isearch-yank-line and field text property

[Stephen Berman]

(I posted this to help-gnu-emacs last Friday but there hasn't been a
response to date, so I'm posting it here, in case it is a bug.)

The following seems like a bug to me, but maybe it's a feature of the
field property or isearch-yank-line that I don't understand; if so,
I'd appreciate a pointer to documentation (I couldn't find anything
apposite in either the Emacs or Elisp manuals).

1. emacs -Q
2. Type the following three lines in an empty buffer:
test
test
test
3. Now put the cursor at the beginning of the second line and type this:
`M-: (add-text-properties (point) (point-max) '(field test))'
4. Now type `C-s C-y'.  The minibuffer contains the prompt "I-search:"
but the line is not yanked into the search string, and in fact nothing
else happens at all as long as you keep typing `C-y'.  

This happens only with isearch-yank-line, and only at that position;
any other isearch command (including isearch-yank-word) at that
position works fine.  Moreover, isearch-yank-line from any following
position also works fine, although they also have the field property;
isearch-yank-line from any preceding position works up to that
position and then stops as above.

This happens in both CVS Emacs and in Emacs 21.3.  The two Emacsen
differ in the return value of field-string called with the cursor over
the first character with the field property: in Emacs 21.3 it is "",
while in CVS Emacs it is "test^J".


In GNU Emacs 22.0.50.14 (i686-pc-linux-gnu, GTK+ Version 2.8.10)
 of 2006-04-17 on escher
X server distributor `The X.Org Foundation', version 11.0.60802000
configured using `configure '--with-x-toolkit=gtk''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8
  default-enable-multibyte-characters: t

Major mode: Summary

Minor modes in effect:
  tabbar-mwheel-mode: t
  tabbar-mode: t
  recentf-mode: t
  show-paren-mode: t
  display-time-mode: t
  tooltip-mode: t
  auto-compression-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: identity

Recent input:
y <select-window> <select-window> <help-echo> <help-echo> 
<down-mouse-3> <mouse-3> C-c r e <tab> <return> . <tab> 
<tab> s <tab> l <tab> <return> <end> <prior> <home> 
<next> C-c r C <return> q C-c r c <tab> <return> i 
<tab> <return> <help-echo> <help-echo> M-x g u <return> 
J j y <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> M-g <return> <return> <down> SPC 
t t <down-mouse-1> <mouse-movement> <mouse-movement> 
<drag-mouse-1> M-x r e p o <tab> r <tab> <return>

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