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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_ALLOW_INCOMPLETE_INPUT = 0x4000
def _maybe_compile(compiler, source, filename, symbol):
# 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
# Disable compiler warnings when checking for incomplete input.
with warnings.catch_warnings():
warnings.simplefilter("ignore", (SyntaxWarning, DeprecationWarning))
try:
compiler(source, filename, symbol)
except SyntaxError: # Let other compile() errors propagate.
try:
compiler(source + "\n", filename, symbol)
return None
except SyntaxError as e:
if "incomplete input" in str(e):
return None
# fallthrough
return compiler(source, filename, symbol, incomplete_input=False)
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"):
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)
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, **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)
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)
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