feat: better error message when lacking permissions

The lock error message has clobbered the check_command_permissions
error message. This is an interim solution, but we should probably
move the permissions check further up for a more informative error.

3 files changed, 40 insertions, 13 deletions

diff --git a/spec/quick/build.q b/spec/quick/build.q
index ee519adf..55bb7519 100644
--- a/spec/quick/build.q
+++ b/spec/quick/build.q
@@ -83,8 +83,15 @@ RUN: luarocks build --tree=/usr ./a_rock-1.0.1-rockspec
 EXIT: 4
 STDERR:
 --------------------------------------------------------------------------------
-requires exclusive access
-use --force-lock
+requires exclusive write access
+--------------------------------------------------------------------------------
+
+We show the OS permission denied error, so we don't show the --force-lock
+message.
+
+NOT_STDERR:
+--------------------------------------------------------------------------------
+try --force-lock
 --------------------------------------------------------------------------------
 
 NOT_EXISTS: %{testing_sys_rocks}/a_rock/1.0-1/a_rock-1.0-1.rockspec
@@ -93,8 +100,15 @@ RUN: luarocks build --tree=/usr ./a_rock-1.0.1-rockspec --force-lock
 EXIT: 4
 STDERR:
 --------------------------------------------------------------------------------
-requires exclusive access
-failed to force the lock
+requires exclusive write access
+--------------------------------------------------------------------------------
+
+We show the OS permission denied error, so we don't show the --force-lock
+message.
+
+NOT_STDERR:
+--------------------------------------------------------------------------------
+try --force-lock
 --------------------------------------------------------------------------------
 
 NOT_EXISTS: %{testing_sys_rocks}/a_rock/1.0-1/a_rock-1.0-1.rockspec
@@ -108,8 +122,15 @@ RUN: luarocks build --tree=/usr/invalid ./a_rock-1.0.1-rockspec
 EXIT: 4
 STDERR:
 --------------------------------------------------------------------------------
-requires exclusive access
-use --force-lock
+requires exclusive write access
+--------------------------------------------------------------------------------
+
+We show the OS permission denied error, so we don't show the --force-lock
+message.
+
+NOT_STDERR:
+--------------------------------------------------------------------------------
+try --force-lock
 --------------------------------------------------------------------------------
 
 NOT_EXISTS: %{testing_sys_rocks}/a_rock/1.0-1/a_rock-1.0-1.rockspec
@@ -118,7 +139,7 @@ RUN: luarocks build --tree=/usr/invalid ./a_rock-1.0.1-rockspec --force-lock
 EXIT: 4
 STDERR:
 --------------------------------------------------------------------------------
-requires exclusive access
+requires exclusive write access
 failed to force the lock
 --------------------------------------------------------------------------------
 
diff --git a/src/luarocks/cmd.lua b/src/luarocks/cmd.lua
index ca22c0db..b6d0d47e 100644
--- a/src/luarocks/cmd.lua
+++ b/src/luarocks/cmd.lua
@@ -732,12 +732,15 @@ function cmd.run_command(description, commands, external_namespace, ...)
    if cmd_mod.needs_lock and cmd_mod.needs_lock(args) then
       lock, err = fs.lock_access(path.root_dir(cfg.root_dir), args.force_lock)
       if not lock then
-         local try_force = args.force_lock
-                           and (" - failed to force the lock" .. (err and ": " .. err or ""))
-                           or  " - use --force-lock to overwrite the lock"
+         err = args.force_lock
+               and ("failed to force the lock" .. (err and ": " .. err or ""))
+               or  (err and err ~= "File exists")
+                   and err
+                   or  "try --force-lock to overwrite the lock"
+
          die("command '" .. args.command .. "' " ..
-             "requires exclusive access to " .. path.root_dir(cfg.root_dir) ..
-             try_force, cmd.errorcodes.LOCK)
+             "requires exclusive write access to " .. path.root_dir(cfg.root_dir) .. " - " ..
+             err, cmd.errorcodes.LOCK)
       end
    end
 
diff --git a/src/luarocks/fs/unix/tools.lua b/src/luarocks/fs/unix/tools.lua
index efd4d624..a0fba784 100644
--- a/src/luarocks/fs/unix/tools.lua
+++ b/src/luarocks/fs/unix/tools.lua
@@ -319,7 +319,10 @@ function tools.is_superuser()
 end
 
 function tools.lock_access(dirname, force)
-   fs.make_dir(dirname)
+   local ok, err = fs.make_dir(dirname)
+   if not ok then
+      return nil, err
+   end
 
    local tempfile = dir.path(dirname, ".lock.tmp." .. tostring(math.random(100000000)))