From c2661efb0bdbf54ee288f50fc49be85ff1714fa8 Mon Sep 17 00:00:00 2001
From: Tom Davies <todavies5@gmail.com>
Date: Mon, 23 Jan 2023 09:00:01 -0800
Subject: [PATCH] dialyzer: Fix crash when adding multiple PLTs to a PLT

The code previously assumed that multiple PLTs would only be used in
combination with an analysis, but adding multiple PLTs to another
without analysis was not considered.

The existing logic for merging PLTs was used in the context of an
analysis, with different data to hand, so here we just validate the
merge, then sequentially add each PLT.
---
 lib/dialyzer/src/dialyzer_cl.erl        | 19 ++++++++++++-----
 lib/dialyzer/test/dialyzer_cl_SUITE.erl | 28 ++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/lib/dialyzer/src/dialyzer_cl.erl b/lib/dialyzer/src/dialyzer_cl.erl
index dd235d90259a..a46336617c5b 100644
--- a/lib/dialyzer/src/dialyzer_cl.erl
+++ b/lib/dialyzer/src/dialyzer_cl.erl
@@ -105,7 +105,16 @@ init_opts_for_build(Opts) ->
 add_to_plt(Opts) ->
   Opts1 = init_opts_for_add(Opts),
   AddFiles = get_files_from_opts(Opts1),
-  plt_common(Opts1, [], AddFiles).
+  case Opts1#options.init_plts of
+    [] -> plt_common(Opts1, [], AddFiles);
+    [_] -> plt_common(Opts1, [], AddFiles);
+    PltFiles ->
+      Plts = [dialyzer_cplt:from_file(F) || F <- PltFiles],
+      % Check merge safety
+      _ = dialyzer_cplt:merge_plts_or_report_conflicts(PltFiles, Plts),
+      _ = [plt_common(Opts#options{init_plts=[Plt]}, [], AddFiles) || Plt <- PltFiles],
+      {{?RET_NOTHING_SUSPICIOUS, []}, [], []}
+  end.
 
 init_opts_for_add(Opts) ->
   case Opts#options.output_plt =:= none of
@@ -229,19 +238,19 @@ plt_common(#options{init_plts = [InitPlt]} = Opts, RemoveFiles, AddFiles) ->
 	  enrich_with_modules_changed(do_analysis(AnalFiles, Opts, Plt, #plt_info{files=Md5, mod_deps=ModDeps1}), ChangedOrRemovedMods)
       end;
     {error, no_such_file} ->
-      Msg = io_lib:format("Could not find the PLT: ~ts\n~s",
+      Msg = io_lib:format("Could not find the PLT: ~ts~n~s",
 			  [InitPlt, default_plt_error_msg()]),
       cl_error(Msg);
     {error, not_valid} ->
-      Msg = io_lib:format("The file: ~ts is not a valid PLT file\n~s",
+      Msg = io_lib:format("The file: ~ts is not a valid PLT file~n~s",
 			  [InitPlt, default_plt_error_msg()]),
       cl_error(Msg);
     {error, read_error} ->
-      Msg = io_lib:format("Could not read the PLT: ~ts\n~s",
+      Msg = io_lib:format("Could not read the PLT: ~ts~n~s",
 			  [InitPlt, default_plt_error_msg()]),
       cl_error(Msg);
     {error, {no_file_to_remove, F}} ->
-      Msg = io_lib:format("Could not remove the file ~ts from the PLT: ~ts\n",
+      Msg = io_lib:format("Could not remove the file ~ts from the PLT: ~ts~n",
 			  [F, InitPlt]),
       cl_error(Msg)
   end.
diff --git a/lib/dialyzer/test/dialyzer_cl_SUITE.erl b/lib/dialyzer/test/dialyzer_cl_SUITE.erl
index ed84fc6068e6..a639b1cae479 100644
--- a/lib/dialyzer/test/dialyzer_cl_SUITE.erl
+++ b/lib/dialyzer/test/dialyzer_cl_SUITE.erl
@@ -9,14 +9,16 @@
 
 %% Test cases must be exported.
 -export([
+    can_add_multiple_plts_to_another_plt/1,
     unknown_function_warning_includes_callsite/1,
     call_to_missing_warning_includes_callsite/1
 ]).
 
-suite() -> [{timetrap, {minutes, 1}}].
+suite() -> [{timetrap, {minutes, 3}}].
 
 all() ->
     [
+        can_add_multiple_plts_to_another_plt,
         unknown_function_warning_includes_callsite,
         call_to_missing_warning_includes_callsite
     ].
@@ -119,6 +121,30 @@ unknown_function_warning_includes_callsite(Config) when is_list(Config) ->
 
     ok.
 
+% See GitHub issue erlang/OTP #6850
+can_add_multiple_plts_to_another_plt(Config) when is_list(Config) ->
+
+    PrivDir = proplists:get_value(priv_dir,Config),
+
+    StdlibPlt = filename:join(PrivDir, "stdlib.plt"),
+    ErtsPlt = filename:join(PrivDir, "erts.plt"),
+    OutputPlt = filename:join(PrivDir, "merged.plt"),
+
+    _ = dialyzer:run([{analysis_type, plt_build},
+                      {apps, [stdlib]},
+                      {output_plt, StdlibPlt}]),
+    _ = dialyzer:run([{analysis_type, plt_build},
+                      {apps, [erts]},
+                      {output_plt, ErtsPlt}]),
+    ?assertEqual(
+       [],
+       dialyzer:run([{analysis_type, plt_add},
+                     {apps, [erts, stdlib]},
+                     {plts, [ErtsPlt, StdlibPlt]},
+                     {output_plt, OutputPlt}])),
+
+    ok.
+
 compile(Config, Module, CompileOpts) ->
     Source = lists:concat([Module, ".erl"]),
     PrivDir = proplists:get_value(priv_dir,Config),