Fix unusable error when migrations are broken.

[ikogan]

Summary

When a migration is defined without a name, Kong fails to start with a fairly useless error message:

/usr/local/share/lua/5.1/kong/cmd/start.lua:62: /usr/local/share/lua/5.1/kong/cmd/utils/log.lua:49: bad argument #6 to 'format' (no value)
stack traceback:
        [C]: in function 'error'
        /usr/local/share/lua/5.1/kong/cmd/start.lua:62: in function 'cmd_exec'
        /usr/local/share/lua/5.1/kong/cmd/init.lua:88: in function </usr/local/share/lua/5.1/kong/cmd/init.lua:88>
        [C]: in function 'xpcall'
        /usr/local/share/lua/5.1/kong/cmd/init.lua:88: in function </usr/local/share/lua/5.1/kong/cmd/init.lua:45>
        /usr/local/bin/kong:7: in function 'file_gen'
        init_worker_by_lua:38: in function <init_worker_by_lua:36>
        [C]: in function 'xpcall'
        init_worker_by_lua:45: in function <init_worker_by_lua:43>

This is because migration.name, being nil, when passed to the log function causes the format string to fail to resolve. This simply uses "(no name)" in place of the name.

[thibaultcha]

Hi,

Names are mandatory for migrations, otherwise Kong has now way to decide whether a migration has been run already or not. Granted, Kong could catch that a migration has no name and should yield an appropriate error if so.

Will you contribute such a patch? 😁

[ikogan]

This actually does end up yielding an error about the migration having never run. I can likely change it to be a more explicit error.

[thibaultcha]

Yes; I meant that Kong should fail earlier in such a case. This log message that you patched is-user friendly, and helps the user identify which migrations haven't run yet.

However, a migration that has no name is a developer error, and should be caught earlier (when the factory loads said migrations from the core/plugins) so that a developer can spot their mistake and fix it before the plugin is distributed. Something more or less like this maybe:

for i, migration in ipairs(migrations) do
  if type(migration.name) ~= "string" then -- cal also check that names are unique (another requirement)
    error("migration ", i, " for DAO ", dao_name, " must have a unique name")
  end
end

[ikogan]

I've implemented the two checks. I noticed some of the CI tests were failing before but I don't see how they would have had to do with my changes.

[thibaultcha]

Thanks, I manually committed this with some refactoring to avoid some back and forth. Thanks again!