Blocks does not work with nested array structure

[yahelnachum]

Summary

In the jsonata playground I was trying out parenthesized expressions and blocks and came across some inconsistent output. I used blocks to turn a selection into an array so that I could pick a single index. Then when I tried adding a key to step into that single index it seemed to revert back to a selection.

More Details

JSON Input 1:

[
  {
    "phone": [
      {"number" : 0}
    ]
  },
  {
    "phone": [
      {"number" : 1}
    ]
  },
  {
    "phone": [
      {"number" : 2}    
    ]
  }
]

Then I tried a series of JSONata expressions

---

Expression 1:

phone

Actual Output 1:

[
  {"number":0},
  {"number":1},
  {"number":2}
]

---

Expression 2:

(phone)[0]

Actual Output 2:

{
  "number": 0
}

---

Expression 3:

(phone)[0].number

Actual Output 3:

[
  0,
  1,
  2
]

---

I would have expected the output of Expression 3 to be the following given that I was able to select a single index in Expression 2.

Expected Output 3:

0

This seems to me like a bug in the code somewhere, but if there is an explanation for this behavior then please let me know what that is. Thanks in advance for reading!

[yahelnachum]

My co-worker was trying some other inputs and got the expected behavior by wrapping my JSON input 1 inside of a JSON Object. I don't know why the code would treat those two cases differently.

JSON input 2:

{
  "account": [
    {
      "phone": [
        {"number" : 0}
      ]
    },
    {
      "phone": [
        {"number" : 1}
      ]
    },
    {
      "phone": [
        {"number" : 2}    
      ]
    }
  ]
}

---

Expression 4:

(account.phone)[0].number

Actual Output 4:

0

[yahelnachum]

Just tried another input with a nested array with the same Expression 3 and it worked this time. Still not sure why its behaving differently.

JSON input 3:

[
  [
    {
      "phone": [
        {"number" : 0}
      ]
    },
    {
      "phone": [
        {"number" : 1}
      ]
    },
    {
      "phone": [
        {"number" : 2}    
      ]
    }
  ]
]

---

Expression 5:

(phone)[0].number

Actual Output 5:

0

[andrew-coleman]

Yes, the result of your expression 3 looks like a bug.

[andrew-coleman]

@yahelnachum - because the input data is an array, to access the first item, you can use $[0]. So your expression 3 could be rewritten as

$[0].phone.number

which will return

0

[andrew-coleman]

This issue is related to how JSONata handles input arrays. There is a lengthy discussion in #170 on this topic. I'm currently prototyping a solution that uses explicit syntax to determine whether to map over the input array verses just use it as a single context value.

[andrew-coleman]

resolved by #363