variable set in azure pipeline gets corrupted when read in template - azure

Question

variable big_var_01 defined with value '3q4w#V$X3q4w#V$X' by following azure pipeline yaml file gets corrupted to become value '3q4w#V#V' when read back in azure pipeline template
cat parent_scott.yaml
variables:
- name: big_var_01
value: ${{ parameters.big_var_01 }}
parameters:
- name: big_var_01
displayName: "this var wants to get written to then read by templates"
type: string
default: '3q4w#V$X3q4w#V$X'
# CI Triggers
trigger:
branches:
exclude:
- '*'
pool:
vmImage: 'ubuntu-latest'
# Release Stages
stages:
- template: child_scott_one.yaml
following azure pipeline template variable big_var_01 is read back however its value is corrupted and does not match above assignment
cat child_scott_one.yaml
# Release Stages
stages:
- stage: A
jobs:
- job: JA
steps:
- script: |
echo "here is big_var_01 -->$(big_var_01)<-- "
local_var_01=$(big_var_01)
echo
echo "here is local_var_01 -->$local_var_01<-- "
echo
echo "length of local_var_01 is ${#local_var_01}"
echo
name: DetermineResult
see run of above pipeline
https://dev.azure.com/sekhemrekhutawysobekhotep/public_project/_build/results?buildId=525&view=logs&j=54e3124b-25ae-54f7-b0df-b26e1988012b&t=52fad91f-d6ac-51fb-b63d-00fda7898bb6&l=13
see code at https://github.com/sekhemrekhutawysobekhotep/shared_variables_across_templates
How to make the string variable big_var_01 get treated as a literal evidently its somehow getting evaluated and thus corrupted ... above code is a simplification of my actual azure pipeline where I get same variable corruption issue even when setting up a Key Value secret with value 3q4w#V$X3q4w#V$X which gets corrupted when read back in a pipeline template
here is another pipeline run which explicitly shows this issue https://dev.azure.com/sekhemrekhutawysobekhotep/public_project/_build/results?buildId=530&view=logs&j=ed5db508-d8c1-5154-7d4e-a21cef45e99c&t=a9f49566-82d0-5c0a-2e98-46af3de0d6e9&l=38 on this run I check marked ON pipeline run option: "Enable system diagnostics" ... next I will try to single quote my shell assignment from the azure variable

Answer 1

At some step Azure DevOps or Ubuntu replaced part of your string. So you have:
3q4w#V$X3q4w#V$X = 3q4w#V + $X3q4w + #V + $X
and this part $X3q4w and this $X was replaced with empty string giving you 3q4w#V + #V.
If you run this with \ before $ like here 3q4w#V\$X3q4w#V\$X
This is job Foo.
here is big_var_01 -->3q4w#V$X3q4w#V$X<--
here is local_var_01 -->3q4w#V$X3q4w#V$X<--
length of local_var_01 is 16
I got an error running this on windows-latest however I got correct string:
"This is job Foo."
"here is big_var_01 -->3q4w#V$X3q4w#V$X<-- "
'local_var_01' is not recognized as an internal or external command,
operable program or batch file.
ECHO is off.
"here is local_var_01 -->$local_var_01<-- "
ECHO is off.
"length of local_var_01 is ${#local_var_01}"
ECHO is off.
##[error]Cmd.exe exited with code '9009'.
so it looks like ubuntu replaces it with env variables however, since there is not variables like $X3q4w and $X it replaces with empty string.

Answer 2

Found a solution ... it works if I single quote around the azure variable during bash shell assignment
local_var_01=$(big_var_01) # bad results with value 3q4w#V#V
local_var_02="$(big_var_01)" # bad results with value 3q4w#V#V
local_var_03='$(big_var_01)' # good this gives value 3q4w#V$X3q4w#V$X
my instincts said to not use single quotes knowing its not the bash shell way however once I accepted the fact azure performs some magic ~~helping~~ interstigal layer pre processing in between pipeline source code and fully resolved bash shell execution I took a chance and tried this ... come to find out this is how bash shell blocks variable expansion