[HOP-1919] Allow plug-able expressions on a field input level

• Type: Task
• Status: Closed
• Priority: High
• Resolution: Fixed
• Fix Version/s: Migrated to GHI
• Labels: architecture pre-apache usability user_experience
• Assignee: Unassigned
• Reporter: Matt Casters
• Created: 04/Oct/20 12:20
• Updated: 20/Mar/23 09:14
• Resolved: 20/Mar/23 09:14

Description

When we look at an input field in any dialog in Hop we can determine different types of input:

On the one hand we have simple input fields like a transform name, a data type and so on.
On the other hand we have input fields pertaining to the context of the pipeline, the transform, the action, ...
These are things like the following:

• A static String value
• A variable expression
• The name of an input field

The goal is now to unify the possibilities and allow the user a choice.
We don't always have input fields but if we have them we should be able to use them in the given context.
The same goes for variable expressions. They're not always available but if variables are present in the context we should give the user the chance to use them. Mostly this is already the case.

On top of that we should give the user the ability to use the available things in the context: input field values, variables, ... in expressions which are plug-able. We could have various expression plugins for JavaScript, Java (Janino) or any JSR-232 scripting language.

This will give the user a lot of flexibility. We need to make sure that we make it easy for the user as well AND remain compatible with existing metadata.

We can do this by adding an attribute to a field. XML attributes haven't been used yet in Kettle or Hop but it's more than possible.