Prerequisites

It is assumed the VSCode Plugin and uip-cli version 2.0.0 are installed.

The development environment will be WSL (Windows Subsystem for Linux), however, it could be any of the supported platforms. The tutorial assumes a folder called demo_template has been opened in VSCode.

Introduction

The custom, starter template that we will create is a contrived example, but it sufficiently covers all the features and its usefulness.

Step 1 - Create the Initial Template

To create a custom starter template, we will first make use of the built-in ue-task template. Open up the terminal to the demo_template folder and run

 uip init -t ue-task -e "extension_name=my_custom_ext" -e "universal_template_name=my_custom_template"

The directory structure should be as follows (not showing the Python *.pyc/__pycache__ files):

demo_template/
├── .uip
│   └── config
│       └── uip.yml
├── __init__.py
├── requirements.txt
├── setup.cfg
├── setup.py
└── src
    ├── __init__.py
    ├── extension.py
    ├── extension.yml
    └── templates
        └── template.json

The basic structure of the custom template is almost finished! Go ahead and create a file called template_config.yml at the same level as the src/ folder. The resulting directory tree is as follows:

demo_template/
├── .uip
│   └── config
│       └── uip.yml
├── __init__.py
├── requirements.txt
├── setup.cfg
├── setup.py
├── src
│   ├── __init__.py
│   ├── extension.py
│   ├── extension.yml
│   └── templates
│       └── template.json
└── template_config.yml

Step 2 - Configuring the Initial Template

To make the template configurable, add the following content below to template_config.yml:

template_config.yml

name: example-template

version: 1.0.0

description: this is the description for example template

files_to_template: 
  - src/extension.py
  - src/templates/template.json

variables:
  msg:
    default: test_message
    description: message to print to STDOUT and STDERR
  log_level:
    default: Info
    description: Universal Template Log Level

template_config.yml details

Each template_config.yml must contain:

name
- A string that identifies the name of the template (this is NOT referring to the Universal Template name). It can be anything other than the name of the built-in templates: ue-task and ue-publisher.
version
- A string that identifies the template version. Not restricted to x.y.z (SemVer); it could be anything (e.g. v1).
description
- A string describing the template.

Although not required, it can also contain:

files_to_template
- An array containing paths to files that will be “templated” using Jinja2. All files must be specified relative to template_config.yml.
variables
- A mapping/dictionary of variables that will be substituted in the relevant files specified by files_to_template. The value of each key/variable is another mapping/dictionary that must contain default and description.

Now, open src/extension.py and replace extension_start() with the code below:

src/extension.py::extension_start()

    def extension_start(self, fields):
        """Required method that serves as the starting point for work performed
        for a task instance.

        Parameters
        ----------
        fields : dict
            populated with field values from the associated task instance
            launched in the Controller

        Returns
        -------
        ExtensionResult
            once the work is done, an instance of ExtensionResult must be
            returned. See the documentation for a full list of parameters that
            can be passed to the ExtensionResult class constructor
        """

        my_msg = "{{ msg }}"

        # Get the value of the 'action' field
        action_field = fields.get('action', [])
        if len(action_field) != 1:
            # 'action' field was not specified or is invalid
            action = ''
        else:
            action = action_field[0]

        if action.lower() == 'print':
            # Print to standard output...
            print(my_msg)
        else:
            # Log to standard error...
            logger.info(my_msg)

        # Return the result with a payload containing a Hello message...
        return ExtensionResult(
            unv_output='Hello Extension!'
        )

On line 19, a variable called my_msg is defined with the value of "{{ msg }}". This is Jinja2 syntax that will eventually be replaced with the specified value for msg (or the default, if they don’t specify anything) during initialization time.

On lines 31 and 34, the message was changed to print the value of my_msg.

Now, open src/templates/template.json and replace the value of logLevel key (should be around line 86) with the change shown below:

template.json

      "sysId": "535c354ed083489cb10413019d71a57c",
      "textType": "Plain"
    }
  ],
  "logLevel": "{{ log_level | title }}",
  "minReleaseLevel": "7.0.0.0",
  "name": "my_custom_template",

On line 86 of the snippet above, the value of logLevel was changed from Inherited to {{ log_level | title }}. Once again, this is Jinja2 syntax that will eventually be replaced with the specified value of log_level (or the default, if nothing is specified). Additionally, the built-in title filter is applied to the value of log_level. This will ensure values like trACe end up as Trace (first letter capitalized and everything else lowercase) as required by template.json.

Step 3 - Packaging the Initial Template

Although the example is a bit contrived, we have managed to create a fully-functional customized template.

To package the template, simply zip up everything into a file called example_template.zip (or whatever you want to call it). Its structure should be as follows (if *.pyc and __pycache__ files are there, it’s fine):

Archive:  example_template.zip
  Length      Date    Time    Name
---------  ---------- -----   ----
        0  2023-04-04 15:37   __init__.py
      306  2023-04-04 15:37   requirements.txt
       43  2023-04-05 11:03   setup.cfg
    12088  2023-04-05 11:03   setup.py
        0  2023-04-05 11:03   src/
     1723  2023-04-05 11:03   src/extension.py
      221  2023-04-05 11:03   src/extension.yml
        0  2023-04-05 11:03   src/templates/
     3278  2023-04-05 11:09   src/templates/template.json
        0  2023-04-04 15:37   src/__init__.py
      349  2023-04-05 11:05   template_config.yml
---------                     -------
    18008                     11 files

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