[`ruff`] Add `assert-with-print-expression` rule (#11974) (#11981)
## Summary
Addresses #11974 to add a `RUF` rule to replace `print` expressions in
`assert` statements with the inner message.
An autofix is available, but is considered unsafe as it changes
behaviour of the execution, notably:
- removal of the printout in `stdout`, and
- `AssertionError` instance containing a different message.
While the detection of the condition is a straightforward matter,
deciding how to resolve the print arguments into a string literal can be
a relatively subjective matter. The implementation of this PR chooses to
be as tolerant as possible, and will attempt to reformat any number of
`print` arguments containing single or concatenated strings or variables
into either a string literal, or a f-string if any variables or
placeholders are detected.
## Test Plan
`cargo test`.
## Examples
For ease of discussion, this is the diff for the tests:
```diff
# Standard Case
# Expects:
# - single StringLiteral
-assert True, print("This print is not intentional.")
+assert True, "This print is not intentional."
# Concatenated string literals
# Expects:
# - single StringLiteral
-assert True, print("This print" " is not intentional.")
+assert True, "This print is not intentional."
# Positional arguments, string literals
# Expects:
# - single StringLiteral concatenated with " "
-assert True, print("This print", "is not intentional")
+assert True, "This print is not intentional"
# Concatenated string literals combined with Positional arguments
# Expects:
# - single stringliteral concatenated with " " only between `print` and `is`
-assert True, print("This " "print", "is not intentional.")
+assert True, "This print is not intentional."
# Positional arguments, string literals with a variable
# Expects:
# - single FString concatenated with " "
-assert True, print("This", print.__name__, "is not intentional.")
+assert True, f"This {print.__name__} is not intentional."
# Mixed brackets string literals
# Expects:
# - single StringLiteral concatenated with " "
-assert True, print("This print", 'is not intentional', """and should be removed""")
+assert True, "This print is not intentional and should be removed"
# Mixed brackets with other brackets inside
# Expects:
# - single StringLiteral concatenated with " " and escaped brackets
-assert True, print("This print", 'is not "intentional"', """and "should" be 'removed'""")
+assert True, "This print is not \"intentional\" and \"should\" be 'removed'"
# Positional arguments, string literals with a separator
# Expects:
# - single StringLiteral concatenated with "|"
-assert True, print("This print", "is not intentional", sep="|")
+assert True, "This print|is not intentional"
# Positional arguments, string literals with None as separator
# Expects:
# - single StringLiteral concatenated with " "
-assert True, print("This print", "is not intentional", sep=None)
+assert True, "This print is not intentional"
# Positional arguments, string literals with variable as separator, needs f-string
# Expects:
# - single FString concatenated with "{U00A0}"
-assert True, print("This print", "is not intentional", sep=U00A0)
+assert True, f"This print{U00A0}is not intentional"
# Unnecessary f-string
# Expects:
# - single StringLiteral
-assert True, print(f"This f-string is just a literal.")
+assert True, "This f-string is just a literal."
# Positional arguments, string literals and f-strings
# Expects:
# - single FString concatenated with " "
-assert True, print("This print", f"is not {'intentional':s}")
+assert True, f"This print is not {'intentional':s}"
# Positional arguments, string literals and f-strings with a separator
# Expects:
# - single FString concatenated with "|"
-assert True, print("This print", f"is not {'intentional':s}", sep="|")
+assert True, f"This print|is not {'intentional':s}"
# A single f-string
# Expects:
# - single FString
-assert True, print(f"This print is not {'intentional':s}")
+assert True, f"This print is not {'intentional':s}"
# A single f-string with a redundant separator
# Expects:
# - single FString
-assert True, print(f"This print is not {'intentional':s}", sep="|")
+assert True, f"This print is not {'intentional':s}"
# Complex f-string with variable as separator
# Expects:
# - single FString concatenated with "{U00A0}", all placeholders preserved
condition = "True is True"
maintainer = "John Doe"
-assert True, print("Unreachable due to", condition, f", ask {maintainer} for advice", sep=U00A0)
+assert True, f"Unreachable due to{U00A0}{condition}{U00A0}, ask {maintainer} for advice"
# Empty print
# Expects:
# - `msg` entirely removed from assertion
-assert True, print()
+assert True
# Empty print with separator
# Expects:
# - `msg` entirely removed from assertion
-assert True, print(sep=" ")
+assert True
# Custom print function that actually returns a string
# Expects:
@@ -100,4 +100,4 @@
# Use of `builtins.print`
# Expects:
# - single StringLiteral
-assert True, builtins.print("This print should be removed.")
+assert True, "This print should be removed."
```
## Known Issues
The current implementation resolves all arguments and separators of the
`print` expression into a single string, be it
`StringLiteralValue::single` or a `FStringValue::single`. This:
- potentially joins together strings well beyond the ideal character
limit for each line, and
- does not preserve multi-line strings in their original format, in
favour of a single line `"...\n...\n..."` format.
These are purely formatting issues only occurring in unusual scenarios.
Additionally, the autofix will tolerate `print` calls that were
previously invalid:
```python
assert True, print("this", "should not be allowed", sep=42)
```
This will be transformed into
```python
assert True, f"this{42}should not be allowed"
```
which some could argue is an alteration of behaviour.
---------
Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>
