bug#29821: Ensure quick substitution only occurs at start of line

[Jay Kamat <jaygkamat@gmail.com>]

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Noam Postavsky <npostavs@users.sourceforge.net> writes:
> Oh, yes, I was confused by your docstring.  By "if no match found" you
> meant when the line doesn't match ^foo^bar^ at all; I had somehow got
> the impression you meant that there was no match for "foo".

Ah, yes, I'll try to make the docstring a bit more clear!

> This eq test will always be nil, right?  Because the only time it's t
> is when you pass something that's not a history reference, but the thing
> we passed is a history reference by construction.  So this could be
> simplified to

Yup, that's true, I'll simplify that down.

Here's a patch which tries to fix those issues.

Thanks again,
-Jay


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From e7632214858e9f12eed5d9c3cba1fb3c37529db5 Mon Sep 17 00:00:00 2001
From: Jay Kamat <jaygkamat@gmail.com>
Date: Fri, 22 Dec 2017 15:34:44 -0800
Subject: [PATCH] Prevent expansion of quick substitutions when not at start of
 line

See bug #29157 for an initial report

Also, allow spaces inside substitutions, so ^foo bar^baz works.

* lisp/eshell/em-hist.el (eshell-expand-history-references): Expand
  history substitution before other types of expansions, and expand
  them with the whole line.
(eshell-history-substitution): New function to expand only
substitutions, taking in the entire typed line rather than individual
arguments.
---
 lisp/eshell/em-hist.el | 55 ++++++++++++++++++++++++++++++++------------------
 lisp/eshell/em-pred.el |  3 ++-
 2 files changed, 37 insertions(+), 21 deletions(-)

diff --git a/lisp/eshell/em-hist.el b/lisp/eshell/em-hist.el
index df462a7058..b75d218110 100644
--- a/lisp/eshell/em-hist.el
+++ b/lisp/eshell/em-hist.el
@@ -581,21 +581,30 @@ eshell-hist-parse-arguments
 
 (defun eshell-expand-history-references (beg end)
   "Parse and expand any history references in current input."
-  (let ((result (eshell-hist-parse-arguments beg end)))
+  (let ((result (eshell-hist-parse-arguments beg end))
+	(full-line (buffer-substring-no-properties beg end)))
     (when result
       (let ((textargs (nreverse (nth 0 result)))
 	    (posb (nreverse (nth 1 result)))
-	    (pose (nreverse (nth 2 result))))
+	    (pose (nreverse (nth 2 result)))
+	    (full-line-subst (eshell-history-substitution full-line)))
 	(save-excursion
-	  (while textargs
-	    (let ((str (eshell-history-reference (car textargs))))
-	      (unless (eq str (car textargs))
-		(goto-char (car posb))
-		(insert-and-inherit str)
-		(delete-char (- (car pose) (car posb)))))
-	    (setq textargs (cdr textargs)
-		  posb (cdr posb)
-		  pose (cdr pose))))))))
+	  (if full-line-subst
+	      ;; Found a ^foo^bar substitution
+	      (progn
+		(goto-char beg)
+		(insert-and-inherit full-line-subst)
+		(delete-char (- end beg)))
+	    ;; Try to expand other substitutions
+	    (while textargs
+	      (let ((str (eshell-history-reference (car textargs))))
+		(unless (eq str (car textargs))
+		  (goto-char (car posb))
+		  (insert-and-inherit str)
+		  (delete-char (- (car pose) (car posb)))))
+	      (setq textargs (cdr textargs)
+		    posb (cdr posb)
+		    pose (cdr pose)))))))))
 
 (defvar pcomplete-stub)
 (defvar pcomplete-last-completion-raw)
@@ -630,20 +639,26 @@ eshell-complete-history-reference
 		   (setq history (cdr history)))
 		 (cdr fhist)))))))
 
+(defun eshell-history-substitution (line)
+  "Expand quick hist substitutions formatted as ^foo^bar^.
+Returns nil if string does not match quick substitution format,
+and acts like !!:s/foo/bar/ otherwise."
+  ;; `^string1^string2^'
+  ;;      Quick Substitution.  Repeat the last command, replacing
+  ;;      STRING1 with STRING2.  Equivalent to `!!:s/string1/string2/'
+  (when (and (eshell-using-module 'eshell-pred)
+	     (string-match "^\\^\\([^^]+\\)\\^\\([^^]+\\)\\^?\\s-*$"
+			   line))
+    (eshell-history-reference
+     (format "!!:s/%s/%s/"
+	     (match-string 1 line)
+	     (match-string 2 line)))))
+
 (defun eshell-history-reference (reference)
   "Expand directory stack REFERENCE.
 The syntax used here was taken from the Bash info manual.
 Returns the resultant reference, or the same string REFERENCE if none
 matched."
-  ;; `^string1^string2^'
-  ;;      Quick Substitution.  Repeat the last command, replacing
-  ;;      STRING1 with STRING2.  Equivalent to `!!:s/string1/string2/'
-  (if (and (eshell-using-module 'eshell-pred)
-	   (string-match "\\^\\([^^]+\\)\\^\\([^^]+\\)\\^?\\s-*$"
-			 reference))
-      (setq reference (format "!!:s/%s/%s/"
-			      (match-string 1 reference)
-			      (match-string 2 reference))))
   ;; `!'
   ;;      Start a history substitution, except when followed by a
   ;;      space, tab, the end of the line, = or (.
diff --git a/lisp/eshell/em-pred.el b/lisp/eshell/em-pred.el
index 72a7bc4afc..86a9d4262a 100644
--- a/lisp/eshell/em-pred.el
+++ b/lisp/eshell/em-pred.el
@@ -545,7 +545,8 @@ eshell-pred-substitute
 	  (function
 	   (lambda (str)
 	     (if (string-match ,match str)
-		 (setq str (replace-match ,replace t nil str)))
+		 (setq str (replace-match ,replace t nil str))
+	       (error (concat str ": substitution failed")))
 	     str)) lst)))))
 
 (defun eshell-include-members (&optional invert-p)
-- 
2.11.0