* lisp/multifile.el: New file, extracted from etags.el

The main motivation for this change was the introduction of
project-query-replace.  dired's multi-file query&replace was implemented
on top of etags.el even though it did not use TAGS in any way, so I moved
this generic multifile code into its own package, with a nicer interface,
and then used that in project.el.

* lisp/progmodes/project.el (project-files): New generic function.
(project-search, project-query-replace): New commands.

* lisp/dired-aux.el (dired-do-search, dired-do-query-replace-regexp):
Use multifile.el instead of etags.el.

* lisp/progmodes/etags.el: Remove redundant :groups.
(next-file-list): Remove var.
(tags-loop-revert-buffers): Make it an obsolete alias.
(next-file): Don't autoload (it can't do anything useful before some
other etags.el function setup the multifile operation).
(tags--all-files): New function, extracted from next-file.
(tags-next-file): Rename from next-file.
Rewrite using tags--all-files and multifile-next-file.
(next-file): Keep it as an obsolete alias.
(tags-loop-operate, tags-loop-scan): Mark as obsolete.
(tags--compat-files, tags--compat-initialize): New function.
(tags-loop-continue): Rewrite using multifile-continue.  Mark as obsolete.
(tags--last-search-operate-function): New var.
(tags-search, tags-query-replace): Rewrite using multifile.el.

* lisp/emacs-lisp/generator.el (iter-end-of-sequence): Use 'define-error'.
(iter-make): New macro.
(iter-empty): New iterator.

* lisp/menu-bar.el (menu-bar-search-menu, menu-bar-replace-menu):
tags-loop-continue -> multifile-continue.

1 files changed, 13 insertions, 2 deletions

diff --git a/lisp/emacs-lisp/generator.el b/lisp/emacs-lisp/generator.el
index 506df59d8e2..e38c7d91096 100644
--- a/lisp/emacs-lisp/generator.el
+++ b/lisp/emacs-lisp/generator.el
@@ -567,8 +567,11 @@ modified copy."
            (unless ,normal-exit-symbol
              ,@unwind-forms))))))
 
-(put 'iter-end-of-sequence 'error-conditions '(iter-end-of-sequence))
-(put 'iter-end-of-sequence 'error-message "iteration terminated")
+(define-error 'iter-end-of-sequence "Iteration terminated"
+  ;; FIXME: This was not defined originally as an `error' condition, so
+  ;; we reproduce this by passing itself as the parent, which avoids the
+  ;; default `error' parent.  Maybe it *should* be in the `error' category?
+  'iter-end-of-sequence)
 
 (defun cps--make-close-iterator-form (terminal-state)
   (if cps--cleanup-table-symbol
@@ -700,6 +703,14 @@ of values.  Callers can retrieve each value using `iter-next'."
   `(lambda ,arglist
      ,(cps-generate-evaluator body)))
 
+(defmacro iter-make (&rest body)
+  "Return a new iterator."
+  (declare (debug t))
+  (cps-generate-evaluator body))
+
+(defconst iter-empty (lambda (_op _val) (signal 'iter-end-of-sequence nil))
+  "Trivial iterator that always signals the end of sequence.")
+
 (defun iter-next (iterator &optional yield-result)
   "Extract a value from an iterator.
 YIELD-RESULT becomes the return value of `iter-yield' in the