algmyr.se
Common library code for other vc*.nvim projects.
Add patch handling code.
+189
lua/vclib/patch.lua
+189
lua/vclib/patch.lua
···
1
+
--- Utilities for working with git-format patches.
2
+
local M = {}
3
+
4
+
---@class PatchLine
5
+
---@field type "context"|"add"|"remove" The type of line in the patch.
6
+
---@field content string The actual line content (without the leading +/- marker).
7
+
8
+
---@class Hunk
9
+
---@field old_start integer Starting line number in the old file.
10
+
---@field old_count integer Number of lines in the old file.
11
+
---@field new_start integer Starting line number in the new file.
12
+
---@field new_count integer Number of lines in the new file.
13
+
---@field lines PatchLine[] The lines in this hunk.
14
+
15
+
---@class Patch
16
+
---@field hunks Hunk[] The hunks in this patch.
17
+
18
+
--- Parse a single file git-format diff into a structured patch.
19
+
--- (single file to keep things simple, and was sufficient for our use cases)
20
+
---@param patch_text string The git diff output.
21
+
---@return Patch|nil The parsed patch, or nil if no hunks found.
22
+
function M.parse_single_file_patch(patch_text)
23
+
local lines = vim.split(patch_text, "\n", { plain = true })
24
+
25
+
-- Skip metadata until we hit the first @@.
26
+
local i = 1
27
+
while i <= #lines and not lines[i]:match "^@@" do
28
+
i = i + 1
29
+
end
30
+
31
+
if i > #lines then
32
+
-- No hunks found.
33
+
return nil
34
+
end
35
+
36
+
local hunks = {}
37
+
local current_hunk = nil
38
+
39
+
while i <= #lines do
40
+
local line = lines[i]
41
+
42
+
if line:match "^@@" then
43
+
-- Save previous hunk if any.
44
+
if current_hunk then
45
+
table.insert(hunks, current_hunk)
46
+
end
47
+
48
+
-- Parse hunk header: @@ -old_start,old_count +new_start,new_count @@.
49
+
local old_start, old_count, new_start, new_count =
50
+
line:match "^@@ %-(%d+),?(%d*) %+(%d+),?(%d*) @@"
51
+
52
+
if old_start and new_start then
53
+
current_hunk = {
54
+
old_start = tonumber(old_start),
55
+
old_count = tonumber(old_count) or 1,
56
+
new_start = tonumber(new_start),
57
+
new_count = tonumber(new_count) or 1,
58
+
lines = {},
59
+
}
60
+
end
61
+
i = i + 1
62
+
else
63
+
local first_char = line:sub(1, 1)
64
+
if first_char == " " then
65
+
-- Context line.
66
+
if current_hunk then
67
+
table.insert(current_hunk.lines, {
68
+
type = "context",
69
+
content = line:sub(2),
70
+
})
71
+
end
72
+
i = i + 1
73
+
elseif first_char == "-" then
74
+
-- Removed line.
75
+
if current_hunk then
76
+
table.insert(current_hunk.lines, {
77
+
type = "remove",
78
+
content = line:sub(2),
79
+
})
80
+
end
81
+
i = i + 1
82
+
elseif first_char == "+" then
83
+
-- Added line.
84
+
if current_hunk then
85
+
table.insert(current_hunk.lines, {
86
+
type = "add",
87
+
content = line:sub(2),
88
+
})
89
+
end
90
+
i = i + 1
91
+
elseif first_char == "\\" then
92
+
-- "\ No newline at end of file" marker - ignore for now.
93
+
i = i + 1
94
+
else
95
+
-- End of hunks or unknown line.
96
+
break
97
+
end
98
+
end
99
+
end
100
+
101
+
-- Save last hunk.
102
+
if current_hunk then
103
+
table.insert(hunks, current_hunk)
104
+
end
105
+
106
+
if #hunks == 0 then
107
+
return nil
108
+
end
109
+
110
+
return { hunks = hunks }
111
+
end
112
+
113
+
--- Invert a patch (swap add/remove operations and old/new positions).
114
+
---@param patch Patch The patch to invert.
115
+
---@return Patch The inverted patch.
116
+
function M.invert_patch(patch)
117
+
local inverted_hunks = {}
118
+
119
+
for _, hunk in ipairs(patch.hunks) do
120
+
local inverted_lines = {}
121
+
122
+
for _, line in ipairs(hunk.lines) do
123
+
local inverted_type = line.type
124
+
if line.type == "add" then
125
+
inverted_type = "remove"
126
+
elseif line.type == "remove" then
127
+
inverted_type = "add"
128
+
end
129
+
130
+
table.insert(inverted_lines, {
131
+
type = inverted_type,
132
+
content = line.content,
133
+
})
134
+
end
135
+
136
+
-- Swap old and new positions.
137
+
table.insert(inverted_hunks, {
138
+
old_start = hunk.new_start,
139
+
old_count = hunk.new_count,
140
+
new_start = hunk.old_start,
141
+
new_count = hunk.old_count,
142
+
lines = inverted_lines,
143
+
})
144
+
end
145
+
146
+
return { hunks = inverted_hunks }
147
+
end
148
+
149
+
--- Apply a patch to file contents.
150
+
---@param file_lines string[] The current file contents.
151
+
---@param patch Patch The patch to apply.
152
+
---@return string[] The file contents after applying the patch.
153
+
function M.apply_patch(file_lines, patch)
154
+
local result = {}
155
+
local i = 1
156
+
157
+
for _, hunk in ipairs(patch.hunks) do
158
+
-- Copy unchanged lines before this hunk.
159
+
while i < hunk.old_start do
160
+
table.insert(result, file_lines[i])
161
+
i = i + 1
162
+
end
163
+
164
+
-- Process hunk lines.
165
+
for _, line in ipairs(hunk.lines) do
166
+
if line.type == "context" then
167
+
-- Context line - should match current file.
168
+
table.insert(result, line.content)
169
+
i = i + 1
170
+
elseif line.type == "remove" then
171
+
-- Line removed - skip it in the result, advance in current file.
172
+
i = i + 1
173
+
elseif line.type == "add" then
174
+
-- Line added - add to result, don't advance in current file.
175
+
table.insert(result, line.content)
176
+
end
177
+
end
178
+
end
179
+
180
+
-- Copy any remaining unchanged lines.
181
+
while i <= #file_lines do
182
+
table.insert(result, file_lines[i])
183
+
i = i + 1
184
+
end
185
+
186
+
return result
187
+
end
188
+
189
+
return M
+38
-3
lua/vclib/testing.lua
+38
-3
lua/vclib/testing.lua
···
1
1
local M = {}
2
2
3
+
--- Helper to parse multiline strings into lines, stripping common indentation.
4
+
---@param s string
5
+
---@return string[]
6
+
function M.dedent_into_lines(s)
7
+
local l = 1
8
+
while s:sub(l, l) == "\n" do
9
+
l = l + 1
10
+
end
11
+
local r = #s
12
+
while true do
13
+
local c = s:sub(r, r)
14
+
if c ~= "\n" and c ~= " " then
15
+
break
16
+
end
17
+
r = r - 1
18
+
end
19
+
local stripped = s:sub(l, r)
20
+
local lines = vim.split(stripped, "\n", { plain = true })
21
+
local min_indent = math.huge
22
+
for _, line in ipairs(lines) do
23
+
local indent = #line - #line:gsub("^%s*", "")
24
+
if #line > 0 and indent < min_indent then
25
+
min_indent = indent
26
+
end
27
+
end
28
+
if min_indent == math.huge then
29
+
min_indent = 0
30
+
end
31
+
for i, line in ipairs(lines) do
32
+
lines[i] = line:sub(min_indent + 1)
33
+
end
34
+
return lines
35
+
end
36
+
3
37
local function _run_test_suite(suite_name, test_suite)
4
38
local suite_failed = 0
5
39
local suite_total = 0
···
59
93
end
60
94
end
61
95
62
-
function M.assert_list_eq(actual, expected)
96
+
function M.assert_list_eq(actual, expected, msg_prefix)
97
+
msg_prefix = msg_prefix or ""
63
98
assert(
64
99
#actual == #expected,
65
-
string.format("Lists have different lengths: %d vs %d", #actual, #expected)
100
+
string.format(msg_prefix .. "Lists have different lengths: %d vs %d", #actual, #expected)
66
101
)
67
102
local diff = ""
68
103
for i = 1, #expected do
···
72
107
end
73
108
end
74
109
if diff ~= "" then
75
-
error("Lists differ:" .. diff)
110
+
error(msg_prefix .. "Lists differ:" .. diff)
76
111
end
77
112
end
78
113
+1
lua/vclib_tests/init.lua
+1
lua/vclib_tests/init.lua
+356
lua/vclib_tests/patch.lua
+356
lua/vclib_tests/patch.lua
···
1
+
local M = {}
2
+
3
+
local patch = require "vclib.patch"
4
+
local testing = require "vclib.testing"
5
+
6
+
-- Helper function to create a git diff output.
7
+
local function make_git_diff_from_string(hunks)
8
+
local lines = {
9
+
"diff --git a/test.txt b/test.txt",
10
+
"index abc123..def456 100644",
11
+
"--- a/test.txt",
12
+
"+++ b/test.txt",
13
+
}
14
+
for _, line in ipairs(testing.dedent_into_lines(hunks)) do
15
+
lines[#lines + 1] = line
16
+
end
17
+
return table.concat(lines, "\n")
18
+
end
19
+
20
+
-- Helper to compare patch structures.
21
+
local function assert_patch_eq(actual, expected)
22
+
assert(actual ~= nil, "actual patch is nil")
23
+
assert(expected ~= nil, "expected patch is nil")
24
+
assert(
25
+
#actual.hunks == #expected.hunks,
26
+
string.format("Expected %d hunks, got %d", #expected.hunks, #actual.hunks)
27
+
)
28
+
29
+
for h = 1, #expected.hunks do
30
+
local ah = actual.hunks[h]
31
+
local eh = expected.hunks[h]
32
+
33
+
assert(
34
+
ah.old_start == eh.old_start,
35
+
string.format(
36
+
"Hunk %d: old_start mismatch: %d vs %d",
37
+
h,
38
+
ah.old_start,
39
+
eh.old_start
40
+
)
41
+
)
42
+
assert(
43
+
ah.old_count == eh.old_count,
44
+
string.format(
45
+
"Hunk %d: old_count mismatch: %d vs %d",
46
+
h,
47
+
ah.old_count,
48
+
eh.old_count
49
+
)
50
+
)
51
+
assert(
52
+
ah.new_start == eh.new_start,
53
+
string.format(
54
+
"Hunk %d: new_start mismatch: %d vs %d",
55
+
h,
56
+
ah.new_start,
57
+
eh.new_start
58
+
)
59
+
)
60
+
assert(
61
+
ah.new_count == eh.new_count,
62
+
string.format(
63
+
"Hunk %d: new_count mismatch: %d vs %d",
64
+
h,
65
+
ah.new_count,
66
+
eh.new_count
67
+
)
68
+
)
69
+
assert(
70
+
#ah.lines == #eh.lines,
71
+
string.format(
72
+
"Hunk %d: Expected %d lines, got %d",
73
+
h,
74
+
#eh.lines,
75
+
#ah.lines
76
+
)
77
+
)
78
+
79
+
for l = 1, #eh.lines do
80
+
local al = ah.lines[l]
81
+
local el = eh.lines[l]
82
+
assert(
83
+
al.type == el.type,
84
+
string.format(
85
+
"Hunk %d, line %d: type mismatch: %s vs %s",
86
+
h,
87
+
l,
88
+
al.type,
89
+
el.type
90
+
)
91
+
)
92
+
assert(
93
+
al.content == el.content,
94
+
string.format(
95
+
"Hunk %d, line %d: content mismatch: '%s' vs '%s'",
96
+
h,
97
+
l,
98
+
al.content,
99
+
el.content
100
+
)
101
+
)
102
+
end
103
+
end
104
+
end
105
+
106
+
M.parse_single_file_patch = {
107
+
test_cases = {
108
+
single_hunk = {
109
+
patch_text = make_git_diff_from_string [[
110
+
@@ -1,3 +1,4 @@
111
+
line1
112
+
line2
113
+
+NEW LINE
114
+
line3
115
+
]],
116
+
expected = {
117
+
hunks = {
118
+
{
119
+
old_start = 1,
120
+
old_count = 3,
121
+
new_start = 1,
122
+
new_count = 4,
123
+
lines = {
124
+
{ type = "context", content = "line1" },
125
+
{ type = "context", content = "line2" },
126
+
{ type = "add", content = "NEW LINE" },
127
+
{ type = "context", content = "line3" },
128
+
},
129
+
},
130
+
},
131
+
},
132
+
},
133
+
multiple_hunks = {
134
+
patch_text = make_git_diff_from_string [[
135
+
@@ -1,2 +1,3 @@
136
+
line1
137
+
+NEW1
138
+
line2
139
+
@@ -5,2 +6,3 @@
140
+
line5
141
+
+NEW2
142
+
line6
143
+
]],
144
+
expected = {
145
+
hunks = {
146
+
{
147
+
old_start = 1,
148
+
old_count = 2,
149
+
new_start = 1,
150
+
new_count = 3,
151
+
lines = {
152
+
{ type = "context", content = "line1" },
153
+
{ type = "add", content = "NEW1" },
154
+
{ type = "context", content = "line2" },
155
+
},
156
+
},
157
+
{
158
+
old_start = 5,
159
+
old_count = 2,
160
+
new_start = 6,
161
+
new_count = 3,
162
+
lines = {
163
+
{ type = "context", content = "line5" },
164
+
{ type = "add", content = "NEW2" },
165
+
{ type = "context", content = "line6" },
166
+
},
167
+
},
168
+
},
169
+
},
170
+
},
171
+
no_hunks = {
172
+
patch_text = "diff --git a/test.txt b/test.txt\nindex abc123..abc123 100644\n",
173
+
expected = nil,
174
+
},
175
+
file_header_no_hunks = {
176
+
expected = nil,
177
+
patch_text = "diff --git a/test.txt b/test.txt\nindex abc123..abc123 100644\n--- a/test.txt\n+++ b/test.txt",
178
+
},
179
+
mixed_operations = {
180
+
patch_text = make_git_diff_from_string [[
181
+
@@ -1,4 +1,4 @@
182
+
context1
183
+
-removed
184
+
+added
185
+
context2
186
+
]],
187
+
expected = {
188
+
hunks = {
189
+
{
190
+
old_start = 1,
191
+
old_count = 4,
192
+
new_start = 1,
193
+
new_count = 4,
194
+
lines = {
195
+
{ type = "context", content = "context1" },
196
+
{ type = "remove", content = "removed" },
197
+
{ type = "add", content = "added" },
198
+
{ type = "context", content = "context2" },
199
+
},
200
+
},
201
+
},
202
+
},
203
+
},
204
+
},
205
+
test = function(case)
206
+
local result = patch.parse_single_file_patch(case.patch_text)
207
+
if case.expected == nil then
208
+
assert(result == nil, "Expected nil for patch with no hunks")
209
+
else
210
+
assert_patch_eq(result, case.expected)
211
+
end
212
+
end,
213
+
}
214
+
215
+
M.roundtrip = {
216
+
test_cases = {
217
+
simple_addition = {
218
+
old_file = { "line1", "line2", "line3" },
219
+
new_file = { "line1", "line2", "NEW LINE", "line3" },
220
+
patch_text = make_git_diff_from_string [[
221
+
@@ -1,3 +1,4 @@
222
+
line1
223
+
line2
224
+
+NEW LINE
225
+
line3
226
+
]],
227
+
},
228
+
simple_deletion = {
229
+
old_file = { "line1", "line2", "line3", "line4" },
230
+
new_file = { "line1", "line2", "line4" },
231
+
patch_text = make_git_diff_from_string [[
232
+
@@ -1,4 +1,3 @@
233
+
line1
234
+
line2
235
+
-line3
236
+
line4
237
+
]],
238
+
},
239
+
simple_modification = {
240
+
old_file = { "line1", "original line", "line3" },
241
+
new_file = { "line1", "modified line", "line3" },
242
+
patch_text = make_git_diff_from_string [[
243
+
@@ -1,3 +1,3 @@
244
+
line1
245
+
-original line
246
+
+modified line
247
+
line3
248
+
]],
249
+
},
250
+
multiple_hunks = {
251
+
old_file = { "line1", "line2", "unchanged", "line3", "line4" },
252
+
new_file = {
253
+
"line1",
254
+
"NEW1",
255
+
"line2",
256
+
"unchanged",
257
+
"line3",
258
+
"NEW2",
259
+
"line4",
260
+
},
261
+
patch_text = make_git_diff_from_string [[
262
+
@@ -1,2 +1,3 @@
263
+
line1
264
+
+NEW1
265
+
line2
266
+
@@ -4,2 +5,3 @@
267
+
line3
268
+
+NEW2
269
+
line4
270
+
]],
271
+
},
272
+
complex_changes = {
273
+
old_file = {
274
+
"header",
275
+
"old line 1",
276
+
"old line 2",
277
+
"more content",
278
+
"old footer",
279
+
},
280
+
new_file = { "header", "new line 1", "content", "more content", "footer" },
281
+
patch_text = make_git_diff_from_string [[
282
+
@@ -1,5 +1,5 @@
283
+
header
284
+
-old line 1
285
+
-old line 2
286
+
+new line 1
287
+
+content
288
+
more content
289
+
-old footer
290
+
+footer
291
+
]],
292
+
},
293
+
add_to_empty_file = {
294
+
old_file = {},
295
+
new_file = { "line1", "line2" },
296
+
patch_text = make_git_diff_from_string [[
297
+
@@ -0,0 +1,2 @@
298
+
+line1
299
+
+line2
300
+
]],
301
+
},
302
+
delete_entire_file = {
303
+
old_file = { "line1", "line2" },
304
+
new_file = {},
305
+
patch_text = make_git_diff_from_string [[
306
+
@@ -1,2 +0,0 @@
307
+
-line1
308
+
-line2
309
+
]],
310
+
},
311
+
addition_at_beginning = {
312
+
old_file = { "line1", "line2" },
313
+
new_file = { "NEW", "line1", "line2" },
314
+
patch_text = make_git_diff_from_string [[
315
+
@@ -1,2 +1,3 @@
316
+
+NEW
317
+
line1
318
+
line2
319
+
]],
320
+
},
321
+
addition_at_end = {
322
+
old_file = { "line1", "line2" },
323
+
new_file = { "line1", "line2", "NEW" },
324
+
patch_text = make_git_diff_from_string [[
325
+
@@ -1,2 +1,3 @@
326
+
line1
327
+
line2
328
+
+NEW
329
+
]],
330
+
},
331
+
},
332
+
test = function(case)
333
+
-- Validate parsing.
334
+
local parsed = patch.parse_single_file_patch(case.patch_text)
335
+
assert(parsed ~= nil, "Failed to parse patch")
336
+
337
+
-- Validate patch application.
338
+
local forward_result = patch.apply_patch(case.old_file, parsed)
339
+
testing.assert_list_eq(
340
+
forward_result,
341
+
case.new_file,
342
+
"Forward application failed: "
343
+
)
344
+
345
+
-- Validate patch inversion and reverse application.
346
+
local inverted = patch.invert_patch(parsed)
347
+
local reverse_result = patch.apply_patch(case.new_file, inverted)
348
+
testing.assert_list_eq(
349
+
reverse_result,
350
+
case.old_file,
351
+
"Reverse application failed: "
352
+
)
353
+
end,
354
+
}
355
+
356
+
return M