better_twill.py

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#!/usr/bin/python
"""better_twill is a small wrapper around twill to set some sane defaults and
monkey-patch some better versions of some of twill's methods.
It also handles twill's absense.
"""

import os
import sys
try:
    from cStringIO import StringIO
except ImportError:
    from StringIO import StringIO

try:
    import twill
except ImportError:
    twill = None

# When twill tries to connect to a site before the site is up, it raises an
# exception.  In 0.9b1, it's urlib2.URLError, but in -latest, it's
# _mechanize_dist._mechanize.BrowserStateError.
try:
    from _mechanize_dist._mechanize import BrowserStateError as ConnectError
except ImportError:
    from urllib2 import URLError as ConnectError


if twill:
    # We want Trac to generate valid html, and therefore want to test against
    # the html as generated by Trac.  "tidy" tries to clean up broken html, and
    # is responsible for one difficult to track down testcase failure (for
    # #5497).  Therefore we turn it off here.
    twill.commands.config('use_tidy', '0')

    # setup short names to reduce typing
    # This twill browser (and the tc commands that use it) are essentially
    # global, and not tied to our test fixture.
    tc = twill.commands
    b = twill.get_browser()

    # When we can't find something we expected, or find something we didn't
    # expect, it helps the debugging effort to have a copy of the html to
    # analyze.
    def twill_write_html():
        """Write the current html to a file.  Name the file based on the
        current testcase.
        """
        frame = sys._getframe()
        while frame:
            if frame.f_code.co_name in ('runTest', 'setUp', 'tearDown'):
                testcase = frame.f_locals['self']
                testname = testcase.__class__.__name__
                tracdir = testcase._testenv.tracdir
                break
            frame = frame.f_back
        else:
            # We didn't find a testcase in the stack, so we have no clue what's
            # going on.
            raise Exception("No testcase was found on the stack.  This was "
                "really not expected, and I don't know how to handle it.")

        filename = os.path.join(tracdir, 'log', "%s.html" % testname)
        html_file = open(filename, 'w')
        html_file.write(b.get_html())
        html_file.close()

        return filename

    # Twill isn't as helpful with errors as I'd like it to be, so we replace
    # the formvalue function.  This would be better done as a patch to Twill.
    def better_formvalue(form, field, value, fv=tc.formvalue):
        try:
            fv(form, field, value)
        except (twill.errors.TwillAssertionError,
                twill.utils.ClientForm.ItemNotFoundError), e:
            filename = twill_write_html()
            args = e.args + (filename,)
            raise twill.errors.TwillAssertionError(*args)
    tc.formvalue = better_formvalue

    # Twill's formfile function leaves a filehandle open which prevents the
    # file from being deleted on Windows.  Since we would just assume use a
    # StringIO object in the first place, allow the file-like object to be
    # provided directly.
    def better_formfile(formname, fieldname, filename, content_type=None,
                        fp=None):
        if not fp:
            filename = filename.replace('/', os.path.sep)
            temp_fp = open(filename, 'rb')
            data = temp_fp.read()
            temp_fp.close()
            fp = StringIO(data)

        form = b.get_form(formname)
        control = b.get_form_field(form, fieldname)

        if not control.is_of_kind('file'):
            raise twill.errors.TwillException('ERROR: field is not a file '
                                              'upload field!')

        b.clicked(form, control)
        control.add_file(fp, content_type, filename)
    tc.formfile = better_formfile

    # Twill's tc.find() does not provide any guidance on what we got instead of
    # what was expected.
    def better_find(what, flags='', tcfind=tc.find):
        try:
            tcfind(what, flags)
        except twill.errors.TwillAssertionError, e:
            filename = twill_write_html()
            args = e.args + (filename,)
            raise twill.errors.TwillAssertionError(*args)
    tc.find = better_find
    def better_notfind(what, flags='', tcnotfind=tc.notfind):
        try:
            tcnotfind(what, flags)
        except twill.errors.TwillAssertionError, e:
            filename = twill_write_html()
            args = e.args + (filename,)
            raise twill.errors.TwillAssertionError(*args)
    tc.notfind = better_notfind
else:
    b = tc = None