How can I run a command in a shell script function that requires access to the current shell instance? [closed]

Question

I am using a custom package manager called spack, which allows me to load installed modules using the spack load command. It is similar to the familiar module load command in many ways. I am using zsh.

I have set up a shell script with a function that I would later like to insert into my .zshrc file. It is currently located in a standalone file for testing purposes, which looks as following:

#!/bin/bash
load-standard () {
    echo "loading $1"
    spack load $1
}
load-standard $1

When I run this script with source ./script_name package_name, I get an error message that says

`spack load` requires Spack's shell support.

To enable Spack's shell support, a file called setup-env.sh must be run which enables the user to make use of the spack command.

However, directly typing in the commands spack load package_name works with no problem.

I always assumed that running a command from a shell script is the same as typing it into the current shell. How can I make my shell interpret the spack load commands exactly as if I had directly typed them in?

EDIT: Placing the function in my .zshrc file solved this problem.