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r"""Utilities to compile possibly incomplete Python source code.

This module provides two interfaces, broadly similar to the builtin

function compile(), which take program text, a filename and a 'mode'

and:

- Return code object if the command is complete and valid

- Return None if the command is incomplete

- Raise SyntaxError, ValueError or OverflowError if the command is a

syntax error (OverflowError and ValueError can be produced by

malformed literals).

The two interfaces are:

compile_command(source, filename, symbol):

Compiles a single command in the manner described above.

CommandCompiler():

Instances of this class have __call__ methods identical in

signature to compile_command; the difference is that if the

instance compiles program text containing a __future__ statement,

the instance 'remembers' and compiles all subsequent program texts

with the statement in force.

The module also provides another class:

Compile():

Instances of this class act like the built-in function compile,

but with 'memory' in the sense described above.

"""

import __future__

import warnings

_features = [getattr(__future__, fname)

for fname in __future__.all_feature_names]

__all__ = ["compile_command", "Compile", "CommandCompiler"]

# The following flags match the values from Include/cpython/compile.h

# Caveat emptor: These flags are undocumented on purpose and depending

# on their effect outside the standard library is **unsupported**.

PyCF_DONT_IMPLY_DEDENT = 0x200

PyCF_ONLY_AST = 0x400

PyCF_ALLOW_INCOMPLETE_INPUT = 0x4000

def _maybe_compile(compiler, source, filename, symbol, flags):

# Check for source consisting of only blank lines and comments.

for line in source.split("\n"):

line = line.strip()

if line and line[0] != '#':

break # Leave it alone.

else:

if symbol != "eval":

source = "pass" # Replace it with a 'pass' statement

incomplete_input = False

# Disable compiler warnings when checking for incomplete input.

with warnings.catch_warnings():

warnings.simplefilter("ignore", (SyntaxWarning, DeprecationWarning))

try:

compiler(source, filename, symbol, flags=flags)

except _IncompleteInputError:

return None

except SyntaxError as error: # Let other compile() errors propagate.

# Preserve escape errors that a missing closing quote can hide.

incomplete_input = error.msg.startswith("(unicode error)")

return compiler(source, filename, symbol, incomplete_input=incomplete_input)

def _compile(source, filename, symbol, incomplete_input=True, *, flags=0):

if incomplete_input:

flags |= PyCF_ALLOW_INCOMPLETE_INPUT

flags |= PyCF_DONT_IMPLY_DEDENT

return compile(source, filename, symbol, flags)

def compile_command(source, filename="<input>", symbol="single", flags=0):

r"""Compile a command and determine whether it is incomplete.

Arguments:

source -- the source string; may contain \n characters

filename -- optional filename from which source was read; default

"<input>"

symbol -- optional grammar start symbol; "single" (default), "exec"

or "eval"

Return value / exceptions raised:

- Return a code object if the command is complete and valid

- Return None if the command is incomplete

- Raise SyntaxError, ValueError or OverflowError if the command is a

syntax error (OverflowError and ValueError can be produced by

malformed literals).

"""

return _maybe_compile(_compile, source, filename, symbol, flags)

class Compile:

"""Instances of this class behave much like the built-in compile

function, but if one is used to compile text containing a future

statement, it "remembers" and compiles all subsequent program texts

with the statement in force."""

def __init__(self):

self.flags = PyCF_DONT_IMPLY_DEDENT | PyCF_ALLOW_INCOMPLETE_INPUT

def __call__(self, source, filename, symbol, flags=0, **kwargs):

flags |= self.flags

if kwargs.get('incomplete_input', True) is False:

flags &= ~PyCF_DONT_IMPLY_DEDENT

flags &= ~PyCF_ALLOW_INCOMPLETE_INPUT

codeob = compile(source, filename, symbol, flags, True)

if flags & PyCF_ONLY_AST:

return codeob # this is an ast.Module in this case

for feature in _features:

if codeob.co_flags & feature.compiler_flag:

self.flags |= feature.compiler_flag

return codeob

class CommandCompiler:

"""Instances of this class have __call__ methods identical in

signature to compile_command; the difference is that if the

instance compiles program text containing a __future__ statement,

the instance 'remembers' and compiles all subsequent program texts

with the statement in force."""

def __init__(self,):

self.compiler = Compile()

def __call__(self, source, filename="<input>", symbol="single"):

r"""Compile a command and determine whether it is incomplete.

Arguments:

source -- the source string; may contain \n characters

filename -- optional filename from which source was read;

default "<input>"

symbol -- optional grammar start symbol; "single" (default) or

"eval"

Return value / exceptions raised:

- Return a code object if the command is complete and valid

- Return None if the command is incomplete

- Raise SyntaxError, ValueError or OverflowError if the command is a

syntax error (OverflowError and ValueError can be produced by

malformed literals).

"""

return _maybe_compile(self.compiler, source, filename, symbol, flags=self.compiler.flags)