highlight.py

import difflib
import itertools

import pygments
import pygments.lexers
import pygments.formatters

class Line:
    def __init__(self, is_diff=True, tag=None,
            line_before=None, line_after=None, contents='', comments=()):
        self.is_diff = is_diff
        self.tag = tag
        self.line_before = line_before
        self.line_after = line_after
        self.contents = contents
        self.comments = comments



def highlight(filename, source):
    """Highlights an input string into a list of HTML strings, one per line."""
    try:
        highlighted = pygments.highlight(source,
            pygments.lexers.guess_lexer_for_filename(filename, source, stripnl=False),
            pygments.formatters.HtmlFormatter(nowrap=True))
    except pygments.util.ClassNotFound:
        highlighted = source
    return highlighted.splitlines(keepends=True)

def highlight_file(filename, source):
    """Given a source file, generate a sequence of (line index, HTML) pairs."""
    for i, contents in zip(itertools.count(1), highlight(filename, source)):
        yield Line(is_diff=False, tag='equal', line_after=i, contents=contents)

def highlight_diff(filename, a, b, diff_type='short'):
    """Given two input strings, generate a sequence of 4-tuples. The elements
    of each tuple are:
        * 'delete', 'insert', 'equal', or 'header' (the tag)
        * the line number of the first file (or None)
        * the line number of the second file (or None)
        * the rendered HTML string of the line

    DIFF_TYPE is either 'short' (3 lines of context) or
    'full' (all context lines).
    """
    highlighted_a = highlight(filename, a)
    highlighted_b = highlight(filename, b)

    def delete(i1, i2):
        for i in range(i1, i2):
            yield Line(
                tag='delete',
                line_before=i + 1,
                contents='-' + highlighted_a[i])

    def insert(i1, i2):
        for j in range(j1, j2):
            yield Line(
                tag='insert',
                line_after=j + 1,
                contents='+' + highlighted_b[j])

    def equal(i1, i2, j1, j2):
        for i, j in zip(range(i1, i2), range(j1, j2)):
            yield Line(
                tag='equal',
                line_before=i + 1,
                line_after=j + 1,
                contents=' ' + highlighted_b[j])

    def format_range_unified(start, stop):
        """Convert range to the "ed" format. From difflib.py"""
        # Per the diff spec at http://www.unix.org/single_unix_specification/
        beginning = start + 1     # lines start numbering with one
        length = stop - start
        if length == 1:
            return '{}'.format(beginning)
        if not length:
            beginning -= 1        # empty ranges begin at line just before the range
        return '{},{}'.format(beginning, length)

    matcher = difflib.SequenceMatcher(None, a.splitlines(), b.splitlines())
    if diff_type == 'short':
        groups = matcher.get_grouped_opcodes()
    elif diff_type == 'full':
        groups = [matcher.get_opcodes()]
    else:
        raise ValueError('Unknown diff type {}'.format(diff_type))
    for group in groups:
        first, last = group[0], group[-1]
        header = '@@ -{} +{} @@\n'.format(
            format_range_unified(first[1], last[2]),
            format_range_unified(first[3], last[4]))
        yield Line(tag='header', contents=header)
        for tag, i1, i2, j1, j2 in group:
            if tag == 'replace':
                yield from delete(i1, i2)
                yield from insert(j1, j2)
            elif tag == 'delete':
                yield from delete(i1, i2)
            elif tag == 'insert':
                yield from insert(j1, j2)
            elif tag == 'equal':
                yield from equal(i1, i2, j1, j2)

def diff_files(files_before, files_after, diff_type, inputoutputID):
    if diff_type:
        files = {}
        for filename in files_before.keys() | files_after.keys():
            lines = highlight_diff(
                filename,
                files_before.get(filename, ''),
                files_after.get(filename, ''),
                diff_type)
            files[filename] = (list(lines), inputoutputID)
    else:
        files = {filename: list(highlight_file(filename, source))
            for filename, source in files_after.items()}
    return files

import json

def diff_file(filename, file_before, file_after, diff_type):
    if diff_type:
        lines = highlight_diff(
            filename,
            file_before,
            file_after,
            diff_type
        )
    else:
        lines = []
    return list(lines)