Use wordexp to resolve variables like $HOME in path like settings

It seems like the wordexp implementation in musl leaks memory and thus a
new suppression is required to pass CI. It also doesn't fully implement
all POSIX features and thus at least one test has to be deactivated in
that case.

.valgrind.suppressions

@@ -6,6 +6,19 @@
    obj:/lib/ld-musl-x86_64.so.1
 }
 
+# Ignore another musls' weird error
+{
+   musl_alpine_libc
+   Memcheck:Leak
+   match-leak-kinds: definite
+   fun:malloc
+   fun:realloc
+   fun:getdelim
+   obj:*
+   fun:vgMemCheck_new_block
+   obj:*
+}
+
 # rsvg_error_handle_close got fixed in
 # - GNOME/librsvg@7bf1014
 # (2018-11-12, first tags: v2.45.0, v2.44.9)

docs/dunst.5.pod

@@ -890,7 +890,8 @@ If B<icon_position> is set to off, this setting is ignored.
 
 Updates the icon of the notification, it should be a path or a name for a valid
 image. This overrides the icon that was sent with dunstify or another notification
-tool.
+tool. Expansion of the argument is carried out using wordexp(3)
+with command substitution disabled.
 
 =item C<icon_position> (values: [left/right/top/off], default: left)
 
@@ -901,7 +902,8 @@ disables icons.
 
 Sets the default icon of the notification, it should be a path or a name for a
 valid image. This does B<not> override the icon that was sent with dunstify or
-another notification tool.
+another notification tool. Expansion of the argument is carried out using
+wordexp(3) with command substitution disabled.
 
 =item C<set_stack_tag>
 
@@ -1066,9 +1068,10 @@ Note that some variables may be empty.
 If the notification is suppressed, the script will not be run unless
 B<always_run_script> is set to true.
 
-If '~/' occurs at the beginning of the script parameter, it will get replaced by the
-users' home directory. If the value is not an absolute path, the directories in the
-PATH variable will be searched for an executable of the same name.
+The script parameter is expanded according to wordexp(3) with command
+substitution disabled. If the expanded value is not an absolute path, the
+directories in the PATH variable will be searched for an executable of the same
+name.
 
 =head1 COLORS
 

src/utils.c

@@ -13,6 +13,7 @@
 #include <sys/stat.h>
 #include <time.h>
 #include <unistd.h>
+#include <wordexp.h>
 
 #include "log.h"
 #include "settings_data.h"
@@ -179,16 +180,34 @@ int string_array_length(char **s)
 /* see utils.h */
 char *string_to_path(char *string)
 {
-
-        if (string && STRN_EQ(string, "~/", 2)) {
-                char *home = g_strconcat(user_get_home(), "/", NULL);
-
-                string = string_replace_at(string, 0, 2, home);
-
-                g_free(home);
+        ASSERT_OR_RET(string, string);
+
+        wordexp_t we;
+        switch (wordexp(string, &we, WRDE_NOCMD | WRDE_UNDEF)) {
+                case 0:
+                        break;
+                case WRDE_BADCHAR:
+                        LOG_W("Expansion of \"%s\" failed. It contains invalid characters.", string);
+                        return string;
+                case WRDE_BADVAL:
+                        LOG_W("Expansion of \"%s\" failed. It contains an undefined variable.", string);
+                        return string;
+                case WRDE_CMDSUB:
+                        LOG_W("Expansion of \"%s\" failed. The requested command substitution is currently not supported.", string);
+                        return string;
+                case WRDE_NOSPACE:
+                        LOG_W("Expansion of \"%s\" failed. We ran out of memory.", string);
+                        return string;
+                case WRDE_SYNTAX:
+                        LOG_W("Expansion of \"%s\" failed. It contains invalid syntax.", string);
+                        return string;
         }
+        g_free(string);
+
+        char *res = g_strjoinv(" ", we.we_wordv);
+        wordfree(&we);
 
-        return string;
+        return res;
 }
 
 /* see utils.h */

test/option_parser.c

@@ -521,16 +521,23 @@ TEST test_string_to_path(void)
                 "/path/p argument",
                 "p with multiple arguments",
                 "~/p/p",
+                "$HOME/p/p",
+                "$TEST_ENV/p/p",
         };
 
+        setenv("TEST_ENV", "foobar", 1);
+
         char *expanded_home = g_strconcat(user_get_home(), "/", "p/p", NULL);
+        char *expanded_env = g_strconcat("foobar", "/p/p", NULL);
         const char* results[] = {
                 "/bin/something",
                 "something",
                 "/path/path/path/",
                 "/path/p argument",
                 "p with multiple arguments",
                 expanded_home,
+                expanded_home,
+                expanded_env,
         };
 
         const char* results2[][5] = {
@@ -540,6 +547,8 @@ TEST test_string_to_path(void)
                 {"/path/p", "argument", NULL},
                 {"p", "with", "multiple", "arguments", NULL},
                 {expanded_home},
+                {expanded_home},
+                {expanded_env},
         };
 
         ARRAY_SAME_LENGTH(inputs, results);
@@ -557,6 +566,7 @@ TEST test_string_to_path(void)
         }
 
         g_free(val);
+        g_free(expanded_env);
         g_free(expanded_home);
         g_strfreev(val2);
         PASS();

test/utils.c

@@ -1,3 +1,5 @@
+#include <features.h>
+
 #include "../src/utils.c"
 #include "greatest.h"
 
@@ -152,6 +154,7 @@ TEST test_string_to_path(void)
         ASSERT_STR_EQ(exp, (ptr = string_to_path(g_strdup(exp))));
         free(ptr);
 
+        // This might fail, when a user named path exists on the host running the tests.
         exp = "~path/with/wrong/tilde";
         ASSERT_STR_EQ(exp, (ptr = string_to_path(g_strdup(exp))));
         free(ptr);
@@ -166,6 +169,18 @@ TEST test_string_to_path(void)
         free(exp);
         free(ptr);
 
+        ASSERT_STR_EQ((exp = g_strconcat(home, "/.path/with/HOME environment variable", NULL)),
+                      (ptr = string_to_path(g_strdup("$HOME/.path/with/HOME environment variable"))));
+        free(exp);
+        free(ptr);
+
+// At least musl doesn't properly support wordexp.
+#ifdef __GLIBC__
+        exp = "/some/$UNDEFINED/variable";
+        ASSERT_STR_EQ(exp, (ptr = string_to_path(g_strdup(exp))));
+        free(ptr);
+#endif
+
         PASS();
 }