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 _is_syntax_error(err1, err2): rep1 = repr(err1) rep2 = repr(err2) if "was never closed" in rep1 and "was never closed" in rep2: return False if rep1 == rep2: return True return 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)