Subversion diff for zipped xml file

Question

I\'m using MySQL Workbench to maintain the database schema for an application. The .mwb file that Workbench uses, which is a zipped XML document, is kept in a S

Answer 1

I've written a diff script for workbench files which can be integrated with TortoiseSVN and TortoiseGit, which will exactly do what Jim Lewis suggests: Extract the actual XML from the archive and diff it.

The script will also eliminate all the ptr-Attribute noise in the diff. Merging is not possible and would be a bit more complicated (discover how the ptr-attributes would behave, re-pack the XML into the archive, what's with the other metadata in the archive?, ...)

The python script is available at pastebin under CC-BY 3.0:

http://pastebin.com/AcD7dBNH

# extensions: mwb
# TortoiseSVN Diff script for MySQL Workbench scheme files
# 2012 by Oliver Iking, Z-Software GmbH, oliverikingREPLACETHISWITHANATz-software.net, http://www.z-software.net/
# This work is licensed under a Creative Commons Attribution 3.0 Unported License - http://creativecommons.org/licenses/by/3.0/

# Will produce two diffable documents, which don't resemble the FULL MWB content, but the scheme relevant data. 
# Merging is not possible

# Open your TortoiseSVN (or TortoiseSomething) settings, go to the "Diff Viewer" tab and click on "Advanced". Add 
# a row with the extension ".mwb" and a command line of 
# "path\to\python.exe" "path\to\diff-mwb.py" %base %mine
# Apply changes and now you can diff mysql workbench scheme files

import sys
import zipfile
import os
import time
import tempfile
import re

# mysql workbench XML will have _ptr_ attributes which are modified on each save for almost each XML node. Remove the visual litter, 
# make actual changes stand out.
def sanitizeMwbXml( xml ):
    return re.sub('_ptr_="([0-9a-fA-F]{8})"', '', xml)

try:
    if len(sys.argv) < 2:
        print("Not enough parameters, cannot diff documents!")
        sys.exit(1)

    docOld = sys.argv[1]
    docNew = sys.argv[2]

    if not os.path.exists(docOld) or not os.path.exists(docNew):
        print("Documents don't exist, cannot diff!")
        sys.exit(1)

    # Workbench files are actually zip archives
    zipA = zipfile.ZipFile( docOld, 'r' )
    zipB = zipfile.ZipFile( docNew, 'r' )

    tempSubpath = os.tempnam(None,"mwbcompare")

    docA = os.path.join( tempSubpath, "mine.document.mwb.xml" )
    docB = os.path.join( tempSubpath, "theirs.document.mwb.xml" )

    os.makedirs( tempSubpath )

    if os.path.exists(docA) or os.path.exists(docB):
        print("Cannot extract documents, files exist!")
        sys.exit(1)

    # Read, sanitize and write actual scheme XML contents to temporary files

    docABytes = sanitizeMwbXml(zipA.read("document.mwb.xml" ))
    docBBytes = sanitizeMwbXml(zipB.read("document.mwb.xml" ))

    docAFile = open(docA, "w")
    docBFile = open(docB, "w")

    docAFile.write(docABytes)
    docBFile.write(docBBytes)

    docAFile.close()
    docBFile.close()

    os.system("TortoiseProc /command:diff /path:\"" + docA + "\" /path2:\"" + docB + "\"");

    # TortoiseProc will spawn a subprocess so we can't delete the files. They're in the tempdir, so they
    # will be cleaned up eventually
    #os.unlink(docA)
    #os.unlink(docB)

    sys.exit(0)
except Exception as e:
    print str(e)
    # Sleep, or the command window will close
    time.sleep(5)