This PR contains the scaffolding for a new control flow graph
implementation, along with its application to the `unreachable` rule. At
the moment, the implementation is a maximal over-approximation: no
control flow is modeled and all statements are counted as reachable.
With each additional statement type we support, this approximation will
improve.
So this PR just contains:
- A `ControlFlowGraph` struct and builder
- Support for printing the flow graph as a Mermaid graph
- Snapshot tests for the actual graphs
- (a very bad!) reimplementation of `unreachable` using the new structs
- Snapshot tests for `unreachable`
# Instructions for Viewing Mermaid snapshots
Unfortunately I don't know how to convince GitHub to render the Mermaid
graphs in the snapshots. However, you can view these locally in VSCode
if you install an extension that supports Mermaid graphs in Markdown,
and then add this to your `settings.json`:
```json
"files.associations": {
"*.md.snap": "markdown",
}
```
## Summary
Follow-up release for Ruff v0.10 that now includes the following two
changes that we intended to ship but slipped:
* Changes to how the Python version is inferred when a `target-version`
is not specified (#16319)
* `blanket-noqa` (`PGH004`): Also detect blanked file-level noqa
comments (and not just line level comments).
## Test plan
I verified that the binary built on this branch respects the
`requires-python` setting
([logs](https://www.diffchecker.com/qyJWYi6W/), left: v0.10, right:
v0.11)
This is pretty much just moving to the new API and taking care to use
byte offsets. This is *almost* enough. The next commit will fix a bug
involving the handling of unprintable characters as a result of
switching to byte offsets.
## Summary
This PR re-introduces the control-flow graph implementation which was
first introduced in #5384, and then removed in #9463 due to not being
feature complete. Mainly, it lacked the ability to process
`try`-`except` blocks, along with some more minor bugs.
Closes#8958 and #8959 and #14881.
## Overview of Changes
I will now highlight the major changes implemented in this PR, in order
of implementation.
1. Introduced a post-processing step in loop handling to find any
`continue` or `break` statements within the loop body and redirect them
appropriately.
2. Introduced a loop-continue block which is always placed at the end of
loop blocks, and ensures proper looping regardless of the internal logic
of the block. This resolves#8958.
3. Implemented `try` processing with the following logic (resolves
#8959):
1. In the example below the cfg first encounters a conditional
`ExceptionRaised` forking if an exception was (or will be) raised in the
try block. This is not possible to know (except for trivial cases) so we
assume both paths can be taken unconditionally.
2. Going down the `try` path the cfg goes `try`->`else`->`finally`
unconditionally.
3. Going down the `except` path the cfg will meet several conditional
`ExceptionCaught` which fork depending on the nature of the exception
caught. Again there's no way to know which exceptions may be raised so
both paths are assumed to be taken unconditionally.
4. If none of the exception blocks catch the exception then the cfg
terminates by raising a new exception.
5. A post-processing step is also implemented to redirect any `raises`
or `returns` within the blocks appropriately.
```python
def func():
try:
print("try")
except Exception:
print("Exception")
except OtherException as e:
print("OtherException")
else:
print("else")
finally:
print("finally")
```
```mermaid
flowchart TD
start(("Start"))
return(("End"))
block0[["`*(empty)*`"]]
block1["print(#quot;finally#quot;)\n"]
block2["print(#quot;else#quot;)\n"]
block3["print(#quot;try#quot;)\n"]
block4[["Exception raised"]]
block5["print(#quot;OtherException#quot;)\n"]
block6["try:
print(#quot;try#quot;)
except Exception:
print(#quot;Exception#quot;)
except OtherException as e:
print(#quot;OtherException#quot;)
else:
print(#quot;else#quot;)
finally:
print(#quot;finally#quot;)\n"]
block7["print(#quot;Exception#quot;)\n"]
block8["try:
print(#quot;try#quot;)
except Exception:
print(#quot;Exception#quot;)
except OtherException as e:
print(#quot;OtherException#quot;)
else:
print(#quot;else#quot;)
finally:
print(#quot;finally#quot;)\n"]
block9["try:
print(#quot;try#quot;)
except Exception:
print(#quot;Exception#quot;)
except OtherException as e:
print(#quot;OtherException#quot;)
else:
print(#quot;else#quot;)
finally:
print(#quot;finally#quot;)\n"]
start --> block9
block9 -- "Exception raised" --> block8
block9 -- "else" --> block3
block8 -- "Exception" --> block7
block8 -- "else" --> block6
block7 --> block1
block6 -- "OtherException" --> block5
block6 -- "else" --> block4
block5 --> block1
block4 --> return
block3 --> block2
block2 --> block1
block1 --> block0
block0 --> return
```
6. Implemented `with` processing with the following logic:
1. `with` statements have no conditional execution (apart from the
hidden logic handling the enter and exit), so the block is assumed to
execute unconditionally.
2. The one exception is that exceptions raised within the block may
result in control flow resuming at the end of the block. Since it is not
possible know if an exception will be raised, or if it will be handled
by the context manager, we assume that execution always continues after
`with` blocks even if the blocks contain `raise` or `return` statements.
This is handled in a post-processing step.
## Test Plan
Additional test fixtures and control-flow fixtures were added.
---------
Co-authored-by: Micha Reiser <micha@reiser.io>
Co-authored-by: dylwil3 <dylwil3@gmail.com>
## Summary
Follow-up from #13268, this PR updates the test case to use
`assert_snapshot` now that the output is limited to only include the
rules with diagnostics.
## Test Plan
`cargo insta test`
Dylan
Brent Westbrook
Micha Reiser
Dhruv Manilawala
Dylan
Andrew Gallant
Auguste Lalande
renovate[bot]
Alex Waygood
Charlie Marsh