Unexpected order when adding multiple elements to array

[ryenus]

Describe the bug

When trying to sequentially append two objects to an array, say array + o1 + o2, instead of appending o1 then appending o2, yq combined the objects o1 and o2, then appended the new object to the array.

Version of yq: 4.44.3
Operating system: mac
Installed via: homebrew

Input Yaml
N/A

Command

The command you ran:

yq -n '[] + {"a":1} + {"b":2}'

Actual behavior

- a: 1
  b: 2

Expected behavior

- a: 1
- b: 2

Additional context
Add any other context about the problem here.

[jandubois]

It looks like operators have right associativity, i.e. a + b + c means a + (b + c).

Normally + should be non-associative (so the order should not matter), but the type coercion properties of the left hand side breaks this.

I'm not sure if making all the operators right-associative was intentional; I suspect it is a side-effect of transforming expressions into a postfix representation internally.

This is even more surprising for operators like subtraction that are normally left-associative:

$ yq -n '6 - 5 - 4'
5

Here the expression is processed as 6 - (5 - 4).

I don't see how this could be fixed without breaking backwards compatibility, but it would help a lot if this was documented (see #1648).

[ryenus]

Thank you @jandubois ! Verifying with subtraction indeed make it more obvious:

Command/Expression	Result
jq -n '3 - 2 - 1'	0
yq -n '3 - 2 - 1'	2

[jandubois]

@ryenus Just in case it wasn't obvious, you can avoid these issues by always adding parenthesis explicitly:

$ yq -n '([] + {"a":1}) + {"b":2}'
- a: 1
- b: 2

[ryenus]

Just in case it wasn't obvious, you can avoid these issues by always adding parenthesis explicitly:

Agreed, for array concatenation, another workaround is to wrap the 2nd operand also in an array:

$ yq -n '[] + [{"a":1}] + {"b":2}'
- a: 1
- b: 2