libubox: Add ability to find ordinal position inside a table

[pprindeville]

When adding anonymous objects to an array, the only way to select them (as in json_select) is via their ordinality. This function returns a selectable index to those members.

[pprindeville]

cc: @robimarko @ynezz

[pprindeville]

@ynezz Any idea why the test is failing with:

...
test_jshn_append_no_leading_space
test_jshn_get_index
/home/runner/work/libubox/libubox/tests/shunit2/tests.sh: 1: eval: JSON_UNSET: parameter not set

Errors while running CTest

50% tests passed, 1 tests failed out of 2

Total Test time (real) =  45.45 sec

The following tests FAILED:
	  2 - shunit2 (Failed)
make: *** [Makefile:71: test] Error 8

It looks like a problem with setup or teardown of the test. Trying to go by your example, it calls __jshn_append which is an internal, low-level function... I don't see any examples that use the user-visible functions that I can follow as a template.

cc: @Noltari

[Noltari]

@ynezz Any idea why the test is failing with:

...
test_jshn_append_no_leading_space
test_jshn_get_index
/home/runner/work/libubox/libubox/tests/shunit2/tests.sh: 1: eval: JSON_UNSET: parameter not set

Errors while running CTest

50% tests passed, 1 tests failed out of 2

Total Test time (real) =  45.45 sec

The following tests FAILED:
	  2 - shunit2 (Failed)
make: *** [Makefile:71: test] Error 8

It looks like a problem with setup or teardown of the test. Trying to go by your example, it calls __jshn_append which is an internal, low-level function... I don't see any examples that use the user-visible functions that I can follow as a template.

cc: @Noltari

@pprindeville adding set +u as @ynezz did on #30 seems to fix the issue you're having:

test_jshn_get_index() {
	JSON_PREFIX="${JSON_PREFIX:-}"
	. ../../sh/jshn.sh

	set +u

	local index

	json_init
	json_add_object "Dhcp4"

	json_add_array "subnet4"

	json_add_object ""
	json_get_index index

	json_add_int "id" 1
	json_add_string "subnet" "192.168.1.0/24"

	json_close_object

	json_add_object ""

	json_add_int "id" 2
	json_add_string "subnet" "192.168.2.0/24"

	json_close_object

	json_select "$index"		# revisit first anonymous object
	json_add_int "valid-lifetime" 3600
	json_select ..			# pop back into array

	json_close_array		# subnet4

	json_close_object		# Dhcp4

	local json="$(json_dump)"

	assertEquals '{ "Dhcp4": { "subnet4": [ { "id": 1, "subnet": "192.168.1.0\/24", "valid-lifetime": 3600 }, { "id": 2, "subnet": "192.168.2.0\/24" } ] } }' "$json"

	set -u
}

(And removing one of the double \ in the subnets)

[Noltari]

@pprindeville you need to rebase it on top of #34 in order to get it working.

[Noltari]

@pprindeville I rebased your branch on top of master, and made some minor changes.
It would be great if other OpenWrt developers could review this since I don't really have a deep libubox knowledge...

CC @nbd168 @ynezz @jow-

[pprindeville]

@pprindeville I rebased your branch on top of master, and made some minor changes. It would be great if other OpenWrt developers could review this since I don't really have a deep libubox knowledge...

@Noltari Understood. Given that getting traction on this package has been challenging, and that the new function isn't callable anywhere else but by Kea, should we merge it in the absence of objections in... say... 2 weeks?