-- LuaDiffer: A simple Lua diff library
--
-- This file returns a function that can be called on two strings to return a table
-- containing the details of the difference between them. Usage:
-- >> local diff = require("diff")
-- >> diff("hello\nworld", "hello\nWORLD\n!!!")
-- {{old="hello", old_first=1, old_last=1, new="hello\n", new_first=1, new_last=1},
-- {old="world", old_first=2, old_last=2, new="WORLD\n!!!", new_first=2, new_last=3}}
-- The returned diff table also has a diff:print() method on it that can be used to print
-- the diff in a human-readable form. See below for the print options.
--
-- This implementation uses the Hunt-McIlroy algorithm, and is inspired by Jason Orendorff's
-- lovely python implementation at: http://pynash.org/2013/02/26/diff-in-50-lines/
--
-- Copyright 2017 Bruce Hill
--
-- Permission is hereby granted, free of charge, to any person obtaining a copy of
-- this software and associated documentation files (the "Software"), to deal in
-- the Software without restriction, including without limitation the rights to
-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-- of the Software, and to permit persons to whom the Software is furnished to do
-- so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.
local diff_mt = {__index={}}
-- ANSI color codes
local function color(n) return string.char(27)..("[%dm"):format(n) end
local COLORS = {green=color(32), red=color(31), bright=color(1), underscore=color(4), reset=color(0)}
-- Return a new diff as if it were a diff of strings, rather than tables.
diff_mt.__index.stringify = function(d, sep)
if #d > 0 and type(d[1].old) == 'string' then return d end
sep = sep or ", "
local stringified = {}
for i,chunk in ipairs(d) do
stringified[i] = {
old=table.concat(chunk.old,sep), old_first=chunk.old_first, old_last=chunk.old_last,
new=table.concat(chunk.new,sep), new_first=chunk.new_first, new_last=chunk.new_last,
}
end
return setmetatable(stringified, diff_mt)
end
-- With a diff, you can call diff:print{...} to print it out. The options available are:
-- color = (true/false), true by default, whether or not to print with colors.
-- context = <number>, how many lines of context to print around the diff, (default: infinite)
-- sep = <string>, the separator used for context (default: "\n")
-- numbers = (true/false), whether or not to print the (line) numbers where the chunks
-- came from in the input (default: false)
diff_mt.__index.print = function(d, options)
options = options or {}
if #d > 0 and type(d[1].old) == 'table' then
d = d:stringify(options.sep)
end
local colors = (options.color ~= false) and COLORS or setmetatable({}, {__index=function() return "" end})
local numbers = options.numbers or false
local context_pattern = nil
options.context = options.context or math.huge
if options.context ~= 0 and options.context ~= math.huge then
local sep = options.sep or "\n"
local lines = ("[^"..sep.."]*"..sep):rep(options.context)
context_pattern = ("^("..lines..").*"..sep.."("..lines..")$")
end
for i,chunk in ipairs(d) do
if chunk.old == chunk.new then
-- Unchanged
local same = chunk.old
if context_pattern then
local before, after = same:match(context_pattern)
if before and after then
-- "\b" is used as a hack to make sure the ellipsis is unindented
if i == 1 then same = "\b\b…\n"..after
elseif i == #d then same = before.."\n\b\b…"
else same = before.."\b\b…\n"..after end
end
end
if not (options and options.context == 0) then
io.write((same:gsub("([^\n]*)\n?", " %1\n")))
end
else
-- Changed
if #chunk.old > 0 then
if numbers then
print(colors.underscore..colors.bright..colors.red..
("Old #%d-%d:"):format(chunk.old_first, chunk.old_last)..colors.reset)
end
io.write(colors.red..(chunk.old:gsub("([^\n]*)\n?", "- %1\n"))..colors.reset)
end
if #chunk.new > 0 then
if numbers then
print(colors.underscore..colors.bright..colors.green..
("New #%d-%d:"):format(chunk.new_first, chunk.new_last)..colors.reset)
end
io.write(colors.green..(chunk.new:gsub("([^\n]*)\n?", "+ %1\n"))..colors.reset)
end
end
end
end
-- Take two strings or tables, and return a table representing a chunk-by-chunk diff of the two.
-- By default, strings are broken up by lines, but the optional third parameter "sep" lets
-- you provide a different separator to break on.
-- The return value is a list of chunks that have .old, .new corresponding to the old and
-- new versions. For identical chunks, .old == .new.
local function diff(old, new, sep)
local insert, concat = table.insert, table.concat
local A, B, slice
if type(old) == 'string' and type(new) == 'string' then
-- Split into a table using sep (default: newline)
sep = sep or "\n"
A, B = {}, {}
for c in old:gmatch("[^"..sep.."]*"..sep.."?") do insert(A, c) end
for c in new:gmatch("[^"..sep.."]*"..sep.."?") do insert(B, c) end
slice = function(X,start,stop) return concat(X,"",start,stop) end
elseif type(old) == 'table' and type(new) == 'table' then
A, B = old, new
slice = function(X,start,stop)
local s = {}
for i=start,stop do s[#s+1] = X[i] end
return s
end
else
error("Two different types passed to diff: "..type(old).." and "..type(new))
end
-- Find the longest common subsequence between A[a_min..a_max] and B[b_min..b_max] (inclusive),
-- and return (the starting position in a), (the starting position in b), (the length)
local longest_common_subsequence = function(a_min,a_max, b_min,b_max)
local longest = {a=a_min, b=b_min, length=0}
local runs = {}
for a = a_min, a_max do
local new_runs = {}
for b = b_min, b_max do
if A[a] == B[b] then
local new_run_len = 1 + (runs[b-1] or 0)
new_runs[b] = new_run_len
if new_run_len > longest.length then
longest.a = a - new_run_len + 1
longest.b = b - new_run_len + 1
longest.length = new_run_len
end
end
end
runs = new_runs
end
return longest
end
-- Find *all* the common subsequences between A[a_min..a_max] and B[b_min..b_max] (inclusive)
-- and put them into the common_subsequences table.
local common_subsequences = {}
local find_common_subsequences
find_common_subsequences = function(a_min,a_max, b_min,b_max)
-- Take a greedy approach and pull out the longest subsequences first
local lcs = longest_common_subsequence(a_min,a_max, b_min,b_max)
if lcs.length == 0 then return end
find_common_subsequences(a_min, lcs.a - 1, b_min, lcs.b - 1)
insert(common_subsequences, lcs)
find_common_subsequences(lcs.a + lcs.length, a_max, lcs.b + lcs.length, b_max)
end
find_common_subsequences(1,#A, 1,#B)
-- For convenience in iteration (this catches matching chunks at the end):
insert(common_subsequences, {a=#A+1, b=#B+1, length=0})
local chunks = setmetatable({}, diff_mt)
local a, b = 1, 1
for _,subseq in ipairs(common_subsequences) do
if subseq.a > a or subseq.b > b then
insert(chunks, {
old=slice(A, a, subseq.a-1), old_first=a, old_last=subseq.a-1,
new=slice(B, b, subseq.b-1), new_first=b, new_last=subseq.b-1})
end
if subseq.length > 0 then
-- Ensure that the *same* table is used for .old and .new so equality checks
-- suffice and you don't need to do element-wise comparisons.
local same = slice(A, subseq.a, subseq.a+subseq.length-1)
insert(chunks, {
old=same, old_first=subseq.a, old_last=subseq.a+subseq.length-1,
new=same, new_first=subseq.b, new_last=subseq.b+subseq.length-1})
end
a = subseq.a + subseq.length
b = subseq.b + subseq.length
end
return chunks
end
return diff