jim.c: fix some dict/list shimmering issues

Only do fast dict->list conversion if there is no string rep
When converting list->dict, generate the string rep of a shared list to avoid
loss of info when converting to dict.

Also add a relevent test to dict.test

Signed-off-by: Steve Bennett <steveb@workware.net.au>

2 files changed, 19 insertions, 6 deletions

diff --git a/jim.c b/jim.c
index 084d513..f3f43e9 100644
--- a/jim.c
+++ b/jim.c
@@ -6313,11 +6313,11 @@ static int SetListFromAny(Jim_Interp *interp, struct Jim_Obj *objPtr)
         return JIM_OK;
     }
 
-    /* Optimise dict -> list for unshared object. Note that this may only save a little time, but
+    /* Optimise dict -> list for object with no string rep. Note that this may only save a little time, but
      * it also preserves any source location of the dict elements
      * which can be very useful
      */
-    if (Jim_IsDict(objPtr) && !Jim_IsShared(objPtr)) {
+    if (Jim_IsDict(objPtr) && objPtr->bytes == NULL) {
         Jim_Obj **listObjPtrPtr;
         int len;
         int i;
@@ -7020,10 +7020,12 @@ static int SetDictFromAny(Jim_Interp *interp, struct Jim_Obj *objPtr)
         return JIM_OK;
     }
 
-    /* Get the string representation. Do this first so we don't
-     * change order in case of fast conversion to dict.
-     */
-    Jim_String(objPtr);
+    if (Jim_IsList(objPtr) && Jim_IsShared(objPtr)) {
+        /* A shared list, so get the string representation now to avoid
+         * changing the order in case of fast conversion to dict.
+         */
+        Jim_String(objPtr);
+    }
 
     /* For simplicity, convert a non-list object to a list and then to a dict */
     listlen = Jim_ListLength(interp, objPtr);
diff --git a/tests/dict.test b/tests/dict.test
index 6387cd0..c0528e8 100644
--- a/tests/dict.test
+++ b/tests/dict.test
@@ -237,5 +237,16 @@ test dict-24.3 {dict/list shimmering with embedded nulls} {
 	lassign $dictVar k v
 	string length $v
 } {3}
+test dict-24.4 {dict/list shimmering with lappend and foreach} {
+	set a [list 1 2 3 4]
+
+	foreach b $a {
+		# convert to dict
+		dict size $a
+		# append to list
+		lappend a x y
+	}
+	llength $a
+} 12
 
 testreport