edoc, syntax_tools: Don't fail on invalid UTF-8

As a temporary measure to ease the transition to default UTF-8
encoding, automatically fall back to the Latin-1 encoding (without any
warnings; the Erlang Compiler will emit a proper warning).

The intention is to remove this workaround in OTP 18 or 19.

7 files changed, 114 insertions, 7 deletions

diff --git a/lib/edoc/src/edoc.erl b/lib/edoc/src/edoc.erl
index a87a8471e3..983f04e8b6 100644
--- a/lib/edoc/src/edoc.erl
+++ b/lib/edoc/src/edoc.erl
@@ -696,15 +696,44 @@ read_source_2(Name, Opts) ->
 %% The line of the dot token will be copied to the integer token.
 
 parse_file(Name, Includes, Macros) ->
-    case epp:open(Name, Includes, Macros) of
-        {ok, Epp} ->
-            try {ok, parse_file(Epp)}
+    case parse_file(utf8, Name, Includes, Macros) of
+        invalid_unicode ->
+            parse_file(latin1, Name, Includes, Macros);
+        Ret ->
+            Ret
+    end.
+
+parse_file(DefEncoding, Name, Includes, Macros) ->
+    Options = [{name, Name},
+               {includes, Includes},
+               {macros, Macros},
+               {default_encoding, DefEncoding}],
+    case epp:open([extra | Options]) of
+        {ok, Epp, Extra} ->
+            try parse_file(Epp) of
+                Forms ->
+                    Encoding = proplists:get_value(encoding, Extra),
+                    case find_invalid_unicode(Forms) of
+                        invalid_unicode when Encoding =/= utf8 ->
+                            invalid_unicode;
+                        _ ->
+                            {ok, Forms}
+                    end
             after _ = epp:close(Epp)
             end;
         Error ->
             Error
     end.
 
+find_invalid_unicode([H|T]) ->
+    case H of
+	{error,{_Line,file_io_server,invalid_unicode}} ->
+	    invalid_unicode;
+	_Other ->
+	    find_invalid_unicode(T)
+    end;
+find_invalid_unicode([]) -> none.
+
 parse_file(Epp) ->
     case scan_and_parse(Epp) of
 	{ok, Form} ->
diff --git a/lib/edoc/test/edoc_SUITE.erl b/lib/edoc/test/edoc_SUITE.erl
index c9c7811afb..c63660c8c0 100644
--- a/lib/edoc/test/edoc_SUITE.erl
+++ b/lib/edoc/test/edoc_SUITE.erl
@@ -22,12 +22,12 @@
 	 init_per_group/2,end_per_group/2]).
 
 %% Test cases
--export([app/1,appup/1,build_std/1,build_map_module/1]).
+-export([app/1,appup/1,build_std/1,build_map_module/1,otp_12008/1]).
 
 suite() -> [{ct_hooks,[ts_install_cth]}].
 
 all() -> 
-    [app,appup,build_std,build_map_module].
+    [app,appup,build_std,build_map_module,otp_12008].
 
 groups() -> 
     [].
@@ -77,3 +77,21 @@ build_map_module(Config) when is_list(Config) ->
     Filename = filename:join(DataDir, "map_module.erl"),
     ok = edoc:file(Filename, [{dir, PrivDir}]),
     ok.
+
+otp_12008(Config) when is_list(Config) ->
+    DataDir  = ?config(data_dir, Config),
+    PrivDir  = ?config(priv_dir, Config),
+    Un1 = filename:join(DataDir, "un1.erl"),
+    Un2 = filename:join(DataDir, "un2.erl"),
+    Un3 = filename:join(DataDir, "un3.erl"),
+    %% epp_dodger
+    Opts1 = [{dir, PrivDir}],
+    ok = edoc:files([Un1], Opts1),
+    ok = edoc:files([Un2], Opts1),
+    {'EXIT', error} = (catch edoc:files([Un3], Opts1)),
+    %% epp
+    Opts2 = [{preprocess, true}, {dir, PrivDir}],
+    ok = edoc:files([Un1], Opts2),
+    ok = edoc:files([Un2], Opts2),
+    {'EXIT', error} = (catch edoc:files([Un3], Opts2)),
+    ok.
diff --git a/lib/edoc/test/edoc_SUITE_data/un1.erl b/lib/edoc/test/edoc_SUITE_data/un1.erl
new file mode 100644
index 0000000000..0c48e7f940
--- /dev/null
+++ b/lib/edoc/test/edoc_SUITE_data/un1.erl
@@ -0,0 +1,7 @@
+-module(un1).
+
+-export([t/0]).
+
+%% @doc F�pp
+t() ->
+    �rlig.
diff --git a/lib/edoc/test/edoc_SUITE_data/un2.erl b/lib/edoc/test/edoc_SUITE_data/un2.erl
new file mode 100644
index 0000000000..a6d13f4723
--- /dev/null
+++ b/lib/edoc/test/edoc_SUITE_data/un2.erl
@@ -0,0 +1,8 @@
+-module(un2).
+%% coding: latin-1
+
+-export([t/0]).
+
+%% @doc F�pp
+t() ->
+    �rlig.
diff --git a/lib/edoc/test/edoc_SUITE_data/un3.erl b/lib/edoc/test/edoc_SUITE_data/un3.erl
new file mode 100644
index 0000000000..fbe9591dce
--- /dev/null
+++ b/lib/edoc/test/edoc_SUITE_data/un3.erl
@@ -0,0 +1,8 @@
+-module(un3).
+%% coding: utf-8
+
+-export([t/0]).
+
+%% @doc F�pp
+t() ->
+    �rlig.
diff --git a/lib/syntax_tools/src/epp_dodger.erl b/lib/syntax_tools/src/epp_dodger.erl
index 131be4e8e4..7e12eab1b5 100644
--- a/lib/syntax_tools/src/epp_dodger.erl
+++ b/lib/syntax_tools/src/epp_dodger.erl
@@ -184,9 +184,27 @@ quick_parse_file(File, Options) ->
     parse_file(File, fun quick_parse/3, Options ++ [no_fail]).
 
 parse_file(File, Parser, Options) ->
+    case do_parse_file(utf8, File, Parser, Options) of
+        {ok, Forms}=Ret ->
+            case find_invalid_unicode(Forms) of
+                none ->
+                    Ret;
+                invalid_unicode ->
+                    case epp:read_encoding(File) of
+                        utf8 ->
+                            Ret;
+                        _ ->
+                            do_parse_file(latin1, File, Parser, Options)
+                    end
+            end;
+        Else ->
+            Else
+    end.
+
+do_parse_file(DefEncoding, File, Parser, Options) ->
     case file:open(File, [read]) of
         {ok, Dev} ->
-            _ = epp:set_encoding(Dev),
+            _ = epp:set_encoding(Dev, DefEncoding),
             try Parser(Dev, 1, Options)
             after ok = file:close(Dev)
 	    end;
@@ -194,6 +212,14 @@ parse_file(File, Parser, Options) ->
             Error
     end.
 
+find_invalid_unicode([H|T]) ->
+    case H of
+	{error, {_Line, file_io_server, invalid_unicode}} ->
+	    invalid_unicode;
+	_Other ->
+	    find_invalid_unicode(T)
+    end;
+find_invalid_unicode([]) -> none.
 
 %% =====================================================================
 %% @spec parse(IODevice) -> {ok, Forms} | {error, errorinfo()}
diff --git a/lib/syntax_tools/src/erl_comment_scan.erl b/lib/syntax_tools/src/erl_comment_scan.erl
index dae7530ce7..03429d4d42 100644
--- a/lib/syntax_tools/src/erl_comment_scan.erl
+++ b/lib/syntax_tools/src/erl_comment_scan.erl
@@ -72,13 +72,24 @@ file(Name) ->
 	{ok, V} ->
 	    case V of
 		{ok, B} ->
-                    Enc = case epp:read_encoding(Name) of
+                    Encoding = epp:read_encoding_from_binary(B),
+                    Enc = case Encoding of
                               none -> epp:default_encoding();
                               Enc0 -> Enc0
                           end,
                     case catch unicode:characters_to_list(B, Enc) of
                         String when is_list(String) ->
                             string(String);
+                        R when Encoding =:= none ->
+                            case
+                              catch unicode:characters_to_list(B, latin1)
+                            of
+                                String when is_list(String) ->
+                                    string(String);
+                                _ ->
+                                    error_read_file(Name1),
+                                    exit(R)
+                            end;
                         R ->
                             error_read_file(Name1),
                             exit(R)