bug#8576: 23.2; js-mode doesn't support multi-line variable declarations

["Felix H. Dahlke" <fhd@ubercode.de>]

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Okay, I've prepared a patch for this, based on Dimitriv's work. I've
been using this for a while now and haven't run into any problems.

The attached patch is against the latest revision in the emacs-23
branch. I can provide a patch for emacs-24 or trunk if that's desirable.

Here's the patched version if you'd like to try it out:
https://gist.github.com/2849799

And here's one that should work in Emacs 24:
https://gist.github.com/2849595

There's still one thing that I'd like to behave differently, but I
thought I'd best discuss this first.

The patched js.el will indent the following code like this:

var foo = 5,
      bar = function() {
      };

That's fine. But if a function or an object literal come first, it
indents it like this:

var bar = function() {
},
    foo = 5;

Which I consider somewhat ugly. I'd like to make it indent as follows:

var bar = function() {
    },
    foo = 5;

That should only happen for multi var declarations, single declarations
should indent just like before:

var bar = function() {
};

Would that be acceptable? It'll make the code a bit more complicated,
but I think it's worth it.


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# Bazaar merge directive format 2 (Bazaar 0.90)
# revision_id: fhd@ubercode.de-20120601072216-wsfs98ornfd1mugv
# target_branch: file:///home/fhd/Projects/emacs/emacs-23/
# testament_sha1: 101562a7a137d29600bd25ef2b014ca7e5e91ae1
# timestamp: 2012-06-01 09:22:39 +0200
# base_revision_id: handa@m17n.org-20120304120609-saqksj43mnq1tz4n
# 
# Begin patch
=== modified file 'lisp/progmodes/js.el'
--- lisp/progmodes/js.el	2012-01-11 07:52:35 +0000
+++ lisp/progmodes/js.el	2012-06-01 07:22:16 +0000
@@ -418,6 +418,16 @@
    :paren-depth most-negative-fixnum
    :type 'toplevel))
 
+(defconst js--indent-operator-re
+  (concat "[-+*/%<>=&^|?:.]\\([^-+*/]\\|$\\)\\|"
+          (regexp-opt '("in" "instanceof") 'words))
+  "Regular expression matching operators that affect indentation
+of continued expressions.")
+
+(defconst js--declaration-keyword-re
+  (regexp-opt '("var" "let" "const") 'words)
+  "Regular expression matching variable declaration keywords.")
+
 ;;; User Customization
 
 (defgroup js nil
@@ -1758,41 +1768,78 @@
          (list (cons 'c js-comment-lineup-func))))
     (c-get-syntactic-indentation (list (cons symbol anchor)))))
 
+(defun js--multiline-decl-indentation ()
+  "Returns the declaration indentation column if the current line belongs
+to a multiline declaration statement.  All declarations are lined up vertically:
+
+var a = 10,
+    b = 20,
+    c = 30;
+"
+  (let (at-opening-bracket)
+    (save-excursion
+      (back-to-indentation)
+      (when (not (looking-at js--declaration-keyword-re))
+        (when (looking-at js--indent-operator-re)
+          (goto-char (match-end 0)))
+        (while (and (not at-opening-bracket)
+                    (not (bobp))
+                    (let ((pos (point)))
+                      (save-excursion
+                        (js--backward-syntactic-ws)
+                        (or (eq (char-before) ?,)
+                            (and (not (eq (char-before) ?\;))
+                                 (and
+                                  (prog2
+                                      (skip-chars-backward "[[:punct:]]")
+                                      (looking-at js--indent-operator-re)
+                                    (js--backward-syntactic-ws))
+                                  (not (eq (char-before) ?\;))))
+                            (and (>= pos (point-at-bol))
+                                 (<= pos (point-at-eol)))))))
+          (condition-case err
+              (backward-sexp)
+            (scan-error (setq at-opening-bracket t))))
+        (when (looking-at js--declaration-keyword-re)
+          (- (1+ (match-end 0)) (point-at-bol)))))))
+
 (defun js--proper-indentation (parse-status)
   "Return the proper indentation for the current line."
-  (save-excursion
-    (back-to-indentation)
-    (cond ((nth 4 parse-status)
-           (js--get-c-offset 'c (nth 8 parse-status)))
-          ((nth 8 parse-status) 0) ; inside string
-          ((js--ctrl-statement-indentation))
-          ((eq (char-after) ?#) 0)
-          ((save-excursion (js--beginning-of-macro)) 4)
-          ((nth 1 parse-status)
-           (let ((same-indent-p (looking-at
-                                 "[]})]\\|\\_<case\\_>\\|\\_<default\\_>"))
-                 (continued-expr-p (js--continued-expression-p)))
-             (goto-char (nth 1 parse-status))
-             (if (looking-at "[({[]\\s-*\\(/[/*]\\|$\\)")
-                 (progn
-                   (skip-syntax-backward " ")
-		   (when (eq (char-before) ?\)) (backward-list))
-                   (back-to-indentation)
-                   (cond (same-indent-p
-                          (current-column))
-                         (continued-expr-p
-                          (+ (current-column) (* 2 js-indent-level)
-                             js-expr-indent-offset))
-                         (t
-                          (+ (current-column) js-indent-level))))
-               (unless same-indent-p
-                 (forward-char)
-                 (skip-chars-forward " \t"))
-               (current-column))))
+  (or
+   (js--multiline-decl-indentation)
+   (save-excursion
+     (back-to-indentation)
+     (cond ((nth 4 parse-status)
+            (js--get-c-offset 'c (nth 8 parse-status)))
+           ((nth 8 parse-status) 0)     ; inside string
+           ((js--ctrl-statement-indentation))
+           ((eq (char-after) ?#) 0)
+           ((save-excursion (js--beginning-of-macro)) 4)
+           ((nth 1 parse-status)
+            (let ((same-indent-p (looking-at
+                                  "[]})]\\|\\_<case\\_>\\|\\_<default\\_>"))
+                  (continued-expr-p (js--continued-expression-p)))
+              (goto-char (nth 1 parse-status))
+              (if (looking-at "[({[]\\s-*\\(/[/*]\\|$\\)")
+                  (progn
+                    (skip-syntax-backward " ")
+                    (when (eq (char-before) ?\)) (backward-list))
+                    (back-to-indentation)
+                    (cond (same-indent-p
+                           (current-column))
+                          (continued-expr-p
+                           (+ (current-column) (* 2 js-indent-level)
+                              js-expr-indent-offset))
+                          (t
+                           (+ (current-column) js-indent-level))))
+                (unless same-indent-p
+                  (forward-char)
+                  (skip-chars-forward " \t"))
+                (current-column))))
 
-          ((js--continued-expression-p)
-           (+ js-indent-level js-expr-indent-offset))
-          (t 0))))
+           ((js--continued-expression-p)
+            (+ js-indent-level js-expr-indent-offset))
+           (t 0)))))
 
 (defun js-indent-line ()
   "Indent the current line as JavaScript."

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