fix: adjust tag association in optional and repeat expressions

[tomtau]

fixes #984, fixes #982

Summary by CodeRabbit

• New Features
  • Introduced grammar rule for expressions with optional components.
• Tests
  • Added tests for new grammar rule parsing and multi-tag parsing with implicit whitespace handling.
• Refactor
  • Enhanced expression generation logic for improved efficiency and token stream handling.

[coderabbitai]

Walkthrough

This update primarily addresses issues related to parsing grammar rules with optional components and tagging within expressions. It introduces new tests to ensure correctness in scenarios involving optional prefixes and suffixes, as well as multiple tags. The refactoring within the generator module aims to optimize expression handling, particularly for NodeTag cases, enhancing the efficiency of token stream generation. These changes collectively strive to fix bugs and improve the parsing capabilities of the system.

Changes

Files	Change Summary
derive/tests/implicit.rs	Added test test_implicit_whitespace_multitag for parsing with multiple tags.
derive/tests/opt.rs	Introduces a test for parsing a specific grammar rule using the pest parser generator.
generator/src/generator.rs	Refactored generate_expr and generate_expr_atomic functions to optimize OptimizedExpr handling.

Assessment against linked issues

Objective	Addressed	Explanation
Understand and fix the wrong tag association with optional expressions (#984)	❌	The changes do not directly address the issue of wrong tag association with optional expressions.
Clarify behavior of tags on rules yielding multiple pairs and ensure correct tag retrieval (#982)	✅	The changes address the need to handle multiple tags and improve tag retrieval in parsing rules.
Verify if the observed behaviors are bugs or limitations and improve documentation/implementation accordingly (#982, #984)	❓	While improvements have been made, further validation is needed to confirm if all issues are resolved.

Poem

In the code where bugs once dwelled,
A rabbit hopped, and spells it spelled.
🌟 With a twitch of nose, and a thump of feet,
Bugs vanished, and the code did greet.
A world so clear, with tags aligned,
Where expressions and rules, perfectly intertwined.
🐇 "Hop forward," it cheered, "to a future so bright,
Where parsing's a joy, and everything's right!"

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[coderabbitai]

Review Status

Actionable comments generated: 2

Configuration used: CodeRabbit UI

Commits

Files that changed from the base of the PR and between a0a92fb and d55aa76.

Files selected for processing (4)

• derive/tests/implicit.rs (1 hunks)
• derive/tests/opt.pest (1 hunks)
• derive/tests/opt.rs (1 hunks)
• generator/src/generator.rs (2 hunks)

Additional comments: 3

derive/tests/opt.pest (1)

• 1-8: The grammar definition in opt.pest correctly implements optional prefix and suffix components using ? to denote optionality. This change should address the incorrect tag assignment issue (Wrong tag associated with expression? #984) by explicitly defining the optional nature of STAR and DOT tokens with associated tags #prefix and #suffix. Ensure that the rest of the grammar and the parser logic correctly interpret these optional components and their tags.

generator/src/generator.rs (2)

• 574-609: The refactoring for handling OptimizedExpr::NodeTag in generate_expr introduces a more structured approach to tagging nodes in optional (Opt) and repeat (Rep) expressions. This change is crucial for addressing the issues mentioned in the PR objectives, specifically the correct assignment of tags in these contexts. The use of state.tag_node(#tag) after the optional and repeat expressions ensures that tags are correctly applied, which aligns with the objectives of fixing tag association issues.

However, there are a few considerations:

• Ensure that the performance impact of these changes is minimal. The additional calls to state.tag_node could potentially introduce overhead, especially in deeply nested or highly repetitive structures.
• Verify that this approach does not introduce any unintended side effects, particularly in complex grammars where optional and repeat expressions are heavily used.

Overall, the changes appear to address the issues effectively, but it would be beneficial to conduct thorough testing with various grammars to confirm that the behavior aligns with expectations and does not introduce new issues.

• 759-784: The changes to generate_expr_atomic for handling OptimizedExpr::NodeTag mirror those in generate_expr, focusing on the atomic context. This consistency between the handling of NodeTag in both atomic and non-atomic contexts is important for ensuring that tags are applied uniformly across different types of expressions.

Similar considerations apply here as with the changes in generate_expr:

• The impact on performance should be monitored, especially for grammars that make extensive use of atomic expressions.
• Comprehensive testing is necessary to ensure that these changes do not introduce unexpected behavior in complex grammars.

Given the alignment with the PR's objectives and the structured approach to handling tags, these changes are also approved. However, it's crucial to validate the implementation through testing.

[coderabbitai]

Review Status

Actionable comments generated: 0

Configuration used: CodeRabbit UI

Commits

Files that changed from the base of the PR and between d55aa76 and 3f57932.

Files selected for processing (2)

• derive/tests/implicit.rs (1 hunks)
• derive/tests/opt.rs (1 hunks)

Files skipped from review as they are similar to previous changes (2)

• derive/tests/implicit.rs
• derive/tests/opt.rs

[coderabbitai]

Review Status

Actionable comments generated: 0

Configuration used: CodeRabbit UI

Commits

Files that changed from the base of the PR and between 3f57932 and c7c2ff0.

Files ignored due to path filters (7)

• debugger/Cargo.toml is excluded by: !**/*.toml
• derive/Cargo.toml is excluded by: !**/*.toml
• generator/Cargo.toml is excluded by: !**/*.toml
• grammars/Cargo.toml is excluded by: !**/*.toml
• meta/Cargo.toml is excluded by: !**/*.toml
• pest/Cargo.toml is excluded by: !**/*.toml
• vm/Cargo.toml is excluded by: !**/*.toml

Files selected for processing (1)

• derive/tests/opt.rs (1 hunks)

Files skipped from review as they are similar to previous changes (1)

• derive/tests/opt.rs

[NoahTheDuke]

Nice fix.