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