rebar_erl_vsn

defines for erlang versions

Build

$ rebar3 compile

Use

Add the plugin to your rebar config:

{plugins, [rebar_erl_vsn]}.
{provider_hooks, [{pre, [{compile, erl_vsn}]}]}.

Then just call your plugin directly in an existing application:

$ rebar3 compile
===> Fetching rebar_erl_vsn
===> Compiling rebar_erl_vsn
<Plugin Output>

Defines

When added to your project, this plugin adds a define for each major/minor pair, such as 17.5 or 18.0. These are defined whenever the current version detected by the plugin is greater than the major/minor pair, so for example a build done running 19.0 will have '19.0', '18.3', '18.2', '18.1', & so on defined, down to '14.0'.

For clarity, some major breakages have their own special defines. The following are defined (in addition to their corresponding version defines):

• new_hash (16.0) - new crypto:hash functions are the default and old ones deprecated.
• long_schedule (16.1) - long_schedule warnings.
• maps, namespaced_types (17.0) - maps are introduced, types like dict() now require a namespace.
• large_maps (18) - large maps are now feasible, while in R17 they caused performance problems
• rand (19) - introduction of the rand module.
• ceil_bif, high_bit_uniform, fsm_deprecated (20) - we get a ceil bif, and fsm is deprecated, uniform for high bits is improved.
• ssl_accept_deprecated (21) - ssh:ssl_accept is deprecated use ssl:handshake instead instead .

Examples

Code that runs on R18 and above:

-ifdef('18.0').
version() ->
  "18 and above".
-else.
version() ->
  "before 17".
-endif.

Targeting R17 (all variants) specially

-ifdef('17.0').
-ifndef('18.0').
%% Code only executed in R17.*
-else.
%% Code executed for R18+
-endif.
-else.
%% Code executed < R17
-endif.

md5 function that does not throw deprecation warnings:

-ifdef(new_hash).
md5(Data) ->
  crypto:hash(md5, Data).
-elseif.
md5(Data) ->
  crypto:md5(Data).
-endif.