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76 lines
3.2 KiB
76 lines
3.2 KiB
2 years ago
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# This file contains a class and a main program that perform three
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# related (though complimentary) formatting operations on Python
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# programs. When called as "pindent -c", it takes a valid Python
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# program as input and outputs a version augmented with block-closing
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# comments. When called as "pindent -d", it assumes its input is a
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# Python program with block-closing comments and outputs a commentless
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# version. When called as "pindent -r" it assumes its input is a
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# Python program with block-closing comments but with its indentation
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# messed up, and outputs a properly indented version.
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# A "block-closing comment" is a comment of the form '# end <keyword>'
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# where <keyword> is the keyword that opened the block. If the
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# opening keyword is 'def' or 'class', the function or class name may
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# be repeated in the block-closing comment as well. Here is an
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# example of a program fully augmented with block-closing comments:
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# def foobar(a, b):
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# if a == b:
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# a = a+1
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# elif a < b:
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# b = b-1
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# if b > a: a = a-1
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# # end if
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# else:
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# print 'oops!'
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# # end if
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# # end def foobar
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# Note that only the last part of an if...elif...else... block needs a
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# block-closing comment; the same is true for other compound
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# statements (e.g. try...except). Also note that "short-form" blocks
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# like the second 'if' in the example must be closed as well;
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# otherwise the 'else' in the example would be ambiguous (remember
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# that indentation is not significant when interpreting block-closing
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# comments).
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# The operations are idempotent (i.e. applied to their own output
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# they yield an identical result). Running first "pindent -c" and
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# then "pindent -r" on a valid Python program produces a program that
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# is semantically identical to the input (though its indentation may
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# be different). Running "pindent -e" on that output produces a
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# program that only differs from the original in indentation.
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# Other options:
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# -s stepsize: set the indentation step size (default 8)
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# -t tabsize : set the number of spaces a tab character is worth (default 8)
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# -e : expand TABs into spaces
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# file ... : input file(s) (default standard input)
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# The results always go to standard output
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# Caveats:
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# - comments ending in a backslash will be mistaken for continued lines
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# - continuations using backslash are always left unchanged
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# - continuations inside parentheses are not extra indented by -r
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# but must be indented for -c to work correctly (this breaks
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# idempotency!)
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# - continued lines inside triple-quoted strings are totally garbled
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# Secret feature:
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# - On input, a block may also be closed with an "end statement" --
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# this is a block-closing comment without the '#' sign.
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# Possible improvements:
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# - check syntax based on transitions in 'next' table
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# - better error reporting
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# - better error recovery
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# - check identifier after class/def
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# The following wishes need a more complete tokenization of the source:
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# - Don't get fooled by comments ending in backslash
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# - reindent continuation lines indicated by backslash
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# - handle continuation lines inside parentheses/braces/brackets
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# - handle triple quoted strings spanning lines
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# - realign comments
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# - optionally do much more thorough reformatting, a la C indent
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