JMESPath current array index - indexof

Question

In JMESPath with this query:
people[].{"index":#.index,"name":name, "state":state.name}
On this example data:
{
"people": [
{
"name": "a",
"state": {"name": "up"}
},
{
"name": "b",
"state": {"name": "down"}
},
{
"name": "c",
"state": {"name": "up"}
}
]
}
I get:
[
{
"index": null,
"name": "a",
"state": "up"
},
{
"index": null,
"name": "b",
"state": "down"
},
{
"index": null,
"name": "c",
"state": "up"
}
]
How do I get the index property to actually have the index of the array? I realize that #.index is not the correct syntax but have not been able to find a function that would return the index. Is there a way to include the current array index?

Answer 1

Use-case
Use Jmespath query syntax to extract the numeric index of the current array element, from a series of array elements.
Pitfalls
As of this writing (2019-03-22) this feature is not a part of the standard Jmespath specification.
Workaround
This is possible when running Jmespath from within any of various programming languages, however this must be done outside of Jmespath.

Answer 2

This is not exactly the form you requested but I have a possible answer for you:
people[].{"name":name, "state":state.name} | merge({count: length(#)}, #[*])
this request give this result:
{
"0": {
"name": "a",
"state": "up"
},
"1": {
"name": "b",
"state": "down"
},
"2": {
"name": "c",
"state": "up"
},
"count": 3
}
So each attribute of this object have a index except the last one count it just refer the number of attribute, so if you want to browse the attribute of the object with a loop for example you can do it because you know that the attribute count give the number of attribute to browse.