From e1308c8f6aea05ad6dbcaa33b9bee4eb7e05ee39 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Krzywkowski?= <k.michal@zoho.com>
Date: Sun, 2 Dec 2018 12:07:06 +0100
Subject: [PATCH] Per #4: Add implicit parenthesized expression

---
 README.org |  7 +++++++
 ialign.el  | 32 +++++++++++++++++++++++++++-----
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/README.org b/README.org
index cd4f684..22d0286 100644
--- a/README.org
+++ b/README.org
@@ -130,6 +130,13 @@
 ** ~ialign-initial-repeat~
    Default state of ~repeat~ argument passed to ~align-regexp~.
 
+   The default value is ~nil~.
+** ~ialign-implicit-regexp~
+   String to prepend to the regexp, if the regex doesn't have a subgroup.
+   
+   Set this to ~\\(\\s-*\\)~ to implicitly prepend that string to
+   the regexp, if the regexp doesn't contain a subgroup expression.
+
    The default value is ~nil~.
 * License
   This program is free software: you can redistribute it and/or modify
diff --git a/ialign.el b/ialign.el
index 543992f..8652cc5 100644
--- a/ialign.el
+++ b/ialign.el
@@ -101,6 +101,20 @@ or equal to this, otherwise do not update."
   :group 'ialign
   :type 'boolean)
 
+(defcustom ialign-implicit-regexp nil
+  "String to prepend to the regexp, if the regexp doesn't have a subgroup.
+
+`align-regexp' expects the align regexp to contain a
+parenthesized subexpression whose characters are replaced.
+However, it adds such an expression automatically to the regexp
+if necessary.  This option allows you to specify the string to
+implicitly prepend to the string in case there's no group
+subexpression."
+  :group 'ialign
+  :type '(choice (const :tag "Don't add implicit group" nil)
+                 (const :tag "Whitespace" "\\(\\s-*\\)")
+                 string))
+
 (defvaralias 'ialign-initial-spacing 'ialign-default-spacing)
 
 (defvar ialign--buffer nil)
@@ -193,11 +207,19 @@ help"))))
 (defun ialign--align ()
   "Revert the current region, then align it."
   (ialign--revert)
-  (ialign--with-region-narrowed
-   (let ((case-fold-search ialign--case-fold-search)
-	 (indent-tabs-mode (ialign--enable-tabs-p)))
-     (align-regexp (point-min) (point-max) ialign--regexp
-		   ialign--group ialign--spacing ialign--repeat))))
+  (let ((reg ialign--regexp))
+    (when (and (null (string-match-p (regexp-quote "\\(") reg))
+               (stringp ialign-implicit-regexp)
+               (= 1 ialign--group))
+      (setq reg (concat ialign-implicit-regexp reg))
+      (setq ialign--error "Using implicit regexp")
+      (when (minibufferp)
+        (ialign--update-minibuffer-prompt)))
+    (ialign--with-region-narrowed
+     (let ((case-fold-search ialign--case-fold-search)
+           (indent-tabs-mode (ialign--enable-tabs-p)))
+       (align-regexp (point-min) (point-max) reg
+                     ialign--group ialign--spacing ialign--repeat)))))
 
 (defun ialign--undo (beg end orig)
   "Delete region BEG END and insert ORIG at BEG.