electric-layout-mode kicks in before electric-pair-mode

This aims to solve problems with indentation.  Previously in, say, a
js-mode buffer with electric-layout-rules set to

   (?\{ before after)
   (?\} before)

would produce an intended:

   function ()
   {
     <indented point>
   }

The initial state

  function () {

Would go immediately to the following by e-p-m

  function () {}

Only then would e-l-m be applied to } first, and then again to {.
This makes lines indent in the wrong order, which can be a problem in
some modes.

The way we fix this is by reversing the order of e-p-m and e-l-m in
the post-self-insert-hook (and also fixing a number of details that
this uncovered).  In the end this changes the sequence from

  function () {

By way of e-l-m becomes:

  function () <newline>
  {
  <newline>

The e-p-m inserts the pair

  function () <newline>
  {
  <newline>}

And then e-l-m kicks in for the pair again, yielding the desired result

  function () <newline>
  {
  <indented point>
  }

* lisp/elec-pair.el (electric-pair--insert): Bind
electric-layout-no-duplicate-newlines.
(electric-pair-inhibit-if-helps-balance)
(electric-pair-skip-if-helps-balance): Use insert-before-markers,
playing nice with save-excurion.
(electric-pair-post-self-insert-function): Go to correct position
before checking electric-pair-inhibit-predicate and
electric-pair-skip-self predicate.
(electric-pair-post-self-insert-function): Increase priority to
50.

* lisp/electric.el (electric-indent-post-self-insert-function):
Delete trailing space in reindented line only if line was
really reindented.  Rewrite comment.
(electric-layout-allow-duplicate-newlines): New variable.
(electric-layout-post-self-insert-function-1): Rewrite comments.
Honours electric-layout-allow-duplicate-newlines.  Don't reindent
previous line because racecar.

* test/lisp/electric-tests.el: New test.
(plainer-c-mode): Move up.
(electric-modes-int-main-allman-style)
(electric-layout-int-main-kernel-style): Simplify
electric-layout-rules.
(electric-layout-for-c-style-du-jour): New helper.
(electric-layout-plainer-c-mode-use-c-style): New test.

1 files changed, 50 insertions, 7 deletions

diff --git a/test/lisp/electric-tests.el b/test/lisp/electric-tests.el
index 0b076e4be01..4f1e5729be1 100644
--- a/test/lisp/electric-tests.el
+++ b/test/lisp/electric-tests.el
@@ -391,11 +391,12 @@ baz\"\""
   :bindings '((electric-pair-skip-whitespace . chomp))
   :test-in-comments nil)
 
-(define-electric-pair-test whitespace-chomping-2
-  " ( \n\t\t\n  )  " "--)------" :expected-string " ()  " :expected-point 4
-  :bindings '((electric-pair-skip-whitespace . chomp))
-  :modes '(c++-mode)
-  :test-in-comments nil)
+(ert-deftest electric-pair-whitespace-chomping-2-at-point-4-in-c++-mode-in-strings nil
+  "Check if whitespace chomping works in `c++' unterminated strings."
+  (electric-pair-test-for
+   "\" ( \n		\n  )  \"" 4 41 "\" ()  \"" 5 'c++-mode
+   '((electric-pair-skip-whitespace . chomp))
+   (lambda () (electric-pair-mode 1))))
 ;; A test failure introduced by:
 ;;
 ;;    bb591f139f: Enhance CC Mode's fontification, etc., of unterminated strings.
@@ -513,6 +514,7 @@ baz\"\""
   :fixture-fn #'(lambda ()
                   (electric-pair-mode 1)))
 
+
 (define-electric-pair-test js-mode-braces-with-layout
   "" "{" :expected-string "{\n\n}" :expected-point 3
   :modes '(js-mode)
@@ -532,6 +534,16 @@ baz\"\""
                   (electric-indent-mode 1)
                   (electric-layout-mode 1)))
 
+(define-electric-pair-test js-mode-braces-with-layout-and-indent
+  "" "{" :expected-string "{\n    \n}" :expected-point 7
+  :modes '(js-mode)
+  :test-in-comments nil
+  :test-in-strings nil
+  :fixture-fn #'(lambda ()
+                  (electric-pair-mode 1)
+                  (electric-indent-mode 1)
+                  (electric-layout-mode 1)))
+
 
 ;;; Backspacing
 ;;; TODO: better tests
@@ -821,6 +833,35 @@ baz\"\""
 
 ;;; tests for `electric-layout-mode'
 
+(define-derived-mode plainer-c-mode c-mode "pC"
+  "A plainer/saner C-mode with no internal electric machinery."
+  (c-toggle-electric-state -1)
+  (setq-local electric-indent-local-mode-hook nil)
+  (setq-local electric-indent-mode-hook nil)
+  (electric-indent-local-mode 1)
+  (dolist (key '(?\" ?\' ?\{ ?\} ?\( ?\) ?\[ ?\]))
+    (local-set-key (vector key) 'self-insert-command)))
+
+(defun electric-layout-for-c-style-du-jour (inserted)
+  "A function to use in `electric-layout-rules'"
+  (when (memq inserted '(?{ ?}))
+    (save-excursion
+      (backward-char 2) (c-point-syntax) (forward-char) ; silly, but needed
+      (c-brace-newlines (c-point-syntax)))))
+
+(ert-deftest electric-layout-plainer-c-mode-use-c-style ()
+  (ert-with-test-buffer ()
+    (plainer-c-mode)
+    (electric-layout-local-mode 1)
+    (electric-pair-local-mode 1)
+    (electric-indent-local-mode 1)
+    (setq-local electric-layout-rules
+                '(electric-layout-for-c-style-du-jour))
+    (insert "int main () ")
+    (let ((last-command-event ?\{))
+      (call-interactively (key-binding `[,last-command-event])))
+    (should (equal (buffer-string) "int main ()\n{\n  \n}\n"))))
+
 (ert-deftest electric-layout-int-main-kernel-style ()
   (ert-with-test-buffer ()
     (plainer-c-mode)
@@ -828,7 +869,8 @@ baz\"\""
     (electric-pair-local-mode 1)
     (electric-indent-local-mode 1)
     (setq-local electric-layout-rules
-                '((?\{ . (after-stay after))))
+                '((?\{ . (after))
+                  (?\} . (before))))
     (insert "int main () ")
     (let ((last-command-event ?\{))
       (call-interactively (key-binding `[,last-command-event])))
@@ -850,7 +892,8 @@ baz\"\""
     (electric-pair-local-mode 1)
     (electric-indent-local-mode 1)
     (setq-local electric-layout-rules
-                '((?\{ . (before after-stay after))))
+                '((?\{ . (before after))
+                  (?\} . (before))))
     (insert "int main () ")
     (let ((last-command-event ?\{))
       (call-interactively (key-binding `[,last-command-event])))