bug#25904: Formatting bug with js-mode

[Felipe Ochoa <felipe.nospam.ochoa@gmail.com>]

This has taken a *little* longer than I'd hoped, but here's a new
patch with all the discussed changes. Hopefully I got the commit
message formatting and content right

From 0c7eed3fd9f7f77a071296c191e8569471bac4e5 Mon Sep 17 00:00:00 2001
From: Felipe Ochoa <felipe.nospam.ochoa@gmail.com>
Date: Tue, 7 Nov 2017 16:50:42 -0500
Subject: [PATCH] Fixes js indentation after arrow function without parens

From: felipe <felipe@fov.space>

* lisp/progmodes/js.el (js--proper-indentation)
(js--looking-at-broken-arrow-function-p)
* test/manual/indent/js.js: Indent expression following an arrow as
though it were enclosed in parentheses

(Bug#25904)
---
 lisp/progmodes/js.el     | 24 ++++++++++++++++++++++--
 test/manual/indent/js.js |  9 +++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/lisp/progmodes/js.el b/lisp/progmodes/js.el
index f30e591..5a333a9 100644
--- a/lisp/progmodes/js.el
+++ b/lisp/progmodes/js.el
@@ -1849,7 +1849,9 @@ js--continued-expression-p
              (skip-chars-backward " \t")
              (or (bobp) (backward-char))
              (and (> (point) (point-min))
-                  (save-excursion (backward-char) (not (looking-at "[/*]/")))
+                  ;; Need to exclude => here since
js--looking-at-operator-p thinks
+                  ;; it's looking at an assignment operator
+                  (save-excursion (backward-char) (not (looking-at
"[/*]/\\|=>")))
                   (js--looking-at-operator-p)
                   (and (progn (backward-char)
                               (not (looking-at "+\\+\\|--\\|/[/*]"))))))))))
@@ -2078,6 +2080,23 @@ js--maybe-goto-declaration-keyword-end
         (when comma-p
           (goto-char (1+ declaration-keyword-end))))))))

+(defconst js--line-terminating-arrow "\\s-*=>\\s-*\\(/[/*]\\|$\\)"
+  "Regexp to match a \"=>\" token if it's the last non-whitespace,
non-comment token in a line.")
+
+(defun js--looking-at-broken-arrow-function-p ()
+  "Helper function for `js--proper-indentation'.
+Return t if point is at the start of a (possibly async) arrow
+function and the last non-comment, non-whitespace token of the
+current like is the \"=>\" token."
+  (when (looking-at "\\s-*async\\s-*")
+    (goto-char (match-end 0)))
+  (cond
+   ((eq (char-after) ?\()
+    (forward-list)
+    (looking-at-p js--line-terminating-arrow))
+   (t (looking-at-p
+       (concat js--name-re js--line-terminating-arrow)))))
+
 (defun js--proper-indentation (parse-status)
   "Return the proper indentation for the current line."
   (save-excursion
@@ -2108,7 +2127,8 @@ js--proper-indentation
                  (continued-expr-p (js--continued-expression-p)))
              (goto-char (nth 1 parse-status)) ; go to the opening char
              (if (or (not js-indent-align-list-continuation)
-                     (looking-at "[({[]\\s-*\\(/[/*]\\|$\\)"))
+                     (looking-at "[({[]\\s-*\\(/[/*]\\|$\\)")
+                     (progn (forward-char)
(js--looking-at-broken-arrow-function-p)))
                  (progn ; nothing following the opening paren/bracket
                    (skip-syntax-backward " ")
                    (when (eq (char-before) ?\)) (backward-list))
diff --git a/test/manual/indent/js.js b/test/manual/indent/js.js
index b0d8bca..fc39c12 100644
--- a/test/manual/indent/js.js
+++ b/test/manual/indent/js.js
@@ -144,6 +144,15 @@ bar(
   /abc/
 )

+// bug#25904
+foo.bar.baz(very => // A comment
+  very
+).biz(([baz={a: [123]}, boz]) =>
+  baz
+).snarf((snorf) => /* Another comment */
+  snorf
+);
+
 // Local Variables:
 // indent-tabs-mode: nil
 // js-indent-level: 2
-- 
2.7.4