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simpleeval.py
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# The MIT License
#
# Copyright (c) 2015 the bpython authors.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
"""simple evaluation of side-effect free code
In order to provide fancy completion, some code can be executed safely.
"""
importast
importbuiltins
fromtypingimportAny
from .importlineasline_properties
from .inspectionimportgetattr_safe
_numeric_types= (int,float,complex)
classEvaluationError(Exception):
"""Raised if an exception occurred in safe_eval."""
defsafe_eval(expr:str,namespace:dict[str,Any])->Any:
"""Not all that safe, just catches some errors"""
try:
returneval(expr,namespace)
except (NameError,AttributeError,SyntaxError):
# If debugging safe_eval, raise this!
# raise
raiseEvaluationError
# This function is under the Python License, Version 2
# This license requires modifications to the code be reported.
# Based on ast.literal_eval
# Modifications:
# * checks that objects used as operands of + and - are numbers
# instead of checking they are constructed with number literals
# * new docstring describing different functionality
# * looks up names from namespace
# * indexing syntax is allowed
# * evaluates tuple() and list()
defsimple_eval(node_or_string,namespace=None):
"""
Safely evaluate an expression node or a string containing a Python
expression without triggering any user code.
The string or node provided may only consist of:
* the following Python literal structures: strings, numbers, tuples,
lists, dicts, and sets
* variable names causing lookups in the passed in namespace or builtins
* getitem calls using the [] syntax on objects of the types above
Like Python 3's literal_eval, unary and binary + and - operations are
allowed on all builtin numeric types.
The optional namespace dict-like ought not to cause side effects on lookup.
"""
ifnamespaceisNone:
namespace= {}
ifisinstance(node_or_string,str):
node_or_string=ast.parse(node_or_string,mode="eval")
ifisinstance(node_or_string,ast.Expression):
node_or_string=node_or_string.body
def_convert(node):
ifisinstance(node,ast.Constant):
returnnode.value
elifisinstance(node,ast.Tuple):
returntuple(map(_convert,node.elts))
elifisinstance(node,ast.List):
returnlist(map(_convert,node.elts))
elifisinstance(node,ast.Dict):
return {
_convert(k):_convert(v)fork,vinzip(node.keys,node.values)
}
elifisinstance(node,ast.Set):
returnset(map(_convert,node.elts))
elif (
isinstance(node,ast.Call)
andisinstance(node.func,ast.Name)
andnode.func.id=="set"
andnode.args==node.keywords== []
):
returnset()
# this is a deviation from literal_eval: we evaluate tuple() and list()
elif (
isinstance(node,ast.Call)
andisinstance(node.func,ast.Name)
andnode.func.id=="tuple"
andnode.args==node.keywords== []
):
returntuple()
elif (
isinstance(node,ast.Call)
andisinstance(node.func,ast.Name)
andnode.func.id=="list"
andnode.args==node.keywords== []
):
returnlist()
# this is a deviation from literal_eval: we allow non-literals
elifisinstance(node,ast.Name):
try:
returnnamespace[node.id]
exceptKeyError:
try:
returngetattr(builtins,node.id)
exceptAttributeError:
raiseEvaluationError("can't lookup %s"%node.id)
# unary + and - are allowed on any type
elifisinstance(node,ast.UnaryOp)andisinstance(
node.op, (ast.UAdd,ast.USub)
):
# ast.literal_eval does ast typechecks here, we use type checks
operand=_convert(node.operand)
ifnottype(operand)in_numeric_types:
raiseValueError("unary + and - only allowed on builtin nums")
ifisinstance(node.op,ast.UAdd):
return+operand
else:
return-operand
elifisinstance(node,ast.BinOp)andisinstance(
node.op, (ast.Add,ast.Sub)
):
# this is a deviation from literal_eval: ast.literal_eval accepts
# (+/-) int, float and complex literals as left operand, and complex
# as right operation, we evaluate as much as possible
left=_convert(node.left)
right=_convert(node.right)
ifnot (
isinstance(left,_numeric_types)
andisinstance(right,_numeric_types)
):
raiseValueError("binary + and - only allowed on builtin nums")
ifisinstance(node.op,ast.Add):
returnleft+right
else:
returnleft-right
# this is a deviation from literal_eval: we allow indexing
elifisinstance(node,ast.Subscript)andisinstance(
node.slice, (ast.Constant,ast.Name)
):
obj=_convert(node.value)
index=_convert(node.slice)
returnsafe_getitem(obj,index)
# this is a deviation from literal_eval: we allow attribute access
ifisinstance(node,ast.Attribute):
obj=_convert(node.value)
attr=node.attr
returngetattr_safe(obj,attr)
raiseValueError(f"malformed node or string:{node!r}")
return_convert(node_or_string)
defsafe_getitem(obj,index):
"""Safely tries to access obj[index]"""
iftype(obj)in (list,tuple,dict,bytes,str):
try:
returnobj[index]
except (KeyError,IndexError):
raiseEvaluationError(f"can't lookup key{index!r} on{obj!r}")
raiseValueError(f"unsafe to lookup on object of type{type(obj)}")
deffind_attribute_with_name(node,name):
ifisinstance(node,ast.Attribute)andnode.attr==name:
returnnode
foriteminast.iter_child_nodes(node):
r=find_attribute_with_name(item,name)
ifr:
returnr
defevaluate_current_expression(
cursor_offset:int,line:str,namespace:dict[str,Any]|None=None
)->Any:
"""
Return evaluated expression to the right of the dot of current attribute.
Only evaluates builtin objects, and do any attribute lookup.
"""
# Builds asts from with increasing numbers of characters back from cursor.
# Find the biggest valid ast.
# Once our attribute access is found, return its .value subtree
# in case attribute is blank, e.g. foo.| -> foo.xxx|
temp_line=line[:cursor_offset]+"xxx"+line[cursor_offset:]
temp_cursor=cursor_offset+3
temp_attribute=line_properties.current_expression_attribute(
temp_cursor,temp_line
)
iftemp_attributeisNone:
raiseEvaluationError("No current attribute")
attr_before_cursor=temp_line[temp_attribute.start :temp_cursor]
defparse_trees(cursor_offset,line):
foriinrange(cursor_offset-1,-1,-1):
try:
tree=ast.parse(line[i:cursor_offset])
yieldtree
exceptSyntaxError:
continue
largest_ast=None
fortreeinparse_trees(temp_cursor,temp_line):
attribute_access=find_attribute_with_name(tree,attr_before_cursor)
ifattribute_access:
largest_ast=attribute_access.value
iflargest_astisNone:
raiseEvaluationError(
"Corresponding ASTs to right of cursor are invalid"
)
try:
returnsimple_eval(largest_ast,namespace)
exceptValueError:
raiseEvaluationError("Could not safely evaluate")
defevaluate_current_attribute(cursor_offset,line,namespace=None):
"""Safely evaluates the expression having an attributed accessed"""
# this function runs user code in case of custom descriptors,
# so could fail in any way
obj=evaluate_current_expression(cursor_offset,line,namespace)
attr=line_properties.current_expression_attribute(cursor_offset,line)
ifattrisNone:
raiseEvaluationError("No attribute found to look up")
try:
returngetattr(obj,attr.word)
exceptAttributeError:
raiseEvaluationError(f"can't lookup attribute{attr.word} on{obj!r}")