From eed29c8e7164cbc13df4d7b4e3974ae90d9ecb51 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Fri, 11 May 2018 13:44:46 -0400
Subject: [PATCH] Honor print-charset-text-property value of nil (Bug#31376)

* src/print.c (print_check_string_charset_prop): Move check
for nil Vprint_charset_text_property from here...
(print_prune_string_charset): ... to here.
(syms_of_print) <print-charset-text-property>: Clarify that any
non-boolean values are treated the same as `default'.
* doc/lispref/streams.texi (Output Variables): Add
print-prune-string-charset.
---
 doc/lispref/streams.texi | 13 +++++++++++++
 src/print.c              | 11 ++++++-----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/doc/lispref/streams.texi b/doc/lispref/streams.texi
index ebd806601e..ae3b982080 100644
--- a/doc/lispref/streams.texi
+++ b/doc/lispref/streams.texi
@@ -809,6 +809,19 @@ Output Variables
 one.
 @end defvar
 
+@defvar print-charset-text-property
+This variable controls printing of `charset' text property on printing
+a string.  The value should be @code{nil}, @code{t}, or
+@code{default}.
+
+If the value is @code{nil}, @code{charset} text properties are never
+printed.  If @code{t}, they are always printed.  If the value is
+@code{default}, print the text property @code{charset} only when the
+value is different from what is guessed in the current charset
+priorities.  Values other than @code{nil} or @code{t} are treated the
+same as @code{default}.
+@end defvar
+
 @defvar print-length
 @cindex printing limits
 The value of this variable is the maximum number of elements to print in
diff --git a/src/print.c b/src/print.c
index 15177759cf..427ab7d158 100644
--- a/src/print.c
+++ b/src/print.c
@@ -1317,8 +1317,7 @@ print_check_string_charset_prop (INTERVAL interval, Lisp_Object string)
 	  || CONSP (XCDR (XCDR (val))))
 	print_check_string_result |= PRINT_STRING_NON_CHARSET_FOUND;
     }
-  if (NILP (Vprint_charset_text_property)
-      || ! (print_check_string_result & PRINT_STRING_UNSAFE_CHARSET_FOUND))
+  if (! (print_check_string_result & PRINT_STRING_UNSAFE_CHARSET_FOUND))
     {
       int i, c;
       ptrdiff_t charpos = interval->position;
@@ -1348,7 +1347,8 @@ print_prune_string_charset (Lisp_Object string)
   print_check_string_result = 0;
   traverse_intervals (string_intervals (string), 0,
 		      print_check_string_charset_prop, string);
-  if (! (print_check_string_result & PRINT_STRING_UNSAFE_CHARSET_FOUND))
+  if (NILP (Vprint_charset_text_property)
+      || ! (print_check_string_result & PRINT_STRING_UNSAFE_CHARSET_FOUND))
     {
       string = Fcopy_sequence (string);
       if (print_check_string_result & PRINT_STRING_NON_CHARSET_FOUND)
@@ -2422,7 +2422,7 @@ representation) and `#N#' in place of each subsequent occurrence,
 
   DEFVAR_LISP ("print-charset-text-property", Vprint_charset_text_property,
 	       doc: /* A flag to control printing of `charset' text property on printing a string.
-The value must be nil, t, or `default'.
+The value should be nil, t, or `default'.
 
 If the value is nil, don't print the text property `charset'.
 
@@ -2430,7 +2430,8 @@ representation) and `#N#' in place of each subsequent occurrence,
 
 If the value is `default', print the text property `charset' only when
 the value is different from what is guessed in the current charset
-priorities.  */);
+priorities.  Values other than nil or t are also treated as
+`default'.  */);
   Vprint_charset_text_property = Qdefault;
 
   /* prin1_to_string_buffer initialized in init_buffer_once in buffer.c */
-- 
2.11.0