Question

How do I create a diff of two json objects such that they are in the manual diff format which can be sent to reviewboard? I need to generate the diff from inside a python script.I think manual diffs are generated using the “diff file1 file2” command line utility. Can I generate a similar reviewboard compatible diff using difflib? Or is there another library that I need to use? Thanks!

Answer 1

Use difflib:

def show_diff(seqm):
    output= []
    for opcode, a0, a1, b0, b1 in seqm.get_opcodes():
        if opcode == 'equal':
            output.append(seqm.a[a0:a1])
        elif opcode == 'insert':
            output.append("<ins>" + seqm.b[b0:b1] + "</ins>")
        elif opcode == 'delete':
            output.append("<del>" + seqm.a[a0:a1] + "</del>")
        elif opcode == 'replace':
            output.append("<del>" + seqm.a[a0:a1] + "</del>" + "<ins>" + seqm.b[b0:b1] + "</ins>" )
        else:
            raise RuntimeError, "Unexpected opcode"
    return ''.join(output)

In your situation, you compare your json files (I just used dummy text):

In [4]: sm = difflib.SequenceMatcher(None, 'hello', 'hello world')

In [6]: diff = show_diff(sm)

In [7]: diff
Out[7]: 'hello<ins> world</ins>'

Look at the documentation if you need a different output from difflib