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W0021 - Cannot Evaluate Common Test Callbacks

Error​

   -module(my_SUITE).~

   -export([all/0]).
   -export([a/1]).

   all() -> my_external_helper:all().
%% ^^^ warning: Could not evaluate function. No code lenses for tests will be available.

   a(_Config) ->
     ok.

Explanation​

The error indicates that the all/0 and/or the groups/0 callback functions could not be evaluated successfully by the ELP language server, resulting in a degraded IDE experience. This can happen in two cases:

  • The test suite has significant compilation times (i.e. several seconds)
  • The all/0 or groups/0 function contain code which depends on external modules, a scenario currently not supported by ELP

The warning only indicates a degradation for the IDE experience where certain features won't be available, such as the Debug/Run code lenses and CT diagnostics such as the Unreachable Test Case one.

When encountering the warning, you should considering simplifying or splitting your test suite.