luatest does not report LuaCov reporter errors clearly when `--coverage` is enabled

[tulzke]

Summary

When luatest is started with --coverage, errors raised by LuaCov during report generation are not handled by luatest. A test suite can finish successfully, but then the process exits with a fatal Tarantool error instead of a clear luatest failure explaining that LuaCov failed.

In the reproduced case, .luacov references a reporter that is not installed. LuaCov raises module 'luacov.reporter.missing_reporter' not found, but luatest does not catch/report it as a normal test runner error.

Environment

• Tarantool: 3.7.0
• luatest: 1.4.4
• luacov: 0.13.0
• Commands: luatest --coverage, luacov .

Minimal Reproducer

.luacov:

return {
  runreport = true,
  reporter = "missing_reporter",
}

test/pass_test.lua:

local t = require('luatest')

local g = t.group('pass')

g.test_pass = function()
    t.assert_equals(1 + 1, 2)
end

Run:

luatest --coverage

Actual Behavior

The test itself succeeds, but the process exits with a fatal Tarantool error after LuaCov tries to generate the report.

Example output:

Tarantool version is 3.7.0-0-g78b01ace947d
started logging into a pipe, SIGHUP log rotation disabled
luatest | 2026-06-26 07:07:52.897 [1] main/104/luatest/luatest.log runner.lua:306 I> Bootstrap finished: 1 test(s), 0 group(s)
.2026-06-26 07:07:52.922 [1] main say.c:88 F> fatal error, exiting the event loop

Ran 1 tests in 0.007 seconds, 1 succeeded, 0 failed

The original LuaCov error can be obtained by running LuaCov explicitly:

luacov .

In that case, LuaCov reports the real configuration/dependency problem directly, while the same problem is obscured when LuaCov is executed indirectly via luatest --coverage.

Expected Behavior

luatest should surface LuaCov failures as a normal runner error, for example:

luatest | 2026-06-26 07:07:52.897 [1] main/104/luatest/luatest.log runner.lua:306 I> Bootstrap finished: 1 test(s), 0 group(s)
Ran 1 tests in 0.007 seconds, 1 succeeded, 0 failed

Coverage report generation failed:
/.rocks/share/tarantool/luacov/runner.lua:134: module 'luacov.reporter.missing_reporter' not found:
        no field package.preload['luacov.reporter.missing_reporter']

and exit with a non-zero status without Tarantool's generic fatal error, exiting the event loop.

Ideally, luatest should wrap LuaCov initialization/shutdown/report generation with pcall/xpcall, print the original LuaCov error and traceback, and return a regular failure status.