lib, tests: major rework in the operational-data callbacks

The northbound infrastructure for operational data was subpar compared
to the infrastructure for configuration data. This commit addresses most
of the existing problems, making it possible to write operational-data
callbacks for more complex YANG models.

Summary of the changes:
* Add support for nested YANG lists.
* Add support for leaf-lists.
* Add support for leafs of type "empty".
* Introduce the "show yang operational-data XPATH" command, and write an
  unit test for it. The main purpose of this command is to make it
  easier to test the operational-data northbound callbacks.
* Introduce the nb_oper_data_iterate() function, that can be used
  to iterate over operational data. Make the CLI and sysrepo use this
  function.
* Since ConfD has a very peculiar API, it can't reuse the
  nb_oper_data_iterate() like the other northbound clients. In this
  case, adapt the existing ConfD callbacks to support the new features
  (and make some performance improvements in the process).

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

1 files changed, 112 insertions, 0 deletions

diff --git a/lib/northbound_cli.c b/lib/northbound_cli.c
index c7378d2440..1ffd65af42 100644
--- a/lib/northbound_cli.c
+++ b/lib/northbound_cli.c
@@ -1097,6 +1097,117 @@ DEFPY (show_config_transaction,
 #endif /* HAVE_CONFIG_ROLLBACKS */
 }
 
+static int nb_cli_oper_data_cb(const struct lys_node *snode,
+			       struct yang_translator *translator,
+			       struct yang_data *data, void *arg)
+{
+	struct lyd_node *dnode = arg;
+	struct ly_ctx *ly_ctx;
+
+	if (translator) {
+		int ret;
+
+		ret = yang_translate_xpath(translator,
+					   YANG_TRANSLATE_FROM_NATIVE,
+					   data->xpath, sizeof(data->xpath));
+		switch (ret) {
+		case YANG_TRANSLATE_SUCCESS:
+			break;
+		case YANG_TRANSLATE_NOTFOUND:
+			goto exit;
+		case YANG_TRANSLATE_FAILURE:
+			goto error;
+		}
+
+		ly_ctx = translator->ly_ctx;
+	} else
+		ly_ctx = ly_native_ctx;
+
+	ly_errno = 0;
+	dnode = lyd_new_path(dnode, ly_ctx, data->xpath, (void *)data->value, 0,
+			     LYD_PATH_OPT_UPDATE);
+	if (!dnode && ly_errno) {
+		flog_warn(EC_LIB_LIBYANG, "%s: lyd_new_path() failed",
+			  __func__);
+		goto error;
+	}
+
+exit:
+	yang_data_free(data);
+	return NB_OK;
+
+error:
+	yang_data_free(data);
+	return NB_ERR;
+}
+
+DEFPY (show_yang_operational_data,
+       show_yang_operational_data_cmd,
+       "show yang operational-data XPATH$xpath\
+         [{\
+	   format <json$json|xml$xml>\
+	   |translate WORD$translator_family\
+	 }]",
+       SHOW_STR
+       "YANG information\n"
+       "Show YANG operational data\n"
+       "XPath expression specifying the YANG data path\n"
+       "Set the output format\n"
+       "JavaScript Object Notation\n"
+       "Extensible Markup Language\n"
+       "Translate operational data\n"
+       "YANG module translator\n")
+{
+	LYD_FORMAT format;
+	struct yang_translator *translator = NULL;
+	struct ly_ctx *ly_ctx;
+	struct lyd_node *dnode;
+	char *strp;
+
+	if (xml)
+		format = LYD_XML;
+	else
+		format = LYD_JSON;
+
+	if (translator_family) {
+		translator = yang_translator_find(translator_family);
+		if (!translator) {
+			vty_out(vty, "%% Module translator \"%s\" not found\n",
+				translator_family);
+			return CMD_WARNING;
+		}
+
+		ly_ctx = translator->ly_ctx;
+	} else
+		ly_ctx = ly_native_ctx;
+
+	/* Obtain data. */
+	dnode = yang_dnode_new(ly_ctx, false);
+	if (nb_oper_data_iterate(xpath, translator, 0, nb_cli_oper_data_cb,
+				 dnode)
+	    != NB_OK) {
+		vty_out(vty, "%% Failed to fetch operational data.\n");
+		yang_dnode_free(dnode);
+		return CMD_WARNING;
+	}
+	lyd_validate(&dnode, LYD_OPT_DATA | LYD_OPT_DATA_NO_YANGLIB, ly_ctx);
+
+	/* Display the data. */
+	if (lyd_print_mem(&strp, dnode, format,
+			  LYP_FORMAT | LYP_WITHSIBLINGS | LYP_WD_ALL)
+		    != 0
+	    || !strp) {
+		vty_out(vty, "%% Failed to display operational data.\n");
+		yang_dnode_free(dnode);
+		return CMD_WARNING;
+	}
+	vty_out(vty, "%s", strp);
+	free(strp);
+	yang_dnode_free(dnode);
+
+	return CMD_SUCCESS;
+}
+
 DEFPY (show_yang_module,
        show_yang_module_cmd,
        "show yang module [module-translator WORD$translator_family]",
@@ -1436,6 +1547,7 @@ void nb_cli_init(void)
 	/* Other commands. */
 	install_element(CONFIG_NODE, &yang_module_translator_load_cmd);
 	install_element(CONFIG_NODE, &yang_module_translator_unload_cmd);
+	install_element(ENABLE_NODE, &show_yang_operational_data_cmd);
 	install_element(ENABLE_NODE, &show_yang_module_cmd);
 	install_element(ENABLE_NODE, &show_yang_module_detail_cmd);
 	install_element(ENABLE_NODE, &show_yang_module_translator_cmd);