rework spw/eshell-jump, esp. wrt C-x p e, and restore prev-buffers

1 files changed, 111 insertions, 106 deletions

diff --git a/.emacs.d/init.el b/.emacs.d/init.el
index e00000b4..31920916 100644
--- a/.emacs.d/init.el
+++ b/.emacs.d/init.el
@@ -1056,18 +1056,6 @@ don't consider windows satisfying the predicate EXCLUDE."
       (if (> count 0) (tab-bar-history-forward) (tab-bar-history-back))))
   :cycle-backwards-key [left] :cycle-forwards-key [right])
 
-(with-eval-after-load 'project
-  (when (boundp 'project-prefix-map)	; for Emacs 27
-    (transient-cycles-define-commands ()
-      (("e" .  project-eshell))
-      (transient-cycles-buffer-ring-cycler)
-      ;; Bind into project-prefix-map, rather than just a remap, so that works
-      ;; under C-x 4 p too.
-      :keymap project-prefix-map)
-    ;; Update project-switch-commands accordingly.
-    (when-let ((cell (assoc 'project-eshell project-switch-commands)))
-      (setcar cell #'transient-cycles-cmd-project-eshell))))
-
 ;; For when the buffer's name isn't much help for switching to it, as is often
 ;; the case with notmuch buffers.  Commented out for now because the transient
 ;; cycling appended to C-x b and C-x 4 C-o now includes buffers of the same
@@ -1431,36 +1419,45 @@ don't consider windows satisfying the predicate EXCLUDE."
 
 ;;; getting to Eshell buffers
 
-(defun spw/eshell-jump (arg &optional chdir)
-  "Pop to *eshell*, and offer cycling among other Eshells, unless
-one of the following special circumstances applies:
+(defun spw/eshell-jump (&optional arg chdir)
+  "Pop to the most recently used Eshell not already running a
+command, and offer transient cycling among other Eshells, unless
+one or more of the following apply:
 
-- If a command is running in *eshell*, rename that buffer out of
-  the way and start a new one.  Similarly if the buffer is
-  narrowed; that was probably done with C-u C-c C-r, and the
-  buffer is similarly in use.
+- If a command is running in all Eshells, start a new one.
+  Similarly if all buffers are narrowed; that was probably done
+  with C-u C-c C-r, and so such buffers are probably in use.
 
-- If CHDIR, and there is no Eshell in `default-directory', also
-  change the directory of *eshell* to `default-directory'.
+- If CHDIR, and there is no Eshell in `default-directory' nor any
+  Eshell under the current project root, start a new Eshell in
+  `default-directory'
 
-- If CHDIR and there is an Eshell in `default-directory',
-  including one generated by `project-eshell', switch to that
-  Eshell instead of *eshell*.
+- If CHDIR and there is an Eshell in `default-directory', switch
+  to that Eshell instead.
+
+- If CHDIR and there is an Eshell under the current project root,
+  switch to that Eshell instead, and change its directory to
+  `default-directory'.
 
 - If both ARG and CHDIR, or if CHDIR and the current buffer is an
-  Eshell buffer which is not running a command, unconditionally
-  start a new Eshell in `default-directory'.
+  Eshell buffer, unconditionally start a new Eshell in
+  `default-directory'.
+
+  (I.e. C-u may be used to override reusing an existing Eshell,
+  and separately, if we are already in the buffer that the
+  command would have taken us to, assume we want a fresh one.)
 
-- If not CHDIR and the current buffer is *eshell*, activate
-  transient cycling to make it easy to get back to another
-  Eshell.  (This is the only case in which we do not use
-  `pop-to-buffer' or equivalent, so C-x 4 4 must be used to cycle
-  in another window.)
+- If not CHDIR and the current buffer is an Eshell that's not
+  running a command, activate transient cycling to make it easy
+  to get back to another Eshell.  (This is the only case in which
+  we do not use `pop-to-buffer' or equivalent, so C-x 4 4 must be
+  used to cycle in another window.)
 
-For the purpose of cycling, Eshells generated by `project-eshell'
-are sorted below Eshells generated by this function.
+- If CHDIR is `project', as above except that use the root of the
+  current project instead of `default-directory', and select an
+  Eshell already in the root of the project even if it's busy.
 
-The ideas behind this behaviour are as follows.
+The ideas behind these behaviours are as follows.
 
 - Just like Lisp REPLs, we do not normally need a lot of
   different Eshells; it is fine for shell history associated with
@@ -1474,83 +1471,73 @@ The ideas behind this behaviour are as follows.
   you to the unnumbered buffer, possibly renaming the numbered one
   out of the way.
 
-  This is why we don't try to reuse Eshells especially
-  aggressively; for example, we could find an *eshell*<N> not
-  running a command a rename it to *eshell*, but we don't.
-
-- Don't pay attention to the current project, as an old version
-  of this code did, because if we're using C-c e e and/or C-c e h
-  rather than C-x p e, we are probably working in a
-  project-agnostic way.
-
-  Thus, among the `project-eshell' Eshells available to cycle
-  through, don't prioritise those of the current project (for
-  example by moving them to the front) -- if we explicitly want
-  those, can use C-x p e.
-
-- Treat C-x p e as the primary way to get to Eshells in project
-  roots, and avoid changing the directories of those Eshells, as
-  it is surprising when C-x p e doesn't take us to an Eshell
-  which is ready to run commands in the project root (another
-  possibility would be to change the dir back to the project root
-  in this case).
-
-- It is assumed we'll sometimes use C-x 4 1 in front of this
-  command, and if we're already in Eshell, we might use C-x 4 4
-  to start the cycling in another window."
+  We do nevertheless reuse Eshells, not for the sake of creating
+  fewer, but just so that this command can be used to get back to
+  the most recent few Eshells you were working in, to see output.
+
+- We'll sometimes use C-x 4 1 in front of this command, and if
+  we're already in Eshell, we might use C-x 4 4 to start the
+  cycling in another window.
+
+- It's not especially convenient to distinguish between
+  `project-eshell' and `eshell' Eshells.  We just want a way to
+  quickly obtain an Eshell in the project root, and bind that to
+  C-x p e."
   (interactive "P")
   (require 'eshell)
-  (cl-flet ((project-eshell-eshell-p ()
-              (string-match "\\`\\*.+-eshell\\*[><0-9]*\\'" (buffer-name)))
-	    (busy-p (buffer)
-	      (or (get-buffer-process buffer)
-		  (with-current-buffer buffer (buffer-narrowed-p))))
-	    (fresh-eshell ()
-              (when-let ((buffer (get-buffer eshell-buffer-name)))
-		(with-current-buffer buffer (rename-uniquely)))
-	      (let ((default-directory
-		      (if chdir default-directory (expand-file-name "~"))))
-		(eshell))))
-    (let ((current-eshell (and (eq major-mode 'eshell-mode)
-			       (not (project-eshell-eshell-p))
-			       (not (busy-p (current-buffer)))
-			       (current-buffer)))
-	  (initial-default-directory default-directory)
-	  default-directory-eshell
-	  project-eshells
-	  other-eshells)
-      ;; Populate our two lists of all Eshells.
+  (let* ((current-project (and (not (file-remote-p default-directory))
+			       (project-current)))
+	 (project-root (and current-project (project-root current-project)))
+	 (target-directory (expand-file-name
+			    (or (and (eq chdir 'project) project-root)
+				default-directory)))
+	 target-directory-eshell same-project-eshell all-eshells)
+    (cl-flet ((busy-p (buffer)
+		(or (get-buffer-process buffer)
+		    (with-current-buffer buffer (buffer-narrowed-p))))
+	      (fresh-eshell ()
+		(when-let ((buffer (get-buffer eshell-buffer-name)))
+		  (with-current-buffer buffer (rename-uniquely)))
+		(let ((default-directory
+		       (if chdir target-directory (expand-file-name "~"))))
+		  (eshell))))
       (dolist (buffer (buffer-list))
 	(with-current-buffer buffer
 	  (when (eq major-mode 'eshell-mode)
-	    (if (and chdir (not default-directory-eshell)
-		     (string= default-directory initial-default-directory)
-		     (not (busy-p buffer)))
-		(setq default-directory-eshell buffer)
-	      (push buffer
-		    (if (project-eshell-eshell-p)
-			project-eshells other-eshells))))))
-      ;; Now `pop-to-buffer' if we're going to do that.
-      (cond ((and chdir (or arg current-eshell))
-	     (fresh-eshell))
-	    ((and chdir default-directory-eshell)
-	     (pop-to-buffer default-directory-eshell))
-	    ((or chdir (not (string= (buffer-name) eshell-buffer-name)))
-	     (if-let ((buffer (get-buffer eshell-buffer-name)))
-		 (if (busy-p buffer)
-		     (fresh-eshell)
-		   (pop-to-buffer buffer)
-		   (goto-char (point-max))
-		   (when chdir (spw/eshell-cd initial-default-directory)))
-	       (fresh-eshell)))
-	    ;; If `display-buffer-overriding-action' has some entries, pop to
-	    ;; ourselves, to allow subsequent cycling to a different Eshell in
-	    ;; another window.  E.g. C-c e e C-x 4 4 C-c e e.
-	    ((cl-find-if-not #'null display-buffer-overriding-action)
-	     (pop-to-buffer (current-buffer))))
-      ;; Finally, generate and return a ring for cycling purposes.
-      (let* ((all (delete (current-buffer)
-			  (nconc project-eshells other-eshells)))
+	    (push buffer all-eshells)
+	    (when chdir
+	      (cond ((and (not target-directory-eshell)
+			  (or (not (busy-p buffer)) (eq chdir 'project))
+			  (string= default-directory target-directory))
+		     (setq target-directory-eshell buffer))
+		    ((and project-root (not same-project-eshell)
+			  (not (busy-p buffer))
+			  (file-in-directory-p default-directory project-root))
+		     (setq same-project-eshell buffer)))))))
+      (let ((current-eshell (and (eq major-mode 'eshell-mode)
+				 (not (busy-p (current-buffer)))
+				 (current-buffer))))
+	(cond ((and chdir (or arg current-eshell))
+	       (fresh-eshell))
+	      ((and chdir target-directory-eshell)
+	       (pop-to-buffer target-directory-eshell))
+	      ((and chdir same-project-eshell)
+	       (pop-to-buffer same-project-eshell)
+	       (goto-char (point-max))
+	       (spw/eshell-cd target-directory))
+	      (chdir
+	       (fresh-eshell))
+	      ((not current-eshell)
+	       (if-let ((buf (cl-find-if-not #'busy-p (reverse all-eshells))))
+		   (pop-to-buffer buf)
+		 (fresh-eshell)))
+	      ;; If `display-buffer-overriding-action' has some entries, pop
+	      ;; to ourselves, to allow subsequent cycling to a different
+	      ;; Eshell in another window, and similar.  E.g. M-! C-x 4 4 M-!.
+	      ((or (car display-buffer-overriding-action)
+		   (cdr display-buffer-overriding-action))
+	       (pop-to-buffer (current-buffer)))))
+      (let* ((all (delete (current-buffer) all-eshells))
 	     (ring (make-ring (1+ (length all)))))
 	(dolist (buffer all)
 	  (ring-insert ring buffer))
@@ -1566,6 +1553,24 @@ The ideas behind this behaviour are as follows.
       (spw/eshell-jump arg t)))
   (transient-cycles-buffer-ring-cycler :ring ret-val))
 
+(with-eval-after-load 'project
+  (when (boundp 'project-prefix-map)	; for Emacs 27
+    (transient-cycles-define-commands (prev-buffers)
+      ((("e" .  spw/project-eshell) (arg)
+	  (interactive "P")
+	  (prog1 (spw/eshell-jump arg 'project)
+	    (setq prev-buffers (window-prev-buffers)))))
+      (transient-cycles-buffer-ring-cycler :ring ret-val)
+      :on-exit (progn (switch-to-buffer (current-buffer) nil t)
+		      (set-window-next-buffers nil nil)
+		      (set-window-prev-buffers nil prev-buffers))
+      ;; Bind into project-prefix-map, rather than adding a remap, so that we
+      ;; have it under C-x 4 p, C-x 5 p etc. too.
+      :keymap project-prefix-map)
+    ;; Update project-switch-commands accordingly.
+    (when-let ((cell (assoc 'project-eshell project-switch-commands)))
+      (setcar cell #'transient-cycles-cmd-spw/project-eshell))))
+
 ;;; my commands -- like defining functions in .bashrc where simple aliases are
 ;;; not enough