
self.offset = offset
handler()
@property
def scope(self):
return self.scopeStack[-1]
def popScope(self):
self.deadScopes.append(self.scopeStack.pop())
def checkDeadScopes(self):
"""
Look at scopes which have been fully examined and report names in them
which were imported but unused.
"""
for scope in self.deadScopes:
if isinstance(scope.get('__all__'), ExportBinding):
all_names = set(scope['__all__'].names)
if not scope.importStarred and \
os.path.basename(self.filename) != '__init__.py':
# Look for possible mistakes in the export list
undefined = all_names.difference(scope)
for name in undefined:
self.report(messages.UndefinedExport,
scope['__all__'].source, name)
else:
all_names = []
# Look for imported names that aren't used.
for value in scope.values():
if isinstance(value, Importation):
used = value.used or value.name in all_names
if not used:
messg = messages.UnusedImport
self.report(messg, value.source, value.name)
for node in value.redefined:
if isinstance(self.getParent(node), ast.For):
messg = messages.ImportShadowedByLoopVar
elif used:
continue
else:
messg = messages.RedefinedWhileUnused
self.report(messg, node, value.name, value.source)
def pushScope(self, scopeClass=FunctionScope):
self.scopeStack.append(scopeClass())
def report(self, messageClass, *args, **kwargs):
self.messages.append(messageClass(self.filename, *args, **kwargs))
def getParent(self, node):
# Lookup the first parent which is not Tuple, List or Starred
while True:
node = node.parent
if not hasattr(node, 'elts') and not hasattr(node, 'ctx'):
return node
def getCommonAncestor(self, lnode, rnode, stop):
if stop in (lnode, rnode) or not (hasattr(lnode, 'parent') and
hasattr(rnode, 'parent')):
return None
if lnode is rnode:
return lnode
if (lnode.depth > rnode.depth):
return self.getCommonAncestor(lnode.parent, rnode, stop)
if (lnode.depth < rnode.depth):
return self.getCommonAncestor(lnode, rnode.parent, stop)
return self.getCommonAncestor(lnode.parent, rnode.parent, stop)
def descendantOf(self, node, ancestors, stop):
for a in ancestors:
if self.getCommonAncestor(node, a, stop):
return True
return False
def differentForks(self, lnode, rnode):
"""True, if lnode and rnode are located on different forks of IF/TRY"""
ancestor = self.getCommonAncestor(lnode, rnode, self.root)
parts = getAlternatives(ancestor)
if parts:
for items in parts:
if self.descendantOf(lnode, items, ancestor) ^ \
self.descendantOf(rnode, items, ancestor):
return True
return False
def addBinding(self, node, value):
"""
Called when a binding is altered.
- `node` is the statement responsible for the change
- `value` is the new value, a Binding instance
"""
# assert value.source in (node, node.parent):
for scope in self.scopeStack[::-1]:
if value.name in scope:
break
existing = scope.get(value.name)
if existing and not self.differentForks(node, existing.source):
parent_stmt = self.getParent(value.source)
if isinstance(existing, Importation) and isinstance(parent_stmt, ast.For):
self.report(messages.ImportShadowedByLoopVar,
node, value.name, existing.source)
elif scope is self.scope:
if (isinstance(parent_stmt, ast.comprehension) and
not isinstance(self.getParent(existing.source),
(ast.For, ast.comprehension))):
self.report(messages.RedefinedInListComp,
node, value.name, existing.source)
elif not existing.used and value.redefines(existing):
self.report(messages.RedefinedWhileUnused,
node, value.name, existing.source)
elif isinstance(existing, Importation) and value.redefines(existing):
existing.redefined.append(node)
self.scope[value.name] = value
def getNodeHandler(self, node_class):
try:
return self._nodeHandlers[node_class]
except KeyError:
nodeType = getNodeType(node_class)
self._nodeHandlers[node_class] = handler = getattr(self, nodeType)
return handler
def handleNodeLoad(self, node):
name = getNodeName(node)
if not name:
return
# try local scope
try:
self.scope[name].used = (self.scope, node)
except KeyError:
pass
else:
return
scopes = [scope for scope in self.scopeStack[:-1]
if isinstance(scope, (FunctionScope, ModuleScope, GeneratorScope))]
if isinstance(self.scope, GeneratorScope) and scopes[-1] != self.scopeStack[-2]:
scopes.append(self.scopeStack[-2])
# try enclosing function scopes and global scope
importStarred = self.scope.importStarred
for scope in reversed(scopes):
importStarred = importStarred or scope.importStarred
try:
scope[name].used = (self.scope, node)
except KeyError:
pass
else:
return
# look in the built-ins
if importStarred or name in self.builtIns:
return
if name == '__path__' and os.path.basename(self.filename) == '__init__.py':
# the special name __path__ is valid only in packages
return
# protected with a NameError handler?
if 'NameError' not in self.exceptHandlers[-1]:
self.report(messages.UndefinedName, node, name)
def handleNodeStore(self, node):
name = getNodeName(node)
if not name:
return
# if the name hasn't already been defined in the current scope
if isinstance(self.scope, FunctionScope) and name not in self.scope:
# for each function or module scope above us
for scope in self.scopeStack[:-1]:
if not isinstance(scope, (FunctionScope, ModuleScope)):
continue
# if the name was defined in that scope, and the name has
# been accessed already in the current scope, and hasn't
# been declared global
used = name in scope and scope[name].used
if used and used[0] is self.scope and name not in self.scope.globals:
# then it's probably a mistake
self.report(messages.UndefinedLocal,
scope[name].used[1], name, scope[name].source)
break
parent_stmt = self.getParent(node)
if isinstance(parent_stmt, (ast.For, ast.comprehension)) or (
parent_stmt != node.parent and
not self.isLiteralTupleUnpacking(parent_stmt)):
binding = Binding(name, node)
elif name == '__all__' and isinstance(self.scope, ModuleScope):
binding = ExportBinding(name, node.parent, self.scope)
else:
binding = Assignment(name, node)
if name in self.scope:
binding.used = self.scope[name].used
self.addBinding(node, binding)
def handleNodeDelete(self, node):
name = getNodeName(node)
if not name:
return
if isinstance(self.scope, FunctionScope) and name in self.scope.globals:
self.scope.globals.remove(name)
else:
try:
del self.scope[name]
except KeyError:
self.report(messages.UndefinedName, node, name)
def handleChildren(self, tree, omit=None):
for node in iter_child_nodes(tree, omit=omit):
self.handleNode(node, tree)
def isLiteralTupleUnpacking(self, node):
if isinstance(node, ast.Assign):
for child in node.targets + [node.value]:
if not hasattr(child, 'elts'):
return False
return True
def isDocstring(self, node):
"""
Determine if the given node is a docstring, as long as it is at the
correct place in the node tree.
"""
return isinstance(node, ast.Str) or (isinstance(node, ast.Expr) and
isinstance(node.value, ast.Str))
def getDocstring(self, node):
if isinstance(node, ast.Expr):
node = node.value
if not isinstance(node, ast.Str):
return (None, None)
# Computed incorrectly if the docstring has backslash
doctest_lineno = node.lineno - node.s.count('\n') - 1
return (node.s, doctest_lineno)
def handleNode(self, node, parent):
if node is None:
return
if self.offset and getattr(node, 'lineno', None) is not None:
node.lineno += self.offset[0]
node.col_offset += self.offset[1]
if self.traceTree:
print(' ' * self.nodeDepth + node.__class__.__name__)
if self.futuresAllowed and not (isinstance(node, ast.ImportFrom) or
self.isDocstring(node)):
self.futuresAllowed = False
self.nodeDepth += 1
node.depth = self.nodeDepth
node.parent = parent
try:
handler = self.getNodeHandler(node.__class__)
handler(node)
finally:
self.nodeDepth -= 1
if self.traceTree:
print(' ' * self.nodeDepth + 'end ' + node.__class__.__name__)
_getDoctestExamples = doctest.DocTestParser().get_examples
def handleDoctests(self, node):
try:
(docstring, node_lineno) = self.getDocstring(node.body[0])
examples = docstring and self._getDoctestExamples(docstring)
except (ValueError, IndexError):
# e.g. line 6 of the docstring for <string> has inconsistent
# leading whitespace: ...
return
if not examples:
return
node_offset = self.offset or (0, 0)
self.pushScope()
underscore_in_builtins = '_' in self.builtIns
if not underscore_in_builtins:
self.builtIns.add('_')
for example in examples:
try:
tree = compile(example.source, "<doctest>", "exec", ast.PyCF_ONLY_AST)
except SyntaxError:
e = sys.exc_info()[1]
position = (node_lineno + example.lineno + e.lineno,
example.indent + 4 + (e.offset or 0))
self.report(messages.DoctestSyntaxError, node, position)
else:
self.offset = (node_offset[0] + node_lineno + example.lineno,
node_offset[1] + example.indent + 4)
self.handleChildren(tree)
self.offset = node_offset
if not underscore_in_builtins:
self.builtIns.remove('_')
self.popScope()
def ignore(self, node):
pass
# "stmt" type nodes
DELETE = PRINT = FOR = WHILE = IF = WITH = WITHITEM = RAISE = \
TRYFINALLY = ASSERT = EXEC = EXPR = ASSIGN = handleChildren
CONTINUE = BREAK = PASS = ignore
# "expr" type nodes
BOOLOP = BINOP = UNARYOP = IFEXP = DICT = SET = \
COMPARE = CALL = REPR = ATTRIBUTE = SUBSCRIPT = LIST = TUPLE = \
STARRED = NAMECONSTANT = handleChildren
NUM = STR = BYTES = ELLIPSIS = ignore
# "slice" type nodes
SLICE = EXTSLICE = INDEX = handleChildren
# expression contexts are node instances too, though being constants
LOAD = STORE = DEL = AUGLOAD = AUGSTORE = PARAM = ignore
# same for operators
AND = OR = ADD = SUB = MULT = DIV = MOD = POW = LSHIFT = RSHIFT = \
BITOR = BITXOR = BITAND = FLOORDIV = INVERT = NOT = UADD = USUB = \
EQ = NOTEQ = LT = LTE = GT = GTE = IS = ISNOT = IN = NOTIN = ignore
# additional node types
LISTCOMP = COMPREHENSION = KEYWORD = handleChildren
def GLOBAL(self, node):
"""
Keep track of globals declarations.
"""
if isinstance(self.scope, FunctionScope):
self.scope.globals.update(node.names)
NONLOCAL = GLOBAL
def GENERATOREXP(self, node):
self.pushScope(GeneratorScope)
self.handleChildren(node)
self.popScope()
DICTCOMP = SETCOMP = GENERATOREXP
def NAME(self, node):
"""
Handle occurrence of Name (which can be a load/store/delete access.)
"""
# Locate the name in locals / function / globals scopes.
if isinstance(node.ctx, (ast.Load, ast.AugLoad)):
self.handleNodeLoad(node)
if (node.id == 'locals' and isinstance(self.scope, FunctionScope)
and isinstance(node.parent, ast.Call)):
# we are doing locals() call in current scope
self.scope.usesLocals = True
elif isinstance(node.ctx, (ast.Store, ast.AugStore)):
self.handleNodeStore(node)
elif isinstance(node.ctx, ast.Del):
self.handleNodeDelete(node)
else:
# must be a Param context -- this only happens for names in function
# arguments, but these aren't dispatched through here
raise RuntimeError("Got impossible expression context: %r" % (node.ctx,))
def RETURN(self, node):
if (
node.value and
hasattr(self.scope, 'returnValue') and
not self.scope.returnValue
):
self.scope.returnValue = node.value
self.handleNode(node.value, node)
def YIELD(self, node):
self.scope.isGenerator = True
self.handleNode(node.value, node)
YIELDFROM = YIELD
def FUNCTIONDEF(self, node):
for deco in node.decorator_list:
self.handleNode(deco, node)
self.LAMBDA(node)
self.addBinding(node, FunctionDefinition(node.name, node))
if self.withDoctest:
self.deferFunction(lambda: self.handleDoctests(node))
def LAMBDA(self, node):
args = []
annotations = []
if PY2:
def addArgs(arglist):
for arg in arglist:
if isinstance(arg, ast.Tuple):
addArgs(arg.elts)
else:
args.append(arg.id)
addArgs(node.args.args)
defaults = node.args.defaults
else:
for arg in node.args.args + node.args.kwonlyargs:
args.append(arg.arg)
annotations.append(arg.annotation)
defaults = node.args.defaults + node.args.kw_defaults
# Only for Python3 FunctionDefs
is_py3_func = hasattr(node, 'returns')
for arg_name in ('vararg', 'kwarg'):
wildcard = getattr(node.args, arg_name)
if not wildcard:
continue
args.append(wildcard if PY33 else wildcard.arg)
if is_py3_func:
if PY33: # Python 2.5 to 3.3
argannotation = arg_name + 'annotation'
annotations.append(getattr(node.args, argannotation))
else: # Python >= 3.4
annotations.append(wildcard.annotation)
if is_py3_func:
annotations.append(node.returns)
if len(set(args)) < len(args):
for (idx, arg) in enumerate(args):
if arg in args[:idx]:
self.report(messages.DuplicateArgument, node, arg)
for child in annotations + defaults:
if child:
self.handleNode(child, node)
def runFunction():
self.pushScope()
for name in args:
self.addBinding(node, Argument(name, node))
if isinstance(node.body, list):
# case for FunctionDefs
for stmt in node.body:
self.handleNode(stmt, node)
else:
# case for Lambdas
self.handleNode(node.body, node)
def checkUnusedAssignments():
"""
Check to see if any assignments have not been used.
"""
for name, binding in self.scope.unusedAssignments():
self.report(messages.UnusedVariable, binding.source, name)
self.deferAssignment(checkUnusedAssignments)
if PY32:
def checkReturnWithArgumentInsideGenerator():
"""
Check to see if there is any return statement with
arguments but the function is a generator.
"""
if self.scope.isGenerator and self.scope.returnValue:
self.report(messages.ReturnWithArgsInsideGenerator,
self.scope.returnValue)
self.deferAssignment(checkReturnWithArgumentInsideGenerator)
self.popScope()
self.deferFunction(runFunction)
def CLASSDEF(self, node):
"""
Check names used in a class definition, including its decorators, base
classes, and the body of its definition. Additionally, add its name to
the current scope.
"""
for deco in node.decorator_list:
self.handleNode(deco, node)
for baseNode in node.bases:
self.handleNode(baseNode, node)
if not PY2:
for keywordNode in node.keywords:
self.handleNode(keywordNode, node)
self.pushScope(ClassScope)
if self.withDoctest:
self.deferFunction(lambda: self.handleDoctests(node))
for stmt in node.body:
self.handleNode(stmt, node)
self.popScope()
self.addBinding(node, ClassDefinition(node.name, node))
def AUGASSIGN(self, node):
self.handleNodeLoad(node.target)
self.handleNode(node.value, node)
self.handleNode(node.target, node)
def IMPORT(self, node):
for alias in node.names:
name = alias.asname or alias.name
importation = Importation(name, node)
self.addBinding(node, importation)
def IMPORTFROM(self, node):
if node.module == '__future__':
if not self.futuresAllowed:
self.report(messages.LateFutureImport,
node, [n.name for n in node.names])
else:
self.futuresAllowed = False
for alias in node.names:
if alias.name == '*':
self.scope.importStarred = True
self.report(messages.ImportStarUsed, node, node.module)
continue
name = alias.asname or alias.name
importation = Importation(name, node)
if node.module == '__future__':
importation.used = (self.scope, node)
self.addBinding(node, importation)
def TRY(self, node):
handler_names = []
# List the exception handlers
for handler in node.handlers:
if isinstance(handler.type, ast.Tuple):
for exc_type in handler.type.elts:
handler_names.append(getNodeName(exc_type))
elif handler.type:
handler_names.append(getNodeName(handler.type))
# Memorize the except handlers and process the body
self.exceptHandlers.append(handler_names)
for child in node.body:
self.handleNode(child, node)
self.exceptHandlers.pop()
# Process the other nodes: "except:", "else:", "finally:"
self.handleChildren(node, omit='body')
TRYEXCEPT = TRY
def EXCEPTHANDLER(self, node):
# 3.x: in addition to handling children, we must handle the name of
# the exception, which is not a Name node, but a simple string.
if isinstance(node.name, str):
self.handleNodeStore(node)
self.handleChildren(node)
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