data FEATURE printer for YANG data in JSON format
diff --git a/src/printer_json.c b/src/printer_json.c
index 705d2eb..171d30f 100644
--- a/src/printer_json.c
+++ b/src/printer_json.c
@@ -1,10 +1,9 @@
 /**
  * @file printer_json.c
- * @author Michal Vasko <mvasko@cesnet.cz>
  * @author Radek Krejci <rkrejci@cesnet.cz>
  * @brief JSON printer for libyang data structure
  *
- * Copyright (c) 2015 - 2019 CESNET, z.s.p.o.
+ * Copyright (c) 2015 - 2020 CESNET, z.s.p.o.
  *
  * This source code is licensed under BSD 3-Clause License (the "License").
  * You may not use this file except in compliance with the License.
@@ -13,11 +12,51 @@
  *     https://opensource.org/licenses/BSD-3-Clause
  */
 
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
 #include "common.h"
 #include "config.h"
+#include "log.h"
+#include "parser_data.h"
+#include "plugins_types.h"
+#include "printer_data.h"
+#include "printer_internal.h"
+#include "set.h"
+#include "tree.h"
+#include "tree_data.h"
+#include "tree_data_internal.h"
 #include "tree_schema.h"
 
 /**
+ * @brief JSON printer context.
+ */
+struct jsonpr_ctx {
+    struct ly_out *out;  /**< output specification */
+    unsigned int level; /**< current indentation level: 0 - no formatting, >= 1 indentation levels */
+    int options;        /**< [Data printer flags](@ref dataprinterflags) */
+    const struct ly_ctx *ctx; /**< libyang context */
+
+    unsigned int level_printed; /* level where some dara were already printed */
+    struct ly_set open; /* currently open array(s) */
+    const struct lyd_node *print_sibling_metadata;
+};
+
+/**
+ * @brief Mark that something was already written in the current level,
+ * used to decide if a comma is expected between the items
+ */
+#define LEVEL_PRINTED ctx->level_printed = ctx->level
+
+#define PRINT_COMMA \
+    if (ctx->level_printed >= ctx->level) {\
+        ly_print(ctx->out, ",%s", (DO_FORMAT ? "\n" : ""));\
+    }
+
+static LY_ERR json_print_node(struct jsonpr_ctx *ctx, const struct lyd_node *node);
+
+/**
  * @brief JSON mapping of YANG modules to prefixes in values.
  *
  * Implementation of ly_get_prefix_clb.
@@ -28,3 +67,832 @@
     return mod->name;
 }
 
+/**
+ * Compare 2 nodes, despite it is regular data node or an opaq node, and
+ * decide if they corresponds to the same schema node.
+ *
+ * TODO: rewrite lyd_compare_single and use it instead of this
+ *
+ * @return 1 - matching nodes, 0 - non-matching nodes
+ */
+static int
+matching_node(const struct lyd_node *node1, const struct lyd_node *node2)
+{
+    assert(node1 || node2);
+
+    if (!node1 || !node2) {
+        return 0;
+    } else if (node1->schema != node2->schema) {
+        return 0;
+    }
+    if (!node1->schema) {
+        /* compare node names */
+        struct lyd_node_opaq *onode1 = (struct lyd_node_opaq*)node1;
+        struct lyd_node_opaq *onode2 = (struct lyd_node_opaq*)node2;
+        if (onode1->name != onode2->name || onode1->prefix.id != onode2->prefix.id) {
+            return 0;
+        }
+    }
+
+    return 1;
+}
+
+/**
+ * @brief Open the JSON array ('[') for the specified @p node
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node First node of the array.
+ */
+static void
+json_print_array_open(struct jsonpr_ctx *ctx, const struct lyd_node *node)
+{
+    /* leaf-list's content is always printed on a single line */
+    ly_print(ctx->out, "[%s", (!node->schema || node->schema->nodetype != LYS_LEAFLIST) && DO_FORMAT ? "\n" : "");
+    ly_set_add(&ctx->open, (void*)node, 0);
+    LEVEL_INC;
+}
+
+/**
+ * @brief Get know if the array for the provided @p node is currently open.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Data node to check.
+ * @return 1 in case the printer is currently in the array belonging to the provided @p node.
+ * @return 0 in case the provided @p node is not connected with the currently open array (or there is no open array).
+ */
+static int
+is_open_array(struct jsonpr_ctx *ctx, const struct lyd_node *node)
+{
+    if (ctx->open.count && matching_node(node, (const struct lyd_node*)ctx->open.objs[ctx->open.count - 1])) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+/**
+ * @brief Close the most inner JSON array.
+ *
+ * @param[in] ctx JSON printer context.
+ */
+static void
+json_print_array_close(struct jsonpr_ctx *ctx)
+{
+    const struct lysc_node *schema = ((const struct lyd_node*)ctx->open.objs[ctx->open.count - 1])->schema;
+
+    LEVEL_DEC;
+    ly_set_rm_index(&ctx->open, ctx->open.count - 1, NULL);
+    if (schema && schema->nodetype == LYS_LEAFLIST) {
+        /* leaf-list's content is always printed on a single line */
+        ly_print(ctx->out, "]");
+    } else {
+        ly_print(ctx->out, "%s%*s]", DO_FORMAT ? "\n" : "", INDENT);
+    }
+}
+
+/**
+ * @brief Get the node's module name to use as the @p node prefix in JSON.
+ * @param[in] node Node to process.
+ * @return The name of the module where the @p node belongs, it can be NULL in case the module name
+ * cannot be determined (source format is XML and the refered namespace is unknown/not implemented in the current context).
+ */
+static const char *
+node_prefix(const struct lyd_node *node)
+{
+    if (node->schema) {
+        return node->schema->module->name;
+    } else {
+        struct lyd_node_opaq *onode = (struct lyd_node_opaq*)node;
+        const struct lys_module *mod;
+
+        switch (onode->format) {
+        case LYD_JSON:
+            return onode->prefix.module_name;
+        case LYD_XML:
+            mod = ly_ctx_get_module_implemented_ns(onode->ctx, onode->prefix.module_ns);
+            if (!mod) {
+                return NULL;
+            }
+            return mod->name;
+        case LYD_SCHEMA:
+        case LYD_LYB:
+            /* cannot be created */
+            LOGINT(LYD_NODE_CTX(node));
+        }
+    }
+
+    return NULL;
+}
+
+/**
+ * @brief Compare 2 nodes if the belongs to the same module (if they come from the same namespace)
+ *
+ * Accepts both regulard a well as opaq nodes.
+ *
+ * @param[in] node1 The first node to compare.
+ * @param[in] node2 The second node to compare.
+ * @return 0 in case the nodes' modules are the same
+ * @return 1 in case the nodes belongs to different modules
+ */
+int
+json_nscmp(const struct lyd_node *node1, const struct lyd_node *node2)
+{
+    assert(node1 || node2);
+
+    if (!node1 || !node2) {
+        return 1;
+    } else if (node1->schema && node2->schema) {
+        if (node1->schema->module == node2->schema->module) {
+            /* belongs to the same module */
+            return 0;
+        } else {
+            /* different modules */
+            return 1;
+        }
+    } else {
+        const char *pref1 = node_prefix(node1);
+        const char *pref2 = node_prefix(node2);
+        if ((pref1 && pref2) && pref1 == pref2) {
+            return 0;
+        } else {
+            return 1;
+        }
+    }
+}
+
+/**
+ * @brief Print the @p text as JSON string - encode special characters and add quotation around the string.
+ *
+ * @param[in] out The output handler.
+ * @param[in] text The string to print.
+ * @return The number of printed characters.
+ */
+static int
+json_print_string(struct ly_out *out, const char *text)
+{
+    unsigned int i, n;
+
+    if (!text) {
+        return 0;
+    }
+
+    ly_write(out, "\"", 1);
+    for (i = n = 0; text[i]; i++) {
+        const unsigned char ascii = text[i];
+        if (ascii < 0x20) {
+            /* control character */
+            n += ly_print(out, "\\u%.4X", ascii);
+        } else {
+            switch (ascii) {
+            case '"':
+                n += ly_print(out, "\\\"");
+                break;
+            case '\\':
+                n += ly_print(out, "\\\\");
+                break;
+            default:
+                ly_write(out, &text[i], 1);
+                n++;
+            }
+        }
+    }
+    ly_write(out, "\"", 1);
+
+    return n + 2;
+}
+
+/**
+ * @brief Print JSON object's member name, ending by ':'. It resolves if the prefix is supposed to be printed.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node The data node being printed.
+ * @param[in] is_attr Flag if the metadata sign (@) is supposed to be added before the identifier.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_member(struct jsonpr_ctx *ctx, const struct lyd_node *node, int is_attr)
+{
+    PRINT_COMMA;
+    if (LEVEL == 1 || json_nscmp(node, (const struct lyd_node*)node->parent)) {
+        /* print "namespace" */
+        ly_print(ctx->out, "%*s\"%s%s:%s\":%s", INDENT, is_attr ? "@" : "",
+                 node_prefix(node), node->schema->name, DO_FORMAT ? " " : "");
+    } else {
+        ly_print(ctx->out, "%*s\"%s%s\":%s", INDENT, is_attr ? "@" : "",
+                 node->schema->name, DO_FORMAT ? " " : "");
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief More generic alternative to json_print_member() to print some special cases of the member names.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] parent Parent node to compare modules deciding if the prefix is printed.
+ * @param[in] format Format to decide how to process the @p prefix.
+ * @param[in] prefix Prefix structure to provide prefix string if prefix to print.
+ * @param[in] name Name of the memeber to print.
+ * @param[in] is_attr Flag if the metadata sign (@) is supposed to be added before the identifier.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_member2(struct jsonpr_ctx *ctx, const struct lyd_node *parent, LYD_FORMAT format, const struct ly_prefix *prefix, const char *name, int is_attr)
+{
+    const char *module_name = NULL;
+
+    PRINT_COMMA;
+
+    /* determine prefix string */
+    if (prefix) {
+        const struct lys_module *mod;
+
+        switch (format) {
+        case LYD_JSON:
+            module_name = prefix->module_name;
+            break;
+        case LYD_XML:
+            mod = ly_ctx_get_module_implemented_ns(ctx->ctx, prefix->module_ns);
+            if (mod) {
+                module_name = mod->name;
+            }
+            break;
+        case LYD_SCHEMA:
+        case LYD_LYB:
+            /* cannot be created */
+            LOGINT_RET(ctx->ctx);
+        }
+    }
+
+    /* print the member */
+    if (module_name && (!parent || node_prefix(parent) != module_name)) {
+        ly_print(ctx->out, "%*s\"%s%s:%s\":%s", INDENT, is_attr ? "@" : "", module_name, name, DO_FORMAT ? " " : "");
+    } else {
+        ly_print(ctx->out, "%*s\"%s%s\":%s", INDENT, is_attr ? "@" : "", name, DO_FORMAT ? " " : "");
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print data value.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] val Data value to be printed.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_value(struct jsonpr_ctx *ctx, const struct lyd_value *val)
+{
+    int dynamic = 0;
+    const char *value = val->realtype->plugin->print(val, LYD_JSON, json_print_get_prefix, NULL, &dynamic);
+
+    /* leafref is not supported */
+    switch (val->realtype->basetype) {
+    case LY_TYPE_BINARY:
+    case LY_TYPE_STRING:
+    case LY_TYPE_BITS:
+    case LY_TYPE_ENUM:
+    case LY_TYPE_INST:
+    case LY_TYPE_INT64:
+    case LY_TYPE_UINT64:
+    case LY_TYPE_DEC64:
+    case LY_TYPE_IDENT:
+        json_print_string(ctx->out, value);
+        break;
+
+    case LY_TYPE_INT8:
+    case LY_TYPE_INT16:
+    case LY_TYPE_INT32:
+    case LY_TYPE_UINT8:
+    case LY_TYPE_UINT16:
+    case LY_TYPE_UINT32:
+    case LY_TYPE_BOOL:
+        ly_print(ctx->out, "%s", value[0] ? value : "null");
+        break;
+
+    case LY_TYPE_EMPTY:
+        ly_print(ctx->out, "[null]");
+        break;
+
+    default:
+        /* error */
+        LOGINT_RET(ctx->ctx);
+    }
+
+    if (dynamic) {
+        free((char*)value);
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print all the attributes of the opaq node.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Opaq node where the attributes are placed.
+ * @param[in] wdmod With-defaults module to mark that default attribute is supposed to be printed.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_attribute(struct jsonpr_ctx *ctx, const struct lyd_node_opaq *node, const struct lys_module *wdmod)
+{
+    struct lyd_attr *attr;
+
+    if (wdmod) {
+        ly_print(ctx->out, "%*s\"%s:default\":\"true\"", INDENT, wdmod->name);
+        LEVEL_PRINTED;
+    }
+
+    for (attr = node->attr; attr; attr = attr->next) {
+        PRINT_COMMA;
+        json_print_member2(ctx, (struct lyd_node*)node, attr->format, &attr->prefix, attr->name, 0);
+
+        if (attr->hint & (LYD_NODE_OPAQ_ISBOOLEAN | LYD_NODE_OPAQ_ISNUMBER)) {
+            ly_print(ctx->out, "%s", attr->value[0] ? attr->value : "null");
+        } else if (attr->hint & LYD_NODE_OPAQ_ISEMPTY) {
+            ly_print(ctx->out, "[null]");
+        } else {
+            json_print_string(ctx->out, attr->value);
+        }
+        LEVEL_PRINTED;
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print all the metadata of the node.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Node where the metadata are placed.
+ * @param[in] wdmod With-defaults module to mark that default attribute is supposed to be printed.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_metadata(struct jsonpr_ctx *ctx, const struct lyd_node *node, const struct lys_module *wdmod)
+{
+    struct lyd_meta *meta;
+
+    if (wdmod) {
+        ly_print(ctx->out, "%*s\"%s:default\":\"true\"", INDENT, wdmod->name);
+        LEVEL_PRINTED;
+    }
+
+    for (meta = node->meta; meta; meta = meta->next) {
+        PRINT_COMMA;
+        ly_print(ctx->out, "%*s\"%s:%s\":%s", INDENT, meta->annotation->module->name, meta->name, DO_FORMAT ? " " : "");
+        LY_CHECK_RET(json_print_value(ctx, &meta->value));
+        LEVEL_PRINTED;
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print attributes/metadata of the given @p node. Accepts both regular as well as opaq nodes.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Data node where the attributes/metadata are placed.
+ * @param[in] wdmod With-defaults module to mark that default attribute is supposed to be printed.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_attributes(struct jsonpr_ctx *ctx, const struct lyd_node *node, int inner)
+{
+    const struct lys_module *wdmod = NULL;
+
+    if ((node->flags & LYD_DEFAULT) && (ctx->options & (LYD_PRINT_WD_ALL_TAG | LYD_PRINT_WD_IMPL_TAG))) {
+        /* we have implicit OR explicit default node */
+        /* get with-defaults module */
+        wdmod = ly_ctx_get_module_implemented(LYD_NODE_CTX(node), "ietf-netconf-with-defaults");
+    }
+
+    if (node->schema && node->meta) {
+        if (inner) {
+            LY_CHECK_RET(json_print_member2(ctx, NULL, LYD_JSON, NULL, "", 1));
+        } else {
+            LY_CHECK_RET(json_print_member(ctx, node, 1));
+        }
+        ly_print(ctx->out, "{%s", (DO_FORMAT ? "\n" : ""));
+        LEVEL_INC;
+        LY_CHECK_RET(json_print_metadata(ctx, node, wdmod));
+        LEVEL_DEC;
+        ly_print(ctx->out, "%s%*s}", DO_FORMAT ? "\n" : "", INDENT);
+        LEVEL_PRINTED;
+    } else if (!node->schema && ((struct lyd_node_opaq*)node)->attr) {
+        if (inner) {
+            LY_CHECK_RET(json_print_member2(ctx, NULL, LYD_JSON, NULL, "", 1));
+        } else {
+            LY_CHECK_RET(json_print_member2(ctx, node, ((struct lyd_node_opaq*)node)->format,
+                                            &((struct lyd_node_opaq*)node)->prefix, ((struct lyd_node_opaq*)node)->name, 1));
+        }
+        ly_print(ctx->out, "{%s", (DO_FORMAT ? "\n" : ""));
+        LEVEL_INC;
+        LY_CHECK_RET(json_print_attribute(ctx, (struct lyd_node_opaq*)node, wdmod));
+        LEVEL_DEC;
+        ly_print(ctx->out, "%s%*s}", DO_FORMAT ? "\n" : "", INDENT);
+        LEVEL_PRINTED;
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print leaf data node including its metadata.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Data node to print.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_leaf(struct jsonpr_ctx *ctx, const struct lyd_node *node)
+{
+    LY_CHECK_RET(json_print_member(ctx, node, 0));
+    LY_CHECK_RET(json_print_value(ctx, &((const struct lyd_node_term*)node)->value));
+    LEVEL_PRINTED;
+
+    /* print attributes as sibling */
+    json_print_attributes(ctx, node, 0);
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print anydata data node including its metadata.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] any Anydata node to print.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_anydata(struct jsonpr_ctx *ctx, struct lyd_node_any *any)
+{
+    LY_ERR ret = LY_SUCCESS;
+    struct lyd_node *iter;
+    int prev_opts, prev_lo;
+
+    if (!any->value.tree) {
+        /* no content */
+        return LY_SUCCESS;
+    }
+
+    if (any->value_type == LYD_ANYDATA_LYB) {
+        int parser_options = LYD_PARSE_ONLY | LYD_PARSE_OPAQ | LYD_PARSE_STRICT;
+
+        /* turn logging off */
+        prev_lo = ly_log_options(0);
+
+        /* try to parse it into a data tree */
+        if (lyd_parse_data_mem(ctx->ctx, any->value.mem, LYD_LYB, parser_options, 0, &iter) == LY_SUCCESS) {
+            /* successfully parsed */
+            free(any->value.mem);
+            any->value.tree = iter;
+            any->value_type = LYD_ANYDATA_DATATREE;
+        }
+
+        /* turn loggin on again */
+        ly_log_options(prev_lo);
+    }
+
+    switch (any->value_type) {
+    case LYD_ANYDATA_DATATREE:
+        /* close opening tag and print data */
+        prev_opts = ctx->options;
+        ctx->options &= ~LYD_PRINT_WITHSIBLINGS;
+
+        LY_LIST_FOR(any->value.tree, iter) {
+            ret = json_print_node(ctx, iter);
+            LY_CHECK_ERR_RET(ret, LEVEL_DEC, ret);
+        }
+
+        ctx->options = prev_opts;
+        break;
+    case LYD_ANYDATA_JSON:
+        /* print without escaping special characters */
+        if (!any->value.str[0]) {
+            return LY_SUCCESS;
+        }
+        ly_print(ctx->out, "%*s%s", INDENT, any->value.str);
+        break;
+    case LYD_ANYDATA_STRING:
+    case LYD_ANYDATA_XML:
+    case LYD_ANYDATA_LYB:
+        /* JSON and LYB format is not supported */
+        LOGWRN(ctx->ctx, "Unable to print anydata content (type %d) as XML.", any->value_type);
+        return LY_SUCCESS;
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print content of a single container/list data node including its metadata.
+ * The envelope specific to container and list are expected to be printed by the caller.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Data node to print.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_inner(struct jsonpr_ctx *ctx, const struct lyd_node *node)
+{
+    struct lyd_node *child;
+    struct lyd_node *children = lyd_node_children(node, 0);
+    int has_content = 0;
+
+    if (node->meta || children) {
+        has_content = 1;
+    } else if (node->schema && (node->schema->nodetype & LYD_NODE_ANY) && ((struct lyd_node_any*)node)->value.tree) {
+        has_content = 1;
+    }
+
+    if (!node->schema || node->schema->nodetype != LYS_LIST) {
+        ly_print(ctx->out, "%s{%s", (is_open_array(ctx, node) && ctx->level_printed >= ctx->level) ? "," : "",
+                 (DO_FORMAT && has_content) ? "\n" : "");
+    } else {
+        ly_print(ctx->out, "%s%*s{%s", (is_open_array(ctx, node) && ctx->level_printed >= ctx->level) ? "," : "",
+                 INDENT, (DO_FORMAT && has_content) ? "\n" : "");
+    }
+    LEVEL_INC;
+
+    json_print_attributes(ctx, node, 1);
+
+    if (!node->schema || !(node->schema->nodetype & LYS_ANYDATA)) {
+        /* print children */
+        LY_LIST_FOR(children, child) {
+            LY_CHECK_RET(json_print_node(ctx, child));
+        }
+    } else {
+        /* anydata */
+        json_print_anydata(ctx, (struct lyd_node_any *)node);
+    }
+
+
+    LEVEL_DEC;
+    if (DO_FORMAT && has_content) {
+        ly_print(ctx->out, "\n%*s}", INDENT);
+    } else {
+        ly_print(ctx->out, "}");
+    }
+    LEVEL_PRINTED;
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print container data node including its metadata.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Data node to print.
+ * @return LY_ERR value.
+ */
+static int
+json_print_container(struct jsonpr_ctx *ctx, const struct lyd_node *node)
+{
+    LY_CHECK_RET(json_print_member(ctx, node, 0));
+    LY_CHECK_RET(json_print_inner(ctx, node));
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print single leaf-list or list instance.
+ *
+ * In case of list, metadata are printed inside the list object. For the leaf-list,
+ * metadata are marked in the context for later printing after closing the array next to it using
+ * json_print_metadata_leaflist().
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Data node to print.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_leaf_list(struct jsonpr_ctx *ctx, const struct lyd_node *node)
+{
+    if (!is_open_array(ctx, node)) {
+        LY_CHECK_RET(json_print_member(ctx, node, 0));
+        json_print_array_open(ctx, node);
+    } else if (node->schema->nodetype == LYS_LEAFLIST) {
+        ly_print(ctx->out, ",");
+    }
+
+    if (node->schema->nodetype == LYS_LIST) {
+        if (!lyd_node_children(node, 0)) {
+            /* empty, e.g. in case of filter */
+            ly_print(ctx->out, "%s%snull", (ctx->level_printed >= ctx->level) ? "," : "", DO_FORMAT ? " " : "");
+            LEVEL_PRINTED;
+        } else {
+            /* print list's content */
+            LY_CHECK_RET(json_print_inner(ctx, node));
+        }
+    } else {
+        assert(node->schema->nodetype == LYS_LEAFLIST);
+        LY_CHECK_RET(json_print_value(ctx, &((const struct lyd_node_term*)node)->value));
+
+        if (node->meta && !ctx->print_sibling_metadata) {
+            ctx->print_sibling_metadata = node;
+        }
+    }
+
+    if (is_open_array(ctx, node) && (!node->next || node->next->schema != node->schema)) {
+        json_print_array_close(ctx);
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print leaf-list's metadata in case they were marked in the last call to json_print_leaf_list().
+ * This function is supposed to be called when the leaf-list array is closed.
+ *
+ * @param[in] ctx JSON printer context.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_metadata_leaflist(struct jsonpr_ctx *ctx)
+{
+    const struct lyd_node *prev, *node, *iter;
+
+    if (!ctx->print_sibling_metadata) {
+        return LY_SUCCESS;
+    }
+
+    for (node = ctx->print_sibling_metadata, prev = ctx->print_sibling_metadata->prev;
+            prev->next && matching_node(node, prev);
+            node = prev, prev = node->prev) {}
+
+    /* node is the first instance of the leaf-list */
+
+    LY_CHECK_RET(json_print_member(ctx, node, 1));
+    ly_print(ctx->out, "[%s", (DO_FORMAT ? "\n" : ""));
+    LEVEL_INC;
+    LY_LIST_FOR(node, iter) {
+        PRINT_COMMA;
+        if (iter->meta) {
+            ly_print(ctx->out, "%*s%s", INDENT, DO_FORMAT ? "{\n" : "{");
+            LEVEL_INC;
+            LY_CHECK_RET(json_print_metadata(ctx, iter, NULL));
+            LEVEL_DEC;
+            ly_print(ctx->out, "%s%*s}", DO_FORMAT ? "\n" : "", INDENT);
+        } else {
+            ly_print(ctx->out, "null");
+        }
+        LEVEL_PRINTED;
+        if (!matching_node(iter, iter->next)) {
+            break;
+        }
+    }
+    LEVEL_DEC;
+    ly_print(ctx->out, "%s%*s]", DO_FORMAT ? "\n" : "", INDENT);
+    LEVEL_PRINTED;
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print opaq data node including its attributes.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Opaq node to print.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_opaq(struct jsonpr_ctx *ctx, const struct lyd_node_opaq *node)
+{
+    int first = 1, last = 1;
+
+    if (node->hint & LYD_NODE_OPAQ_ISLIST) {
+        const struct lyd_node_opaq *prev = (const struct lyd_node_opaq*)node->prev;
+        const struct lyd_node_opaq *next = (const struct lyd_node_opaq*)node->next;
+        if (prev->next && matching_node((const struct lyd_node*)prev, (const struct lyd_node*)node)) {
+            first = 0;
+        }
+        if (next && matching_node((const struct lyd_node*)node, (const struct lyd_node*)next)) {
+            last = 0;
+        }
+    }
+
+    if (first) {
+        LY_CHECK_RET(json_print_member2(ctx, node->parent, node->format, &node->prefix, node->name, 0));
+
+        if (node->hint & LYD_NODE_OPAQ_ISLIST) {
+            json_print_array_open(ctx, (struct lyd_node*)node);
+            LEVEL_INC;
+        }
+    }
+    if (node->child || (node->hint & LYD_NODE_OPAQ_ISLIST)) {
+        LY_CHECK_RET(json_print_inner(ctx, (struct lyd_node*)node));
+        LEVEL_PRINTED;
+    } else {
+        if (node->hint & LYD_VALUE_PARSE_ISEMPTY) {
+            ly_print(ctx->out, "[null]");
+        } else if (node->hint & (LYD_VALUE_PARSE_ISBOOLEAN | LYD_VALUE_PARSE_ISNUMBER)) {
+            ly_print(ctx->out, "%s", node->value);
+        } else {
+            /* string */
+            ly_print(ctx->out, "\"%s\"", node->value);
+        }
+        LEVEL_PRINTED;
+
+        /* attributes */
+        json_print_attributes(ctx, (const struct lyd_node*)node, 0);
+
+    }
+    if (last && (node->hint & LYD_NODE_OPAQ_ISLIST)) {
+        json_print_array_close(ctx);
+        LEVEL_DEC;
+        LEVEL_PRINTED;
+    }
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Print all the types of data node including its metadata.
+ *
+ * @param[in] ctx JSON printer context.
+ * @param[in] node Data node to print.
+ * @return LY_ERR value.
+ */
+static LY_ERR
+json_print_node(struct jsonpr_ctx *ctx, const struct lyd_node *node)
+{
+    if (!ly_should_print(node, ctx->options)) {
+        if (is_open_array(ctx, node) && (!node->next || node->next->schema != node->schema)) {
+            json_print_array_close(ctx);
+        }
+        return LY_SUCCESS;
+    }
+
+    if (!node->schema) {
+        LY_CHECK_RET(json_print_opaq(ctx, (const struct lyd_node_opaq *)node));
+    } else {
+        switch (node->schema->nodetype) {
+        case LYS_RPC:
+        case LYS_ACTION:
+        case LYS_NOTIF:
+        case LYS_CONTAINER:
+            LY_CHECK_RET(json_print_container(ctx, node));
+            break;
+        case LYS_LEAF:
+            LY_CHECK_RET(json_print_leaf(ctx, node));
+            break;
+        case LYS_LEAFLIST:
+        case LYS_LIST:
+            LY_CHECK_RET(json_print_leaf_list(ctx, node));
+            break;
+        case LYS_ANYXML:
+        case LYS_ANYDATA:
+            LY_CHECK_RET(json_print_container(ctx, node));
+            break;
+        default:
+            LOGINT(node->schema->module->ctx);
+            return EXIT_FAILURE;
+        }
+    }
+
+    ctx->level_printed = ctx->level;
+
+    if (ctx->print_sibling_metadata && !matching_node(node->next, ctx->print_sibling_metadata)) {
+        json_print_metadata_leaflist(ctx);
+        ctx->print_sibling_metadata = NULL;
+    }
+
+    return LY_SUCCESS;
+}
+
+LY_ERR
+json_print_data(struct ly_out *out, const struct lyd_node *root, int options)
+{
+    const struct lyd_node *node;
+    struct jsonpr_ctx ctx = {0};
+    const char *delimiter = (options & LYD_PRINT_FORMAT) ? "\n" : "";
+
+    ctx.out = out;
+    ctx.level = 1;
+    ctx.level_printed = 0;
+    ctx.options = options;
+    ctx.ctx = LYD_NODE_CTX(root);
+
+    /* start */
+    ly_print(ctx.out, "{%s", delimiter);
+
+    /* content */
+    LY_LIST_FOR(root, node) {
+        LY_CHECK_RET(json_print_node(&ctx, node));
+        if (!(options & LYD_PRINT_WITHSIBLINGS)) {
+            break;
+        }
+    }
+
+    /* end */
+    ly_print(out, "%s}%s", delimiter, delimiter);
+
+    assert(!ctx.open.count);
+    ly_set_erase(&ctx.open, NULL);
+
+    ly_print_flush(out);
+    return LY_SUCCESS;
+}