bug#16593: 24.3.50; ruby-mode: align chained method calls on multiple lines

[Dmitry Gutov <dgutov@yandex.ru>]

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On 30.01.2014 16:35, Stefan Monnier wrote:
>> Warning (smie): Conflict: . </= .
>> Warning (smie): Conflict: . </= .
>
> The smie-precs->prec2 part of your grammar says that "." = "." (because
> of the new (assoc ".") you add there).
>
> But the BNF part of your grammar says "." < "." (i.e. "foo . bar . baz"
> is parsed as "foo . (bar . baz)" because of (id "." exp).

Fantastic, thanks for the explanation. With (assoc ".") changed to 
(right "."), the warning is gone.

I've also fixed the precedence of "." vs "? :" and modified a test case 
respectively. See the new patch attached.

Do you think it's not too late in the feature freeze to install a change 
like this, or should we wait until the trunk reopens?

We have a decent number of test cases, so it's not like the patch is 
likely to introduce major breakage.

> Apparently there is no more conflict in the BNF in this respect so the
> disambiguation constraint (assoc ".") that's passed to it is ignored.

Without that constraint there, SMIE showed warnings about ambiguities 
between ".", "," and "=". It somehow ignored the associativity, though.

The warnings with the previous patch also were gone when only the second 
one (assoc ".") were changed to (right "."). The first one, in the BNF 
disambiguation part, could be either.

Bozhidar, would you care to test the new patch?

[-- Attachment #2: ruby-chained-calls.diff --]
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=== modified file 'lisp/progmodes/ruby-mode.el'
--- lisp/progmodes/ruby-mode.el	2014-01-17 03:15:02 +0000
+++ lisp/progmodes/ruby-mode.el	2014-01-31 03:17:28 +0000
@@ -264,6 +264,13 @@
   :safe 'listp
   :version "24.4")
 
+(defcustom ruby-align-chained-calls nil
+  "If non-nil, chained method calls on multiple lines will be
+aligned to the same column."
+  :type 'boolean
+  :group 'ruby
+  :safe 'booleanp)
+
 (defcustom ruby-deep-arglist t
   "Deep indent lists in parenthesis when non-nil.
 Also ignores spaces after parenthesis when `space'.
@@ -350,10 +357,10 @@
              ;; but avoids lots of conflicts:
              (exp "and" exp) (exp "or" exp))
        (exp  (exp1) (exp "," exp) (exp "=" exp)
-             (id " @ " exp)
-             (exp "." id))
+             (id " @ " exp))
        (exp1 (exp2) (exp2 "?" exp1 ":" exp1))
-       (exp2 ("def" insts "end")
+       (exp2 (exp3) (exp3 "." exp2))
+       (exp3 ("def" insts "end")
              ("begin" insts-rescue-insts "end")
              ("do" insts "end")
              ("class" insts "end") ("module" insts "end")
@@ -380,7 +387,7 @@
        (ielsei (itheni) (itheni "else" insts))
        (if-body (ielsei) (if-body "elsif" if-body)))
      '((nonassoc "in") (assoc ";") (right " @ ")
-       (assoc ",") (right "=") (assoc "."))
+       (assoc ",") (right "="))
      '((assoc "when"))
      '((assoc "elsif"))
      '((assoc "rescue" "ensure"))
@@ -399,7 +406,8 @@
        (nonassoc ">" ">=" "<" "<=")
        (nonassoc "==" "===" "!=")
        (nonassoc "=~" "!~")
-       (left "<<" ">>"))))))
+       (left "<<" ">>")
+       (right "."))))))
 
 (defun ruby-smie--bosp ()
   (save-excursion (skip-chars-backward " \t")
@@ -609,7 +617,18 @@
         ;; When after `.', let's always de-indent,
         ;; because when `.' is inside the line, the
         ;; additional indentation from it looks out of place.
-        ((smie-rule-parent-p ".") (smie-rule-parent (- ruby-indent-level)))
+        ((smie-rule-parent-p ".")
+         (let (smie--parent)
+           (save-excursion
+             ;; Traverse up the parents until the parent is "." at
+             ;; indentation, or any other token.
+             (while (and (progn
+                           (goto-char (1- (cadr (smie-indent--parent))))
+                           (not (ruby-smie--bosp)))
+                         (progn
+                           (setq smie--parent nil)
+                           (smie-rule-parent-p "."))))
+             (smie-rule-parent))))
         (t (smie-rule-parent))))))
     (`(:after . ,(or `"(" "[" "{"))
      ;; FIXME: Shouldn't this be the default behavior of
@@ -622,7 +641,10 @@
        (unless (or (eolp) (forward-comment 1))
          (cons 'column (current-column)))))
     (`(:before . "do") (ruby-smie--indent-to-stmt))
-    (`(:before . ".") ruby-indent-level)
+    (`(:before . ".")
+     (if (smie-rule-sibling-p)
+         (and ruby-align-chained-calls 0)
+       ruby-indent-level))
     (`(:after . "=>") ruby-indent-level)
     (`(:before . ,(or `"else" `"then" `"elsif" `"rescue" `"ensure"))
      (smie-rule-parent))

=== modified file 'test/automated/ruby-mode-tests.el'
--- test/automated/ruby-mode-tests.el	2014-01-01 07:43:34 +0000
+++ test/automated/ruby-mode-tests.el	2014-01-30 04:15:02 +0000
@@ -333,6 +333,20 @@
      |      42
      |    end")))
 
+(ert-deftest ruby-align-chained-calls ()
+  (let ((ruby-align-chained-calls t))
+    (ruby-should-indent-buffer
+     "one.two.three
+     |       .four
+     |
+     |my_array.select { |str| str.size > 5 }
+     |        .map    { |str| str.downcase }"
+     "one.two.three
+     |  .four
+     |
+     |my_array.select { |str| str.size > 5 }
+     |   .map    { |str| str.downcase }")))
+
 (ert-deftest ruby-move-to-block-stops-at-indentation ()
   (ruby-with-temp-buffer "def f\nend"
     (beginning-of-line)

=== modified file 'test/indent/ruby.rb'
--- test/indent/ruby.rb	2014-01-17 03:15:02 +0000
+++ test/indent/ruby.rb	2014-01-31 02:55:31 +0000
@@ -257,8 +257,8 @@
   bar
 
 foo_bar_tee(1, 2, 3)
-  .qux
-  .bar
+  .qux.bar
+  .tee
 
 foo do
   bar
@@ -338,7 +338,7 @@
 %^abc^
 ddd
 
-qux = foo ?
+qux = foo.fee ?
         bar :
         tee
 
@@ -348,7 +348,7 @@
 
 zoo
   .lose(
-  q, p)
+    q, p)
 
 foo(bar:
       tee)