Summary

Remove LicenseInfo.private_data and help extensibility.

Review Request #14496 — Created June 29, 2025 and submitted Sept. 14, 2025, 7:03 p.m.

Information

Owner

chipx86

Repository

Review Board

Branch

release-7.1.x

Bugs

Depends On

Reviewers

Groups

reviewboard

People

Description

Originally when the new licensing code was added, the intent was to back
license representations by a LicenseInfo and to allow license
providers to extend that by plugging state into a private_data member.

Since the original design, support for LicenseInfo subclasses was
added, largely removing the need for private_data. In practice,
though, the LicenseInfo dataclass could not be extended with new
required arguments due to the way that the dataclass was registered.
By default, dataclasses register fields as positional arguments instead
of keyword-only arguments, and this means that any field registered
after the last field with a default must itself have a default, even in
subclasses. This isn't ideal for this purpose.

We can't use kw_only=True, since that's only available on Python 3.10
and higher, and there's no getting around the internal logic that
impacts subclasses. Plus, dataclasses are slow and truly necessary, just
a convenience.

So to help facilitate License Provider backends with custom state, and
avoid the dataclass issues, this has been converted to a standard class.
This will also make it easier for subclasses to override it in a
consistent way without having to tie into the dataclass-specific
post-construction hooks.

Testing Done

Unit tests pass.

Successfully created and used subclasses of LicenseInfo with new
required fields.

Commits

Summary	ID
Remove LicenseInfo.private_data and help extensibility. Originally when the new licensing code was added, the intent was to back license representations by a `LicenseInfo` and to allow license providers to extend that by plugging state into a `private_data` member. Since the original design, support for `LicenseInfo` subclasses was added, largely removing the need for `private_data`. In practice, though, the `LicenseInfo` dataclass could not be extended with new required arguments due to the way that the dataclass was registered. By default, dataclasses register fields as positional arguments instead of keyword-only arguments, and this means that any field registered after the last field with a default must itself have a default, even in subclasses. This isn't ideal for this purpose. We can't use `kw_only=True`, since that's only available on Python 3.10 and higher, and there's no getting around the internal logic that impacts subclasses. Plus, dataclasses are slow and truly necessary, just a convenience. So to help facilitate License Provider backends with custom state, and avoid the dataclass issues, this has been converted to a standard class. This will also make it easier for subclasses to override it in a consistent way without having to tie into the dataclass-specific post-construction hooks.	9982f25aa7714bd7119795589848679e127073e2

Summary

Remove LicenseInfo.private_data and help extensibility.

Originally when the new licensing code was added, the intent was to back license representations by a `LicenseInfo` and to allow license providers to extend that by plugging state into a `private_data` member. Since the original design, support for `LicenseInfo` subclasses was added, largely removing the need for `private_data`. In practice, though, the `LicenseInfo` dataclass could not be extended with new required arguments due to the way that the dataclass was registered. By default, dataclasses register fields as positional arguments instead of keyword-only arguments, and this means that any field registered after the last field with a default must itself have a default, even in subclasses. This isn't ideal for this purpose. We can't use `kw_only=True`, since that's only available on Python 3.10 and higher, and there's no getting around the internal logic that impacts subclasses. Plus, dataclasses are slow and truly necessary, just a convenience. So to help facilitate License Provider backends with custom state, and avoid the dataclass issues, this has been converted to a standard class. This will also make it easier for subclasses to override it in a consistent way without having to tie into the dataclass-specific post-construction hooks.

9982f25aa7714bd7119795589848679e127073e2

Issues

Description	From	Last Updated
I thought we can't use this on Python 3.8 or 3.9?	david	June 30, 2025, 2:31 p.m.

flake8 passed.

JSHint passed.

reviewboard/licensing/license.py (Diff revision 1)

The issue has been resolved. Show all issues

I thought we can't use this on Python 3.8 or 3.9?

chipx86 June 30, 2025, 2 p.m.

We can't. I realized this after putting it up yesterday, and went off in search of the best solution here.

Tried backporting the 3.13 version of dataclasses, which has this and a bunch more features. But that uses match syntax.

Tried 3.10, which is the minimum with kw_only. That had other issues that weren't worth pursuing.

Ultimately I decided to just rewrite this as a normal class, but called it a night before I finished. That'll be up today.

Fun fact: dataclasses turn out to be about 33x slower to define or subclass than a normal equivalent class. Not a big deal unless doing it dynamically and a lot, but I feel less good about sprinkling them everywhere. Curious how Django and Pydantic models compare.

Change Summary:

Changed LicenseInfo to be a standard class.

Description:

		Originally when the new licensing code was added, the intent was to back
		license representations by a `LicenseInfo` and to allow license
		providers to extend that by plugging state into a `private_data` member.

		Since the original design, support for `LicenseInfo` subclasses was
		added, largely removing the need for `private_data`. In practice,
		though, the `LicenseInfo` dataclass could not be extended with new
		required arguments due to the way that the dataclass was registered.
		By default, dataclasses register fields as positional arguments instead
		of keyword-only arguments, and this means that any field registered
		after the last field with a default must itself have a default, even in
		subclasses. This isn't ideal for this purpose.

~		To help facilitate License Provider backends with custom state, we now
~		register the dataclass with `kw_only=True`, and remove `private_data`.
	~	We can't use `kw_only=True`, since that's only available on Python 3.10
	~	and higher, and there's no getting around the internal logic that
	+	impacts subclasses. Plus, dataclasses are slow and truly necessary, just
	+	a convenience.

~		Going forward, we should ensure that all dataclasses use `kw_only=True`
~		to help with forward-compatibility and extensibility.
	~	So to help facilitate License Provider backends with custom state, and
	~	avoid the dataclass issues, this has been converted to a standard class.
	+	This will also make it easier for subclasses to override it in a
	+	consistent way without having to tie into the dataclass-specific
	+	post-construction hooks.

Commits:

	Summary	ID
	Remove LicenseInfo.private_data and help extensibility. Originally when the new licensing code was added, the intent was to back license representations by a `LicenseInfo` and to allow license providers to extend that by plugging state into a `private_data` member. Since the original design, support for `LicenseInfo` subclasses was added, largely removing the need for `private_data`. In practice, though, the `LicenseInfo` dataclass could not be extended with new required arguments due to the way that the dataclass was registered. By default, dataclasses register fields as positional arguments instead of keyword-only arguments, and this means that any field registered after the last field with a default must itself have a default, even in subclasses. This isn't ideal for this purpose. To help facilitate License Provider backends with custom state, we now register the dataclass with `kw_only=True`, and remove `private_data`. Going forward, we should ensure that all dataclasses use `kw_only=True` to help with forward-compatibility and extensibility.	d32f241fc16c3c8db291f6786813f703474c57f4
	Remove LicenseInfo.private_data and help extensibility. Originally when the new licensing code was added, the intent was to back license representations by a `LicenseInfo` and to allow license providers to extend that by plugging state into a `private_data` member. Since the original design, support for `LicenseInfo` subclasses was added, largely removing the need for `private_data`. In practice, though, the `LicenseInfo` dataclass could not be extended with new required arguments due to the way that the dataclass was registered. By default, dataclasses register fields as positional arguments instead of keyword-only arguments, and this means that any field registered after the last field with a default must itself have a default, even in subclasses. This isn't ideal for this purpose. We can't use `kw_only=True`, since that's only available on Python 3.10 and higher, and there's no getting around the internal logic that impacts subclasses. Plus, dataclasses are slow and truly necessary, just a convenience. So to help facilitate License Provider backends with custom state, and avoid the dataclass issues, this has been converted to a standard class. This will also make it easier for subclasses to override it in a consistent way without having to tie into the dataclass-specific post-construction hooks.	9982f25aa7714bd7119795589848679e127073e2

Diff:

Revision 2 (+236 -66)

Show changes

reviewboard/licensing/license.py

Checks run (2 succeeded)

flake8 passed.

JSHint passed.

Ship it!

```
Ship It!
```

Ship it!

```
Ship It!
```

Status:: Completed
Change Summary:: Pushed to release-7.1.x (0c2a5bd)