emacs: avoid unnecessary let-bindings

To some extend this is a personal preference, but the preference is
strongly dependent on whether one is used to a language that makes it
necessary to use variables like this.

This makes it perfectly clear that we are first getting and then using
a "foo":

  (use-foo (get-foo))

Sure this has to be read "inside out", but that's something one better
gets used to quickly when dealing with lisp.  I don't understand why
one would want to write this instead:

  (let ((the-foo (get-foo)))
    (use-foo the-foo))

Both `get-foo' and `use-foo' are named in a way that make it very
clear that we are dealing with a "foo".  Storing the value in an
additional variable `the-foo' does not make this any more clear.

On the contrary I makes the reader wonder why the author choose to
use a variable.  Is the value used more than once?  Is the value
being retrieved in one context and then used in another (e.g. when
the current buffer changes)?

emacs/notmuch-address.el

@@ -260,8 +260,8 @@ requiring external commands."
 ;;; Harvest
 
 (defun notmuch-address-harvest-addr (result)
-  (let ((name-addr (plist-get result :name-addr)))
-    (puthash name-addr t notmuch-address-completions)))
+  (puthash (plist-get result :name-addr)
+	   t notmuch-address-completions))
 
 (defun notmuch-address-harvest-filter (proc string)
   (when (buffer-live-p (process-buffer proc))

emacs/notmuch-lib.el

@@ -416,9 +416,9 @@ A command that supports a prefix argument can explicitly document
 its prefixed behavior by setting the 'notmuch-prefix-doc property
 of its command symbol."
   (interactive)
-  (let* ((mode major-mode)
-	 (doc (substitute-command-keys
-	       (notmuch-substitute-command-keys (documentation mode t)))))
+  (let ((doc (substitute-command-keys
+	      (notmuch-substitute-command-keys
+	       (documentation major-mode t)))))
     (with-current-buffer (generate-new-buffer "*notmuch-help*")
       (insert doc)
       (goto-char (point-min))

emacs/notmuch-maildir-fcc.el

@@ -207,11 +207,11 @@ This inserts the current buffer as a message into the notmuch
 database in folder FOLDER. If CREATE is non-nil it will supply
 the --create-folder flag to create the folder if necessary. TAGS
 should be a list of tag changes to apply to the inserted message."
-  (let* ((args (append (and create (list "--create-folder"))
-		       (list (concat "--folder=" folder))
-		       tags)))
-    (apply 'notmuch-call-notmuch-process
-	   :stdin-string (buffer-string) "insert" args)))
+  (apply 'notmuch-call-notmuch-process
+	 :stdin-string (buffer-string) "insert"
+	 (append (and create (list "--create-folder"))
+		 (list (concat "--folder=" folder))
+		 tags)))
 
 (defun notmuch-maildir-fcc-with-notmuch-insert (fcc-header &optional create)
   "Store message with notmuch insert.

emacs/notmuch-show.el

@@ -1666,13 +1666,13 @@ It gets property PROP from PROPS or, if PROPS is nil, the current
 message in either tree or show. This means that several utility
 functions in notmuch-show can be used directly by notmuch-tree as
 they just need the correct message properties."
-  (let ((props (or props
-		   (cond ((eq major-mode 'notmuch-show-mode)
-			  (notmuch-show-get-message-properties))
-			 ((eq major-mode 'notmuch-tree-mode)
-			  (notmuch-tree-get-message-properties))
-			 (t nil)))))
-    (plist-get props prop)))
+  (plist-get (or props
+		 (cond ((eq major-mode 'notmuch-show-mode)
+			(notmuch-show-get-message-properties))
+		       ((eq major-mode 'notmuch-tree-mode)
+			(notmuch-tree-get-message-properties))
+		       (t nil)))
+	     prop))
 
 (defun notmuch-show-get-message-id (&optional bare)
   "Return an id: query for the Message-Id of the current message.

emacs/notmuch-tag.el

@@ -406,8 +406,9 @@ Return all tags if no search terms are given."
    "\n+" t))
 
 (defun notmuch-select-tag-with-completion (prompt &rest search-terms)
-  (let ((tag-list (apply #'notmuch-tag-completions search-terms)))
-    (completing-read prompt tag-list nil nil nil 'notmuch-select-tag-history)))
+  (completing-read prompt
+		   (apply #'notmuch-tag-completions search-terms)
+		   nil nil nil 'notmuch-select-tag-history))
 
 (defun notmuch-read-tag-changes (current-tags &optional prompt initial-input)
   "Prompt for tag changes in the minibuffer.
@@ -455,10 +456,9 @@ present or a \"-\" to indicate that the tag should be removed
 from TAGS if present."
   (let ((result-tags (copy-sequence tags)))
     (dolist (tag-change tag-changes)
-      (let ((op (aref tag-change 0))
-	    (tag (and (not (string= tag-change ""))
+      (let ((tag (and (not (string= tag-change ""))
 		      (substring tag-change 1))))
-	(cl-case op
+	(cl-case (aref tag-change 0)
 	  (?+ (unless (member tag result-tags)
 		(push tag result-tags)))
 	  (?- (setq result-tags (delete tag result-tags)))

emacs/notmuch-tree.el

@@ -401,9 +401,8 @@ Some useful entries are:
     (notmuch-tree-set-message-properties props)))
 
 (defun notmuch-tree-get-prop (prop &optional props)
-  (let ((props (or props
-		   (notmuch-tree-get-message-properties))))
-    (plist-get props prop)))
+  (plist-get (or props (notmuch-tree-get-message-properties))
+	     prop))
 
 (defun notmuch-tree-set-tags (tags)
   "Set the tags of the current message."

emacs/notmuch.el

@@ -521,17 +521,16 @@ With a prefix argument, invert the default value of
 `notmuch-show-only-matching-messages' when displaying the
 thread."
   (interactive "P")
-  (let ((thread-id (notmuch-search-find-thread-id))
-	(subject (notmuch-search-find-subject)))
-    (if (> (length thread-id) 0)
+  (let ((thread-id (notmuch-search-find-thread-id)))
+    (if thread-id
 	(notmuch-show thread-id
 		      elide-toggle
 		      (current-buffer)
 		      notmuch-search-query-string
 		      ;; Name the buffer based on the subject.
-		      (concat "*"
-			      (truncate-string-to-width subject 30 nil nil t)
-			      "*"))
+		      (format "*%s*" (truncate-string-to-width
+				      (notmuch-search-find-subject)
+				      30 nil nil t)))
       (message "End of search results."))))
 
 (defun notmuch-tree-from-search-current-query ()
@@ -556,20 +555,21 @@ thread."
 (defun notmuch-search-reply-to-thread (&optional prompt-for-sender)
   "Begin composing a reply-all to the entire current thread in a new buffer."
   (interactive "P")
-  (let ((message-id (notmuch-search-find-thread-id)))
-    (notmuch-mua-new-reply message-id prompt-for-sender t)))
+  (notmuch-mua-new-reply (notmuch-search-find-thread-id)
+			 prompt-for-sender t))
 
 (defun notmuch-search-reply-to-thread-sender (&optional prompt-for-sender)
   "Begin composing a reply to the entire current thread in a new buffer."
   (interactive "P")
-  (let ((message-id (notmuch-search-find-thread-id)))
-    (notmuch-mua-new-reply message-id prompt-for-sender nil)))
+  (notmuch-mua-new-reply (notmuch-search-find-thread-id)
+			 prompt-for-sender nil))
 
 ;;; Tags
 
 (defun notmuch-search-set-tags (tags &optional pos)
-  (let ((new-result (plist-put (notmuch-search-get-result pos) :tags tags)))
-    (notmuch-search-update-result new-result pos)))
+  (notmuch-search-update-result
+   (plist-put (notmuch-search-get-result pos) :tags tags)
+   pos))
 
 (defun notmuch-search-get-tags (&optional pos)
   (plist-get (notmuch-search-get-result pos) :tags))
@@ -1013,10 +1013,9 @@ the configured default sort order."
     (setq notmuch-search-target-thread target-thread)
     (setq notmuch-search-target-line target-line)
     (notmuch-tag-clear-cache)
-    (let ((proc (get-buffer-process (current-buffer)))
-	  (inhibit-read-only t))
-      (when proc
-	(error "notmuch search process already running for query `%s'" query))
+    (when (get-buffer-process buffer)
+      (error "notmuch search process already running for query `%s'" query))
+    (let ((inhibit-read-only t))
       (erase-buffer)
       (goto-char (point-min))
       (save-excursion
@@ -1045,13 +1044,12 @@ the new search results, then point will be placed on the same
 thread. Otherwise, point will be moved to attempt to be in the
 same relative position within the new buffer."
   (interactive)
-  (let ((target-line (line-number-at-pos))
-	(oldest-first notmuch-search-oldest-first)
-	(target-thread (notmuch-search-find-thread-id 'bare))
-	(query notmuch-search-query-string))
-    ;; notmuch-search erases the current buffer.
-    (notmuch-search query oldest-first target-thread target-line t)
-    (goto-char (point-min))))
+  (notmuch-search notmuch-search-query-string
+		  notmuch-search-oldest-first
+		  (notmuch-search-find-thread-id 'bare)
+		  (line-number-at-pos)
+		  t)
+  (goto-char (point-min)))
 
 (defun notmuch-search-toggle-order ()
   "Toggle the current search order.
@@ -1160,9 +1158,9 @@ Used as`imenu-prev-index-position-function' in notmuch buffers."
   "Return imenu name for line at point.
 Used as `imenu-extract-index-name-function' in notmuch buffers.
 Point should be at the beginning of the line."
-  (let ((subject (notmuch-search-find-subject))
-	(author (notmuch-search-find-authors)))
-    (format "%s (%s)" subject author)))
+  (format "%s (%s)"
+	  (notmuch-search-find-subject)
+	  (notmuch-search-find-authors)))
 
 ;;; _