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87 lines
2.8 KiB
Python
87 lines
2.8 KiB
Python
"""Utility to compile possibly incomplete Python source code."""
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import sys
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import string
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import traceback
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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 "<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 or OverflowError if the command is a syntax error
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(OverflowError if the error is in a numeric constant)
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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
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it compiles as is, it's complete. If it compiles with one \n
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appended, we expect more. If it doesn't compile either way, we
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compare the error we get when compiling with \n or \n\n appended.
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If the errors are the same, the code is broken. But if the errors
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are different, we expect more. Not intuitive; not even guaranteed
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to hold in future releases; but this matches the compiler's
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behavior from Python 1.4 through 1.5.2, at least.
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Caveat:
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It is possible (but not likely) that the parser stops parsing
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with a successful outcome before reaching the end of the source;
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in this case, trailing symbols may be ignored instead of causing an
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error. For example, a backslash followed by two newlines may be
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followed by arbitrary garbage. This will be fixed once the API
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for the parser is better.
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"""
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# Check for source consisting of only blank lines and comments
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for line in string.split(source, "\n"):
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line = string.strip(line)
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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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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 = compile(source, filename, symbol)
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except SyntaxError, err:
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pass
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try:
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code1 = compile(source + "\n", filename, symbol)
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except SyntaxError, err1:
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pass
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try:
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code2 = compile(source + "\n\n", filename, symbol)
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except SyntaxError, err2:
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pass
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if code:
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return code
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try:
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e1 = err1.__dict__
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except AttributeError:
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e1 = err1
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try:
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e2 = err2.__dict__
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except AttributeError:
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e2 = err2
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if not code1 and e1 == e2:
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raise SyntaxError, err1
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