# Copyright 2016 Grist Labs, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import ast
import collections
import token
from six import iteritems
def token_repr(tok_type, string):
"""Returns a human-friendly representation of a token with the given type and string."""
# repr() prefixes unicode with 'u' on Python2 but not Python3; strip it out for consistency.
return '%s:%s' % (token.tok_name[tok_type], repr(string).lstrip('u'))
class Token(collections.namedtuple('Token', 'type string start end line index startpos endpos')):
"""
TokenInfo is an 8-tuple containing the same 5 fields as the tokens produced by the tokenize
module, and 3 additional ones useful for this module:
- [0] .type Token type (see token.py)
- [1] .string Token (a string)
- [2] .start Starting (row, column) indices of the token (a 2-tuple of ints)
- [3] .end Ending (row, column) indices of the token (a 2-tuple of ints)
- [4] .line Original line (string)
- [5] .index Index of the token in the list of tokens that it belongs to.
- [6] .startpos Starting character offset into the input text.
- [7] .endpos Ending character offset into the input text.
"""
def __str__(self):
return token_repr(self.type, self.string)
def match_token(token, tok_type, tok_str=None):
"""Returns true if token is of the given type and, if a string is given, has that string."""
return token.type == tok_type and (tok_str is None or token.string == tok_str)
def expect_token(token, tok_type, tok_str=None):
"""
Verifies that the given token is of the expected type. If tok_str is given, the token string
is verified too. If the token doesn't match, raises an informative ValueError.
"""
if not match_token(token, tok_type, tok_str):
raise ValueError("Expected token %s, got %s on line %s col %s" % (
token_repr(tok_type, tok_str), str(token),
token.start[0], token.start[1] + 1))
# These were previously defined in tokenize.py and distinguishable by being greater than
# token.N_TOKEN. As of python3.7, they are in token.py, and we check for them explicitly.
if hasattr(token, 'ENCODING'):
def is_non_coding_token(token_type):
"""
These are considered non-coding tokens, as they don't affect the syntax tree.
"""
return token_type in (token.NL, token.COMMENT, token.ENCODING)
else:
def is_non_coding_token(token_type):
"""
These are considered non-coding tokens, as they don't affect the syntax tree.
"""
return token_type >= token.N_TOKENS
def iter_children_func(node):
"""
Returns a function which yields all direct children of a AST node,
skipping children that are singleton nodes.
The function depends on whether ``node`` is from ``ast`` or from the ``astroid`` module.
"""
return iter_children_astroid if hasattr(node, 'get_children') else iter_children_ast
def iter_children_astroid(node):
# Don't attempt to process children of JoinedStr nodes, which we can't fully handle yet.
if is_joined_str(node):
return []
return node.get_children()
SINGLETONS = {c for n, c in iteritems(ast.__dict__) if isinstance(c, type) and
issubclass(c, (ast.expr_context, ast.boolop, ast.operator, ast.unaryop, ast.cmpop))}
def iter_children_ast(node):
# Don't attempt to process children of JoinedStr nodes, which we can't fully handle yet.
if is_joined_str(node):
return
if isinstance(node, ast.Dict):
# override the iteration order: instead of <all keys>, <all values>,
# yield keys and values in source order (key1, value1, key2, value2, ...)
for (key, value) in zip(node.keys, node.values):
if key is not None:
yield key
yield value
return
for child in ast.iter_child_nodes(node):
# Skip singleton children; they don't reflect particular positions in the code and break the
# assumptions about the tree consisting of distinct nodes. Note that collecting classes
# beforehand and checking them in a set is faster than using isinstance each time.
if child.__class__ not in SINGLETONS:
yield child
stmt_class_names = {n for n, c in iteritems(ast.__dict__)
if isinstance(c, type) and issubclass(c, ast.stmt)}
expr_class_names = ({n for n, c in iteritems(ast.__dict__)
if isinstance(c, type) and issubclass(c, ast.expr)} |
{'AssignName', 'DelName', 'Const', 'AssignAttr', 'DelAttr'})
# These feel hacky compared to isinstance() but allow us to work with both ast and astroid nodes
# in the same way, and without even importing astroid.
def is_expr(node):
"""Returns whether node is an expression node."""
return node.__class__.__name__ in expr_class_names
def is_stmt(node):
"""Returns whether node is a statement node."""
return node.__class__.__name__ in stmt_class_names
def is_module(node):
"""Returns whether node is a module node."""
return node.__class__.__name__ == 'Module'
def is_joined_str(node):
"""Returns whether node is a JoinedStr node, used to represent f-strings."""
# At the moment, nodes below JoinedStr have wrong line/col info, and trying to process them only
# leads to errors.
return node.__class__.__name__ == 'JoinedStr'
def is_starred(node):
"""Returns whether node is a starred expression node."""
return node.__class__.__name__ == 'Starred'
def is_slice(node):
"""Returns whether node represents a slice, e.g. `1:2` in `x[1:2]`"""
# Before 3.9, a tuple containing a slice is an ExtSlice,
# but this was removed in https://bugs.python.org/issue34822
return (
node.__class__.__name__ in ('Slice', 'ExtSlice')
or (
node.__class__.__name__ == 'Tuple'
and any(map(is_slice, node.elts))
)
)
# Sentinel value used by visit_tree().
_PREVISIT = object()
def visit_tree(node, previsit, postvisit):
"""
Scans the tree under the node depth-first using an explicit stack. It avoids implicit recursion
via the function call stack to avoid hitting 'maximum recursion depth exceeded' error.
It calls ``previsit()`` and ``postvisit()`` as follows:
* ``previsit(node, par_value)`` - should return ``(par_value, value)``
``par_value`` is as returned from ``previsit()`` of the parent.
* ``postvisit(node, par_value, value)`` - should return ``value``
``par_value`` is as returned from ``previsit()`` of the parent, and ``value`` is as
returned from ``previsit()`` of this node itself. The return ``value`` is ignored except
the one for the root node, which is returned from the overall ``visit_tree()`` call.
For the initial node, ``par_value`` is None. ``postvisit`` may be None.
"""
if not postvisit:
postvisit = lambda node, pvalue, value: None
iter_children = iter_children_func(node)
done = set()
ret = None
stack = [(node, None, _PREVISIT)]
while stack:
current, par_value, value = stack.pop()
if value is _PREVISIT:
assert current not in done # protect againt infinite loop in case of a bad tree.
done.add(current)
pvalue, post_value = previsit(current, par_value)
stack.append((current, par_value, post_value))
# Insert all children in reverse order (so that first child ends up on top of the stack).
ins = len(stack)
for n in iter_children(current):
stack.insert(ins, (n, pvalue, _PREVISIT))
else:
ret = postvisit(current, par_value, value)
return ret
def walk(node):
"""
Recursively yield all descendant nodes in the tree starting at ``node`` (including ``node``
itself), using depth-first pre-order traversal (yieling parents before their children).
This is similar to ``ast.walk()``, but with a different order, and it works for both ``ast`` and
``astroid`` trees. Also, as ``iter_children()``, it skips singleton nodes generated by ``ast``.
"""
iter_children = iter_children_func(node)
done = set()
stack = [node]
while stack:
current = stack.pop()
assert current not in done # protect againt infinite loop in case of a bad tree.
done.add(current)
yield current
# Insert all children in reverse order (so that first child ends up on top of the stack).
# This is faster than building a list and reversing it.
ins = len(stack)
for c in iter_children(current):
stack.insert(ins, c)
def replace(text, replacements):
"""
Replaces multiple slices of text with new values. This is a convenience method for making code
modifications of ranges e.g. as identified by ``ASTTokens.get_text_range(node)``. Replacements is
an iterable of ``(start, end, new_text)`` tuples.
For example, ``replace("this is a test", [(0, 4, "X"), (8, 9, "THE")])`` produces
``"X is THE test"``.
"""
p = 0
parts = []
for (start, end, new_text) in sorted(replacements):
parts.append(text[p:start])
parts.append(new_text)
p = end
parts.append(text[p:])
return ''.join(parts)
class NodeMethods(object):
"""
Helper to get `visit_{node_type}` methods given a node's class and cache the results.
"""
def __init__(self):
self._cache = {}
def get(self, obj, cls):
"""
Using the lowercase name of the class as node_type, returns `obj.visit_{node_type}`,
or `obj.visit_default` if the type-specific method is not found.
"""
method = self._cache.get(cls)
if not method:
name = "visit_" + cls.__name__.lower()
method = getattr(obj, name, obj.visit_default)
self._cache[cls] = method
return method