Make eshell history expansion more like bash (Bug#29821)

- Prevent expansion of quick substitutions when the initial "^" is not
  at start of line (Bug#29157).
- Allow spaces inside substitutions, so "^foo bar^baz" works.
- Allow trailing characters after substitution, so "^foo^bar^trailing"
  works.
- Throw an error when substitution does not match.

* 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.

2 files changed, 42 insertions, 21 deletions

diff --git a/lisp/eshell/em-hist.el b/lisp/eshell/em-hist.el
index 83595847bdf..62e2f57d0fd 100644
--- a/lisp/eshell/em-hist.el
+++ b/lisp/eshell/em-hist.el
@@ -581,21 +581,30 @@ See also `eshell-read-history'."
 
 (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 +639,31 @@ See also `eshell-read-history'."
                    (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
+              "^\\^\\([^^]+\\)\\^\\([^^]+\\)\\(?:\\^\\(.*\\)\\)?$"
+              line))
+    ;; Save trailing match as `eshell-history-reference' runs string-match.
+    (let ((matched-end (match-string 3 line)))
+      (concat
+       (eshell-history-reference
+        (format "!!:s/%s/%s/"
+                (match-string 1 line)
+                (match-string 2 line)))
+       matched-end))))
+
 (defun eshell-history-reference (reference)
   "Expand directory stack REFERENCE.
 The syntax used here was taken from the Bash info manual.
 Returns the resultant reference, or the same string REFERENCE if none
 matched."
-  ;; `^string1^string2^'
-  ;;      Quick Substitution.  Repeat the last command, replacing
-  ;;      STRING1 with STRING2.  Equivalent to `!!:s/string1/string2/'
-  (if (and (eshell-using-module 'eshell-pred)
-           (string-match "\\^\\([^^]+\\)\\^\\([^^]+\\)\\^?\\s-*$"
-                         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 2c12cacfff8..61af4048d54 100644
--- a/lisp/eshell/em-pred.el
+++ b/lisp/eshell/em-pred.el
@@ -545,7 +545,8 @@ that `ls -l' will show in the first column of its display. "
           (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)