feat: Auto Name Field for Auto-attach XML File feature

[HenningWendtland]

Is your feature request related to a problem? Please describe.
My customer wants to auto attach XML invoices on submit, but requires the file to be named after a custom invoice number field.

Describe the solution you'd like
A field to enter the auto-name pattern in E Invoice Settings, similar to the solution in PDF On Submit Settings

Reference: (IBT-164)

[dafrose]

I have a question regarding implementation. Current recommendation for naming scheme in PDF On Submit is format:EXAMPLE-{MM}-{fieldname1}-{fieldname2}-{#####}¹. This represents the "old" naming expression format which is supposed to be deprecated from version 16 onward². The new style uses . to separate placeholders³. Furthermore, the use of the format: prefix is discouraged for expression naming on doctype-level⁴.

It would be easy to implement the XML autonaming the exact same way as in PDF on Submit. That would probably also make it easier for existing customers. However, future releases of frappe might remove this behaviour, considering that is marked as deprecated for doctype autonaming. Note that the new version already works in the version-15-branch of frappe. What implementation would you prefer @barredterra and @HenningWendtland?

In the end it comes down to what should be recommended in the description string. Everything else could stay the same under the hood.

[0xD0M1M0]

First thought: patch old expressions to new format and use the new one only in both. I had already so much trouble, because format: was forgotten.

[dafrose]

Thanks for your thoughts @0xD0M1M0
I think you can have the same problems with the new format, when people forget the dots in some places while not in others, because they don't understand how it works under the hood. There is probably no version of exposing this type of programmatic interface without things going wrong. With great power comes great responsibility.

[0xD0M1M0]

Additionally, maybe for an additional PR, I propose a format builder, which could be a drag and drop option for easier UI Interfaces. Maybe as drag&drop contribution in https://ui.frappe.io/

[HenningWendtland]

@dafrose I agree with @0xD0M1M0 . Forgot that PDF on Submit uses the old style. Since it's a new feature here, going with the new format in eu_einvoice is the right way to go. For PDF_on_Submit we could also change to the new pattern in v16 branch and then decide if we backport

[dafrose]

Additionally, maybe for an additional PR, I propose a format builder, which could be a drag and drop option for easier UI Interfaces. Maybe as drag&drop contribution in https://ui.frappe.io/

For future reference: here is the image that @0xD0M1M0 sent me in an off-site discussion:

I think, a GUI would be a nice solution to allow customers to set autonaming patterns. Of course, not inside the scope of this issue.