programmatically reading bicepparam files using Powershell

[eosfor]

Is it possible to programmatically parse a bicepparam file and convert it into objects somehow. Can someone show or point me at an example? I know I can do regexp, but it is not really a "powershell" way. Point here is that if a config file contains some parameters, I want a Powershell script to be able to read it, parse it, extract some values, perform some actions, like listing some resources, and set some env vars.

AN example would be the following scenario. We have a hub resource group containing a VNET and a set of Private DNS Zones created elsewhere, so it is better not to make any assumptions on which zones area there. When we create spoke VNETs connected to the hub VNET, we need to also link all these private DNS zones. Spoke template knows nothing about hub DNS zones, and hardcoding them there as existing resources is not a good idea as the list might change. Current approach, perhaps, is to read the bicepparam file, which stores a name of the hub sesouce group, extract this name, let Powershell extract all DNS Zone resource IDs and pass them to the param file back through environment variables. THat makes all this more dynamic, avoiding a necessity to store whole bunch of parameters somewhere else, referencing them and so on.

In general, it would be great if there were a function in bicep, which could enumerate existing resources in a resource group, filter them by a type or a name or both and return them an array. That way we can avoid hardcoding a lot of things, I believe.

[slavizh]

+1 on this one. Although this is possible to do now by converting the biceparam file to json and from json to PS object. The problem is that some syntax will not be converted back once you do object -> json -> biepparam. There also could be some issues in turning to object when using some of the functions in bicep like loading content, etc.

[brwilkinson]

Side comment based on your scenario. You could use "private DNS resolver" service in the hub. Then use the hub private resolver IP for the DNS for the hub & spokes. That way you do not need to link the private zones anywhere except in the hub.

[brwilkinson]

@eosfor Can we mark this as answered ?

in short I believe:

1. decompile to json bicep build-params params.bicepparam
2. read the json file: Get-Content params.json | convertfrom-json

Seems like this would work for the scenario you mentioned, then pass in the DNS zones as params to your bicep deployment, other template.

I do recommend DNS resolver, it's a bit pricey, however it's about a similar cost to just running Compute yourself, without having to worry about security and patching of VM's that would just be forwarding DNS. Plus it's super easy to get configured and using that model scales very well.

[eosfor]

well, I'd expect to have .NET interface rather than going through json. looks like a 'dirty hack' to me :).

In general, the question was not about DNS. The solution you offered is good, i agree. But the question was more like about finding a native way of peeking into bicep config files in general. Something I can use to pull various config objects from a config, sharing it between multiple "pipelines", some of which may not be using bicep, but purely powershell

[brwilkinson]

If you haven't seen it yet, check out this community project, which is in active development.

• https://github.com/PSBicep/PSBicep

[brwilkinson]

One additional comment. Both bicep and bicepparam are compiled to json prior to sending to Azure, so it's still the source of truth for deployments. So not really a hack.

Also for other examples, check the projects that depend on Bicep for more info

• https://github.com/Azure/bicep/network/dependents

[jensmh]

@brwilkinson 's previous answer mentions decompiling to JSON, then loading the resulting file. You can also skip the intermediate step and just load the parameters directly into a PowerShell object by sending the bicep output to --stdout (note the need to convert from JSON twice):

$parameters = (bicep build-params .\main.bicepparam --stdout | ConvertFrom-Json).parametersJson | ConvertFrom-Json

You can then access any parameter as $parameters.parameters.paramName.value.

If you only need a single parameter, you can get it directly:

$paramValue = ((bicep build-params .\main.bicepparam --stdout | ConvertFrom-Json).parametersJson | ConvertFrom-Json).parameters.paramName.value

Note that az bicep build-param --file .\main.bicepparam --stdout works as well.