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There are some common requirements in the library: some parameters need to be
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unicode safe, some need byte strings, and so on. At the moment we have
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only codified one specific pattern: Parameters that need to be unicode
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should be checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
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should be checked via 'bzrlib.osutils.safe_unicode'. This will coerce the
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input into unicode in a consistent fashion, allowing trivial strings to be
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used for programmer convenience, but not performing unpredictably in the
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presence of different locales.
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The copyright policy for bzr was recently made clear in this email (edited
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for grammatical correctness)::
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The attached patch cleans up the copyright and license statements in
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the bzr source. It also adds tests to help us remember to add them
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with the correct text.
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We had the problem that lots of our files were "Copyright Canonical
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Development Ltd" which is not a real company, and some other variations
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on this theme. Also, some files were missing the GPL statements.
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I want to be clear about the intent of this patch, since copyright can
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be a little controversial.
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1) The big motivation for this is not to shut out the community, but
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just to clean up all of the invalid copyright statements.
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2) It has been the general policy for bzr that we want a single
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copyright holder for all of the core code. This is following the model
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set by the FSF, which makes it easier to update the code to a new
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license in case problems are encountered. (For example, if we want to
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upgrade the project universally to GPL v3 it is much simpler if there is
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a single copyright holder). It also makes it clearer if copyright is
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ever debated, there is a single holder, which makes it easier to defend
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in court, etc. (I think the FSF position is that if you assign them
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copyright, they can defend it in court rather than you needing to, and
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I'm sure Canonical would do the same).
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As such, Canonical has requested copyright assignments from all of the
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3) If someone wants to add code and not attribute it to Canonical, there
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is a specific list of files that are excluded from this check. And the
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test failure indicates where that is, and how to update it.
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4) If anyone feels that I changed a copyright statement incorrectly, just
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let me know, and I'll be happy to correct it. Whenever you have large
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mechanical changes like this, it is possible to make some mistakes.
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Just to reiterate, this is a community project, and it is meant to stay
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that way. Core bzr code is copyright Canonical for legal reasons, and
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the tests are just there to help us maintain that.
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from bzrlib import (
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revision as _mod_revision,
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import bzrlib.transport
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import bzrlib.xml5
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At this point, all of these exist as a ``ImportReplacer`` object, ready to
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be imported once a member is accessed. Also, when importing a module into
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the local namespace, which is likely to clash with variable names, it is
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recommended to prefix it as ``_mod_<module>``. This makes it clean that
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the variable is a module, and these object should be hidden anyway, since
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they shouldn't be imported into other namespaces.
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be imported once a member is accessed.
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Modules versus Members
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Errors and exceptions
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=====================
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Errors are handled through Python exceptions.
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We broadly classify errors as either being either internal or not,
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depending on whether ``user_error`` is set or not. If we think it's our
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fault, we show a backtrace, an invitation to report the bug, and possibly
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other details. This is the default for errors that aren't specifically
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recognized as being caused by a user error. Otherwise we show a briefer
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message, unless -Derror was given.
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Many errors originate as "environmental errors" which are raised by Python
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or builtin libraries -- for example IOError. These are treated as being
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our fault, unless they're caught in a particular tight scope where we know
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that they indicate a user errors. For example if the repository format
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is not found, the user probably gave the wrong path or URL. But if one of
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the files inside the repository is not found, then it's our fault --
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either there's a bug in bzr, or something complicated has gone wrong in
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the environment that means one internal file was deleted.
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Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
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to be added near the place where they are used.
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Exceptions are formatted for the user by conversion to a string
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(eventually calling their ``__str__`` method.) As a convenience the
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``._fmt`` member can be used as a template which will be mapped to the
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error's instance dict.
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New exception classes should be defined when callers might want to catch
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that exception specifically, or when it needs a substantially different
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Exception strings should start with a capital letter and should not have a
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final fullstop. If long, they may contain newlines to break the text.
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Errors are handled through Python exceptions. They can represent user
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errors, environmental errors or program bugs. Sometimes we can't be sure
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at the time it's raised which case applies. See bzrlib/errors.py for
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details on the error-handling practices.
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====================
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If you'd like to propose a change, please post to the
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bazaar@lists.canonical.com list with a patch, bzr changeset, or link to a
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bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
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branch. Please put '[patch]' in the subject so we can pick them out, and
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include some text explaining the change. Remember to put an update to the NEWS
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file in your diff, if it makes any changes visible to users or plugin
added
removed
HACKING
