fix: keep a d-set favorite from reverting to the init value on restart

wttrin-favorite-location did two jobs: a defcustom the user sets in init, and the savehist-persisted value that `d`/make-default mutated. Setting it in init (setopt) clobbered the `d` choice on every startup. So a favorite promoted with `d` reverted to the init value after a restart, and the mode-line showed the wrong location's weather. wttrin-saved-locations had the same defect.

I split the two roles. The defcustoms stay as the init-set base. New savehist-persisted runtime vars, wttrin--favorite-override and wttrin--saved-locations-runtime, hold what `d`, save, rename, remove, and the geolocation commands write. Reads go through resolvers: wttrin--favorite-location returns the override or the configured favorite, and wttrin--saved-locations overlays the runtime directory on the configured one (runtime wins on a name collision). Init and `d` now write different variables, so neither clobbers the other.

Removing a saved location that only comes from init can't delete it, since the runtime removal has nothing to touch. The command now says so instead of reporting a removal that didn't happen.

There's no automatic migration. A favorite set in init is unaffected, and a favorite set only with `d` before this version is re-set once with `d`. The README documents the behavior.

1 files changed, 80 insertions, 0 deletions

diff --git a/tests/test-wttrin-favorite-override.el b/tests/test-wttrin-favorite-override.el
new file mode 100644
index 0000000..0236901
--- /dev/null
+++ b/tests/test-wttrin-favorite-override.el
@@ -0,0 +1,80 @@
+;;; test-wttrin-favorite-override.el --- Tests for the runtime favorite override -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2026 Craig Jennings
+
+;;; Commentary:
+;; Unit tests for the split between the configured favorite
+;; (`wttrin-favorite-location', a defcustom set in init) and the runtime
+;; favorite (`wttrin--favorite-override', set by `d'/the geolocation commands
+;; and persisted by savehist).  The effective favorite resolves via
+;; `wttrin--favorite-location': the override wins over the config, so a favorite
+;; chosen at runtime is not clobbered by an init that also sets the option.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+(require 'wttrin)
+
+;;; wttrin--favorite-location (resolver)
+
+(ert-deftest test-wttrin-favorite-override-normal-config-when-no-override ()
+  "Normal: with no override, the effective favorite is the configured one."
+  (let ((wttrin-favorite-location "New Orleans, LA")
+        (wttrin--favorite-override nil))
+    (should (equal "New Orleans, LA" (wttrin--favorite-location)))))
+
+(ert-deftest test-wttrin-favorite-override-normal-override-wins ()
+  "Normal: a runtime override shadows the configured favorite."
+  (let ((wttrin-favorite-location "New Orleans, LA")
+        (wttrin--favorite-override "Hyatt Place Warwick, RI"))
+    (should (equal "Hyatt Place Warwick, RI" (wttrin--favorite-location)))))
+
+(ert-deftest test-wttrin-favorite-override-boundary-both-nil ()
+  "Boundary: no config and no override yields nil (favorite disabled)."
+  (let ((wttrin-favorite-location nil)
+        (wttrin--favorite-override nil))
+    (should (null (wttrin--favorite-location)))))
+
+(ert-deftest test-wttrin-favorite-override-boundary-auto-detect-override ()
+  "Boundary: the override carries the tri-state t (auto-detect)."
+  (let ((wttrin-favorite-location "New Orleans, LA")
+        (wttrin--favorite-override t))
+    (should (eq t (wttrin--favorite-location)))))
+
+(ert-deftest test-wttrin-favorite-override-regression-init-does-not-clobber ()
+  "Regression: setting the config after an override (as an init `setopt' would)
+does not change the effective favorite.  This is the bug where a favorite set
+with `d' reverted to the init value on restart."
+  (let ((wttrin--favorite-override "Hyatt Place Warwick, RI")
+        (wttrin-favorite-location nil))
+    ;; Simulate the init running its (setopt wttrin-favorite-location ...).
+    (setq wttrin-favorite-location "New Orleans, LA")
+    (should (equal "Hyatt Place Warwick, RI" (wttrin--favorite-location)))))
+
+;;; wttrin--set-favorite-location writes the override, not the config
+
+(ert-deftest test-wttrin-favorite-override-normal-setter-writes-override ()
+  "Normal: the setter writes the runtime override and leaves the config intact."
+  (let ((wttrin-favorite-location "New Orleans, LA")
+        (wttrin--favorite-override nil)
+        (wttrin--location-history nil))
+    (wttrin--set-favorite-location "Paris, FR")
+    (should (equal "Paris, FR" wttrin--favorite-override))
+    (should (equal "New Orleans, LA" wttrin-favorite-location))
+    (should (equal "Paris, FR" (wttrin--favorite-location)))))
+
+;;; savehist registration targets the runtime vars, not the config defcustoms
+
+(ert-deftest test-wttrin-favorite-override-normal-savehist-registers-override ()
+  "Normal: savehist persists the override, not the config defcustom."
+  (require 'savehist)
+  (let ((savehist-additional-variables '(kill-ring)))
+    (wttrin--savehist-register)
+    (should (memq 'wttrin--favorite-override savehist-additional-variables))
+    (should (memq 'wttrin--saved-locations-runtime savehist-additional-variables))
+    (should-not (memq 'wttrin-favorite-location savehist-additional-variables))
+    (should-not (memq 'wttrin-saved-locations savehist-additional-variables))))
+
+(provide 'test-wttrin-favorite-override)
+;;; test-wttrin-favorite-override.el ends here