Sorts a Unity scene or prefab file so it's consistent and can be diffed in a text diff tool.

SortUnityFile.py

#!/bin/python

import sys;
import os;
import argparse;
import shutil;

parser = argparse.ArgumentParser(description='Sort Unity Files - Sorts Unity files so they can be diffed in text diff tools.', add_help=False)
parser.add_argument('input', help='Input scene file')
parser.add_argument('output', nargs='?', default='', help='Output sorted scene file')

sortArgs, remaining = parser.parse_known_args()

if sortArgs.input == None or sortArgs.input == "":
	print("Input file must be specified!")

	sys.exit(1)

output = str(sortArgs.input).replace(".unity", ".sorted.unity");

if sortArgs.output != None and sortArgs.output != "":
	output = sortArgs.output;

if os.path.exists(sortArgs.input):
	OriginalHandle = None
	IDAndOffset = {}
	IDAndLength = {}
	LastID = ""
	with open(sortArgs.input, 'r') as OriginalHandle:
		OriginalPos = OriginalHandle.tell()
		OriginalLine = OriginalHandle.readline()
		Preamble = ""
		while OriginalLine:
			if OriginalLine.startswith('--- !u!'):
				if LastID != "":
					NewLength = OriginalPos - IDAndOffset[LastID]

#					print("Cleaning up last tag " + LastID + " with total length " + str(NewLength) + "\n")

					IDAndLength[LastID] = NewLength

				NewID = OriginalLine.replace('--- !u!', '').replace(' &', '+')

				NewID = NewID[0:NewID.find(' ')]
				
#				print("Found line \"" + OriginalLine + "\" with ID " + NewID + " at offset " + str(OriginalPos) + "\n");

				IDAndOffset[NewID] = OriginalPos
				LastID = NewID
			elif len(IDAndOffset) == 0:
				Preamble += OriginalLine

			OriginalPos = OriginalHandle.tell()
			OriginalLine = OriginalHandle.readline()

		if LastID != "":
			NewLength = OriginalPos - IDAndOffset[LastID]
			IDAndLength[LastID] = NewLength

		with open(output, 'w') as NewHandle:
			NewHandle.write(Preamble)

			for currentKey in sorted(IDAndOffset):
				ToReadOffset = IDAndOffset[currentKey]
				ToReadLength = IDAndLength[currentKey]
				
				OriginalHandle.seek(ToReadOffset)
				ToWriteString = OriginalHandle.read(ToReadLength)
				
				NewHandle.write(ToWriteString)

#				print("Attempting to write " + str(ToReadLength) + " from offset " + str(ToReadOffset) + ": \n" + ToWriteString)
else:
	print("Input file (" + sortArgs.input + ") does not exist.")

	sys.exit(1)

sys.exit(0)