ct_logs: Eliminate dialyzer warnings

common_test uses its own IO server that is group leader for the
test case processes. By default, the IO server escapes characters
with significance to HTML (e.g. '<'). In order to output HTML
tags directly, the IO server must be told not to escape the output.
The way to tell the IO server is to wrap the format string like this:

  ["$ct_html",Format]

That works with common_test's own IO server, but in general not
with other IO servers. Dialyzer will rightly complain that the
call breaks the contract for io:format/3.

To avoid the Dialyzer warning, we must obscure the wrapping of
the format string.

While we are at it, also refactor print_style/4 to make the code
somewhat cleaner and shorter.

1 files changed, 42 insertions, 24 deletions

diff --git a/lib/common_test/src/ct_logs.erl b/lib/common_test/src/ct_logs.erl
index 29b38e9748..e6d683c8a9 100644
--- a/lib/common_test/src/ct_logs.erl
+++ b/lib/common_test/src/ct_logs.erl
@@ -269,7 +269,7 @@ cast(Msg) ->
 %%% <p>This function is called by ct_framework:init_tc/3</p>
 init_tc(RefreshLog) ->
     call({init_tc,self(),group_leader(),RefreshLog}),
-    io:format(["$tc_html",xhtml("", "<br />")]),
+    tc_io_format(group_leader(), xhtml("", "<br />"), []),
     ok.
 
 %%%-----------------------------------------------------------------
@@ -800,7 +800,8 @@ logger_loop(State) ->
 	    %% make sure no IO for this test case from the
 	    %% CT logger gets rejected
 	    test_server:permit_io(GL, self()),
-	    print_style(GL,GL,State#logger_state.stylesheet),
+	    IoFormat = fun tc_io_format/3,
+	    print_style(GL, IoFormat, State#logger_state.stylesheet),
 	    set_evmgr_gl(GL),
 	    TCGLs = add_tc_gl(TCPid,GL,State),
 	    if not RefreshLog ->
@@ -931,7 +932,7 @@ print_to_log(sync, FromPid, Category, TCGL, Content, EscChars, State) ->
     if FromPid /= TCGL ->
 	    IoFun = create_io_fun(FromPid, CtLogFd, EscChars),
 	    IoList = lists:foldl(IoFun, [], Content),
-	    try io:format(TCGL,["$tc_html","~ts"], [IoList]) of
+	    try tc_io_format(TCGL, "~ts", [IoList]) of
 		ok -> ok
 	    catch
 		_:_ ->
@@ -962,7 +963,7 @@ print_to_log(async, FromPid, Category, TCGL, Content, EscChars, State) ->
 
 			case erlang:is_process_alive(TCGL) of
 			    true ->
-				try io:format(TCGL, ["$tc_html","~ts"],
+				try tc_io_format(TCGL, "~ts",
 					      [lists:foldl(IoFun,[],Content)]) of
 				    _ -> ok
 				catch
@@ -1113,27 +1114,25 @@ open_ctlog(MiscIoName) ->
 	      "View I/O logged after the test run</a></li>\n</ul>\n",
 	      [MiscIoName,MiscIoName]),
 
-    print_style(Fd,group_leader(),undefined),
+    print_style(Fd, fun io:format/3, undefined),
     io:format(Fd, 
 	      xhtml("<br><h2>Progress Log</h2>\n<pre>\n",
 		    "<br />\n<h4>PROGRESS LOG</h4>\n<pre>\n"), []),
     Fd.
 
-print_style(Fd,GL,undefined) ->
+print_style(Fd, IoFormat, undefined) ->
     case basic_html() of
 	true ->
 	    Style = "<style>\n
 		div.ct_internal { background:lightgrey; color:black; }\n
 		div.default     { background:lightgreen; color:black; }\n
 		</style>\n",
-	    if Fd == GL -> io:format(["$tc_html",Style], []);
-	       true     -> io:format(Fd, Style, [])
-	    end;
+	    IoFormat(Fd, Style, []);
 	_ ->
 	    ok
     end;
 
-print_style(Fd,GL,StyleSheet) ->
+print_style(Fd, IoFormat, StyleSheet) ->
     case file:read_file(StyleSheet) of
 	{ok,Bin} ->
 	    Str = b2s(Bin,encoding(StyleSheet)),
@@ -1146,36 +1145,55 @@ print_style(Fd,GL,StyleSheet) ->
 		       N1 -> N1
 		   end,
 	    if (Pos0 == 0) and (Pos1 /= 0) ->
-		    print_style_error(Fd,GL,StyleSheet,missing_style_start_tag);
+		    print_style_error(Fd, IoFormat,
+				      StyleSheet, missing_style_start_tag);
 	       (Pos0 /= 0) and (Pos1 == 0) ->
-		    print_style_error(Fd,GL,StyleSheet,missing_style_end_tag);
+		    print_style_error(Fd, IoFormat,
+				      StyleSheet,missing_style_end_tag);
 	       Pos0 /= 0 ->
 		    Style = string:sub_string(Str,Pos0,Pos1+7),
-		    if Fd == GL -> io:format(Fd,["$tc_html","~ts\n"],[Style]);
-		       true     -> io:format(Fd,"~ts\n",[Style])
-		    end;
+		    IoFormat(Fd,"~ts\n",[Style]);
 	       Pos0 == 0 ->
-		    if Fd == GL -> io:format(Fd,["$tc_html","<style>\n~ts</style>\n"],[Str]);
-		       true     -> io:format(Fd,"<style>\n~ts</style>\n",[Str])
-		    end
+		    IoFormat(Fd,"<style>\n~ts</style>\n",[Str])
 	    end;
 	{error,Reason} ->
-	    print_style_error(Fd,GL,StyleSheet,Reason)  
+	    print_style_error(Fd,IoFormat,StyleSheet,Reason)
     end.
 
-print_style_error(Fd,GL,StyleSheet,Reason) ->
+print_style_error(Fd, IoFormat, StyleSheet, Reason) ->
     IO = io_lib:format("\n<!-- Failed to load stylesheet ~ts: ~p -->\n",
 		       [StyleSheet,Reason]),
-    if Fd == GL -> io:format(Fd,["$tc_html",IO],[]);
-       true     -> io:format(Fd,IO,[])
-    end,
-    print_style(Fd,GL,undefined).    
+    IoFormat(Fd, IO, []),
+    print_style(Fd, IoFormat, undefined).
 
 close_ctlog(Fd) ->
     io:format(Fd, "\n</pre>\n", []),
     io:format(Fd, [xhtml("<br><br>\n", "<br /><br />\n") | footer()], []),
     file:close(Fd).
 
+%%%-----------------------------------------------------------------
+%%% tc_io_format/3
+%%% Tell common_test's IO server (group leader) not to escape
+%%% HTML characters.
+
+-spec tc_io_format(io:device(), io:format(), [term()]) -> 'ok'.
+
+tc_io_format(Fd, Format0, Args) ->
+    %% We know that the specially wrapped format string is handled
+    %% by our IO server, but Dialyzer does not and would tell us
+    %% that the call to io:format/3 would fail. Therefore, we must
+    %% fool dialyzer.
+
+    Format = case cloaked_true() of
+		 true -> ["$tc_html",Format0];
+		 false -> Format0		%Never happens.
+	     end,
+    io:format(Fd, Format, Args).
+
+%% Return 'true', but let dialyzer think that a boolean is returned.
+cloaked_true() ->
+    is_process_alive(self()).
+
 
 %%%-----------------------------------------------------------------
 %%% Make an index page for the last run