From b2734f7b45111f9b7de790c7b334a2ece47675b5 Mon Sep 17 00:00:00 2001
From: Jeremy Harris <jgh146exb@wizmail.org>
Date: Sat, 9 Feb 2019 16:56:59 +0000
Subject: [PATCH] Fix json extract operator for unfound case

(cherry picked from commit e73798976812e652320f096870359ef35ed069ff)
---
 doc/doc-docbook/spec.xfpt    |  4 ++++
 src/src/expand.c             | 13 ++++++++-----
 test/scripts/0000-Basic/0002 |  3 +++
 test/stdout/0002             |  3 +++
 4 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 4d4bab7c2..20b08f693 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -9537,6 +9537,8 @@ The expanded <&'string1'&> must be of the form:
 The braces, commas and colons, and the quoting of the member name are required;
 the spaces are optional.
 Matching of the key against the member names is done case-sensitively.
+If a returned value is a JSON string, it retains its leading and
+trailing quotes.
 . XXX should be a UTF-8 compare
 
 The results of matching are handled as above.
@@ -9584,6 +9586,8 @@ apart from leading and trailing white space, which is ignored.
 
 Field selection and result handling is as above;
 there is no choice of field separator.
+If a returned value is a JSON string, it retains its leading and
+trailing quotes.
 .wen
 
 
diff --git a/src/src/expand.c b/src/src/expand.c
index b2a921701..2c290251d 100644
--- a/src/src/expand.c
+++ b/src/src/expand.c
@@ -3901,7 +3901,8 @@ return NULL;
 /* Pull off the leading array or object element, returning
 a copy in an allocated string.  Update the list pointer.
 
-The element may itself be an abject or array.
+The element may itself be an object or array.
+Return NULL when the list is empty.
 */
 
 uschar *
@@ -3923,6 +3924,7 @@ for (item = s;
     case '}': object_depth--; break;
     }
 *list = *s ? s+1 : s;
+if (item == s) return NULL;
 item = string_copyn(item, s - item);
 DEBUG(D_expand) debug_printf_indent("  json ele: '%s'\n", item);
 return US item;
@@ -5790,10 +5792,11 @@ while (*s != 0)
 	      }
 	    while (field_number > 0 && (item = json_nextinlist(&list)))
 	      field_number--;
-	    s = item;
-	    lookup_value = s;
-	    while (*s) s++;
-	    while (--s >= lookup_value && isspace(*s)) *s = '\0';
+	    if ((lookup_value = s = item))
+	      {
+	      while (*s) s++;
+	      while (--s >= lookup_value && isspace(*s)) *s = '\0';
+	      }
 	    }
 	  else
 	    {
diff --git a/test/scripts/0000-Basic/0002 b/test/scripts/0000-Basic/0002
index e192a5593..7a9b38dba 100644
--- a/test/scripts/0000-Basic/0002
+++ b/test/scripts/0000-Basic/0002
@@ -902,6 +902,9 @@ expect: {"1":116, "2":943, "3":234}
 ${extract json{IDs}{ \{"id": \{"a":101, "b":102\}, "IDs": \{"1":116, "2":943, "3":234\}\} }}
 expect: {"1":116, "2":943, "3":234}
 
+<${extract json{nonexistent}{ \{"id": \{"a":101, "b":102\}, "IDs": \{"1":116, "2":943, "3":234\}\} }}>
+expect: <>
+
 ****
 # Test "escape" with print_topbitchars
 exim -be -DPTBC=print_topbitchars
diff --git a/test/stdout/0002 b/test/stdout/0002
index 949c35eb2..c2f5f2f3c 100644
--- a/test/stdout/0002
+++ b/test/stdout/0002
@@ -845,6 +845,9 @@ xyz
 > {"1":116, "2":943, "3":234}
 > expect: {"1":116, "2":943, "3":234}
 > 
+> <>
+> expect: <>
+> 
 > 
 > escape: B7·F2ò
 > 
-- 
2.30.2