file formatting conventions for text files in our source repo

[zooko]

This makes it so that emacs knows the intended character encoding, BOM, end-of-line markers, and standard line-width of these files.

Also this is a form of documentation. It means that you should put only utf-8-encoded things into text files, only utf-8-encoded things into source code files (and actually you should write only put ASCII-encoded things except possibly in comments or docstrings!), and that you should line-wrap everything at 77 columns wide.

It also specifies that text files should start with a "utf-8 BOM". (Brian questions the point of this, and my answer is that it adds information and doesn't hurt. Whether that information will ever be useful is an open question.)

It also specifies that text files should have unix-style ('\n') end-of-line markers, not windows-style or old-macos-style.

I generated this patch by writing and running the following script, and then reading the resulting diff to make sure it was correct. I then undid the changes that the script had done to the files inside the "setuptools-0.6c16dev4.egg" directory before committing the patch.

import os

magic_header_line_comment_prefix = {
    '.py': u"# ",
    '.rst': u".. ",
    }

def format():
    for dirpath, dirnames, filenames in os.walk('.'):
        for filename in filenames:
            ext = os.path.splitext(filename)[-1]
            if ext in ('.py', '.rst'):
                fname = os.path.join(dirpath, filename)
                info = open(fname, 'rU')
                formattedlines = [ line.decode('utf-8') for line in info ]
                info.close()

                if len(formattedlines) == 0:
                    return

                outfo = open(fname, 'w')
                outfo.write(u"\ufeff".encode('utf-8'))

                commentsign = magic_header_line_comment_prefix[ext]

                firstline = formattedlines.pop(0)
                while firstline.startswith(u"\ufeff"):
                    firstline = firstline[len(u"\ufeff"):]
                if firstline.startswith(u"#!"):
                    outfo.write(firstline.encode('utf-8'))
                    outfo.write(commentsign.encode('utf-8'))
                    outfo.write("-*- coding: utf-8-with-signature-unix; fill-column: 77 -*-\n".encode('utf-8'))
                else:
                    outfo.write(commentsign.encode('utf-8'))
                    outfo.write("-*- coding: utf-8-with-signature-unix; fill-column: 77 -*-\n".encode('utf-8'))
                    if (commentsign in firstline) and ("-*-" in firstline) and ("coding:" in firstline):
                        print "warning there was already a coding line %r in %r"  % (firstline, fname)
                    else:
                        outfo.write(firstline.encode('utf-8'))

                for l in formattedlines:
                    if (commentsign in l) and ("-*-" in l) and ("coding:" in l):
                        print "warning there was already a coding line %r in %r"  % (l, fname)
                    else:
                        outfo.write(l.encode('utf-8'))
                outfo.close()

if __name__ == '__main__':
    format()

[zooko]

​https://github.com/tahoe-lafs/tahoe-lafs/pull/77