Subject: Re: bug#39291: M-: history doesn't store erroneous input

From: Federico Tedin <[email-masked]>
Date: Wed, 29 Jan 2020 22:32:16 +0100

> Federico, please look into fixing this regression.
>
> TIA

I found that the minibuffer input string in `read_minibuf' was being
added to the history list after we tried to parse an object from it (if
`expflag' was true). So if the parsing failed, then the value wasn't
added to the history. I'm attaching a patch with my changes.

My only doubt is that now, the call to `string_to_object' (which calls
`read-from-string', which calls `read1', and then `read0') is located
outside the context (not sure what the right term is) set up with
`specbind'. Could this be a problem? Do any of these functions depend on
the context set up in `read_minibuf'?  (They don't appear to, just want
to be sure).

Thanks.

>From 6a35a1390d1f1924d0fd52dbb885af66d089273c Mon Sep 17 00:00:00 2001
From: Federico Tedin <[email-masked]>
Date: Wed, 29 Jan 2020 22:24:40 +0100
Subject: [PATCH 1/1] Ensure input is added to history in read_minibuf

* src/minibuf.c (read_minibuf): Parse input string after saving the
string to the history list instead of before, in case parsing
fails. (Bug#39291)
---
 src/minibuf.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/minibuf.c b/src/minibuf.c
index 8ebdff1252..9d870ce364 100644
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -697,10 +697,6 @@ read_minibuf (Lisp_Object map, Lisp_Object initial, Lisp_Object prompt,
   else
     histstring = Qnil;
 
-  /* If Lisp form desired instead of string, parse it.  */
-  if (expflag)
-    val = string_to_object (val, defalt);
-
   /* The appropriate frame will get selected
      in set-window-configuration.  */
   unbind_to (count, Qnil);
@@ -711,6 +707,10 @@ read_minibuf (Lisp_Object map, Lisp_Object initial, Lisp_Object prompt,
   if (! (NILP (Vhistory_add_new_input) || NILP (histstring)))
     call2 (intern ("add-to-history"), histvar, histstring);
 
+  /* If Lisp form desired instead of string, parse it.  */
+  if (expflag)
+    val = string_to_object (val, defalt);
+
   return val;
 }
 
-- 
2.17.1