Declarative Transformations API

[arumsey]

Description

Introduce a higher-level Importer API that provides a declarative approach to transformations

• offer a clearer API for developers to access that follows a consistent pattern
• define a no-code configuration for most common transformation phases
• allow for block-level transformation extensions
• provide default metadata handling to avoid code duplication
• opens the door for easier transformation automation
• separates block transformations into their own modules

Related Issue

Fixes: #355

Dependent on: https://github.com/adobe/helix-importer/pull/351

Motivation and Context

The AEM Importer import scripts are a powerful tool for manipulating a DOM into an Edge Delivery compatible format. These scripts however need to be written by developers with a high degree of knowledge of DOM APIs. The addition of a declarative transformation API on top of the existing low-level import script opens mor doors for less technical users to begin importing content by simply defining a collection of CSS selectors. Additionally, a no-code approach to defining import rules also allows them to be more easily created by automation and for them to be POSTED to a service to enable long running imports.

This feature does not introduce any breaking changes to the AEM Importer. The import script however can now be a JSON file or a JS object. This JSON structure (the ruleset) can then be passed to a createImporter factory that generates a valid import script. The Transformer class is able to consume a ruleset and runs through a series of phases to clean up the DOM and then generate any desired blocks through the use of CSS selector logic.

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] I have signed the Adobe Open Source CLA.
• [ ] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.