lib: add and use new yang function for finding schema nodes

Add a wrapper around lys_find_xpath which has an unfortunate API
returning an allocated set of schema nodes when we only ever expect and
want one.

Another libyang function `lys_find_path` returns a single node; however,
that function can assert/abort on invalid path values so is unsuitable
for user input.

Replace previous uses of `lys_find_path` with new API when dealing with
possible invalid path values (i.e., from a user).

Signed-off-by: Christian Hopps <chopps@labn.net>

lib/northbound.c

@@ -167,7 +167,7 @@ struct nb_node *nb_node_find(const char *path)
 	 * Use libyang to find the schema node associated to the path and get
 	 * the northbound node from there (snode private pointer).
 	 */
-	snode = lys_find_path(ly_native_ctx, NULL, path, 0);
+	snode = yang_find_snode(ly_native_ctx, path, 0);
 	if (!snode)
 		return NULL;
 

lib/yang.c

@@ -250,6 +250,23 @@ void yang_snode_get_path(const struct lysc_node *snode,
 	}
 }
 
+struct lysc_node *yang_find_snode(struct ly_ctx *ly_ctx, const char *xpath,
+				  uint32_t options)
+{
+	struct lysc_node *snode;
+	struct ly_set *set;
+	LY_ERR err;
+
+	err = lys_find_xpath(ly_native_ctx, NULL, xpath, options, &set);
+	if (err || !set->count)
+		return NULL;
+
+	snode = set->snodes[0];
+	ly_set_free(set, NULL);
+
+	return snode;
+}
+
 struct lysc_node *yang_snode_real_parent(const struct lysc_node *snode)
 {
 	struct lysc_node *parent = snode->parent;

lib/yang.h

@@ -210,6 +210,27 @@ extern void yang_snode_get_path(const struct lysc_node *snode,
 				enum yang_path_type type, char *xpath,
 				size_t xpath_len);
 
+
+/*
+ * Find libyang schema node for the given xpath. Uses `lys_find_xpath`,
+ * returning only the first of a set of nodes -- normally there should only
+ * be one.
+ *
+ * ly_ctx
+ *    libyang context to operate on.
+ *
+ * xpath
+ *    XPath expression (absolute or relative) to find the schema node for.
+ *
+ * options
+ *    Libyang findxpathoptions value (see lys_find_xpath).
+ *
+ * Returns:
+ *    The libyang schema node if found, or NULL if not found.
+ */
+extern struct lysc_node *yang_find_snode(struct ly_ctx *ly_ctx,
+					 const char *xpath, uint32_t options);
+
 /*
  * Find first parent schema node which is a presence-container or a list
  * (non-presence containers are ignored).

lib/yang_translator.c

@@ -235,8 +235,8 @@ struct yang_translator *yang_translator_load(const char *path)
 		xpath_custom =
 			yang_dnode_get_string(set->dnodes[i], "./custom");
 
-		snode_custom = lys_find_path(translator->ly_ctx, NULL,
+		snode_custom =
-					     xpath_custom, 0);
+			yang_find_snode(translator->ly_ctx, xpath_custom, 0);
 		if (!snode_custom) {
 			flog_warn(EC_LIB_YANG_TRANSLATOR_LOAD,
 				  "%s: unknown data path: %s", __func__,
@@ -247,8 +247,7 @@ struct yang_translator *yang_translator_load(const char *path)
 
 		xpath_native =
 			yang_dnode_get_string(set->dnodes[i], "./native");
-		snode_native =
+		snode_native = yang_find_snode(ly_native_ctx, xpath_native, 0);
-			lys_find_path(ly_native_ctx, NULL, xpath_native, 0);
 		if (!snode_native) {
 			flog_warn(EC_LIB_YANG_TRANSLATOR_LOAD,
 				  "%s: unknown data path: %s", __func__,
@@ -315,7 +314,7 @@ yang_translate_xpath(const struct yang_translator *translator, int dir,
 	else
 		ly_ctx = ly_native_ctx;
 
-	snode = lys_find_path(ly_ctx, NULL, xpath, 0);
+	snode = yang_find_snode(ly_ctx, xpath, 0);
 	if (!snode) {
 		flog_warn(EC_LIB_YANG_TRANSLATION_ERROR,
 			  "%s: unknown data path: %s", __func__, xpath);

lib/yang_wrappers.c

@@ -89,7 +89,7 @@ static const char *yang_get_default_value(const char *xpath)
 	const struct lysc_node *snode;
 	const char *value;
 
-	snode = lys_find_path(ly_native_ctx, NULL, xpath, 0);
+	snode = yang_find_snode(ly_native_ctx, xpath, 0);
 	if (snode == NULL) {
 		flog_err(EC_LIB_YANG_UNKNOWN_DATA_PATH,
 			 "%s: unknown data path: %s", __func__, xpath);
@@ -206,7 +206,7 @@ int yang_str2enum(const char *xpath, const char *value)
 	const struct lysc_type_enum *type;
 	const struct lysc_type_bitenum_item *enums;
 
-	snode = lys_find_path(ly_native_ctx, NULL, xpath, 0);
+	snode = yang_find_snode(ly_native_ctx, xpath, 0);
 	if (snode == NULL) {
 		flog_err(EC_LIB_YANG_UNKNOWN_DATA_PATH,
 			 "%s: unknown data path: %s", __func__, xpath);
@@ -241,7 +241,7 @@ struct yang_data *yang_data_new_enum(const char *xpath, int value)
 	const struct lysc_type_enum *type;
 	const struct lysc_type_bitenum_item *enums;
 
-	snode = lys_find_path(ly_native_ctx, NULL, xpath, 0);
+	snode = yang_find_snode(ly_native_ctx, xpath, 0);
 	if (snode == NULL) {
 		flog_err(EC_LIB_YANG_UNKNOWN_DATA_PATH,
 			 "%s: unknown data path: %s", __func__, xpath);