Fix old files with changed node socket type not loading correctly.

This would lead to sock.default_value pointing to the wrong data type,
possibly causing crashes. Unfortunately, this bug will still exist for
older Blender versions that try to load newer files, which makes
changing the type of a node socket problematic.

source/blender/blenkernel/BKE_node.h

@@ -446,6 +446,7 @@ struct bNodeSocket *nodeInsertStaticSocket(struct bNodeTree *ntree, struct bNode
                                            struct bNodeSocket *next_sock, const char *identifier, const char *name);
 void nodeRemoveSocket(struct bNodeTree *ntree, struct bNode *node, struct bNodeSocket *sock);
 void nodeRemoveAllSockets(struct bNodeTree *ntree, struct bNode *node);
+void nodeModifySocketType(struct bNodeTree *ntree, struct bNode *node, struct bNodeSocket *sock, int type, int subtype);
 
 struct bNode	*nodeAddNode(const struct bContext *C, struct bNodeTree *ntree, const char *idname);
 struct bNode	*nodeAddStaticNode(const struct bContext *C, struct bNodeTree *ntree, int type);

source/blender/blenkernel/intern/node.c

@@ -506,6 +506,26 @@ static bNodeSocket *make_socket(bNodeTree *ntree, bNode *UNUSED(node), int in_ou
 	return sock;
 }
 
+void nodeModifySocketType(bNodeTree *ntree, bNode *UNUSED(node), bNodeSocket *sock,
+                          int type, int subtype)
+{
+	const char *idname = nodeStaticSocketType(type, subtype);
+
+	if (!idname) {
+		printf("Error: static node socket type %d undefined\n", type);
+		return;
+	}
+
+	if (sock->default_value) {
+		MEM_freeN(sock->default_value);
+		sock->default_value = NULL;
+	}
+
+	sock->type = type;
+	BLI_strncpy(sock->idname, idname, sizeof(sock->idname));
+	node_socket_set_typeinfo(ntree, sock, nodeSocketTypeFind(idname));
+}
+
 bNodeSocket *nodeAddSocket(bNodeTree *ntree, bNode *node, int in_out, const char *idname,
                            const char *identifier, const char *name)
 {

source/blender/nodes/intern/node_socket.c

@@ -112,22 +112,21 @@ static bNodeSocket *verify_socket_template(bNodeTree *ntree, bNode *node, int in
 			break;
 	}
 	if (sock) {
-		sock->type = stemp->type;
+		if (sock->type != stemp->type) {
+			nodeModifySocketType(ntree, node, sock, stemp->type, stemp->subtype);
+		}
+
 		sock->limit = (stemp->limit == 0 ? 0xFFF : stemp->limit);
 		sock->flag |= stemp->flag;
-		
-		BLI_remlink(socklist, sock);
-		
-		return sock;
 	}
 	else {
 		/* no socket for this template found, make a new one */
 		sock = node_add_socket_from_template(ntree, node, stemp, in_out);
-		/* remove the new socket from the node socket list first,
-		 * will be added back after verification.
-		 */
-		BLI_remlink(socklist, sock);
 	}
+
+	/* remove the new socket from the node socket list first,
+	 * will be added back after verification. */
+	BLI_remlink(socklist, sock);
 	
 	return sock;
 }