From afab4d67891337527c499c7a5618445bc223b1af Mon Sep 17 00:00:00 2001
From: "Martin T. H. Sandsmark" <martin.sandsmark@kde.org>
Date: Wed, 9 Oct 2019 12:45:10 +0200
Subject: Allow matching on empty properties (class, title, etc.)

Fixes #3308
---
 src/match.c             |  8 +++-----
 testcases/t/119-match.t | 18 +++++++++++++++---
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/match.c b/src/match.c
index 83e37327..f65d8059 100644
--- a/src/match.c
+++ b/src/match.c
@@ -92,11 +92,9 @@ bool match_matches_window(Match *match, i3Window *window) {
 #define CHECK_WINDOW_FIELD(match_field, window_field, type)                                       \
     do {                                                                                          \
         if (match->match_field != NULL) {                                                         \
-            if (window->window_field == NULL) {                                                   \
-                return false;                                                                     \
-            }                                                                                     \
-                                                                                                  \
-            const char *window_field_str = GET_FIELD_##type(window->window_field);                \
+            const char *window_field_str = window->window_field == NULL                           \
+                                               ? ""                                               \
+                                               : GET_FIELD_##type(window->window_field);          \
             if (strcmp(match->match_field->pattern, "__focused__") == 0 &&                        \
                 focused && focused->window && focused->window->window_field &&                    \
                 strcmp(window_field_str, GET_FIELD_##type(focused->window->window_field)) == 0) { \
diff --git a/testcases/t/119-match.t b/testcases/t/119-match.t
index 64ffa4ed..65c41f1f 100644
--- a/testcases/t/119-match.t
+++ b/testcases/t/119-match.t
@@ -33,9 +33,7 @@ my $win = $content->[0];
 # not match it
 ######################################################################
 # TODO: specify more match types
-# we can match on any (non-empty) class here since that window does not have
-# WM_CLASS set
-cmd q|[class=".*"] kill|;
+# Try matching with an empty pattern since there isn't a WM_CLASS set.
 cmd q|[con_id="99999"] kill|;
 
 is_num_children($tmp, 1, 'window still there');
@@ -103,4 +101,18 @@ cmd '[title="^\w [3]$"] kill';
 wait_for_unmap $left;
 is_num_children($tmp, 0, 'window killed');
 
+######################################################################
+# check that we can match empty properties
+######################################################################
+
+$tmp = fresh_workspace;
+
+$left = open_window(name => 'class is empty', wm_class => '');
+ok($left->mapped, 'left window mapped');
+is_num_children($tmp, 1, 'window opened');
+
+cmd '[class="^$"] kill';
+wait_for_unmap $left;
+is_num_children($tmp, 0, 'window killed');
+
 done_testing;
-- 
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