(sh-quoted-exec): New face for quoted exec constructs like `foo bar`.

(sh-quoted-subshell): New helper function to search for a possibly nested
subshell (like `` or $()) within a "" quoted string.
(sh-font-lock-keywords-var): Add sh-quoted-exec for Bash.
(sh-apply-quoted-subshell): Flag quote characters inside a subshell, which is
itself already in a quoted region, as punctuation, since this is the closest
to what they actually are.
(sh-font-lock-syntactic-keywords): Add sh-quoted-subshell and
sh-apply-quoted-subshell.
(sh-font-lock-syntactic-face-function): Apply the new face for text inside ``
instead of the old font-lock-string-face.

2 files changed, 91 insertions, 6 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 9d4a6d0de47..8f29118a10e 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,18 @@
+2006-05-20  Vivek Dasmohapatra  <vivek@etla.org>
+
+        * progmodes/sh-script.el (sh-quoted-exec): New face for quoted
+        exec constructs like `foo bar`.
+        (sh-quoted-subshell): New helper function to search for a possibly
+        nested subshell (like `` or $()) within a "" quoted string.
+        (sh-font-lock-keywords-var): Add sh-quoted-exec for Bash.
+        (sh-apply-quoted-subshell): Flag quote characters inside a
+        subshell, which is itself already in a quoted region, as
+        punctuation, since this is the closest to what they actually are.
+        (sh-font-lock-syntactic-keywords): Add sh-quoted-subshell and
+        sh-apply-quoted-subshell.
+        (sh-font-lock-syntactic-face-function): Apply the new face for
+        text inside `` instead of the old font-lock-string-face.
+
 2006-06-03  YAMAMOTO Mitsuharu  <mituharu@math.s.chiba-u.ac.jp>
 
         * term/mac-win.el (mac-ts-active-input-overlay): Add defvar.
diff --git a/lisp/progmodes/sh-script.el b/lisp/progmodes/sh-script.el
index ab3da050456..ef80d28c578 100644
--- a/lisp/progmodes/sh-script.el
+++ b/lisp/progmodes/sh-script.el
@@ -814,6 +814,18 @@ See `sh-feature'.")
      (:weight bold)))
   "Face to show a here-document"
   :group 'sh-indentation)
+
+;; These colours are probably icky.  It's just a placeholder though.
+(defface sh-quoted-exec
+  '((((class color) (background dark))
+     (:foreground "salmon"))
+    (((class color) (background light))
+     (:foreground "magenta"))
+    (t
+     (:weight bold)))
+  "Face to show quoted execs like ``"
+  :group 'sh-indentation)
+
 ;; backward-compatibility alias
 (put 'sh-heredoc-face 'face-alias 'sh-heredoc)
 (defvar sh-heredoc-face 'sh-heredoc)
@@ -833,7 +845,7 @@ See `sh-feature'.")
          font-lock-variable-name-face))
 
     (rc sh-append es)
-
+    (bash sh-append shell ("\\$(\\(\\sw+\\)" (1 'sh-quoted-exec t) ))
     (sh sh-append shell
         ;; Variable names.
         ("\\$\\({#?\\)?\\([A-Za-z_][A-Za-z0-9_]*\\|[-#?@!]\\)" 2
@@ -967,6 +979,49 @@ Point is at the beginning of the next line."
   ;; This looks silly, but it's because `sh-here-doc-re' keeps changing.
   (re-search-forward sh-here-doc-re limit t))
 
+(defun sh-quoted-subshell (limit)
+  "Search for a subshell embedded in a string. Find all the unescaped
+\" characters within said subshell, remembering that subshells can nest."
+  (if (re-search-forward "\"\\(?:.\\|\n\\)*?\\(\\$(\\|`\\)" limit t)
+      ;; bingo we have a $( or a ` inside a ""
+      (let ((char (char-after (point)))
+            (continue t)
+            (pos (point))
+            (data nil)    ;; value to put into match-data (and return)
+            (last nil)    ;; last char seen
+            (bq  (equal (match-string 1) "`")) ;; ` state flip-flop
+            (seen nil)    ;; list of important positions
+            (nest 1))     ;; subshell nesting level
+        (while (and continue char (<= pos limit))
+          ;; unescaped " inside a $( ... ) construct.
+          ;; state machine time...
+          ;; \ => ignore next char;
+          ;; ` => increase or decrease nesting level based on bq flag
+          ;; ) [where nesting > 0] => decrease nesting
+          ;; ( [where nesting > 0] => increase nesting
+          ;; ( [preceeded by $ ]   => increase nesting
+          ;; " [nesting <= 0 ]     => terminate, we're done.
+          ;; " [nesting >  0 ]     => remember this, it's not a proper "
+          (if (eq ?\\ last) nil
+            (if (eq ?\` char) (setq nest (+ nest (if bq -1 1)) bq (not bq))
+              (if (and (> nest 0) (eq ?\) char))  (setq nest (1- nest))
+                (if (and (eq ?$ last) (eq ?\( char)) (setq nest (1+ nest))
+                  (if (and (> nest 0) (eq ?\( char)) (setq nest (1+ nest))
+                    (if (eq char ?\")
+                        (if (>= 0 nest) (setq continue nil)
+                          (setq seen (cons pos seen)) ) ))))))
+          ;;(message "POS: %d [%d]" pos nest)
+          (setq last char
+                pos  (1+ pos)
+                char (char-after pos)) )
+        (when seen
+          ;;(message "SEEN: %S" seen)
+          (setq data (list (current-buffer)))
+          (mapc (lambda (P)
+                  (setq data (cons P (cons (1+ P) data)) ) ) seen)
+          (store-match-data data))
+        data) ))
+
 (defun sh-is-quoted-p (pos)
   (and (eq (char-before pos) ?\\)
        (not (sh-is-quoted-p (1- pos)))))
@@ -997,6 +1052,17 @@ Point is at the beginning of the next line."
     (when (save-excursion (backward-char 2) (looking-at ";;\\|in"))
       sh-st-punc)))
 
+(defun sh-apply-quoted-subshell ()
+  "Apply the `sh-st-punc' syntax to all the matches in `match-data'.
+This is used to flag quote characters in subshell constructs inside strings
+\(which should therefore not be treated as normal quote characters\)"
+  (let ((m (match-data)) a b)
+    (while m
+      (setq a (car  m)
+            b (cadr m)
+            m (cddr m))
+      (put-text-property a b 'syntax-table sh-st-punc))) sh-st-punc)
+
 (defconst sh-font-lock-syntactic-keywords
   ;; A `#' begins a comment when it is unquoted and at the beginning of a
   ;; word.  In the shell, words are separated by metacharacters.
@@ -1007,6 +1073,9 @@ Point is at the beginning of the next line."
     ("\\(\\\\\\)'" 1 ,sh-st-punc)
     ;; Make sure $@ and @? are correctly recognized as sexps.
     ("\\$\\([?@]\\)" 1 ,sh-st-symbol)
+    ;; highlight (possibly nested) subshells inside "" quoted regions correctly.
+    (sh-quoted-subshell
+     (1 (sh-apply-quoted-subshell) t t))
     ;; Find HEREDOC starters and add a corresponding rule for the ender.
     (sh-font-lock-here-doc
      (2 (sh-font-lock-open-heredoc
@@ -1019,11 +1088,12 @@ Point is at the beginning of the next line."
     (")" 0 (sh-font-lock-paren (match-beginning 0)))))
 
 (defun sh-font-lock-syntactic-face-function (state)
-  (if (nth 3 state)
-      (if (char-valid-p (nth 3 state))
-          font-lock-string-face
-        sh-heredoc-face)
-    font-lock-comment-face))
+  (let ((q (nth 3 state)))
+    (if q
+        (if (char-valid-p q)
+            (if (eq q ?\`) 'sh-quoted-exec font-lock-string-face)
+          sh-heredoc-face)
+      font-lock-comment-face)))
 
 (defgroup sh-indentation nil
   "Variables controlling indentation in shell scripts.