cover: handle undefined module when analysing to file

It is possible that not just the source but even the beam of a module
is not available when calling analyse_to_file.

For example when coverdata is imported from an old file and since then
a module was removed.

Before this fix cover:analyse_to_file/3 could possibly never return
because of a helper process crashed with error:undef and never reply
to the caller.

At the same time link the helper process to cover_server so any
further error won't let the caller waiting indefinitely.

2 files changed, 47 insertions, 2 deletions

diff --git a/lib/tools/test/cover_SUITE.erl b/lib/tools/test/cover_SUITE.erl
index 368fa6c3d1..bc85f3c045 100644
--- a/lib/tools/test/cover_SUITE.erl
+++ b/lib/tools/test/cover_SUITE.erl
@@ -29,7 +29,8 @@
 	 export_import/1,
 	 otp_5031/1, eif/1, otp_5305/1, otp_5418/1, otp_6115/1, otp_7095/1,
          otp_8188/1, otp_8270/1, otp_8273/1, otp_8340/1,
-	 otp_10979_hanging_node/1, compile_beam_opts/1, eep37/1]).
+         otp_10979_hanging_node/1, compile_beam_opts/1, eep37/1,
+         analyse_no_beam/1]).
 
 -export([do_coverage/1]).
 
@@ -52,7 +53,8 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
 
 all() -> 
     NoStartStop = [eif,otp_5305,otp_5418,otp_7095,otp_8273,
-		   otp_8340,otp_8188,compile_beam_opts,eep37],
+                   otp_8340,otp_8188,compile_beam_opts,eep37,
+		   analyse_no_beam],
     StartStop = [start, compile, analyse, misc, stop,
 		 distribution, reconnect, die_and_reconnect,
 		 dont_reconnect_after_stop, stop_node_after_disconnect,
@@ -1687,6 +1689,43 @@ compile_beam_opts(Config) when is_list(Config) ->
     ok = file:set_cwd(Cwd),
     ok.
 
+analyse_no_beam(doc) ->
+    ["Don't crash if beam is not available"];
+analyse_no_beam(suite) -> [];
+analyse_no_beam(Config) when is_list(Config) ->
+    {ok, Cwd} = file:get_cwd(),
+    ok = file:set_cwd(?config(data_dir, Config)),
+
+    code:purge(t),
+    code:delete(t),
+
+    {ok,_} = file:copy("compile_beam/t.erl", "t.erl"),
+    {ok,t} = compile:file(t, [debug_info]),
+    {module,t} = code:load_file(t),
+    {ok,t} = cover:compile_beam(t),
+    t:f(),
+    ok = cover:export("t.coverdata"),
+
+    code:purge(t),
+    code:delete(t),
+
+    %% this is just so that cover realises (without stopping)
+    %% that this module is not cover compiled any more
+    {error, {not_cover_compiled,t}} = cover:analyse(t),
+
+    %% source and beam not available any more
+    ok = file:delete("t.erl"),
+    ok = file:delete("t.beam"),
+
+    ok = cover:import("t.coverdata"),
+
+    {error,{no_source_code_found,t}} = cover:analyse_to_file(t),
+    {result,[],[{no_source_code_found,t}]} = cover:analyse_to_file([t]),
+
+    ok = file:delete("t.coverdata"),
+    ok = file:set_cwd(Cwd),
+    ok.
+
 %%--Auxiliary------------------------------------------------------------
 
 analyse_expr(Expr, Config) ->
diff --git a/lib/tools/test/cover_SUITE_data/compile_beam/t.erl b/lib/tools/test/cover_SUITE_data/compile_beam/t.erl
new file mode 100644
index 0000000000..96dc2f4209
--- /dev/null
+++ b/lib/tools/test/cover_SUITE_data/compile_beam/t.erl
@@ -0,0 +1,6 @@
+-module(t).
+
+-export([f/0]).
+
+f() ->
+    ok.