cover now relies on the compile info to find file sources

Prior to this commit, cover relied on a simple heuristic that
traverses directory from the beam file to find a source file.
The heuristic was maintained with this patch but, if it fails,
it fallbacks to the source value in the module compile info.

In order to illustrate how it works, one of the tests that
could not find its source now passes successfully (showing the
source lookup is more robust).

3 files changed, 33 insertions, 5 deletions

diff --git a/lib/tools/src/cover.erl b/lib/tools/src/cover.erl
index 468225dc13..d7c736b710 100644
--- a/lib/tools/src/cover.erl
+++ b/lib/tools/src/cover.erl
@@ -1945,7 +1945,7 @@ move_clauses([]) ->
 
 %% Given a .beam file, find the .erl file. Look first in same directory as
 %% the .beam file, then in <beamdir>/../src
-find_source(File0) ->
+find_source(Module, File0) ->
     case filename:rootname(File0,".beam") of
 	File0 ->
 	    File0;
@@ -1962,11 +1962,27 @@ find_source(File0) ->
 			true ->
 			    InDotDotSrc;
 			false ->
-			    {beam,File0}
+			    find_source_from_module(Module, File0)
 		    end
 	    end
     end.
 
+%% In case we can't find the file from the given .beam,
+%% we try to get the information directly from the module source
+find_source_from_module(Module, File) ->
+    Compile = Module:module_info(compile),
+    case lists:keyfind(source, 1, Compile) of
+	{source, Path} ->
+	    case filelib:is_file(Path) of
+		true ->
+		    Path;
+		false ->
+		    {beam, File}
+	    end;
+	false ->
+		{beam, File}
+	end.
+
 do_parallel_analysis(Module, Analysis, Level, Loaded, From, State) ->
     analyse_info(Module,State#main_state.imported),
     C = case Loaded of
@@ -2070,7 +2086,7 @@ do_parallel_analysis_to_file(Module, OutFile, Opts, Loaded, From, State) ->
 	       {imported, File0, _} ->
 		   File0
 	   end,
-    case find_source(File) of
+    case find_source(Module, File) of
 	{beam,_BeamFile} ->
 	    reply(From, {error,no_source_code_found});
 	ErlFile ->
diff --git a/lib/tools/test/cover_SUITE.erl b/lib/tools/test/cover_SUITE.erl
index 57260a3869..2156390244 100644
--- a/lib/tools/test/cover_SUITE.erl
+++ b/lib/tools/test/cover_SUITE.erl
@@ -277,12 +277,23 @@ analyse(Config) when is_list(Config) ->
     ?line f:f2(),
     ?line {ok, "f.COVER.out"} = cover:analyse_to_file(f),
 
-    %% Source code cannot be found by analyse_to_file
+    %% Source code can be found via source
     ?line {ok,v} = compile:file("compile_beam/v",[debug_info]),
     ?line code:purge(v),
     ?line {module,v} = code:load_file(v),
     ?line {ok,v} = cover:compile_beam(v),
-    ?line {error,no_source_code_found} = cover:analyse_to_file(v),
+    {ok,"v.COVER.out"} = cover:analyse_to_file(v),
+
+    %% Source code cannot be found
+    {ok,_} = file:copy("compile_beam/z.erl", "z.erl"),
+    {ok,z} = compile:file(z,[debug_info]),
+    code:purge(z),
+    {module,z} = code:load_file(z),
+    {ok,z} = cover:compile_beam(z),
+    ok = file:delete("z.erl"),
+    {error,no_source_code_found} = cover:analyse_to_file(z),
+    code:purge(z),
+    code:delete(z),
 
     ?line {error,{not_cover_compiled,b}} = cover:analyse(b),
     ?line {error,{not_cover_compiled,g}} = cover:analyse(g),
diff --git a/lib/tools/test/cover_SUITE_data/compile_beam/z.erl b/lib/tools/test/cover_SUITE_data/compile_beam/z.erl
new file mode 100644
index 0000000000..7a2b143dde
--- /dev/null
+++ b/lib/tools/test/cover_SUITE_data/compile_beam/z.erl
@@ -0,0 +1 @@
+-module(z).