Why eval(pathexp) prints the input twice?

[lucabalsanelli]

I was trying to understand Merge arrays of objects together, matching on a key from the manual and I noticed something strange to me.

We are given sample.yml and another.yml:

myArray:
  - a: apple
    b: appleB
something: else

newArray:
  - a: banana
    c: bananaC

If I do

originalPath="." \
yq eval-all 'eval(strenv(originalPath))' \
  sample.yml another.yml

I get

myArray:
  - a: apple
    b: appleB
something: else
---
newArray:
  - a: banana
    c: bananaC
myArray:
  - a: apple
    b: appleB
something: else
---
newArray:
  - a: banana
    c: bananaC

that is the output is duplicated. On the other hand, if I do

yq eval-all '.' sample.yml another.yml

I get

myArray:
  - a: apple
    b: appleB
something: else
---
newArray:
  - a: banana
    c: bananaC

that is I get just the expected objects. Why is that the case? Am I missing something?

Thanks,
Luca

[mikefarah]

Eval-All can work a little weirdly, it does a cross function, perhaps even more unexpected when using eval.

This means it will load up both files, as two separate nodes; then it will run the eval expression against each node to get two path expressions (Which happen to be the same). Then it runs those two path expression against the two document nodes, and so you see 4 results.

You may be better off just using the default 'eval'. In fact, since I added the load operator, I think there's little use of eval-all. I should update the example to just use load.