on-the-fly emacs erlang-rebar3 flycheck syntax checking

[Frans Schneider]

Hi list,

Using the erlang flycheck syntax checker, with on-the-fly mode set, 
gives immediate feedback on syntax errors. Using the erlang-rebar3 
checker, syntax errors are displayed only on saving the buffer. How can 
I get the relang-rebar3 checker to behave the same as the default erlang 
checker?

The setup in my init.el file looks like:

(setq-default flycheck-disabled-checkers '(erlang))
(add-hook 'after-init-hook #'global-flycheck-mode)

Not disabling the erlang checker will make flycheck complain it can't 
find the proper.hrl file while editing PropER tests.

The output of C-c ! v is:

Syntax checkers for buffer prop_stateful.erl in erlang-mode:

First checker to run:

   erlang-rebar3
     - may enable: yes
     - predicate:  t
     - executable: Found at /home/frans/.cache/rebar3/bin/rebar3

Checkers that are compatible with this mode, but will not run until 
properly configured:

   erlang (disabled)
     - may enable: Automatically disabled!
     - executable: Found at /usr/lib/erlang/bin/erlc

Flycheck Mode is enabled.  Use C-u C-c ! x to enable disabled
checkers.

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Flycheck version: 32snapshot (package: 20200224.2057)
Emacs version:    26.1