Ignore optional Hex package dependencies

Filter out dependencies marked as optional in Hex package metadata.
Rebar3 does not support optional dependencies, so they should not be
fetched or compiled. This fixes issues where optional Mix-only
transitive dependencies would cause build failures.

Bump PACKAGE_INDEX_VERSION to invalidate existing caches.

Fixes #2977

Author: maennchen

THANKS

@@ -148,3 +148,4 @@ Manas Chaudhari
 Luís Rascão
 Marko Minđek
 LEdoian
+Jonatan Männchen

apps/rebar/src/rebar.hrl

@@ -29,7 +29,7 @@
 -define(LOCK_FILE, "rebar.lock").
 -define(DEFAULT_COMPILER_SOURCE_FORMAT, relative).
 -define(DEFAULT_COMPILER_ERROR_FORMAT, rich). % 'minimal' for default values as of 3.23.0 and earlier
--define(PACKAGE_INDEX_VERSION, 6).
+-define(PACKAGE_INDEX_VERSION, 7).
 -define(PACKAGE_TABLE, package_index).
 -define(INDEX_FILE, "packages.idx").
 -define(HEX_AUTH_FILE, "hex.config").

apps/rebar/src/rebar_packages.erl

@@ -11,7 +11,7 @@
         ,resolve_version/6]).
 
 -ifdef(TEST).
--export([new_package_table/0, find_highest_matching_/5]).
+-export([new_package_table/0, find_highest_matching_/5, parse_deps/1]).
 -endif.
 
 -export_type([package/0]).
@@ -205,10 +205,16 @@ find_highest_matching_(Dep, DepVsn, #{name := Repo}, Table, State) when is_binar
 verify_table(State) ->
     ets:info(?PACKAGE_TABLE, named_table) =:= true orelse load_and_verify_version(State).
 
+%% Filter out optional dependencies. Rebar3 does not support optional
+%% dependencies, so we simply ignore them. For full parity with Mix, we would
+%% need to check if the dependency is included elsewhere (even transitively)
+%% without the optional flag, and only exclude it if all references are
+%% optional.
 parse_deps(Deps) ->
     [{maps:get(app, D, Name), {pkg, Name, Constraint, undefined, undefined}}
      || D=#{package := Name,
-            requirement := Constraint} <- Deps].
+            requirement := Constraint} <- Deps,
+        not maps:get(optional, D, false)].
 
 parse_checksum(<<Checksum:256/big-unsigned>>) ->
     list_to_binary(

apps/rebar/test/rebar_pkg_SUITE.erl

@@ -16,7 +16,8 @@
 
 all() -> [good_uncached, good_cached, badpkg, badhash_nocache,
           badindexchk, badhash_cache, bad_to_good, good_disconnect,
-          bad_disconnect, pkgs_provider, find_highest_matching].
+          bad_disconnect, pkgs_provider, find_highest_matching,
+          parse_deps_ignores_optional].
 
 init_per_suite(Config) ->
     application:start(meck),
@@ -250,6 +251,23 @@ find_highest_matching(_Config) ->
                                                        #{name => <<"hexpm">>}, ?PACKAGE_TABLE, State),
     ?assertEqual({{3,0,0},{[<<"rc">>,0],[]}}, Vsn3).
 
+parse_deps_ignores_optional(_Config) ->
+    %% Test that optional dependencies are filtered out
+    Deps = [
+        #{package => <<"req">>, requirement => <<"~> 1.0">>},
+        #{package => <<"opt">>, requirement => <<"~> 2.0">>, optional => true},
+        #{package => <<"exp">>, requirement => <<"~> 3.0">>, optional => false},
+        #{package => <<"ali">>, requirement => <<"4.0">>, app => <<"alias">>},
+        #{package => <<"ali_opt">>, requirement => <<"~> 5.0">>,
+          app => <<"alias2">>, optional => true}
+    ],
+    Result = rebar_packages:parse_deps(Deps),
+    ?assertEqual(3, length(Result)),
+    ?assertMatch([{<<"req">>, {pkg, <<"req">>, <<"~> 1.0">>, _, _}},
+                  {<<"exp">>, {pkg, <<"exp">>, <<"~> 3.0">>, _, _}},
+                  {<<"alias">>, {pkg, <<"ali">>, <<"4.0">>, _, _}}],
+                 Result).
+
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 %%% Helpers %%%
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