bpython/bpython/simpleeval.py at master · studiovc/bpython · GitHub

History

256 lines (219 loc) · 9.29 KB

Raw

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

# The MIT License

# 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.

"""

import ast

import inspect

import sys

import builtins

from . import line as line_properties

from .inspection import getattr_safe

_string_type_nodes = (ast.Str, ast.Bytes)

_numeric_types = (int, float, complex)

_name_type_nodes = (ast.Name, ast.NameConstant)

class EvaluationError(Exception):

"""Raised if an exception occurred in safe_eval."""

def safe_eval(expr, namespace):

"""Not all that safe, just catches some errors"""

try:

return eval(expr, namespace)

except (NameError, AttributeError, SyntaxError):

# If debugging safe_eval, raise this!

# raise

raise EvaluationError

# 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

def simple_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 the Python 3 (and unlike the Python 2) 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

"""

if namespace is None:

namespace = {}

if isinstance(node_or_string, str):

node_or_string = ast.parse(node_or_string, mode="eval")

if isinstance(node_or_string, ast.Expression):

node_or_string = node_or_string.body

def _convert(node):

if isinstance(node, ast.Constant):

return node.value

elif isinstance(node, _string_type_nodes):

return node.s

elif isinstance(node, ast.Num):

return node.n

elif isinstance(node, ast.Tuple):

return tuple(map(_convert, node.elts))

elif isinstance(node, ast.List):

return list(map(_convert, node.elts))

elif isinstance(node, ast.Dict):

return {

_convert(k): _convert(v) for k, v in zip(node.keys, node.values)

}

elif isinstance(node, ast.Set):

return set(map(_convert, node.elts))

elif (

isinstance(node, ast.Call)

and isinstance(node.func, ast.Name)

and node.func.id == "set"

and node.args == node.keywords == []

return set()

# this is a deviation from literal_eval: we allow non-literals

elif isinstance(node, _name_type_nodes):

try:

return namespace[node.id]

except KeyError:

try:

return getattr(builtins, node.id)

except AttributeError:

raise EvaluationError("can't lookup %s" % node.id)

# unary + and - are allowed on any type

elif isinstance(node, ast.UnaryOp) and isinstance(

node.op, (ast.UAdd, ast.USub)

# ast.literal_eval does ast typechecks here, we use type checks

operand = _convert(node.operand)

if not type(operand) in _numeric_types:

raise ValueError("unary + and - only allowed on builtin nums")

if isinstance(node.op, ast.UAdd):

return +operand

else:

return -operand

elif isinstance(node, ast.BinOp) and isinstance(

node.op, (ast.Add, ast.Sub)

# ast.literal_eval does ast typechecks here, we use type checks

left = _convert(node.left)

right = _convert(node.right)

if not (

type(left) in _numeric_types and type(right) in _numeric_types

raise ValueError("binary + and - only allowed on builtin nums")

if isinstance(node.op, ast.Add):

return left + right

else:

return left - right

# this is a deviation from literal_eval: we allow indexing

elif isinstance(node, ast.Subscript) and isinstance(

node.slice, ast.Index

obj = _convert(node.value)

index = _convert(node.slice.value)

return safe_getitem(obj, index)

elif (

sys.version_info[:2] >= (3, 9)

and isinstance(node, ast.Subscript)

and isinstance(node.slice, (ast.Constant, ast.Name))

obj = _convert(node.value)

index = _convert(node.slice)

return safe_getitem(obj, index)

# this is a deviation from literal_eval: we allow attribute access

if isinstance(node, ast.Attribute):

obj = _convert(node.value)

attr = node.attr

return getattr_safe(obj, attr)

raise ValueError(f"malformed node or string: {node!r}")

return _convert(node_or_string)

def safe_getitem(obj, index):

""" Safely tries to access obj[index] """

if type(obj) in (list, tuple, dict, bytes, str):

try:

return obj[index]

except (KeyError, IndexError):

raise EvaluationError(f"can't lookup key {index!r} on {obj!r}")

raise ValueError("unsafe to lookup on object of type {}".format(type(obj)))

def find_attribute_with_name(node, name):

if isinstance(node, ast.Attribute) and node.attr == name:

return node

for item in ast.iter_child_nodes(node):

r = find_attribute_with_name(item, name)

if r:

return r

def evaluate_current_expression(cursor_offset, line, namespace=None):

"""

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

if namespace is None:

namespace = {}

# 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

)

if temp_attribute is None:

raise EvaluationError("No current attribute")

attr_before_cursor = temp_line[temp_attribute.start : temp_cursor]

def parse_trees(cursor_offset, line):

for i in range(cursor_offset - 1, -1, -1):

try:

tree = ast.parse(line[i:cursor_offset])

yield tree

except SyntaxError:

continue

largest_ast = None

for tree in parse_trees(temp_cursor, temp_line):

attribute_access = find_attribute_with_name(tree, attr_before_cursor)

if attribute_access:

largest_ast = attribute_access.value

if largest_ast is None:

raise EvaluationError(

"Corresponding ASTs to right of cursor are invalid"

)

try:

return simple_eval(largest_ast, namespace)

except ValueError:

raise EvaluationError("Could not safely evaluate")

def evaluate_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)

if attr is None:

raise EvaluationError("No attribute found to look up")

try:

return getattr(obj, attr.word)

except AttributeError:

raise EvaluationError(f"can't lookup attribute {attr.word} on {obj!r}")

bpython/bpython/simpleeval.py at master · studiovc/bpython · GitHub

Expand file tree

Breadcrumbs

simpleeval.py

Latest commit

History

Breadcrumbs

simpleeval.py

File metadata and controls