Replace table.getn with length operator

[kmontag]

table.getn was removed in Lua 5.2, in favor of the # operator - see e.g. https://stackoverflow.com/questions/11890125/lua-table-library-removed.

While Redis itself still seems to support the old syntax, this change allows compatibility with mock libraries which may rely on newer Lua versions. In my case I ran into issues with https://github.com/stipsan/ioredis-mock.

In the meantime, if anyone is looking a solution to use redlock with ioredis-mock or similar, this has worked for me:

const replaceGetn = (lua: string) => {
  // table.getn(KEYS) --> #KEYS
  return lua.replace(/table\.getn\(([A-Za-z0-9]+)\)/g, '#$1');
}
const redlock = new Redlock(clients, {
  lockScript: replaceGetn,
  extendScript: replaceGetn,
});

[coveralls]

Coverage remained the same at 100.0% when pulling 107d986 on kmontag:patch-1 into 75c0772 on mike-marcacci:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 107d986 on kmontag:patch-1 into 75c0772 on mike-marcacci:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 63d8037 on kmontag:patch-1 into 75c0772 on mike-marcacci:master.

[mike-marcacci]

👍This looks great – it appears that redis has always supported lua 5.1, so this doesn't introduce any compatibility issues. I'll release this as a minor shortly.