Issue with LYP_WD_TRIM and empty presence containers

[rwestphal]

The libyang documentation says the following about the LYP_WD_TRIM flag:

Do not print the nodes with the value equal to their default value

However I noticed that this flag also prevents presence containers from being printed if they are empty. The code below can be used to reproduce the problem:

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <string.h>
#include <err.h>

#include <libyang/libyang.h>

int main(int argc, char *argv[])
{
        struct ly_ctx *ly_ctx;
        struct lyd_node *config = NULL;

        /* Initialization. */
        ly_ctx = ly_ctx_new(NULL, 0);
        if (!ly_ctx)
                errx(1, "ly_ctx_new()");

        ly_ctx_set_searchdir(ly_ctx, "/usr/local/share/yang/");

        /* Load YANG module. */
        ly_ctx_load_module(ly_ctx, "frr-ripd", NULL);

        /* Initialize data node. */
        lyd_validate(&config, LYD_OPT_STRICT | LYD_OPT_CONFIG, ly_ctx);

        /* Create presence container. */
        lyd_new_path(config, ly_ctx, "/frr-ripd:ripd/instance", NULL, 0,
                     LYD_PATH_OPT_UPDATE);

        printf("lyd_print_fd(..., LYP_FORMAT | LYP_WD_TRIM | LYP_WITHSIBLINGS):\n");
        lyd_print_fd(1, config, LYD_JSON,
                     LYP_FORMAT | LYP_WD_TRIM | LYP_WITHSIBLINGS);

        printf("\n");
        printf("lyd_print_fd(..., LYP_FORMAT | LYP_WITHSIBLINGS):\n");
        lyd_print_fd(1, config, LYD_JSON, LYP_FORMAT | LYP_WITHSIBLINGS);

        /* Cleanup. */
        ly_ctx_destroy(ly_ctx, NULL);

        return 0;
}

YANG module: https://gist.github.com/rwestphal/2fc93f3f928fee1127c2913977c00e8d

Output of the program:

# ./show 
lyd_print_fd(..., LYP_FORMAT | LYP_WD_TRIM | LYP_WITHSIBLINGS):
{

}

lyd_print_fd(..., LYP_FORMAT | LYP_WITHSIBLINGS):
{
  "frr-ripd:ripd": {
    "instance": {
    }
  }
}

Notice how the instance presence container wasn't printed when LYP_WD_TRIM was used. The same problem happens when printing using the XML format.

Any help would be appreciated.

[michalvasko]

Hi,
it seems this default print mode was not used much because there a lot more cases not covered. Should work now.

Regards,
Michal