Add static analysis tool for Lua code

[GunChleoc]

Following from the discussion in this bug: https://bugs.launchpad.net/widelands/+bug/1378339

Start digging from https://github.com/mpeterv/luacheck which seems mature and maintained. More links & info in the other bug.

See also https://bugs.launchpad.net/widelands/+bug/1502678

[GunChleoc (gunchleoc)]

I had a look at luacheck. The problem with it is that it parses each file separately, so I get a lot of false positives for functions defined in helper scripts. We might be able to solve this problem by defining a rockspec http://www.luarocks.org/en/Rockspec_format

[SirVer (sirver)]

maybe just using grep -v to remove the undefined functions warnings? We do not care about this (as much).

Alternatively we could hack it to understand our "include" function.

[Peter Melnichenko (mpeterval)]

Hello, I hope you don't mind me, I'm curious to see how luacheck is used and how I can improve it.

It looks like helper functions are defined as globals in helper scripts. You can use `-d` and `--no-unused-globals` options to remove warnings about them. It will leave warnings about accessing globals which are never set anywhere. You can also define globals provided by the game engine using `--globals` options.

I played around on trunk and it seems that optimal options are `luacheck . -q -r -a -d --no-unused-globals --globals path __file__ include wl set_textdomain ngettext` which produces only 18 warnings. There are still a bunch of false positives for unused variables in multi-assignments, e.g. `a, b = foo()` and a is then unused. There is a practice to name such ignored variables with `_` but it seems that `_` is already globally used for something.

You can ditch detection of unused values altogether with `luacheck . -q -r -u -d --no-unused-globals --globals path __file__ include wl set_textdomain ngettext`, which produces 4 warnings, 3 of which seem to point to bugs.

Of course, it is possible to use a config file instead of typing all these options. Documentation isn't perfect by far but it should help: http://luacheck.readthedocs.org/en/latest/config.html . And if you have any questions, please open an issue on github: https://github.com/mpeterv/luacheck/issues .

[GunChleoc (gunchleoc)]

Thanks for your imput! I'll have a look next week - I don't have my development machine at the moment.

[GunChleoc (gunchleoc)]

Migrated to https://github.com/widelands/widelands/issues/2988