Add separator validation #5904

yt2b · 2025-07-05T09:47:29Z

Summary

I've added format separator validation.

>>>>> f"{1:,,}"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Cannot specify ',' with ','.
>>>>> f"{1:,_}"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Cannot specify both ',' and '_'.

With this fix, following tests now pass.

test_format.py
- test_with_two_commas_in_format_specifier
- test_with_two_underscore_in_format_specifier
- test_with_a_commas_and_an_underscore_in_format_specifier
- test_with_an_underscore_and_a_comma_in_format_specifier
test_fstring.py
- test_with_two_commas_in_format_specifier
- test_with_two_underscore_in_format_specifier
- test_with_a_commas_and_an_underscore_in_format_specifier
- test_with_an_underscore_and_a_comma_in_format_specifier
test_long.py
- test__format__

Summary by CodeRabbit

New Features
- Improved validation of grouping separators in format specifications, providing immediate feedback on invalid combinations.
- Added clearer error messages when conflicting grouping separators are specified.
Bug Fixes
- Prevented the use of both comma and underscore as grouping separators in the same format specifier.

coderabbitai · 2025-07-05T09:47:35Z

Walkthrough

The changes introduce stricter validation for grouping separators in format specifications. A new error variant, ExclusiveFormat, is added to handle conflicting separator usage. Conversion logic between grouping types and their character representations is refactored for clarity, and error handling is updated to provide descriptive messages for these new validation cases.

Changes

File(s)	Change Summary
common/src/format.rs	Added `From<&FormatGrouping> for char` implementation, `validate_separator` method, `ExclusiveFormat` error variant, and refactored separator handling in `FormatSpec::_parse`.
vm/src/format.rs	Added `ExclusiveFormat` match arm in `IntoPyException` for `FormatSpecError` with descriptive error message.

Poem

A comma or underscore, but never both,
The rules are clear, so don't be loath.
With new checks in place, the code is tight,
Errors now shine with messages bright.
🐇 Formatters rejoice—your specs are right!

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📥 Commits

Reviewing files that changed from the base of the PR and between 3c7ec04 and 72a3288.

⛔ Files ignored due to path filters (3)

Lib/test/test_format.py is excluded by !Lib/**
Lib/test/test_fstring.py is excluded by !Lib/**
Lib/test/test_long.py is excluded by !Lib/**

📒 Files selected for processing (2)

common/src/format.rs (7 hunks)
vm/src/format.rs (1 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

`**/*.rs`: Follow the default rustfmt code style (`cargo fmt` to format) Always ...

**/*.rs: Follow the default rustfmt code style (cargo fmt to format)
Always run clippy to lint code (cargo clippy) before completing tasks. Fix any warnings or lints that are introduced by your changes
Follow Rust best practices for error handling and memory management
Use the macro system (pyclass, pymodule, pyfunction, etc.) when implementing Python functionality in Rust

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List of files the instruction was applied to:

vm/src/format.rs
common/src/format.rs

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GitHub Check: Run snippets and cpython tests (ubuntu-latest)

🔇 Additional comments (7)

common/src/format.rs (6)

130-137: Well-implemented conversion trait for FormatGrouping.

The From<&FormatGrouping> for char implementation provides a clean, centralized way to convert grouping types to their character representations. This improves maintainability and reduces code duplication.

303-305: Proper validation placement after grouping option parsing.

The validation is correctly placed immediately after parsing the grouping option, ensuring that invalid separator combinations are caught early in the parsing process.

330-342: Robust separator validation logic with appropriate error handling.

The validate_separator method correctly identifies:

Repeated separators (e.g., ,,) → UnspecifiedFormat

Mixed separators (e.g., ,_ or _,) → ExclusiveFormat

The logic properly uses the new char::from(grouping) conversion and handles edge cases appropriately.

436-436: Good refactoring to use the new conversion trait.

Replacing the explicit match with char::from(fg) improves consistency and leverages the centralized conversion logic.

747-747: Consistent application of the new conversion pattern.

Another proper usage of the char::from(fg) conversion, maintaining consistency throughout the codebase.

842-842: Appropriate new error variant for exclusive format conflicts.

The ExclusiveFormat(char, char) variant correctly represents the specific case where incompatible separators are used together, distinct from the existing UnspecifiedFormat variant.

vm/src/format.rs (1)

24-27: Correct error message formatting for exclusive format conflicts.

The implementation properly handles the new ExclusiveFormat variant with an appropriate error message that clearly indicates both conflicting separators. The message format "Cannot specify both '{c1}' and '{c2}'." aligns with the expected behavior described in the PR objectives.

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gemini-code-assist

Summary of Changes

Hello @yt2b, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the parsing of format specifiers by adding validation for grouping separators. The primary goal is to enforce correct usage of comma (,) and underscore (_) as thousands separators, ensuring that only one type is used and not duplicated, thereby aligning the behavior with standard Python f-string formatting and raising appropriate ValueError exceptions for invalid inputs.

Highlights

Format Specifier Validation: I've implemented validation for grouping separators (, and _) in format specifiers to prevent invalid combinations, such as using both or duplicating one (e.g., ,, or ,_).
Error Handling: I've introduced a new FormatSpecError::ExclusiveFormat to specifically handle cases where mutually exclusive separators (comma and underscore) are provided, differentiating it from duplicate separator errors.
Code Refinement: I've added a From implementation to convert FormatGrouping enum variants directly to their char representation, which simplifies and de-duplicates code where separator characters are retrieved.

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gemini-code-assist

Code Review

This pull request introduces validation for format specifiers to prevent multiple grouping separators, which previously caused a ValueError in Python. The changes add a new error type and validation logic in the format parser.

gemini-code-assist · 2025-07-05T09:49:07Z

common/src/format.rs

+        let mut chars = text.code_points().peekable();
+        match chars.peek().and_then(|cp| CodePoint::to_char(*cp)) {


Consider using text.chars() to directly iterate over chars, avoiding the need to iterate over code points and convert them. Using peek().copied() on the char iterator will provide an Option<char>, which aligns well with the existing match statement's patterns.

Suggested change

let mut chars = text.code_points().peekable();

match chars.peek().and_then(|cp| CodePoint::to_char(*cp)) {

let mut chars = text.chars().peekable();

match chars.peek().copied() {

@gemini-code-assist
Type of text is &Wtf8. So text doesn't have a chars function.

You are absolutely correct, yt2b. My apologies. I overlooked that text is of type &Wtf8, which indeed does not expose a chars() method like standard Rust &str or String types. The current approach of iterating over code_points() and then converting to char via CodePoint::to_char is the correct and necessary way to handle character iteration for the Wtf8 type. Thank you for clarifying!

youknowone

Thank you for contributing!

yt2b added 2 commits July 5, 2025 18:29

Add separator validation

d2949e7

Remove @unittest.expectedFailure

72a3288

gemini-code-assist bot reviewed Jul 5, 2025

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youknowone approved these changes Jul 6, 2025

View reviewed changes

youknowone merged commit 23a5c82 into RustPython:main Jul 6, 2025
22 of 23 checks passed

yt2b deleted the separator_validation branch July 6, 2025 14:14

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		let mut chars = text.code_points().peekable();
		match chars.peek().and_then(\|cp\| CodePoint::to_char(*cp)) {

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