Usman0111/param_validation_design.md

## param_validation_design.md

      
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              param_validation_design.md
            
          
    Supplemental Params Validation Design

Lets say a user makes the following deployment with Az CLI:
az deployment group create \ 
--template-file 'main.bicep'
--parameters 'params.bicepparam' \
--parameters foo='inline' 
params.bicepparam

using './main.bicep'

param foo = 'test'
param bar = 0
main.bicep

param foo string
param bar int
In order to validate the type of the override value for parameter foo, we need to pass it down to the Bicep CLI while ensuring that no secrects get leaked in the shell history. For this, Az CLI would set a environment variable BICEP_PARAMETERS_OVERRIDES with following value as a JSON string:
{
  "foo" : "inline"
}
Then BICEP CLI would read this value and validate value for parameter foo.
Based on whether the value for --template is given or using delcaratoin is specified in the .bicepparam file, we can run following four secnarios:
1. Both --template and using are given

Template JSON produced from using
Prameters in .bicepparam file already validated
Overrides validate against path from using
2. --template is not given  and using is given

Template JSON produced from using
Prameters in .bicepparam file already validated
Overrides validate against path from using
3. --template is given  and using is not given

Template JSON produced from --template
should the prameters in .bicepparam file already validated?
Overrides validate against path from --template
4. Neither --template or using is given

Throw error since deployment/validation not possible
Two low level design questions that need to be answered:
1. How would inline params would be validated?

First Appraoch

Update the syntax tree and let the Bicep compiler determine which value is incorrect (could lead to confusion with line numbers: inline values don't have line number but compiler would think they do or updating the syntax tree)
Second Approach

Compile .bicepparam and throw errors
if none exits then call a different function to validate params (this produces errors without line numbers)
Then update the file after every value is validated


Note: Question 2 can be answered later (when using is being made optional)
2. How would we incorporate --bicep-file value in .bicepparam file when no using is given?

This can potentialy create line number issues
One strategy is to not edit the syntax tree at all just have two functions that would validate values in .bicepparam and inline values then combine them? (somewhat similar to solution 2 for question 1)