create_workspace_on_output: send workspace init event

Fixes #3595
Like the issue mentions:
> instead of the newly created workspace (not referenced by variable
> here) the `"init"` event is fired with the current workspace (`ws`).

Plus, there was another issue where duplicate workspace init events
where being sent because of workspace_get().

304-ipc-workspace-init.t: Subtest "move workspace to output" fails with
current next.

Fixes #3631
No event was being sent here:
2d6e09a66a/src/randr.c (L487)

533-randr15.t: I confirmed that SKIP still works if the xrandr command
fails.
Added test fails with current next.

src/workspace.c

@@ -289,6 +289,7 @@ Con *create_workspace_on_output(Output *output, Con *content) {
     ws->workspace_layout = config.default_layout;
     _workspace_apply_default_orientation(ws);
 
+    ipc_send_workspace_event("init", ws, NULL);
     return ws;
 }
 
@@ -1004,13 +1005,11 @@ bool workspace_move_to_output(Con *ws, Output *output) {
             break;
         }
 
-        /* if we couldn't create the workspace using an assignment, create
-         * it on the output */
+        /* if we couldn't create the workspace using an assignment, create it on
+         * the output. Workspace init IPC events are sent either by
+         * workspace_get or create_workspace_on_output. */
         if (!used_assignment)
             create_workspace_on_output(current_output, ws->parent);
-
-        /* notify the IPC listeners */
-        ipc_send_workspace_event("init", ws, NULL);
     }
     DLOG("Detaching\n");
 

testcases/t/304-ipc-workspace-init.t

@@ -0,0 +1,69 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • https://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • https://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • https://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Test that the workspace init event is correctly sent.
+# Ticket: #3631
+# Bug still in: 4.16-85-g2d6e09a6
+
+use i3test i3_config => <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+# fake-1 under fake-0 to not interfere with left/right wraping
+fake-outputs 1024x768+0+0,1024x768+0+1024
+workspace X output fake-1
+EOT
+
+sub workspace_init_subtest {
+    my $cmd = shift;
+    my $num_events = shift;
+    my @events = events_for(sub { cmd $cmd }, 'workspace');
+
+    my @init = grep { $_->{change} eq 'init' } @events;
+    my $len = scalar @init;
+    is($len, $num_events, "Received $num_events workspace::init event");
+    $num_events = $len if $len < $num_events;
+    for my $idx (0 .. $num_events - 1) {
+        my $name = shift;
+        my $output = shift;
+        is($init[$idx]->{current}->{name}, $name, "workspace name $name matches");
+        is($init[$idx]->{current}->{output}, $output, "workspace output $output matches");
+    }
+}
+
+subtest 'focus outputs', \&workspace_init_subtest, 'focus output fake-1, focus output fake-0', 0;
+subtest 'new workspaces', \&workspace_init_subtest,
+  'workspace a, workspace b, workspace a, workspace a', 3, 'a',
+  'fake-0', 'b', 'fake-0', 'a', 'fake-0';
+open_window;    # Prevent workspace "a" from being deleted.
+subtest 'return on existing workspace', \&workspace_init_subtest,
+  'workspace a, workspace b, workspace a', 1, 'b', 'fake-0';
+subtest 'assigned workspace is already open', \&workspace_init_subtest,
+  'workspace X, workspace b, workspace a', 1, 'b', 'fake-1';
+subtest 'assigned workspace was deleted and now is initialized again', \&workspace_init_subtest,
+  'workspace X, workspace b, workspace a', 2, 'X', 'fake-1', 'b', 'fake-1';
+subtest 'move workspace to output', \&workspace_init_subtest,
+  'move workspace to output fake-1, move workspace to output fake-0', 2, '1', 'fake-0', 'X',
+  'fake-1';
+subtest 'move window to workspace', \&workspace_init_subtest, 'move to workspace b', 1, 'b',
+  'fake-0';
+subtest 'back_and_forth', \&workspace_init_subtest,
+  'workspace b, workspace back_and_forth, workspace b', 1,
+  'a', 'fake-0';
+subtest 'move window to workspace back_and_forth', \&workspace_init_subtest,
+  'move window to workspace back_and_forth', 1, 'a', 'fake-0';
+
+done_testing;

testcases/t/533-randr15.t

@@ -130,10 +130,16 @@ $tree = i3->get_tree->recv;
 is_deeply(\@outputs, [ '__i3', 'default' ], 'outputs are __i3 and default');
 
 SKIP: {
-    skip 'xrandr --setmonitor failed (xrandr too old?)', 1 unless
-        system(q|xrandr --setmonitor up2414q 3840/527x2160/296+1280+0 none|) == 0;
+    my @events = events_for(
+        sub {
+            skip 'xrandr --setmonitor failed (xrandr too old?)', 1
+              unless system(q|xrandr --setmonitor up2414q 3840/527x2160/296+1280+0 none|) == 0;
+        },
+        "workspace");
 
-    sync_with_i3;
+    my @init = grep { $_->{change} eq 'init' } @events;
+    is(scalar @init, 1, 'Received 1 workspace::init event');
+    is($init[0]->{current}->{output}, 'up2414q', 'Workspace initialized in up2414q');
 
     $tree = i3->get_tree->recv;
     @outputs = map { $_->{name} } @{$tree->{nodes}};