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__ | |
_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, err: | |
pass | |
try: | |
code1 = compiler(source + "\n", filename, symbol) | |
except SyntaxError, err1: | |
pass | |
try: | |
code2 = compiler(source + "\n\n", filename, symbol) | |
except SyntaxError, err2: | |
pass | |
if code: | |
return code | |
if not code1 and repr(err1) == repr(err2): | |
raise SyntaxError, err1 | |
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) 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, 1) | |
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) |