Summary:

Improve typing support for the UNSET symbol.

Review Request #13191 — Created Aug. 7, 2023 and submitted Aug. 10, 2023, 12:41 p.m.

Information
Owner:	chipx86
Repository:	Djblets
Branch:	release-4.x
Bugs:
Depends On:
Reviewers
Groups:	djblets
People:

Description

This reworks the internals of the UNSET symbol (which was introduced in
Djblets 3.3) and makes it easier to integrate it with typing logic and
type checkers.

UnsetSymbol is now an Enum, allowing UNSET to be defined as a
Literal. This works along with a new Unsettable[_T] type alias to
mark whether a parameter or variable allows UNSET to be set.

By making this a Literal, type checkers can type narrow when a code
compares a value to UNSET, avoiding any type errors that still wanted
to consider UnsetSymbol a possible value.

Testing Done

Made use of this in some in-progress code. Verified that mypy and pyright
successfully narrowed the types when comparing against UNSET.

Commits

Summary
	Improve typing support for the UNSET symbol.

Screenshots

Issues

Description	From	Last Updated
'enum.EnumMeta' imported but unused Column: 1 Error code: F401	reviewbot	Aug. 8, 2023, 11:56 a.m.
'typing.Any' imported but unused Column: 1 Error code: F401	reviewbot	Aug. 8, 2023, 11:56 a.m.

flake8 failed.

JSHint passed.

flake8

djblets/util/symbols.py (Diff revision 1)

Show all issues

'enum.EnumMeta' imported but unused

Column: 1
Error code: F401

djblets/util/symbols.py (Diff revision 1)

Show all issues

'typing.Any' imported but unused

Column: 1
Error code: F401

Change Summary:

Removed unused imports.

Commits:

	Summary
-		Improve typing support for the UNSET symbol.
+		Improve typing support for the UNSET symbol.

Diff:

Revision 2 (+70 -6)

Show changes

djblets/util/symbols.py

Checks run (2 succeeded)

flake8 passed.

JSHint passed.

Ship it!

```
Ship It!
```

Status: Closed (submitted)

Change Summary:

Pushed to master (0b0f0de)