Extend an array in YAML? - yaml

Question

Suppose I have:
base_array:
-1
-2
how could I do something like:
my_array: << base_array
-3
so that my_array was [1,2,3]
Update: I should specify that I want the extending to occur inside the YAML itself.

Answer 1

Since the already commented issue#35 exists, merge-keys << doesn't help you. It only merges/inserts referenced keys into a map (see YAML docs merge). Instead you should work with sequences and use anchor & and alias *.
So your example should look like this:
base_list: &base
- 1
- 2
extended: &ext
- 3
extended_list:
[*base, *ext]
Will give result in output like this (JSON):
{
"base_list": [
1,
2
],
"extended": [
3
],
"extended_list": [
[
1,
2
],
[
3
]
]
}
Although not exactly what you expected, but maybe your parsing/loading environment can flatten the nested array/list to a simple array/list.
You can always test YAML online, for example use:
http://ben-kiki.org/ypaste
Online YAML Parser

Answer 2

I needed to do the same thing but to run on Azure DevOps Pipeline. In particular, I had to update the stage dependency dynamically. How I did it:
dependents: [Stage_A, Stage_B]
otherDependents: [Stage_C] # This needed to be added by policy to the pipeline's execution
dependsOn:
- ${{ each dependent in dependents }}:
- ${{ dependent }}
- ${{ each dependent in otherDependents }}:
- ${{ dependent }}
Doing so resulted in the required setup:
dependents: [Stage_A, Stage_B]
otherDependents: [Stage_C] # This needed to be added by policy to the pipeline's execution
dependsOn:
- Stage_A
- Stage_B
- Stage_C
I say dynamically because the variable dependents came from a template to which I had to append Stage_C.