telemetry: fix empty JSON dictionaries

Fix to allow telemetry to handle empty dictionaries correctly.

This patch resolves an issue where empty dictionaries are reported
by telemetry as '[]' rather than '{}'. Initializing the output
buffer based on the container type resolves the issue.

Fixes: c933bb5 ("telemetry: support array values in data object")
Cc: [email protected]

Signed-off-by: Jonathan Erb <[email protected]>
Acked-by: Ciara Power <[email protected]>

Author: Jonathan Erb

.mailmap

@@ -676,7 +676,7 @@ John Ousterhout <[email protected]>
 John Romein <[email protected]>
 John W. Linville <[email protected]>
 Jonas Pfefferle <[email protected]> <[email protected]>
-Jonathan Erb <[email protected]> <[email protected]>
+Jonathan Erb <jonathan.erb@threater.com> <jonathan.erb@threatblockr.com> <[email protected]>
 Jonathan Tsai <[email protected]>
 Jon DeVree <[email protected]>
 Jon Loeliger <[email protected]>

lib/telemetry/telemetry.c

@@ -170,7 +170,11 @@ container_to_json(const struct rte_tel_data *d, char *out_buf, size_t buf_len)
 		d->type != TEL_ARRAY_INT && d->type != TEL_ARRAY_STRING)
 		return snprintf(out_buf, buf_len, "null");
 
-	used = rte_tel_json_empty_array(out_buf, buf_len, 0);
+	if (d->type == TEL_DICT)
+		used = rte_tel_json_empty_obj(out_buf, buf_len, 0);
+	else
+		used = rte_tel_json_empty_array(out_buf, buf_len, 0);
+
 	if (d->type == TEL_ARRAY_UINT)
 		for (i = 0; i < d->data_len; i++)
 			used = rte_tel_json_add_array_uint(out_buf,