A Python command-line utility for validating that the outputs of a given Declarative Form Azure Portal UI JSON template map to the input parameters of a given ARM Deployment Template JSON template.

Declarative Form Output => ARM Template Parameters

What is a Declarative Form?

Developers describe custom Azure Portal user interfaces for ARM deployment templates as JSON.

For many years, Create UI Definition (also known as createUiDefinition.json and CUID) was both the JSON schema and named mechanism for creating custom Azure Portal user interfaces.

Declarative Form is Create UI Definition's successor.

Running the Validator locally

Run the --help command to see the required arguments:

python -h

And you should get back some help:

usage: [-h] form_template_path deployment_template_path 

Validate a Declarative Form UI template against an ARM Deployment Template.

And can execute it like:

python sample-templates/form.json sample-templates/template.json

Running the Validator in an automated workflow

I could use the validator on a *nix agent with python3 by downloading the validator script from this repository, then passing my form template and deployment template as arguments to that script:

curl -s \
  -o \

python path/to/a/form.json path/to/a/template.json


If successful, you'll find this in the stdout:



Any failure will print the errors to stderr and exit code 1.

Some example errors:

Required parameter 'fizz' not found in Declarative Form output
Form output 'fizz2' not found in deployment template parameters
File could not be found: samples/form2.json

Debugging source or running tests

This repository defines a dev container that has everything you need to get up and running quickly with all the tools and configuration you need already installed configured.

It's really simple to get started now in your browser on a GitHub Codespace:

  • on this repository, click the green <> Code button then New Codespace

If you prefer local development, you can use this same dev container in Visual Studio Code:

Debugging the Validator

Debugging in the dev container

There's launch.json editor settings specified that pass command line arguments to any active Python script:

  • Open in the dev container
  • set a breakpoint
  • press F5 to start debugging

See for more information on how to debug Python from the Codespace.

Testing the Validator

Testing in the dev container

There's settings.json editor settings specified that inform where Python unit tests can be discovered:

  • Select "Testing" from the Application menu (or open the Command Pallete (F1) and type View: Show Testing)
  • Expand the validation directory and it's children to see all the unit tests
  • You can run them all selecting the "Run Tests" button (or open the Command Pallete (F1) and type Test: Run All Tests)
  • You can debug individual tests by setting a breakpoint in or and selecting Debug Test from the tests pane

Testing from the terminal

You can run the unit tests by calling the unittest module from Python like:

python -m unittest -v

And you should get output similar to:

test_form_specifies_all_required_parameters (validate_declarative_form_test.ValidateDeclarativeFormTest)
Test that all required parameters not output by the form return errors ... ok
test_form_specifies_valid_parameters (validate_declarative_form_test.ValidateDeclarativeFormTest)
Test that all form outputs exist as deployment template parameters ... ok
test_get_required_parameters (validate_declarative_form_test.ValidateDeclarativeFormTest)
Test that all deployment template parameters that do not have default values are returned ... ok
test_validate_form_captures_extraneous_form_output (validate_declarative_form_test.ValidateDeclarativeFormTest)
Test that if there are extra form outputs that are not template parameters ... ok
test_validate_form_captures_missing_required_parameter (validate_declarative_form_test.ValidateDeclarativeFormTest)
Test that if there is a missing required template parameter ... ok
test_validate_form_catches_invalid_template_json (validate_declarative_form_test.ValidateDeclarativeFormTest)
Test that if invalid JSON is passed that load fails and ... ok
test_validate_form_without_errors (validate_declarative_form_test.ValidateDeclarativeFormTest)
Test that if there are no errors in the validation ... ok

Ran 7 tests in 0.001s

GitHub - glennmusa/validate-declarative-form at
A Python command-line utility for validating that the outputs of a given Declarative Form Azure Portal UI JSON template map to the input parameters of a given ARM Deployment Template JSON template ...