[PR #10005/e0a283bb backport][stable-9] Fix method exists in sysrc (#10033)

Fix method exists in sysrc (#10005)

* Fix method exists.

* Add changelog fragment.

* Update the exists method to pass the present method tests.

* Replace f-string formatting.

* Update changelogs/fragments/10005-fix-method-exists-in-sysrc.yml

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

* Add comment to the method exists.

* Update plugins/modules/sysrc.py

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

* Update changelogs/fragments/10005-fix-method-exists-in-sysrc.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

* The improved comment formatting fixed.

---------

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>
Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit e0a283bb36)

Co-authored-by: Vladimir Botka <vbotka@gmail.com>

changelogs/fragments/10005-fix-method-exists-in-sysrc.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - sysrc - no longer always reporting ``changed=true`` when ``state=absent``. This fixes the method ``exists()`` (https://github.com/ansible-collections/community.general/issues/10004, https://github.com/ansible-collections/community.general/pull/10005).

plugins/modules/sysrc.py

@@ -122,14 +122,19 @@ class Sysrc(object):
         return err.find("unknown variable") > 0 or out.find("unknown variable") > 0
 
     def exists(self):
-        # sysrc doesn't really use exit codes
-        (rc, out, err) = self.run_sysrc(self.name)
+        """
+        Tests whether the name is in the file.  If parameter value is defined,
+        then tests whether name=value is in the file.  These tests are necessary
+        because sysrc doesn't use exit codes.  Instead, let sysrc read the
+        file's content and create a dictionary comprising the configuration.
+        Use this dictionary to preform the tests.
+        """
+        (rc, out, err) = self.run_sysrc('-e', '-a')
+        conf = dict([i.split('=') for i in out.splitlines()])
         if self.value is None:
-            regex = "%s: " % re.escape(self.name)
+            return self.name in conf
         else:
-            regex = "%s: %s$" % (re.escape(self.name), re.escape(self.value))
-
-        return not self.has_unknown_variable(out, err) and re.match(regex, out) is not None
+            return self.name in conf and conf[self.name] == '"%s"' % self.value
 
     def contains(self):
         (rc, out, err) = self.run_sysrc('-n', self.name)
@@ -142,12 +147,9 @@ class Sysrc(object):
         if self.exists():
             return
 
-        if self.module.check_mode:
-            self.changed = True
-            return
-
+        if not self.module.check_mode:
             (rc, out, err) = self.run_sysrc("%s=%s" % (self.name, self.value))
-        if out.find("%s:" % self.name) == 0 and re.search("-> %s$" % re.escape(self.value), out) is not None:
+
         self.changed = True
 
     def absent(self):