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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). | |
| Approach: | |
| First, check if the source consists entirely of blank lines and | |
| comments; if so, replace it with 'pass', because the built-in | |
| parser doesn't always do the right thing for these. | |
| Compile three times: as is, with \n, and with \n\n appended. If it | |
| compiles as is, it's complete. If it compiles with one \n appended, | |
| we expect more. If it doesn't compile either way, we compare the | |
| error we get when compiling with \n or \n\n appended. If the errors | |
| are the same, the code is broken. But if the errors are different, we | |
| expect more. Not intuitive; not even guaranteed to hold in future | |
| releases; but this matches the compiler's behavior from Python 1.4 | |
| through 2.2, at least. | |
| Caveat: | |
| It is possible (but not likely) that the parser stops parsing with a | |
| successful outcome before reaching the end of the source; in this | |
| case, trailing symbols may be ignored instead of causing an error. | |
| For example, a backslash followed by two newlines may be followed by | |
| arbitrary garbage. This will be fixed once the API for the parser is | |
| better. | |
| 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"] | |
| PyCF_DONT_IMPLY_DEDENT = 0x200 # Matches pythonrun.h | |
| 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 | |
| err = err1 = err2 = None | |
| code = code1 = code2 = None | |
| try: | |
| code = compiler(source, filename, symbol) | |
| except SyntaxError: | |
| pass | |
| # Catch syntax warnings after the first compile | |
| # to emit warnings (SyntaxWarning, DeprecationWarning) at most once. | |
| with warnings.catch_warnings(): | |
| warnings.simplefilter("error") | |
| try: | |
| code1 = compiler(source + "\n", filename, symbol) | |
| except SyntaxError as e: | |
| err1 = e | |
| try: | |
| code2 = compiler(source + "\n\n", filename, symbol) | |
| except SyntaxError as e: | |
| err2 = e | |
| try: | |
| if code: | |
| return code | |
| if not code1 and repr(err1) == repr(err2): | |
| raise err1 | |
| finally: | |
| err1 = err2 = None | |
| def _compile(source, filename, symbol): | |
| return compile(source, filename, symbol, PyCF_DONT_IMPLY_DEDENT) | |
| 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 | |
| def __call__(self, source, filename, symbol): | |
| codeob = compile(source, filename, symbol, self.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) |