Improve battery.el UPower support

For discussion, see the following threads:
https://lists.gnu.org/archive/html/emacs-devel/2020-01/msg00843.html
https://lists.gnu.org/archive/html/emacs-devel/2020-02/msg00042.html
https://lists.gnu.org/archive/html/emacs-devel/2020-02/msg00282.html

* etc/NEWS: Announce that battery-upower is enabled by default.

* lisp/battery.el (battery-upower-device): Accept both battery and
line power device names, or a list thereof (bug#39491).
(battery-upower-line-power-device): Remove user option; superseded
by battery-upower-device.
(battery-upower-subscribe): New user option.
(battery-status-function): Check whether a UPower service is
provided without activating it.
(display-battery-mode): Subscribe to UPower signals when using
battery-upower.
(battery-upower): Merge data from multiple power sources.  Calculate
terse battery status %b based on average battery load percentage
rather than coarse and often missing BatteryLevel (bug#39491).  Add
support for average temperature %d.

(battery-upower-dbus-service)
(battery-upower-dbus-interface)
(battery-upower-dbus-path)
(battery-upower-dbus-device-interface)
(battery-upower-dbus-device-path)
(battery-upower-device-all-properties): Rename to...
(battery-upower-service)
(battery-upower-interface)
(battery-upower-path)
(battery-upower-device-interface)
(battery-upower-device-path)
(battery--upower-device-properties): ...these, respectively.

(battery-upower-device-list): Rename to...
(battery--upower-devices) ...this.  Return a flat list of device
names determined by battery-upower-device.
(battery-upower-types, battery-upower-states)
(battery-upower-device-property, battery-upower-device-autodetect):
Remove.
(battery--upower-signals): New variable.
(battery--upower-signal-handler, battery--upower-props-changed)
(battery--upower-unsubscribe, battery--upower-subsribe)
(battery--upower-state): New functions.

* test/lisp/battery-tests.el (battery-upower-state)
(battery-upower-state-unknown): New tests.

1 files changed, 63 insertions, 0 deletions

diff --git a/test/lisp/battery-tests.el b/test/lisp/battery-tests.el
index 92ab013f040..8d7cc7fccf3 100644
--- a/test/lisp/battery-tests.el
+++ b/test/lisp/battery-tests.el
@@ -81,6 +81,69 @@
     (should (equal (match-string 2 str) "mWh")))
   (should-not (string-match (rx battery--acpi-capacity eos) "45 mW")))
 
+(ert-deftest battery-upower-state ()
+  "Test `battery--upower-state'."
+  ;; Charging.
+  (dolist (total '(nil charging discharging empty fully-charged
+                       pending-charge pending-discharge))
+    (should (eq (battery--upower-state '(("State" . 1)) total) 'charging)))
+  (dolist (state '(nil 0 1 2 3 4 5 6))
+    (should (eq (battery--upower-state `(("State" . ,state)) 'charging)
+                'charging)))
+  ;; Discharging.
+  (dolist (total '(nil discharging empty fully-charged
+                       pending-charge pending-discharge))
+    (should (eq (battery--upower-state '(("State" . 2)) total) 'discharging)))
+  (dolist (state '(nil 0 2 3 4 5 6))
+    (should (eq (battery--upower-state `(("State" . ,state)) 'discharging)
+                'discharging)))
+  ;; Pending charge.
+  (dolist (total '(nil empty fully-charged pending-charge pending-discharge))
+    (should (eq (battery--upower-state '(("State" . 5)) total)
+                'pending-charge)))
+  (dolist (state '(nil 0 3 4 5 6))
+    (should (eq (battery--upower-state `(("State" . ,state)) 'pending-charge)
+                'pending-charge)))
+  ;; Pending discharge.
+  (dolist (total '(nil empty fully-charged pending-discharge))
+    (should (eq (battery--upower-state '(("State" . 6)) total)
+                'pending-discharge)))
+  (dolist (state '(nil 0 3 4 6))
+    (should (eq (battery--upower-state `(("State" . ,state)) 'pending-discharge)
+                'pending-discharge)))
+  ;; Empty.
+  (dolist (total '(nil empty))
+    (should (eq (battery--upower-state '(("State" . 3)) total) 'empty)))
+  (dolist (state '(nil 0 3))
+    (should (eq (battery--upower-state `(("State" . ,state)) 'empty) 'empty)))
+  ;; Fully charged.
+  (dolist (total '(nil fully-charged))
+    (should (eq (battery--upower-state '(("State" . 4)) total) 'fully-charged)))
+  (dolist (state '(nil 0 4))
+    (should (eq (battery--upower-state `(("State" . ,state)) 'fully-charged)
+                'fully-charged))))
+
+(ert-deftest battery-upower-state-unknown ()
+  "Test `battery--upower-state' with unknown states."
+  ;; Unknown running total retains new state.
+  (should-not (battery--upower-state () nil))
+  (should-not (battery--upower-state '(("State" . state)) nil))
+  (should-not (battery--upower-state '(("State" . 0)) nil))
+  (should (eq (battery--upower-state '(("State" . 1)) nil) 'charging))
+  (should (eq (battery--upower-state '(("State" . 2)) nil) 'discharging))
+  (should (eq (battery--upower-state '(("State" . 3)) nil) 'empty))
+  (should (eq (battery--upower-state '(("State" . 4)) nil) 'fully-charged))
+  (should (eq (battery--upower-state '(("State" . 5)) nil) 'pending-charge))
+  (should (eq (battery--upower-state '(("State" . 6)) nil) 'pending-discharge))
+  ;; Unknown new state retains running total.
+  (dolist (props '(() (("State" . state)) (("State" . 0))))
+    (dolist (total '(nil charging discharging empty fully-charged
+                         pending-charge pending-discharge))
+      (should (eq (battery--upower-state props total) total))))
+  ;; Conflicting empty and fully-charged.
+  (should-not (battery--upower-state '(("State" . 3)) 'fully-charged))
+  (should-not (battery--upower-state '(("State" . 4)) 'empty)))
+
 (ert-deftest battery-format ()
   "Test `battery-format'."
   (should (equal (battery-format "" ()) ""))