From e82eddd9e007597e8283922653de0e5abb94c0dc Mon Sep 17 00:00:00 2001
From: mitchell <70453897+orbitalquark@users.noreply.github.com>
Date: Sun, 25 Oct 2020 00:43:25 -0400
Subject: Handle recursive symlinks in `lfs.walk()`.

---
 core/lfs_ext.lua | 17 +++++++++++------
 test/test.lua    | 24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/core/lfs_ext.lua b/core/lfs_ext.lua
index c24ee2e9..5bbe609a 100644
--- a/core/lfs_ext.lua
+++ b/core/lfs_ext.lua
@@ -19,9 +19,14 @@ module('lfs')]]
 lfs.default_filter = {--[[Extensions]]'!.a','!.bmp','!.bz2','!.class','!.dll','!.exe','!.gif','!.gz','!.jar','!.jpeg','!.jpg','!.o','!.pdf','!.png','!.so','!.tar','!.tgz','!.tif','!.tiff','!.xz','!.zip',--[[Directories]]'!/%.bzr$','!/%.git$','!/%.hg$','!/%.svn$','!/_FOSSIL_$','!/node_modules$'}
 
 -- Documentation is in `lfs.walk()`.
+-- @param seen Utility table that holds directories seen. If there is a
+--   duplicate, stop walking down that path (it's probably a recursive symlink).
 -- @param level Utility value indicating the directory level this function is
 --   at.
-local function walk(dir, filter, n, include_dirs, level)
+local function walk(dir, filter, n, include_dirs, seen, level)
+  local sep = not WIN32 and '/' or '\\'
+  local os_dir = not WIN32 and dir or dir:gsub('/', sep)
+  seen[os_dir], seen[os_dir .. sep] = true, true
   for basename in lfs.dir(dir) do
     if basename:find('^%.%.?$') then goto continue end -- ignore . and ..
     local filename = dir .. (dir ~= '/' and '/' or '') .. basename
@@ -42,14 +47,14 @@ local function walk(dir, filter, n, include_dirs, level)
       include = include or (not patt:find('^!') and filename:find(patt))
     end
     if not include then goto continue end
-    local sep = not WIN32 and '/' or '\\'
     local os_filename = not WIN32 and filename or filename:gsub('/', sep)
     if mode == 'file' then
       coroutine.yield(os_filename)
-    elseif mode == 'directory' then
+    elseif mode == 'directory' and
+           not seen[lfs.symlinkattributes(filename, 'target')] then
       if include_dirs then coroutine.yield(os_filename .. sep) end
       if n and (level or 0) >= n then goto continue end
-      walk(filename, filter, n, include_dirs, (level or 0) + 1)
+      walk(filename, filter, n, include_dirs, seen, (level or 0) + 1)
     end
     ::continue::
   end
@@ -77,7 +82,7 @@ end
 -- @see filter
 -- @name walk
 function lfs.walk(dir, filter, n, include_dirs)
-  assert_type(dir, 'string', 1)
+  dir = assert_type(dir, 'string', 1):match('^(.-)[/\\]?$')
   if not assert_type(filter, 'string/table/nil', 2) then
     filter = lfs.default_filter
   end
@@ -104,7 +109,7 @@ function lfs.walk(dir, filter, n, include_dirs)
     end
   end
   local co = coroutine.create(
-    function() walk(dir, processed_filter, n, include_dirs) end)
+    function() walk(dir, processed_filter, n, include_dirs, {}) end)
   return function() return select(2, coroutine.resume(co)) end
 end
 
diff --git a/test/test.lua b/test/test.lua
index ee4cbd0f..b1b4ee74 100644
--- a/test/test.lua
+++ b/test/test.lua
@@ -720,6 +720,30 @@ function test_lfs_ext_walk_win32()
   _G.WIN32 = win32 -- reset just in case
 end
 
+function test_lfs_ext_walk_symlinks()
+  local dir = os.tmpname()
+  os.remove(dir)
+  lfs.mkdir(dir)
+  lfs.mkdir(dir .. '/1')
+  io.open(dir .. '/1/foo', 'w'):close()
+  lfs.mkdir(dir .. '/1/bar')
+  io.open(dir .. '/1/bar/baz', 'w'):close()
+  lfs.link(dir .. '/1/', dir .. '/1/bar/quux', true) -- trailing '/' on purpose
+  lfs.mkdir(dir .. '/2')
+  io.open(dir .. '/2/foobar', 'w'):close()
+  lfs.link(dir .. '/2/foobar', dir .. '/2/foobaz', true)
+  lfs.link(dir .. '/2', dir .. '/1/2', true)
+  local files = {}
+  for filename in lfs.walk(dir .. '/1/') do -- trailing '/' on purpose
+    files[#files + 1] = filename
+  end
+  table.sort(files)
+  local expected_files = {dir .. '/1/foo', dir .. '/1/bar/baz', dir .. '/1/2/foobar', dir .. '/1/2/foobaz'}
+  table.sort(expected_files)
+  assert_equal(files, expected_files)
+  os.execute('rm -r ' .. dir)
+end
+
 function test_lfs_ext_abs_path()
   assert_equal(lfs.abspath('bar', '/foo'), '/foo/bar')
   assert_equal(lfs.abspath('./bar', '/foo'), '/foo/bar')
-- 
cgit v1.2.3