fs: add LuaPosix-version of set_permissions

This implemention the ugly side-effect of "exposing" some Unix-specific
utility functions to the public API, so they can be shared by
`luarocks.fs.lua` and `luarocks.fs.unix.tools`. I named those functions
`_unix_*` (with a Python-style `_` at the beginning) to clarify that they
should not be used publicly.

3 files changed, 92 insertions, 51 deletions

diff --git a/src/luarocks/fs/lua.lua b/src/luarocks/fs/lua.lua
index 37e1bffc..b5232a52 100644
--- a/src/luarocks/fs/lua.lua
+++ b/src/luarocks/fs/lua.lua
@@ -788,16 +788,46 @@ local octal_to_rwx = {
    ["7"] = "rwx",
 }
 
-function fs_lua.chmod(file, mode)
-   -- LuaPosix (as of 5.1.15) does not support octal notation...
-   if mode:sub(1,1) == "0" then
-      local new_mode = {}
-      for c in mode:sub(-3):gmatch(".") do
-         table.insert(new_mode, octal_to_rwx[c])
+do
+   local umask_cache
+   function fs_lua._unix_umask()
+      if umask_cache then
+         return umask_cache
+      end
+      -- LuaPosix (as of 34.0.4) only returns the umask as rwx
+      local rwx = posix.umask()
+      local oct = 0
+      for i = 1, 9 do
+         if rwx:sub(10 - i, 10 - i) == "-" then
+            oct = oct + 2^i
+         end
       end
-      mode = table.concat(new_mode)
+      umask_cache = ("%03o"):format(oct)
+      return umask_cache
+   end
+end
+
+function fs_lua.set_permissions(filename, mode, scope)
+   local perms
+   if mode == "read" and scope == "user" then
+      perms = fs._unix_moderate_permissions("600")
+   elseif mode == "exec" and scope == "user" then
+      perms = fs._unix_moderate_permissions("700")
+   elseif mode == "read" and scope == "all" then
+      perms = fs._unix_moderate_permissions("644")
+   elseif mode == "exec" and scope == "all" then
+      perms = fs._unix_moderate_permissions("755")
+   else
+      return false, "Invalid permission " .. mode .. " for " .. scope
+   end
+
+   -- LuaPosix (as of 5.1.15) does not support octal notation...
+   local new_perms = {}
+   for c in perms:sub(-3):gmatch(".") do
+      table.insert(new_perms, octal_to_rwx[c])
    end
-   local err = posix.chmod(file, mode)
+   perms = table.concat(new_perms)
+   local err = posix.chmod(filename, perms)
    return err == 0
 end
 
diff --git a/src/luarocks/fs/unix.lua b/src/luarocks/fs/unix.lua
index dbe48cca..4ca68ce5 100644
--- a/src/luarocks/fs/unix.lua
+++ b/src/luarocks/fs/unix.lua
@@ -165,4 +165,44 @@ function unix.export_cmd(var, val)
    return ("export %s='%s'"):format(var, val)
 end
 
+--- Moderate the given permissions based on the local umask
+-- @param perms string: permissions to moderate
+-- @return string: the moderated permissions
+function unix._unix_moderate_permissions(perms)
+   local octal_to_rwx = {
+      ["0"] = "---",
+      ["1"] = "--x",
+      ["2"] = "-w-",
+      ["3"] = "-wx",
+      ["4"] = "r--",
+      ["5"] = "r-x",
+      ["6"] = "rw-",
+      ["7"] = "rwx",
+   }
+   local rwx_to_octal = {}
+   for octal, rwx in pairs(octal_to_rwx) do
+      rwx_to_octal[rwx] = octal
+   end
+
+   local umask = fs._unix_umask()
+
+   local moderated_perms = ""
+   for i = 1, 3 do
+      local p_rwx = octal_to_rwx[perms:sub(i, i)]
+      local u_rwx = octal_to_rwx[umask:sub(i, i)]
+      local new_perm = ""
+      for j = 1, 3 do
+         local p_val = p_rwx:sub(j, j)
+         local u_val = u_rwx:sub(j, j)
+         if p_val == u_val then
+            new_perm = new_perm .. "-"
+         else
+            new_perm = new_perm .. p_val
+         end
+      end
+      moderated_perms = moderated_perms .. rwx_to_octal[new_perm]
+   end
+   return moderated_perms
+end
+
 return unix
diff --git a/src/luarocks/fs/unix/tools.lua b/src/luarocks/fs/unix/tools.lua
index 06098399..e0b0d22a 100644
--- a/src/luarocks/fs/unix/tools.lua
+++ b/src/luarocks/fs/unix/tools.lua
@@ -160,47 +160,18 @@ function tools.is_file(file)
    return fs.execute(vars.TEST, "-f", file)
 end
 
---- Moderate the given permissions based on the local umask
--- @param perms string: permissions to moderate
--- @return string: the moderated permissions
-local function moderate_permissions(perms)
-   local octal_to_rwx = {
-      ["0"] = "---",
-      ["1"] = "--x",
-      ["2"] = "-w-",
-      ["3"] = "-wx",
-      ["4"] = "r--",
-      ["5"] = "r-x",
-      ["6"] = "rw-",
-      ["7"] = "rwx",
-   }
-   local rwx_to_octal = {}
-   for octal, rwx in pairs(octal_to_rwx) do
-      rwx_to_octal[rwx] = octal
-   end
-
-   local fd = assert(io.popen("umask"))
-   local umask = assert(fd:read("*a"))
-   umask = umask:gsub("\n", "")
-   umask = umask:sub(2, 4)
-
-   local moderated_perms = ""
-   for i = 1, 3 do
-      local p_rwx = octal_to_rwx[perms:sub(i, i)]
-      local u_rwx = octal_to_rwx[umask:sub(i, i)]
-      local new_perm = ""
-      for j = 1, 3 do
-         local p_val = p_rwx:sub(j, j)
-         local u_val = u_rwx:sub(j, j)
-         if p_val == u_val then
-            new_perm = new_perm .. "-"
-         else
-            new_perm = new_perm .. p_val
-         end
+do
+   local umask_cache
+   function tools._unix_umask()
+      if umask_cache then
+         return umask_cache
       end
-      moderated_perms = moderated_perms .. rwx_to_octal[new_perm]
+      local fd = assert(io.popen("umask"))
+      local umask = assert(fd:read("*a"))
+      umask = umask:gsub("\n", "")
+      umask_cache = umask:sub(2, 4)
+      return umask_cache
    end
-   return moderated_perms
 end
 
 --- Set permissions for file or directory
@@ -214,13 +185,13 @@ function tools.set_permissions(filename, mode, scope)
 
    local perms
    if mode == "read" and scope == "user" then
-      perms = moderate_permissions("600")
+      perms = fs._unix_moderate_permissions("600")
    elseif mode == "exec" and scope == "user" then
-      perms = moderate_permissions("700")
+      perms = fs._unix_moderate_permissions("700")
    elseif mode == "read" and scope == "all" then
-      perms = moderate_permissions("644")
+      perms = fs._unix_moderate_permissions("644")
    elseif mode == "exec" and scope == "all" then
-      perms = moderate_permissions("755")
+      perms = fs._unix_moderate_permissions("755")
    else
       return false, "Invalid permission " .. mode .. " for " .. scope
    end