bug#60186: 29.0.60; ruby-mode indentation of multi-line expressions

[Dmitry Gutov <dgutov@yandex.ru>]

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On 24/12/2022 02:17, Aaron Jensen wrote:
> On Fri, Dec 23, 2022 at 5:26 PM Dmitry Gutov <dgutov@yandex.ru> wrote:
>>
>> Is that also true for the other "codebases you've seen" referred to in
>> the first message here?
> 
> Mostly we work with Rails (and I try to avoid looking at that code as
> much as I can, though I often find myself in there...) and the
> Eventide framework: https://github.com/eventide-project

Thanks. It's very neat. I couldn't find any big app in there, though. 
And that's where the things tend to become more hairy.

> Given that the two founders of that are on my team we tend to follow
> their indentation and coding style (and it is well-thought out, with
> everything considered with respect to human cognition/eye tracking
> studies/etc.). That's probably the best example I could offer, though
> what you will find in there is that not many lines of code span more
> than one line. They (and we) tend to allow longer lines when the right
> side of the line is less important.

With code rarely spanning multiple lines, the current indentation logic 
of ruby-mode is probably working fine too.

>>> With either indentation style, the
>>> first argument (which is the most significant one when a method is
>>> properly designed) will have the least presence when scanning. It's
>>> just not a good format in my experience. In our code we take it a step
>>> further and always use parentheses except for in class level "macros".
>>
>> That's also my preference and true of the code I've seen. But "class
>> level macros" are often an important part of projects, be that
>> ActiveRecord validations, or DSL-like calls in Grape (routes, params, etc).
>>
>> So I wonder whether we should alter parenless calls' indentation for the
>> "simplified" style.
> 
> I think I would tend towards saying yes, make it simple/like the chef
> codebase. That's consistent and if one wants to line things up, then
> one can use parens, even with class level macros (or use long lines
> and not care).

All right. In the latest iteration of the patch (attached) I've split 
off the block's indentation behavior into a separate option and altered 
the indentation of the parenless calls.

In the more complex cases the results are definitely interesting:

   method arg1,
     method2 arg2,
     arg3

   zzz = method (a + b),
     c, :d => :e,
     f: g

>> Though they also like to line up the keyword arguments according to
>> Rubocop's defaults
>> (https://github.com/spree/spree/blob/main/core/app/models/spree/product.rb#L63),
>> something we don't support yet.
> 
> This line is rather painful to read and inconsistent with the call
> just below it on line 70. I would certainly not advocate for that.

I think it's consistent in the sense that the "keyword" section of the 
arguments is vertically aligned in both cases. It's a popular Rubocop 
rule, apparently.

Whether it's useful, though, I'm doubtful too.

>> Do you have a source-available example of a project in your preferred
>> coding style?
>>
>> Chef, perhaps?
>>
>> https://github.com/chef/chef/blob/main/lib/chef/application/base.rb
>> https://github.com/chef/chef/blob/main/lib/chef/application/client.rb
> 
> Yeah, I think this is probably the closest with regard to indentation
> aside from Eventide, but again, you won't find much indentation there.
> Whatever you find will likely be Vim's default, which I believe is the
> same simple two space indent we are discussing.

Okay.

>>> This means that any time we decide to split a method invocation on
>>> multiple lines we use the basic newline after ( style.
>>
>> For "class-level macros" as well?
> 
> I found inconsistencies in our codebase, so it is time for us to
> establish a new norm. My guess is that we will land on using parens
> for it. When we do it without parens, it is in the simplified style.
> 
> Thank you for your research and work on this, I appreciate it.

Thank you too.

We could also discuss cases like

   foo = bar({
               tee: 1,
               qux: 2
            })

   baz([
         1,
         2,
         3
       ])

but those would be an orthogonal feature. And I don't see them much in 
the wild, for some reason.

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diff --git a/lisp/progmodes/ruby-mode.el b/lisp/progmodes/ruby-mode.el
index a4aa61905e4..2fe1f4986ee 100644
--- a/lisp/progmodes/ruby-mode.el
+++ b/lisp/progmodes/ruby-mode.el
@@ -285,6 +285,40 @@ ruby-method-params-indent
   :safe (lambda (val) (or (memq val '(t nil)) (numberp val)))
   :version "29.1")
 
+(defcustom ruby-block-indent t
+  "Non-nil to align the body of a block to the statement's start.
+
+The body and the closer will be aligned to the column where the
+statement containing the block starts. Example:
+
+  foo.bar
+    .each do
+    baz
+  end
+
+If nil, it will be aligned instead to the beginning of the line
+containing the block's opener:
+
+  foo.bar
+    .each do
+      baz
+    end
+
+Only has effect when `ruby-use-smie' is t."
+  :type 'boolean
+  :safe 'booleanp)
+
+(defcustom ruby-indent-simplified nil
+  "Non-nil to use the indentation logic with less nesting.
+
+The result is that statements with continuations will have just 1
+level of indentation nesting.  Unless paren grouping or
+hash/array literals are involved.
+
+Only has effect when `ruby-use-smie' is t."
+  :type 'boolean
+  :safe 'booleanp)
+
 (defcustom ruby-deep-arglist t
   "Deep indent lists in parenthesis when non-nil.
 Also ignores spaces after parenthesis when `space'.
@@ -416,6 +450,7 @@ ruby-smie-grammar
      '((right "=")
        (right "+=" "-=" "*=" "/=" "%=" "**=" "&=" "|=" "^="
               "<<=" ">>=" "&&=" "||=")
+       (right "?")
        (nonassoc ".." "...")
        (left "&&" "||")
        (nonassoc "<=>")
@@ -608,10 +643,10 @@ ruby-smie--backward-token
           "def=")
          (t tok)))))))
 
-(defun ruby-smie--indent-to-stmt ()
+(defun ruby-smie--indent-to-stmt (&optional offset)
   (save-excursion
     (smie-backward-sexp ";")
-    (cons 'column (smie-indent-virtual))))
+    (cons 'column (+ (smie-indent-virtual) (or offset 0)))))
 
 (defun ruby-smie--indent-to-stmt-p (keyword)
   (or (eq t ruby-align-to-stmt-keywords)
@@ -642,7 +677,9 @@ ruby-smie-rules
               (forward-comment -1)
               (not (eq (preceding-char) ?:))))
        ;; Curly block opener.
-       (ruby-smie--indent-to-stmt))
+       (if ruby-block-indent
+           (ruby-smie--indent-to-stmt)
+         (cons 'column (current-indentation))))
       ((smie-rule-hanging-p)
        ;; Treat purely syntactic block-constructs as being part of their parent,
        ;; when the opening token is hanging and the parent is not an
@@ -678,12 +715,16 @@ ruby-smie-rules
          (cons 'column (current-column)))))
     ('(:before . " @ ")
      (if (or (eq ruby-method-params-indent t)
+             (eq ruby-indent-simplified nil)
              (not (smie-rule-parent-p "def" "def=")))
          (save-excursion
            (skip-chars-forward " \t")
            (cons 'column (current-column)))
        (smie-rule-parent (or ruby-method-params-indent 0))))
-    ('(:before . "do") (ruby-smie--indent-to-stmt))
+    ('(:before . "do")
+     (if ruby-block-indent
+         (ruby-smie--indent-to-stmt)
+       (cons 'column (current-indentation))))
     ('(:before . ".")
      (if (smie-rule-sibling-p)
          (when ruby-align-chained-calls
@@ -696,8 +737,10 @@ ruby-smie-rules
                    (not (smie-rule-bolp)))))
            (cons 'column (current-column)))
        (smie-backward-sexp ".")
-       (cons 'column (+ (current-column)
-                        ruby-indent-level))))
+       (if ruby-indent-simplified
+           (ruby-smie--indent-to-stmt ruby-indent-level)
+         (cons 'column (+ (current-column)
+                          ruby-indent-level)))))
     (`(:before . ,(or "else" "then" "elsif" "rescue" "ensure"))
      (smie-rule-parent))
     (`(:before . ,(or "when" "in"))
@@ -710,14 +753,16 @@ ruby-smie-rules
                      "<<=" ">>=" "&&=" "||=" "and" "or"))
      (and (smie-rule-parent-p ";" nil)
           (smie-indent--hanging-p)
-          ruby-indent-level))
+          (if ruby-indent-simplified
+              (ruby-smie--indent-to-stmt ruby-indent-level)
+            ruby-indent-level)))
     (`(:before . "=")
      (save-excursion
       (and (smie-rule-parent-p " @ ")
            (goto-char (nth 1 (smie-indent--parent)))
            (smie-rule-prev-p "def=")
            (cons 'column (+ (current-column) ruby-indent-level -3)))))
-    (`(:after . ,(or "?" ":")) ruby-indent-level)
+    (`(:after . ,(or "?" ":")) (unless ruby-indent-simplified ruby-indent-level))
     (`(:before . ,(guard (memq (intern-soft token) ruby-alignable-keywords)))
      (when (not (ruby--at-indentation-p))
        (if (ruby-smie--indent-to-stmt-p token)
@@ -725,7 +770,21 @@ ruby-smie-rules
          (cons 'column (current-column)))))
     ('(:before . "iuwu-mod")
      (smie-rule-parent ruby-indent-level))
-    ))
+    (`(:before . ",")
+     (and ruby-indent-simplified
+          (smie-rule-parent-p " @ ")
+          (ruby-smie--indent-to-stmt ruby-indent-level)))
+    (`(:before . ,_)
+     (when (and ruby-indent-simplified
+                (not (or (member token '(","))
+                         (smie-rule-prev-p ";"))))
+       (let* ((stmt-beg (save-excursion
+                          (smie-backward-sexp ";")
+                          (point)))
+              (nls (1- (count-lines stmt-beg (point)))))
+         (when (smie-indent--hanging-p)
+           (cl-incf nls))
+         (ruby-smie--indent-to-stmt (if (> nls 0) ruby-indent-level 0)))))))
 
 (defun ruby--at-indentation-p (&optional point)
   (save-excursion
diff --git a/test/lisp/progmodes/ruby-mode-resources/ruby-block-indent.rb b/test/lisp/progmodes/ruby-mode-resources/ruby-block-indent.rb
new file mode 100644
index 00000000000..03acdda6fb0
--- /dev/null
+++ b/test/lisp/progmodes/ruby-mode-resources/ruby-block-indent.rb
@@ -0,0 +1,15 @@
+foo
+  .asdasd
+  .proc do |**args|
+    p(**args)
+  end
+
+foo
+  .asdasd
+  .proc { |**args|
+    p(**args)
+  }
+
+# Local Variables:
+# ruby-block-indent: nil
+# End:
diff --git a/test/lisp/progmodes/ruby-mode-resources/ruby-indent-simplified.rb b/test/lisp/progmodes/ruby-mode-resources/ruby-indent-simplified.rb
new file mode 100644
index 00000000000..aaecc7f7422
--- /dev/null
+++ b/test/lisp/progmodes/ruby-mode-resources/ruby-indent-simplified.rb
@@ -0,0 +1,61 @@
+4 +
+  5 +
+  6 +
+  7
+
+foo = obj.bar { |m| tee(m) } +
+  obj.qux { |m| hum(m) }
+
+foo(a,
+    b)
+
+foo.
+  bar
+  .baz
+
+method arg1,                   # bug#15594
+  method2 arg2,
+  arg3
+
+zzz = method (a + b),
+  c, :d => :e,
+  f: g
+
+qux = foo.fee ?
+  bar :
+  tee
+
+foo2 =
+  subject.
+  update(
+    2
+  )
+
+bar.foo do
+  bar
+end
+
+bar.foo(tee) do
+  bar
+end
+
+bar.foo(tee) {
+  bar
+}
+
+# Endless methods.
+class Bar
+  def foo(abc) = bar +
+    baz
+end
+
+x.foo do
+  foo
+end.bar do
+  bar
+end
+
+# Local Variables:
+# ruby-method-params-indent: t
+# ruby-indent-simplified: t
+# End:
diff --git a/test/lisp/progmodes/ruby-mode-resources/ruby.rb b/test/lisp/progmodes/ruby-mode-resources/ruby.rb
index 6a69d9db78a..7f2a665f2f4 100644
--- a/test/lisp/progmodes/ruby-mode-resources/ruby.rb
+++ b/test/lisp/progmodes/ruby-mode-resources/ruby.rb
@@ -226,6 +226,7 @@ def begin
 
 foo.
   bar
+  .baz
 
 # https://github.com/rails/rails/blob/17f5d8e062909f1fcae25351834d8e89967b645e/activesupport/lib/active_support/time_with_zone.rb#L206
 foo # comment intended to confuse the tokenizer
@@ -380,6 +381,18 @@ def bar
   i + 1
 end
 
+m1 = foo
+       .asdasd
+       .proc do |**args|
+  p(**args)
+end
+
+m2 = foo
+       .asdasd
+       .proc { |**args|
+  p(**args)
+}
+
 bar.foo do
   bar
 end
@@ -398,6 +411,12 @@ def bar
   end
 end
 
+x.foo do
+  foo
+end.bar do
+  bar
+end
+
 foo |
   bar
 
@@ -541,4 +560,6 @@ def baz.full_name = "#{bar} 3"
 
 # Local Variables:
 # ruby-method-params-indent: t
+# ruby-indent-simplified: nil
+# ruby-block-indent: t
 # End:
diff --git a/test/lisp/progmodes/ruby-mode-tests.el b/test/lisp/progmodes/ruby-mode-tests.el
index 560f780285a..3b0ec8a0324 100644
--- a/test/lisp/progmodes/ruby-mode-tests.el
+++ b/test/lisp/progmodes/ruby-mode-tests.el
@@ -957,6 +957,8 @@ ruby-deftest-indent
 
 (ruby-deftest-indent "ruby.rb")
 (ruby-deftest-indent "ruby-method-params-indent.rb")
+(ruby-deftest-indent "ruby-indent-simplified.rb")
+(ruby-deftest-indent "ruby-block-indent.rb")
 
 (ert-deftest ruby--test-chained-indentation ()
   (with-temp-buffer