How to validate a pattern in lua

I'm currently creating a search function in lua which basically just goes through a list of items and processes the items that match the input string in a specific way. I use string.find(sourceString, inputString) to identify the items.

The function is called whenever a user types something into a text field so if he t开发者_如何学运维ries to enter a pattern it happens that when using sets or captures the function is called when the search string just contains a [ or a ( without the closing equivalent which of cause throws an error.

The best way to go around this problem I think is to validate the input as beeing a valid pattern, but I've got no idea how to do this. Lua itself doesn't seem to contain a method for this and I am a bit confused of how to check it in a more or less performant way myself. Thanks for your help and ideas in advance :)

You should wrap the call to string.find with pcall to capture the error.

local status, result = pcall(string.find, sourceString, inputString)
if not status then
    -- bad pattern logic, error message is in result
else
    -- good pattern logic, result contains the start index
end

See this for pattern escape function (taken from somewhere in Lua Users wiki, I think). You may convert it to the validation function if you need.