fix: persist runtime favorite and saved locations in a state filerelease/0.4.0

savehist rewrites its whole file on every save, keeping only the variables registered in the running process. Any Emacs that saved savehist without wttrin loaded (a batch tool, a session that never opened wttrin) silently deleted the persisted favorite and saved-location entries. A d-set default then reverted to the init value on the next restart.

The runtime favorite and directory now live in wttrin-state-file, written only by wttrin: write-through on every location command, atomic temp-file + rename, UTF-8 pinned both ways, read with read (never eval), versioned plist. Values restore at load and re-assert on savehist-mode-hook, so a stale legacy savehist restore can't clobber them. With no state file present, legacy savehist values are adopted and written once, so existing users migrate with zero steps. Search history stays on savehist. It's scrub-tolerant throwaway data, exactly what savehist is for.

Also: the README documents the mode-line tooltip forecast option, and the gitignore covers one more local tooling artifact.

1 files changed, 134 insertions, 33 deletions

diff --git a/wttrin.el b/wttrin.el
index 435359a..ca9d0fd 100644
--- a/wttrin.el
+++ b/wttrin.el
@@ -238,24 +238,24 @@ coordinates.  For example:
    (\"Home\" . \"41.37,-71.83\"))
 
 A bare string S used anywhere a location is expected is shorthand for
-\(S . S) — name and query the same.  Persisted across sessions via
-`savehist-mode'; add entries interactively with \\[wttrin-save-location] or the
-`d' key in a weather buffer, or set this in your init."
+\(S . S) — name and query the same.  Entries added interactively with
+\\[wttrin-save-location] or the `d' key in a weather buffer are persisted in
+`wttrin-state-file'; entries set here in your init are re-read each start."
   :group 'wttrin
   :type '(alist :key-type (string :tag "Name")
                 :value-type (string :tag "Query")))
 
 (defvar wttrin--favorite-override nil
-  "Runtime favorite set by `d'/`wttrin-make-default' and the geolocation commands.
-Persisted across sessions via savehist.  When non-nil it shadows the configured
-`wttrin-favorite-location', so a favorite chosen at runtime survives a restart
-even when the user also sets `wttrin-favorite-location' in their init.  Carries
-the same tri-state shape as that option: nil (no override), a string, or t
-\(auto-detect).")
+  "Runtime favorite set by `d'/`wttrin-make-default' and geolocation commands.
+Persisted across sessions in `wttrin-state-file'.  When non-nil it shadows
+the configured `wttrin-favorite-location', so a favorite chosen at runtime
+survives a restart even when the user also sets `wttrin-favorite-location'
+in their init.  Carries the same tri-state shape as that option: nil (no
+override), a string, or t (auto-detect).")
 
 (defvar wttrin--saved-locations-runtime nil
   "Saved-location entries added at runtime via `d' or `wttrin-save-location'.
-Persisted across sessions via savehist.  Overlaid on the configured
+Persisted across sessions in `wttrin-state-file'.  Overlaid on the configured
 `wttrin-saved-locations' by `wttrin--saved-locations', runtime winning on a name
 collision, so directory edits survive a restart without being clobbered by an
 init that also sets `wttrin-saved-locations'.  An alist of (NAME . QUERY).")
@@ -272,10 +272,11 @@ during the resolution window.")
 
 (defun wttrin--favorite-location ()
   "Return the effective favorite: the runtime override, else the configured one.
-`wttrin--favorite-override' (set at runtime by `d' and the geolocation commands,
-persisted by savehist) wins over the `wttrin-favorite-location' defcustom, so a
-runtime choice is not clobbered by an init that also sets the option.  Carries
-the option's tri-state shape: nil, a string, or t."
+`wttrin--favorite-override' (set at runtime by `d' and the geolocation
+commands, persisted in `wttrin-state-file') wins over the
+`wttrin-favorite-location' defcustom, so a runtime choice is not clobbered
+by an init that also sets the option.  Carries the option's tri-state
+shape: nil, a string, or t."
   (or wttrin--favorite-override wttrin-favorite-location))
 
 (defun wttrin--resolve-favorite-location ()
@@ -646,25 +647,122 @@ Persisted across sessions via `savehist-mode'.")
 (defvar savehist-additional-variables)
 
 (defun wttrin--savehist-register ()
-  "Ensure wttrin's persisted runtime state is saved by savehist.
-Registers `wttrin--location-history', `wttrin--favorite-override', and
-`wttrin--saved-locations-runtime' so they survive across restarts without the
-Emacs custom-variable mechanism.  Deliberately registers the runtime override
-and runtime directory rather than the `wttrin-favorite-location' and
-`wttrin-saved-locations' defcustoms: those are configuration the user sets in
-init, and persisting them would fight the init on every restart (the value the
-user last chose with `d' would be clobbered by the init `setopt').
+  "Register the search history with savehist.
+Only `wttrin--location-history' rides savehist: it is scrub-tolerant
+throwaway data, which is what savehist is for.  The runtime favorite and
+runtime directory are deliberately NOT registered — savehist rewrites its
+whole file on every save keeping only currently-registered variables, so any
+Emacs process that saves savehist without wttrin loaded (a deferred-loading
+session where wttrin was never opened, a batch tool) would silently delete
+them.  Those live in `wttrin-state-file' instead, which only wttrin writes.
 Run both at load and on `savehist-save-hook', so the registration survives a
 user `setq' of `savehist-additional-variables' (a common config pattern) that
-would otherwise drop the entries before they could be saved."
-  (add-to-list 'savehist-additional-variables 'wttrin--location-history)
-  (add-to-list 'savehist-additional-variables 'wttrin--favorite-override)
-  (add-to-list 'savehist-additional-variables 'wttrin--saved-locations-runtime))
+would otherwise drop the entry before it could be saved."
+  (add-to-list 'savehist-additional-variables 'wttrin--location-history))
+
+;;;###autoload (with-eval-after-load 'savehist (add-to-list 'savehist-additional-variables 'wttrin--location-history))
 
 (with-eval-after-load 'savehist
   (wttrin--savehist-register)
   (add-hook 'savehist-save-hook #'wttrin--savehist-register))
 
+(defcustom wttrin-state-file (locate-user-emacs-file "wttrin-state.el")
+  "File persisting wttrin's runtime state across sessions.
+Holds the runtime favorite (`wttrin--favorite-override') and the runtime
+saved-locations directory (`wttrin--saved-locations-runtime') — the values
+written by `d'/`wttrin-make-default', `wttrin-save-location', and the
+geolocation commands.  A dedicated file rather than savehist because savehist
+rewrites its whole file keeping only the variables registered in the current
+process: any Emacs session that saved savehist without wttrin loaded would
+silently delete the persisted favorite.  Only wttrin writes this file.
+Customize this before wttrin loads (e.g. via use-package `:custom'); the
+state restores at load time, so a later `setq' takes effect only from the
+next restore (`savehist-mode-hook' or restart)."
+  :group 'wttrin
+  :type 'file)
+
+(defun wttrin--state-save ()
+  "Write the runtime favorite and directory to `wttrin-state-file'.
+Writes atomically (temp file + rename) so a crash mid-write cannot leave a
+truncated file, always as UTF-8 so the file round-trips regardless of the
+session's default coding system (the same reason savehist pins
+`savehist-coding-system').  Never signals: persistence failure must not
+break the location command that triggered it — it messages and moves on."
+  (condition-case err
+      (let* ((file (expand-file-name wttrin-state-file))
+             (dir (file-name-directory file))
+             (tmp (make-temp-name (concat file ".tmp")))
+             (coding-system-for-write 'utf-8-emacs)
+             (print-length nil)
+             (print-level nil))
+        (unless (file-directory-p dir) (make-directory dir t))
+        (unwind-protect
+            (progn
+              (with-temp-buffer
+                (insert ";; wttrin runtime state -- managed by wttrin;"
+                        " do not edit by hand.\n")
+                (prin1 (list :version 1
+                             :favorite-override wttrin--favorite-override
+                             :saved-locations wttrin--saved-locations-runtime)
+                       (current-buffer))
+                (insert "\n")
+                (write-region (point-min) (point-max) tmp nil 'silent))
+              (rename-file tmp file t)
+              (setq tmp nil))
+          ;; Any failure above leaves the temp file behind; remove it.  On
+          ;; success TMP is nil and there is nothing to clean.
+          (when (and tmp (file-exists-p tmp))
+            (delete-file tmp))))
+    (error (message "wttrin: could not save state to %s: %s"
+                    wttrin-state-file (error-message-string err)))))
+
+(defun wttrin--state-read ()
+  "Read `wttrin-state-file' and return its state plist, or nil.
+Returns nil when the file is absent, unreadable, or does not contain a
+versioned plist.  Reads with `read', never `eval', so the state file cannot
+execute code, and as UTF-8, matching how `wttrin--state-save' writes it.
+Never signals — a broken state file must not break load."
+  (when (file-readable-p wttrin-state-file)
+    (condition-case err
+        (with-temp-buffer
+          (let ((coding-system-for-read 'utf-8-emacs))
+            (insert-file-contents wttrin-state-file))
+          (let ((data (read (current-buffer))))
+            (if (and (listp data) (integerp (plist-get data :version)))
+                data
+              (message "wttrin: ignoring malformed state file %s"
+                       wttrin-state-file)
+              nil)))
+      (error (message "wttrin: could not read state file %s: %s"
+                      wttrin-state-file (error-message-string err))
+             nil))))
+
+(defun wttrin--state-load ()
+  "Restore the runtime favorite and directory from `wttrin-state-file'.
+An existing state file is authoritative: its values replace whatever is in
+memory, which is what defeats a later savehist restore of stale legacy
+entries (this function also runs on `savehist-mode-hook').  When the file
+does not exist but either variable is non-nil — savehist restored legacy
+values from a pre-state-file wttrin earlier in init — those values are
+adopted and written, migrating existing users with zero steps.  A corrupt
+file is left in place and ignored: vars keep their current values and no
+adoption write happens over it."
+  (let ((data (wttrin--state-read)))
+    (cond
+     (data
+      (setq wttrin--favorite-override (plist-get data :favorite-override))
+      (setq wttrin--saved-locations-runtime (plist-get data :saved-locations)))
+     ((and (not (file-exists-p wttrin-state-file))
+           (or wttrin--favorite-override wttrin--saved-locations-runtime))
+      (wttrin--state-save)))))
+
+;; Restore persisted state at load — but not in batch (CI, test runners,
+;; scripts), which stays hermetic by design.  The savehist-mode-hook entry
+;; re-asserts the state file after savehist restores, in case a savehist file
+;; still carrying legacy pre-state-file entries loads later in init.
+(unless noninteractive (wttrin--state-load))
+(add-hook 'savehist-mode-hook #'wttrin--state-load)
+
 (defconst wttrin--geolocation-sentinel "Current location (detect)"
   "Picker candidate that triggers geolocation detection.
 Selecting it routes through `wttrin--query-selection' to a
@@ -760,9 +858,10 @@ Used to keep a raw geolocation fix out of history and to decide when the
 
 (defun wttrin--put-saved-location (name query)
   "Add or update NAME -> QUERY in the runtime directory; return the saved name.
-Writes `wttrin--saved-locations-runtime' (savehist-persisted), never the
-`wttrin-saved-locations' defcustom, so a runtime save is not clobbered by an
-init that also sets the option.  Trims NAME and QUERY.  Signals a `user-error'
+Writes `wttrin--saved-locations-runtime' (persisted in `wttrin-state-file'),
+never the `wttrin-saved-locations' defcustom, so a runtime save is not
+clobbered by an init that also sets the option.  Trims NAME and QUERY.
+Signals a `user-error'
 for an empty name or query, or a name equal to the geolocation sentinel.  An
 existing runtime name has its query updated."
   (let ((name (string-trim (or name "")))
@@ -774,6 +873,7 @@ existing runtime name has its query updated."
     (setq wttrin--saved-locations-runtime
           (append (wttrin--saved-locations-runtime-without name)
                   (list (cons name query))))
+    (wttrin--state-save)
     name))
 
 (defun wttrin--remove-saved-location (name)
@@ -782,7 +882,8 @@ Only the runtime layer `wttrin--saved-locations-runtime' is mutated.  An entry
 from the `wttrin-saved-locations' defcustom cannot be deleted here (it is
 re-read from the user's init) and remains in the effective directory."
   (setq wttrin--saved-locations-runtime
-        (wttrin--saved-locations-runtime-without name)))
+        (wttrin--saved-locations-runtime-without name))
+  (wttrin--state-save))
 
 (defvar-local wttrin--current-location nil
   "Query for the weather shown in this buffer (the fetch/cache identity).")
@@ -1523,12 +1624,12 @@ defcustom, so the choice survives a restart even when the user also sets the
 option in their init (the override shadows the config; see
 `wttrin--favorite-location').  LOCATION becomes a permanent default, so it no
 longer needs a history entry, mirroring how `wttrin-default-locations' entries
-are kept out of history.  Persistence is handled by `wttrin--savehist-register',
-which registers the override when savehist loads and again on
-`savehist-save-hook', so setting it works whether or not savehist is loaded."
+are kept out of history.  Persisted immediately to `wttrin-state-file', so the
+choice survives restarts regardless of savehist."
   (let ((changed (not (equal location (wttrin--favorite-location)))))
     (setq wttrin--favorite-override location)
     (setq wttrin--location-history (delete location wttrin--location-history))
+    (wttrin--state-save)
     (when (and changed (bound-and-true-p wttrin-mode-line-mode))
       (wttrin--mode-line-refresh-now))))