From aa141bc281d4895273fe1f9b7003f379a7abfb8f Mon Sep 17 00:00:00 2001
From: mitchell <70453897+orbitalquark@users.noreply.github.com>
Date: Sun, 25 Oct 2020 10:50:01 -0400
Subject: Handle more types of recursive symlinks in `lfs.walk()`.

---
 core/lfs_ext.lua | 13 ++++++++-----
 test/test.lua    | 15 +++++++++++++++
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/core/lfs_ext.lua b/core/lfs_ext.lua
index 5bbe609a..d55dbf0b 100644
--- a/core/lfs_ext.lua
+++ b/core/lfs_ext.lua
@@ -24,9 +24,9 @@ lfs.default_filter = {--[[Extensions]]'!.a','!.bmp','!.bz2','!.class','!.dll','!
 -- @param level Utility value indicating the directory level this function is
 --   at.
 local function walk(dir, filter, n, include_dirs, seen, level)
+  if not seen then seen = {} end
   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
+  seen[not WIN32 and dir or dir:gsub('/', sep)] = true
   for basename in lfs.dir(dir) do
     if basename:find('^%.%.?$') then goto continue end -- ignore . and ..
     local filename = dir .. (dir ~= '/' and '/' or '') .. basename
@@ -50,8 +50,11 @@ local function walk(dir, filter, n, include_dirs, seen, level)
     local os_filename = not WIN32 and filename or filename:gsub('/', sep)
     if mode == 'file' then
       coroutine.yield(os_filename)
-    elseif mode == 'directory' and
-           not seen[lfs.symlinkattributes(filename, 'target')] then
+    elseif mode == 'directory' then
+      local link = lfs.symlinkattributes(filename, 'target')
+      if link and seen[lfs.abspath(link .. sep, dir):gsub('[/\\]+$', '')] then
+        goto continue
+      end
       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, seen, (level or 0) + 1)
@@ -109,7 +112,7 @@ 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 b1b4ee74..563cdb3f 100644
--- a/test/test.lua
+++ b/test/test.lua
@@ -742,6 +742,21 @@ function test_lfs_ext_walk_symlinks()
   table.sort(expected_files)
   assert_equal(files, expected_files)
   os.execute('rm -r ' .. dir)
+
+  lfs.mkdir(dir)
+  io.open(dir .. '/foo', 'w'):close()
+  local cwd = lfs.currentdir()
+  lfs.chdir(dir)
+  lfs.link('.', 'bar', true)
+  lfs.mkdir(dir .. '/baz')
+  lfs.mkdir(dir .. '/baz/quux')
+  lfs.chdir(dir .. '/baz/quux')
+  lfs.link('../../baz/', 'foobar', true)
+  lfs.chdir(cwd)
+  local count = 0
+  for filename in lfs.walk(dir) do count = count + 1 end
+  assert_equal(count, 1)
+  os.execute('rm -r ' .. dir)
 end
 
 function test_lfs_ext_abs_path()
-- 
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