Re: Say No to global-by-default
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- Subject: Re: Say No to global-by-default
- From: Sean Conner <sean@...>
- Date: Wed, 4 Jul 2018 03:28:47 -0400
It was thus said that the Great Axel Kittenberger once stated:
>
> And yes this applies to config files as well. I used Lua like this and got
> negative feedback of people complaining there wasn't any notification
> because they misspelled a variable. So instead after the user config file
> finished, I made a loop that checks if any unknown variables are in global
> space and error if so.
For this use case, I think it would be easier to do this:
CONF =
{
host = "localhost",
port = 8080,
datadir = '/tmp',
syslog =
{
id = 'my-daemon',
facility = 'local1',
},
}
setmetatable(CONF,{
__newindex = function(_,key)
error(string.format("invalid config parameter: %s",key),2)
end
})
f = loadfile(arg[1] or "config.txt","t",CONF)
okay,err = pcall(f)
if not okay then print(err) end
You can set default values, and you get error checking:
[spc]lucy:/tmp/bar>lua-53 read.lua
config.txt:2: invalid config parameter: plort
[spc]lucy:/tmp/bar>
[spc]lucy:/tmp/bar>lua-53 read.lua
config.txt:5: attempt to index a nil value (global 'sylog')
[spc]lucy:/tmp/bar>
-spc