Add config-based initialization for imports and paths

py_import:init/0 now loads imports and paths from application config:

    {erlang_python, [
        {imports, [{json, dumps}, {math, sqrt}]},
        {paths, ["/path/to/modules"]}
    ]}

Initialization is done in erlang_python_sup before contexts and pools start.

Author: benoitc

src/erlang_python_app.erl

@@ -20,8 +20,6 @@
 -export([start/2, stop/1]).
 
 start(_StartType, _StartArgs) ->
-    %% Initialize the import registry ETS tables
-    py_import:init(),
     erlang_python_sup:start_link().
 
 stop(_State) ->

src/erlang_python_sup.erl

@@ -53,6 +53,9 @@ init([]) ->
     %% Initialize shared state ETS table (owned by supervisor for resilience)
     ok = py_state:init_tab(),
 
+    %% Initialize import/path registry and load config (before contexts start)
+    ok = py_import:init(),
+
     %% Register ALL system callbacks early, before any gen_server starts.
     %% This ensures callbacks like _py_sleep and _whereis are available immediately.
     ok = py_callback:register_callbacks(),

src/py_import.erl

@@ -18,6 +18,17 @@
 %%% applied to all Python interpreters. Imports and paths are applied
 %%% immediately to all running interpreters and stored for new interpreters.
 %%%
+%%% == Configuration ==
+%%%
+%%% Imports and paths can be configured in the application environment:
+%%%
+%%% ```
+%%% {erlang_python, [
+%%%     {imports, [{json, dumps}, {math, sqrt}, {os, getcwd}]},
+%%%     {paths, ["/path/to/modules"]}
+%%% ]}
+%%% '''
+%%%
 %%% == Examples ==
 %%%
 %%% ```
@@ -70,28 +81,27 @@
 %% @doc Initialize the import and path registry ETS tables.
 %%
 %% This is called automatically during application startup.
+%% Also loads imports and paths from application config.
 %% Safe to call multiple times - does nothing if already initialized.
 %%
 %% @returns ok
 -spec init() -> ok.
 init() ->
     case ets:info(?IMPORT_REGISTRY) of
         undefined ->
-            %% Use bag type to allow multiple entries with same module name
-            %% e.g., {<<"json">>, all} and {<<"json">>, <<"dumps">>}
             ets:new(?IMPORT_REGISTRY, [bag, public, named_table]),
             ok;
         _ ->
             ok
     end,
     case ets:info(?PATH_REGISTRY) of
         undefined ->
-            %% Use set type - paths are unique, ordered by insertion
             ets:new(?PATH_REGISTRY, [ordered_set, public, named_table]),
             ok;
         _ ->
             ok
-    end.
+    end,
+    load_config().
 
 %%% ============================================================================
 %%% Module Import Registry
@@ -353,6 +363,30 @@ is_path_added(Path) ->
 ensure_binary(S) ->
     py_util:to_binary(S).
 
+%% @private Load imports and paths from application config
+load_config() ->
+    %% Load imports: [{Module, Func}]
+    Imports = application:get_env(erlang_python, imports, []),
+    lists:foreach(
+        fun({Module, Func}) ->
+            ModuleBin = ensure_binary(Module),
+            FuncBin = ensure_binary(Func),
+            ets:insert(?IMPORT_REGISTRY, {ModuleBin, FuncBin})
+        end,
+        Imports
+    ),
+    %% Load paths
+    Paths = application:get_env(erlang_python, paths, []),
+    lists:foreach(
+        fun(Path) ->
+            PathBin = ensure_binary(Path),
+            Key = erlang:monotonic_time(),
+            ets:insert(?PATH_REGISTRY, {Key, PathBin})
+        end,
+        Paths
+    ),
+    ok.
+
 %% @private Apply import to all running interpreters (contexts + event loops)
 apply_import_to_interpreters(ModuleBin) ->
     Imports = [{ModuleBin, all}],

test/py_import_SUITE.erl

@@ -45,7 +45,9 @@
     add_path_test/1,
     %% Immediate application tests
     import_applies_to_running_interpreter_test/1,
-    path_applies_to_running_interpreter_test/1
+    path_applies_to_running_interpreter_test/1,
+    %% Config initialization tests
+    init_from_config_test/1
 ]).
 
 all() ->
@@ -82,7 +84,9 @@ groups() ->
         add_path_test,
         %% Immediate application tests
         import_applies_to_running_interpreter_test,
-        path_applies_to_running_interpreter_test
+        path_applies_to_running_interpreter_test,
+        %% Config initialization tests
+        init_from_config_test
     ]}].
 
 init_per_suite(Config) ->
@@ -845,3 +849,57 @@ path_applies_to_running_interpreter_test(Config) ->
     ok = py_import:clear_paths(),
 
     ct:pal("add_path applies immediately to running interpreter").
+
+%% ============================================================================
+%% Config Initialization Tests
+%% ============================================================================
+
+%% @doc Test that imports and paths are loaded from application config
+init_from_config_test(Config) ->
+    %% Clear existing state
+    ok = py_import:clear_imports(),
+    ok = py_import:clear_paths(),
+
+    %% Create test module in priv_dir
+    PrivDir = ?config(priv_dir, Config),
+    ModuleDir = filename:join(PrivDir, "config_test"),
+    ok = filelib:ensure_dir(filename:join(ModuleDir, "dummy")),
+    ModulePath = filename:join(ModuleDir, "config_test_mod.py"),
+    ok = file:write_file(ModulePath, <<"CONFIG_VALUE = 123\n">>),
+
+    %% Set application config
+    ok = application:set_env(erlang_python, imports, [{json, dumps}, {base64, b64encode}]),
+    ok = application:set_env(erlang_python, paths, [ModuleDir]),
+
+    %% Re-run init to load config
+    ok = py_import:init(),
+
+    %% Verify imports were loaded in registry
+    Imports = py_import:all_imports(),
+    ?assert(lists:member({<<"json">>, <<"dumps">>}, Imports)),
+    ?assert(lists:member({<<"base64">>, <<"b64encode">>}, Imports)),
+
+    %% Verify paths were loaded in registry
+    Paths = py_import:all_paths(),
+    ModuleDirBin = list_to_binary(ModuleDir),
+    ?assert(lists:member(ModuleDirBin, Paths)),
+
+    %% Create a new context and verify imports/paths are applied
+    {ok, Ctx} = py_context:new(#{mode => worker}),
+
+    %% Verify json.dumps works (from config imports)
+    {ok, JsonResult} = py_context:call(Ctx, json, dumps, [[1, 2, 3]], #{}),
+    ?assertEqual(<<"[1, 2, 3]">>, JsonResult),
+
+    %% Verify custom module from config path works
+    {ok, ConfigValue} = py_context:eval(Ctx, <<"__import__('config_test_mod').CONFIG_VALUE">>),
+    ?assertEqual(123, ConfigValue),
+
+    %% Clean up
+    py_context:destroy(Ctx),
+    ok = application:unset_env(erlang_python, imports),
+    ok = application:unset_env(erlang_python, paths),
+    ok = py_import:clear_imports(),
+    ok = py_import:clear_paths(),
+
+    ct:pal("init loads imports and paths from config and applies to new contexts").