Sunday, June 22. 2008
bzr-svn: now with its own Subversion Python bindings
bzr-svn has always been using the standard Python bindings that were provided with Subversion itself. Unfortunately, I had to fix some issues in these bindings since they were incomplete or broken and thus bzr-svn has always depended on a development snapshot of Subversion.
As of today, bzr-svn is using its own Python bindings for Subversion.
There were several reasons for switching to our own bindings:
- There are no requirements for backwards compatibility within bzr-svn. This means the API can be made sane without worrying about the mess it was in the past and users who still rely on that.
- Deployment. It took 2 years for my fixes to the Subversion Python bindings to be part of a release. It'll be even longer before Subversion 1.5 makes it into most available distributions. That makes it very hard to just download and install bzr-svn.
- They're in plain C, not SWIG. SWIG has a big advantage for the Subversion folks since it can generate python, ruby, java or tcl bindings all at once without a lot of overhead per language. However, it has issues as well that make it a bad choice for bzr-svn.
- It generates inefficient code - it generates proxy classes that add more layers in the stack
- Bindings tend to be very much like the C API rather than "Pythonic". To make them more Pythonic, you need tons of typemaps. For example, the Python bindings in bzr-svn provide an iterator when browsing the revision history rather than a callback as C and the SWIG bindings do.
- Hard to write - personally at least, I write bindings in C faster than in SWIG
- Adds an extra dependency to the build process. Several people had trouble building Subversion on their Mac machines because they didn't have the right version of SWIG available.
Since all of the patches that bzr-svn depended on previously were in the Python bindings for Subversion, it is now possible to use bzr-svn with any version of Subversion newer than 1.4.0. Of course, you do need to have the development headers installed as well.
cp: Kathleen Edwards - Independent Thief
Incomplete phrase: "it generates proxy classes that " ... what?
Hello, Congratulation for this effort. I would like to use bzr-svn to work on a project hosted on code.google.com. I am working on windows. Could you please let me know how I could use bzr-svn with google repository. I have installed bzr 1.5 downloaded the latest version of bzr-svn (bzr branch lp:bzr-svn). Could you please let me know what are the next steps? Thank you --yml
setup.py build_ext --inplace
However, I haven't tried this on Windows yet so you may have to patch setup.py to make it find the APR and Subversion development headers.
If you do patch setup.py to get it to work on Windows, please send it to me so I can include it.
Are this bindings feature-complete compared to the old ones already? Should I give it a try?
BTW, yml's question is mine too. How is the progress of svn:externals support as nested trees going? There is a project I'm working that have aprox. 20 external dependencies - I feel tempted to right a quick script to go dir-by-dir doing svn propget svn:externals and fetching the repos.
They're feature complete and should be usable. I'm very much interested in feedback.
externals support is quite some time away. First, Bazaar itself has to support nested trees.
Maybe you could use ctypes, then the compilation step would go away and the installation would be even easier!
CTypes have their own problems - they're bindings to an ABI rather than an API and slower than C-based bindings. They're also a bit harder to write, at least for somebody more fluent in C than CTypes :-)
I am getting this error message : C:\yml_myScript\djthings\webdevelopment\bzr-svn>setup.py buildext --inplace Traceback (most recent call last): File "C:\yml_myScript\djthings\webdevelopment\bzr-svn\setup.py", line 30, in (aprincludedir, aprldflags) = aprbuilddata() File "C:\yml_myScript\djthings\webdevelopment\bzr-svn\setup.py", line 17, in aprbuilddata raise Exception("APR development headers not found") Exception: APR development headers not found
Could you please let me know what APR is ? Thank you
It's the Apache Portable Runtime, see http://apr.apache.org/.
Regarding "svn:externals" it would be great if bzr-svn whould create them as a separate repository inside the orginal one.
--yml
That's not really an option, since bzr doesn't have an internal API for doing things like that. It would involve some evil hacks to bypass bzr and would be a significant amount of work that would become pointless once nested trees land.
Can't seem to find this anywhere that I can use. Tried following the directions on the Bazaar website to install bzr-svn now that Subversion 1.5 has been released and couldn't get anywhere with anything.
Please be a bit more specific - what didn't work exactly in those instructions?
Everything worked until I went to test at the end where it told me that the Subversion client installed didn't have the proper Python bindings.
That would be an older version of bzr-svn (before the switch to our own Python bindings). Did you build Subversion with its Python bindings enabled?
I used the Subversion package for Mac that claims to include the Python bindings.
Sorry, I don't have much experience with running bzr-svn on the Mac :-( Perhaps other people can help here.
Have you released a version with your bindings? Or is the plan to do that with Bazaar 1.6?
Thanks for all your fantastic work!
Yeah, they're going to be released in bzr-svn 0.4.11, which will be released together with Bazaar 1.6.
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