Update function

[anderson-joyle]

Update function implementation.
Doc: https://learn.microsoft.com/en-us/power-platform/power-fx/reference/function-update-updateif

As a reference, check #595. Other fixes came in place after this PR, but it is a good starting point.

Originally test cases were added to Patch.txt file. We are now trying to walk away from handlers (#SETUP: EnableExpressionChaining,MutationFunctionsTestSetup), so these are for reference only.

For your new test cases, please create a new file under ...Tests/MutationScripts.

[coletaylor1]

Can be post GA

[Harshit-Lalwani]

Hi @anderson-joyle , I'm interested in picking this up.

A few questions:

• There's a good first issue label is on this, but looking at the analogous Remove function implementation (PR Remove function #3008) , this seems to require working through the full TexlFunction hierarchy, async interpreter-layer code, and mutation semantics coordination with Power Apps. Would you still consider this appropriate for a first-time contributor?

• Should I follow the Remove/Patch pattern (separate UpdateImpl class in MutationUtils.cs) for the implementation structure?

Happy to take this on if it's still open