Example of passing environment variables from cli

[BusyByte]

Pkl 0.28.2 (macOS 14.7.2, native) (installed with homebrew)

I've defined a bash script

#!/bin/bash

# Check if the correct number of arguments are provided
if [ "$#" -ne 2 ]; then
    echo "Usage: $0 <service_name> <component>"
    exit 1
fi

# Set environment variables
export SERVICE_NAME=$1
export COMPONENT=$2

# Run the pkl command
pkl eval -f json -e SERVICE_NAME -e COMPONENT ./pkl-templates/my-template.pkl

and in the pkl file

COMPONENT = read("env:COMPONENT")
SERVICE_NAME = read("env:SERVICE_NAME")

...
 Tags = new Dynamic {
        component = List(
            "${COMPONENT}"
        )
    }
...

but it is not rendering it correctly here's what I get:

{
...
"Tags": {
    "component": [
      "${COMPONENT}"
    ]
  }
}

Any help? The docs were not very clear that I could find about how to fit the cli and the pkl files together.

[bioball]

Your syntax for variable interpolation is incorrect:

-"${COMPONENT}"
+"\(COMPONENT)"

You actually don't even need interpolation here, because COMPONENT is already a string. So it can just be component = List(COMPONENT).

In case you aren't already, I highly recommend using one of our editor plugins for writing Pkl, because it they will provide feedback about this to you.

Some other notes:

1. List is a data type that's meant for in-language operations (map/flatmap/filter/etc). If you want to describe data, you should use Listing.

2. If your module only makes sense as JSON, you should go ahead and set the output.renderer. Then, you don't need to add -f json anymore as a CLI flag.

   output {
     renderer = new JsonRenderer {}
   }

3. I think it makes more sense to model your inputs as external properties instead of env vars.

   pkl eval -p SERVICE_NAME="$1" -p COMPONENT="$2" pkl-templates/my-template.pkl

   With this, you'd read("prop:SERVICE_NAME")

4. Instead of using Dynamic, try defining classes for your schema. Dynamic is sort of an escape hatch and has its uses, but generally you wouldn't use it for describing data. Also, try separating your data and schema into different files

   // MySchema.pkl
   Tags: Tags
   
   class Tags {
     component: Listing<String>
   }
   
   output {
     renderer = new JsonRenderer {}
   }

   // myData.pkl
   amends "MySchema.pkl"
   
   tags {
     component {
       read("prop:COMPONENT")
     }
   }

[BusyByte]

@bioball I've updated my files based on your feedback and everything is working now, thanks for the prompt help.

[BusyByte]

@bioball I do have to interpolate it into a string somewhere else I omitted :

 PolicyName = "my-github-org-${SERVICE_NAME}-deploy"

So I assume that is not how I should interpolate it.

Updated: I found the doc say \(<expr>) . This is what I get for trusting AI generated content.

[bioball]

Ah, yeah, as far as I can tell, none of the LLMs are good at Pkl