Added invalid precondition syntax checker by PraneethS42 · Pull Request #1300 · pyta-uoft/pyta

PraneethS42 · 2026-02-12T02:55:04Z

Proposed Changes

This pull request works on #1294. Creates a custom checker called invalid_precondition_syntax_checker.py that alerts the user if a function docstring contains invalid syntax within one of its preconditions. This currently only supports single-line preconditions, and leverages the preexisting parse_assertions method from python-ta/contracts/__init__.py.

Adds an example file and appropriate changes in documentation, as well as tests.
...

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🚦 Test update (change that only adds or modifies tests)
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coveralls · 2026-02-12T03:04:26Z

Pull Request Test Coverage Report for Build 22076057401

Details

21 of 21 (100.0%) changed or added relevant lines in 1 file are covered.
No unchanged relevant lines lost coverage.
Overall coverage increased (+0.1%) to 89.958%

Totals
Change from base Build 21888778658:	0.1%
Covered Lines:	3440
Relevant Lines:	3824

💛 - Coveralls

david-yz-liu

Thanks @PraneethS42, this is looking good. I just left a few inline comments.

david-yz-liu · 2026-02-14T15:10:14Z

examples/custom_checkers/e9980_invalid_precondition_syntax.py

+
+def demo_function(x: int, y: int) -> int:
+    """
+    Demonstrates e9980_invalid_precondition_syntax


Write this summary line on the same line as the opening """

david-yz-liu · 2026-02-14T15:10:24Z

examples/custom_checkers/e9980_invalid_precondition_syntax.py

+       - x !== 0  # error on this line
+       - y != 0  # no error on this line
+    """
+    return x//y


add spaces around the //

david-yz-liu · 2026-02-14T15:11:42Z

packages/python-ta/docs/checkers/index.md

    """
 ```

+E(9980)=


The E is in the wrong location. The purpose of this line is to create an anchor to this section, which you can test locally by adding #E9980 to the end of the URL when visiting the documentation. You should be taken directly to this location.

david-yz-liu · 2026-02-14T15:13:37Z

packages/python-ta/docs/checkers/index.md

+```python
+def demo_function(x: int, y: int) -> int:
+    """
+    Demonstrates e9980_invalid_precondition_syntax


Please remember to update the style in this corrected code block, parallel to the comments I made in the example file

david-yz-liu · 2026-02-14T15:14:33Z

packages/python-ta/docs/checkers/index.md

+---
+```
+
+The first precondition incorrectly attempts to use the inequality operator, which is not valid Python syntax.


Just to be explicit, especially for beginners, write "(!=)" immediately after "inequality operator"

david-yz-liu · 2026-02-14T15:15:56Z

packages/python-ta/src/python_ta/checkers/invalid_precondition_syntax_checker.py

+from pylint.checkers.utils import only_required_for_messages
+from pylint.lint import PyLinter
+
+from python_ta.contracts import parse_assertions


For python_ta imports it's better to use relative imports because this is all part of the same package.

david-yz-liu · 2026-02-14T15:17:50Z

packages/python-ta/src/python_ta/checkers/invalid_precondition_syntax_checker.py

+from python_ta.contracts import parse_assertions
+
+
+class InvalidPreconditionSyntaxChecker(BaseChecker):


While it's true that your current task only involves preconditions, in the future this can be extended to other forms of conditions (see #1293).

Please rename this to ContractChecker and update the docstring and name. You don't need to change the name or details of the error message (a single checker can support multiple error messages).

david-yz-liu · 2026-02-14T15:20:03Z

packages/python-ta/docs/checkers/index.md

+
+### Invalid syntax in function precondition (E9980)
+
+This error occurs when a function precondition contains invalid Python syntax.


Here, please specify "invalid Python expression syntax". I would also add an explanatory sentence saying that valid Python statements (e.g. assignment statements like x = 5) are also flagged, as they aren't Python expressions.

david-yz-liu · 2026-02-14T15:20:18Z

packages/python-ta/src/python_ta/checkers/invalid_precondition_syntax_checker.py

+        "E9980": (
+            "Invalid syntax in precondition: %s",
+            "invalid-precondition-syntax",
+            "Reported when a precondition contains invalid Python syntax.",


Similar to my comment in the documentation, please say "invalid Python expression syntax" here

david-yz-liu · 2026-02-14T15:22:06Z

packages/python-ta/CHANGELOG.md


 ### 💫 New checkers

+- `invalid_precondition_syntax_checker`: Added new checker that checks if a function contains invalid syntax within its precondition statements.


The terminology here is a bit misleading, but if you look at past entries, here we actually are documenting the specific errors (by name) and not the checker classes themselves.

Please revise, following the format of past entries

david-yz-liu

Nice work, @PraneethS42!

Added invalid precondition syntax checker

d806053

PraneethS42 requested a review from david-yz-liu February 12, 2026 03:05

test naming fix

3160122

david-yz-liu reviewed Feb 14, 2026

View reviewed changes

PraneethS42 added 2 commits February 16, 2026 14:48

Syntax fixes

adbfbeb

Renamed to ContractChecker

7b9e44c

PraneethS42 requested a review from david-yz-liu February 16, 2026 20:14

david-yz-liu approved these changes Feb 17, 2026

View reviewed changes

david-yz-liu merged commit 736a0c2 into pyta-uoft:master Feb 17, 2026
30 checks passed

		from python_ta.contracts import parse_assertions


		class InvalidPreconditionSyntaxChecker(BaseChecker):


		### Invalid syntax in function precondition (E9980)

		This error occurs when a function precondition contains invalid Python syntax.


		### 💫 New checkers

		- `invalid_precondition_syntax_checker`: Added new checker that checks if a function contains invalid syntax within its precondition statements.

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PraneethS42 commented Feb 12, 2026 •

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coveralls commented Feb 12, 2026 •

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