proposals/POEM-support-array-result.md

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# Title

Currently, OpenWhisk supports returning a JSON object only, e.g.
```shell
# wsk action invoke hello -r
{
    "greeting": "Hello stranger!"
}
```
It is necessary to support returning an array too as an array is also a proper JSON object, e.g.
```shell
# wsk action invoke hello-array -r
[
    "a",
    "b"
]
```
The sequence action should be considered support as well.

# Status
* Current state: In-progress
* Author(s): @ningyougang

# Summary and Motivation

This POEM proposes a new feature that allows user to write their own action which supports an array result.
So actions would be able to return a JSON object or an array.

# Proposed changes
## Openwhisk main repo
Make controller and invoker support both a JSON object and an array result.

## Runtime repos
All runtime images should support an array result. e.g.

* nodejs (supports by default)
* go
* java
* python
* php
* shell
* docker
* ruby
* dotnet
* rust
* swift
* deno
* ballerina

## Openwhisk-cli repo
* The `wsk` CLI needs to support parsing an array result when executing actions.
* The `wsk` CLI needs to support parsing an array result when getting activations.