[NTG-context] How to load external lua library

[krulis.tomas@seznam.cz]

Dear ConTeXt mailing list,

I've been struggling with loading the sqlite external lua library. I tried the following:

1. Instaling the system package and running ConTeXt with the `--permitloadlib` option (I am running Manjaro, an arch-linux derivative: https://archlinux.org/packages/core/x86_64/sqlite/)
2. Installing the luarocks package (https://luarocks.org/modules/dougcurrie/lsqlite3) for the 5.1, 5.3 and 5.4 lua versions. I also tried to symlink the files in $HOME/.luarocks/lib/lua/{version}/lsqlite3.so to the project directory
3. I tried also setting the relevant lua paths with `eval $(luarocks path)`.

The compilation always fails with an error that context can't locate the sqlite3 library.

How can I load data from sqlite database during context compilation? As an MWE, I am adding the example in the documentation for the interaction with sqlite from the context garden (https://www.pragma-ade.nl/general/manuals/sql-mkiv.pdf):

```tex
\starttext

\startluacode
require("util-sql")
utilities.sql.setmethod("sqlite")
require("util-sql-loggers")

local loggers = utilities.sql.loggers
local presets = {
  -- method = "sqlite",
  database = "loggertest",
  datatable = "loggers",
  id = "loggers",
}

os.remove("loggertest.db") -- start fresh
local db = loggers.createdb(presets)
loggers.save(db, { -- variant 1: data subtable
  type = "error",
  action = "process",
  data = { filename = "test-1", message = "whatever a" }
} )

loggers.save(db, { -- variant 2: flat table
  type = "warning",
  action = "process",
  filename = "test-2",
  message = "whatever b"
} )

local result = loggers.collect(db, {
  start = {
  day = 1,
  month = 1,
  year = 2016,
},
  stop = {
  day = 31,
  month = 12,
  year = 2116,
},
  limit = 1000000,
  -- type = "error",
  action = "process"
})

context.starttabulate { "||||||" }

for i=1,#result do
  local r = result[i]
  context.NC() context(r.time)
  context.NC() context(r.type)
  context.NC() context(r.action)

  if r.data then
    context.NC() context(r.data.filename)
    context.NC() context(r.data.message)
  else
    context.NC()
    context.NC()
  end

  context.NC() context.NR()
end

context.stoptabulate()

-- local result = loggers.cleanup(db, {
  -- before = {
  -- day = 1,
  -- month = 1,
  -- year = 2117,
  -- },
-- })
\stopluacode

\stoptext
```

I am sorry for the poor quality of the example, but I don't know how to add an attachment to a message in a mailing list.

I have found a few references on the web and on this mailing list (https://mailman.ntg.nl/archives/list/ntg-context@ntg.nl/message/IDZBJQIXG3JIG5O5CNUNXUIPGR4UFTWE/), but I wasn't able to figure out what I could be doing wrong. I found a reference that the issue might be a version mismatch, so I tested multiple lua versions.

My project is about using multiple data sources in multiple formats and creating reports from them. I know I will definitely need to load YAML as well (with the `lyaml` luarocks package I guess). There's always the alternative of trying to use other programs to get the data, but I was wondering if I could leverage ConTeXt to do that directly.

Thank you for any guidance on this, and I hope this message is not too long ...
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