File 1901-Clarify-how-the-features-parsing-state-works.patch of Package erlang
From 2793dfceab3ae66d579d629e27e85828ec53f99e Mon Sep 17 00:00:00 2001
From: Richard Carlsson <carlsson.richard@gmail.com>
Date: Fri, 12 Dec 2025 13:47:12 +0100
Subject: [PATCH 1/8] Clarify how the features parsing state works
---
lib/compiler/src/compile.erl | 6 ++--
lib/stdlib/src/epp.erl | 4 +--
lib/stdlib/src/erl_features.erl | 38 ++++++++++++++++----
lib/stdlib/src/erl_lint.erl | 4 +++
lib/syntax_tools/src/epp_dodger.erl | 6 ++--
lib/syntax_tools/src/syntax_tools.app.src | 2 +-
lib/syntax_tools/test/syntax_tools_SUITE.erl | 2 +-
7 files changed, 46 insertions(+), 16 deletions(-)
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index f627aec471..ddd7c65def 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -1954,7 +1954,7 @@ do_parse_module(DefEncoding, #compile{ifile=File,options=Opts,dir=Dir}=St) ->
false ->
1
end,
- case erl_features:keyword_fun(Opts, fun erl_scan:f_reserved_word/1) of
+ case erl_features:init_parse_state(Opts, fun erl_scan:f_reserved_word/1) of
{ok, {Features, ResWordFun}} ->
R = epp:parse_file(File,
[{includes,[".",Dir|inc_paths(Opts)]},
@@ -1975,8 +1975,8 @@ do_parse_module(DefEncoding, #compile{ifile=File,options=Opts,dir=Dir}=St) ->
case R of
{ok,Forms0,Extra} ->
Encoding = proplists:get_value(encoding, Extra),
- %% Get features used in the module, indicated by
- %% enabling features with -feature(...).
+ %% epp reports final set of features used by the module,
+ %% including those given by `-feature(...)` declarations
UsedFtrs = proplists:get_value(features, Extra),
St1 = metadata_add_features(UsedFtrs, St),
Forms = case with_columns(Opts ++ compile_options(Forms0)) of
diff --git a/lib/stdlib/src/epp.erl b/lib/stdlib/src/epp.erl
index f4277109f3..fb813632a0 100644
--- a/lib/stdlib/src/epp.erl
+++ b/lib/stdlib/src/epp.erl
@@ -821,7 +821,7 @@ init_server(Pid, FileName, Options, St0) ->
Path = [filename:dirname(FileName) |
proplists:get_value(includes, Options, [])],
{ok,{_,ResWordFun0}} =
- erl_features:keyword_fun([], fun erl_scan:f_reserved_word/1),
+ erl_features:init_parse_state([], fun erl_scan:f_reserved_word/1),
ResWordFun =
proplists:get_value(reserved_word_fun, Options,
ResWordFun0),
@@ -1335,7 +1335,7 @@ update_features(St0, Ind, Ftr, Loc) ->
undefined -> fun erl_scan:f_reserved_word/1;
Fun -> Fun
end,
- case erl_features:keyword_fun(Ind, Ftr, Ftrs0, KeywordFun) of
+ case erl_features:update_parse_state(Ind, Ftr, Ftrs0, KeywordFun) of
{error, Reason} ->
{error, {Reason, Loc}};
{ok, {Ftrs1, ResWordFun1}} ->
diff --git a/lib/stdlib/src/erl_features.erl b/lib/stdlib/src/erl_features.erl
index 3a84c34447..d2f420bc38 100644
--- a/lib/stdlib/src/erl_features.erl
+++ b/lib/stdlib/src/erl_features.erl
@@ -37,12 +37,15 @@ functions that might be useful when writing tools.
enabled/0,
keywords/0,
keywords/1,
- keyword_fun/2,
- keyword_fun/4,
+ init_parse_state/2,
+ update_parse_state/4,
used/1,
format_error/1,
format_error/2]).
+%% temporary export for bootstrapping build
+-export([keyword_fun/2, keyword_fun/4]).
+
-type type() :: 'extension' | 'backwards_incompatible_change'.
-type status() :: 'experimental'
| 'approved'
@@ -220,12 +223,33 @@ keywords(Ftr, Map) ->
maps:get(keywords, maps:get(Ftr, Map)).
%% Utilities
-%% Returns list of enabled features and a new keywords function
--doc false.
+
+%% temporary aliases for bootstrapping build
+
-spec keyword_fun([term()], fun((atom()) -> boolean())) ->
{'ok', {[feature()], fun((atom()) -> boolean())}}
| {'error', error()}.
keyword_fun(Opts, KeywordFun) ->
+ init_parse_state(Opts, KeywordFun).
+
+-doc false.
+-spec keyword_fun('enable' | 'disable', feature(), [feature()],
+ fun((atom()) -> boolean())) ->
+ {'ok', {[feature()], fun((atom()) -> boolean())}}
+ | {'error', error()}.
+keyword_fun(Ind, Feature, Ftrs, KeywordFun) ->
+ update_parse_state(Ind, Feature, Ftrs, KeywordFun).
+
+%% Handles `{feature, F, State}` options and returns the list of enabled
+%% features together with a keywords function, as the initial state for
+%% parsing, starting from the set of statically enabled features. This
+%% is then modified (in epp) using `update_parse_state/4` when a
+%% declaration `-feature(...)` is encountered.
+-doc false.
+-spec init_parse_state([term()], fun((atom()) -> boolean())) ->
+ {'ok', {[feature()], fun((atom()) -> boolean())}}
+ | {'error', error()}.
+init_parse_state(Opts, KeywordFun) ->
%% Get items enabling or disabling features, preserving order.
IsFtr = fun({feature, _, enable}) -> true;
({feature, _, disable}) -> true;
@@ -242,12 +266,14 @@ keyword_fun(Opts, KeywordFun) ->
Error
end.
+%% Modifies the given keyword fun to accept/deny keywords when a feature
+%% is turned on or off. Used by epp when scanning feature declarations.
-doc false.
--spec keyword_fun('enable' | 'disable', feature(), [feature()],
+-spec update_parse_state('enable' | 'disable', feature(), [feature()],
fun((atom()) -> boolean())) ->
{'ok', {[feature()], fun((atom()) -> boolean())}}
| {'error', error()}.
-keyword_fun(Ind, Feature, Ftrs, KeywordFun) ->
+update_parse_state(Ind, Feature, Ftrs, KeywordFun) ->
case is_configurable(Feature) of
true ->
case Ind of
diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index a1ef3078d9..7c0e6e685e 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -798,6 +798,10 @@ start(File, Opts) ->
false ->
undefined
end,
+ %% note: `-feature declarations are collected and stripped by epp,
+ %% and the compiler presents the total set of enabled features as
+ %% the option `{features, ...}` to erl_lint and other passes; they
+ %% do not change after the epp pass
#lint{state = start,
exports = gb_sets:from_list([{module_info,0},{module_info,1}]),
compile = Opts,
diff --git a/lib/syntax_tools/src/epp_dodger.erl b/lib/syntax_tools/src/epp_dodger.erl
index a660928575..83725cf871 100644
--- a/lib/syntax_tools/src/epp_dodger.erl
+++ b/lib/syntax_tools/src/epp_dodger.erl
@@ -330,10 +330,10 @@ parse_form(Dev, L0, Parser, Options) ->
NoFail = proplists:get_bool(no_fail, Options),
Opt = #opt{clever = proplists:get_bool(clever, Options)},
- %% This has the *potential* to read options for enabling/disabling
- %% features for the parsing of the file.
+ %% Note that options `{feature, FeatureName, enable|disable}` may
+ %% enable or disable features that affect the parsing of the file.
{ok, {_Ftrs, ResWordFun}} =
- erl_features:keyword_fun(Options, fun reserved_word/1),
+ erl_features:init_parse_state(Options, fun reserved_word/1),
case io:scan_erl_form(Dev, "", L0, [{reserved_word_fun,ResWordFun}]) of
{ok, Ts, L1} ->
diff --git a/lib/syntax_tools/src/syntax_tools.app.src b/lib/syntax_tools/src/syntax_tools.app.src
index 6b7d9ab180..2002671264 100644
--- a/lib/syntax_tools/src/syntax_tools.app.src
+++ b/lib/syntax_tools/src/syntax_tools.app.src
@@ -23,4 +23,4 @@
{applications, [stdlib]},
{env, []},
{runtime_dependencies,
- ["compiler-9.0","erts-16.0","kernel-10.3","stdlib-7.0"]}]}.
+ ["compiler-9.0","erts-16.0","kernel-10.3","stdlib-@OTP-19927@"]}]}.
diff --git a/lib/syntax_tools/test/syntax_tools_SUITE.erl b/lib/syntax_tools/test/syntax_tools_SUITE.erl
index 43eb7f011d..fb408e40ef 100644
--- a/lib/syntax_tools/test/syntax_tools_SUITE.erl
+++ b/lib/syntax_tools/test/syntax_tools_SUITE.erl
@@ -786,5 +786,5 @@ p_run_loop(Test, List, N, Refs0, Errors0) ->
res_word_option() ->
Options = [{feature, maybe_expr, enable}],
{ok, {_Ftrs, ResWordFun}} =
- erl_features:keyword_fun(Options, fun erl_scan:f_reserved_word/1),
+ erl_features:init_parse_state(Options, fun erl_scan:f_reserved_word/1),
{reserved_word_fun, ResWordFun}.
--
2.51.0
