Merge pull request github#2443 from tausbn/python-finalise-change-notes

Python: Update change note for 1.23.

Author: felicitymay

change-notes/1.23/analysis-python.md

@@ -3,7 +3,19 @@
 
 ## General improvements
 
+### Python 3.8 support
 
+Python 3.8 syntax is now supported. In particular, the following constructs are parsed correctly:
+
+- Assignment expressions using the "walrus" operator, such as `while chunk := file.read(1024): ...`.
+- The positional argument separator `/`, such as in `def foo(a, /, b, *, c): ...`.
+- Self-documenting expressions in f-strings, such as `f"{var=}"`.
+
+### General query improvements
+
+Following the replacement of the `Object` API (for example, `ClassObject`) in favor of the
+`Value` API (for example, `ClassValue`) in the 1.21 release, many of the standard queries have been updated
+to use the `Value` API. This should result in more precise results.
 
 ## New queries
 
@@ -18,10 +30,23 @@
 
 | **Query**                  | **Expected impact**    | **Change** |
 |----------------------------|------------------------|------------|
-| Unreachable code | Fewer false positives | Analysis now accounts for uses of `contextlib.suppress` to suppress exceptions. |
-| `__iter__` method returns a non-iterator | Better alert message | Alert now highlights which class is expected to be an iterator. |
-
+| Explicit export is undefined (`py/undefined-export`) | Fewer false positive results | Instances where an exported value may be defined in a module that lacks points-to information are no longer flagged. |
+| Module-level cyclic import (`py/unsafe-cyclic-import`) | Fewer false positive results | Instances where one of the links in an import cycle is never actually executed are no longer flagged. |
+| Non-iterable used in for loop (`py/non-iterable-in-for-loop`) | Fewer false positive results | `__aiter__` is now recognized as an iterator method. |
+| Unreachable code (`py/unreachable-statement`) | Fewer false positive results | Analysis now accounts for uses of `contextlib.suppress` to suppress exceptions. |
+| Unreachable code (`py/unreachable-statement`) | Fewer false positive results | Unreachable `else` branches that do nothing but `assert` their non-reachability are no longer flagged. |
+| Unused import (`py/unused-import`) | Fewer false positive results | Instances where a module is used in a forward-referenced type annotation, or only during type checking are no longer flagged. |
+| `__iter__` method returns a non-iterator (`py/iter-returns-non-iterator`) | Better alert message | Alert now highlights which class is expected to be an iterator. |
+| `__init__` method returns a value (`py/explicit-return-in-init`) | Fewer false positive results | Instances where the `__init__` method returns the value of a call to a procedure are no longer flagged. |
 
 ## Changes to QL libraries
 
 * Django library now recognizes positional arguments from a `django.conf.urls.url` regex (Django version 1.x)
+* Instances of the `Value` class now support the `isAbsent` method, indicating
+  whether that `Value` lacks points-to information, but inference
+  suggests that it exists. For instance, if a file contains `import
+  django`, but `django` was not extracted properly, there will be a
+  `ModuleValue` corresponding to this "unknown" module, and the `isAbsent`
+  method will hold for this `ModuleValue`.
+* The `Expr` class now has a nullary method `pointsTo` that returns the possible
+  instances of `Value` that this expression may have.