168 lines
5.9 KiB
Python
168 lines
5.9 KiB
Python
r"""Utilities to compile possibly incomplete Python source code.
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This module provides two interfaces, broadly similar to the builtin
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function compile(), which take program text, a filename and a 'mode'
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and:
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- Return code object if the command is complete and valid
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- Return None if the command is incomplete
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- Raise SyntaxError, ValueError or OverflowError if the command is a
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syntax error (OverflowError and ValueError can be produced by
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malformed literals).
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Approach:
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First, check if the source consists entirely of blank lines and
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comments; if so, replace it with 'pass', because the built-in
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parser doesn't always do the right thing for these.
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Compile three times: as is, with \n, and with \n\n appended. If it
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compiles as is, it's complete. If it compiles with one \n appended,
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we expect more. If it doesn't compile either way, we compare the
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error we get when compiling with \n or \n\n appended. If the errors
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are the same, the code is broken. But if the errors are different, we
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expect more. Not intuitive; not even guaranteed to hold in future
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releases; but this matches the compiler's behavior from Python 1.4
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through 2.2, at least.
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Caveat:
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It is possible (but not likely) that the parser stops parsing with a
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successful outcome before reaching the end of the source; in this
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case, trailing symbols may be ignored instead of causing an error.
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For example, a backslash followed by two newlines may be followed by
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arbitrary garbage. This will be fixed once the API for the parser is
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better.
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The two interfaces are:
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compile_command(source, filename, symbol):
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Compiles a single command in the manner described above.
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CommandCompiler():
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Instances of this class have __call__ methods identical in
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signature to compile_command; the difference is that if the
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instance compiles program text containing a __future__ statement,
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the instance 'remembers' and compiles all subsequent program texts
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with the statement in force.
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The module also provides another class:
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Compile():
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Instances of this class act like the built-in function compile,
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but with 'memory' in the sense described above.
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"""
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import __future__
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_features = [getattr(__future__, fname)
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for fname in __future__.all_feature_names]
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__all__ = ["compile_command", "Compile", "CommandCompiler"]
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PyCF_DONT_IMPLY_DEDENT = 0x200 # Matches pythonrun.h
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def _maybe_compile(compiler, source, filename, symbol):
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# Check for source consisting of only blank lines and comments
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for line in source.split("\n"):
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line = line.strip()
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if line and line[0] != '#':
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break # Leave it alone
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else:
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if symbol != "eval":
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source = "pass" # Replace it with a 'pass' statement
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err = err1 = err2 = None
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code = code1 = code2 = None
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try:
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code = compiler(source, filename, symbol)
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except SyntaxError as err:
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pass
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try:
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code1 = compiler(source + "\n", filename, symbol)
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except SyntaxError as e:
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err1 = e
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try:
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code2 = compiler(source + "\n\n", filename, symbol)
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except SyntaxError as e:
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err2 = e
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if code:
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return code
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if not code1 and repr(err1) == repr(err2):
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raise err1
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def _compile(source, filename, symbol):
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return compile(source, filename, symbol, PyCF_DONT_IMPLY_DEDENT)
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def compile_command(source, filename="<input>", symbol="single"):
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r"""Compile a command and determine whether it is incomplete.
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Arguments:
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source -- the source string; may contain \n characters
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filename -- optional filename from which source was read; default
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"<input>"
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symbol -- optional grammar start symbol; "single" (default) or "eval"
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Return value / exceptions raised:
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- Return a code object if the command is complete and valid
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- Return None if the command is incomplete
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- Raise SyntaxError, ValueError or OverflowError if the command is a
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syntax error (OverflowError and ValueError can be produced by
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malformed literals).
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"""
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return _maybe_compile(_compile, source, filename, symbol)
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class Compile:
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"""Instances of this class behave much like the built-in compile
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function, but if one is used to compile text containing a future
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statement, it "remembers" and compiles all subsequent program texts
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with the statement in force."""
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def __init__(self):
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self.flags = PyCF_DONT_IMPLY_DEDENT
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def __call__(self, source, filename, symbol):
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codeob = compile(source, filename, symbol, self.flags, 1)
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for feature in _features:
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if codeob.co_flags & feature.compiler_flag:
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self.flags |= feature.compiler_flag
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return codeob
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class CommandCompiler:
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"""Instances of this class have __call__ methods identical in
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signature to compile_command; the difference is that if the
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instance compiles program text containing a __future__ statement,
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the instance 'remembers' and compiles all subsequent program texts
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with the statement in force."""
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def __init__(self,):
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self.compiler = Compile()
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def __call__(self, source, filename="<input>", symbol="single"):
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r"""Compile a command and determine whether it is incomplete.
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Arguments:
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source -- the source string; may contain \n characters
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filename -- optional filename from which source was read;
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default "<input>"
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symbol -- optional grammar start symbol; "single" (default) or
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"eval"
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Return value / exceptions raised:
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- Return a code object if the command is complete and valid
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- Return None if the command is incomplete
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- Raise SyntaxError, ValueError or OverflowError if the command is a
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syntax error (OverflowError and ValueError can be produced by
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malformed literals).
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"""
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return _maybe_compile(self.compiler, source, filename, symbol)
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