feat: port rule @typescript-eslint/prefer-optional-chain

[fansenze]

Summary

Port the @typescript-eslint/prefer-optional-chain rule from TypeScript-ESLint to Go.

This rule enforces using concise optional chain expressions (?.) instead of chained logical ANDs (&&), negated logical ORs (||), or empty object coalescing patterns ((foo || {}).bar).

Implementation highlights

• Operand gathering & classification: Flattens &&/|| chains into operands, classifying each as boolean, strict/loose null/undefined equality, typeof, or negation
• Node comparison: Detects subset/prefix relationships between AST nodes to identify valid optional chain candidates, including support for type parameters (foo<string>()), type references (foo<T>()), and qualified names
• DeMorgan inversion: For || chains, correctly inverts comparison operators during classification and restores original operators for output generation
• Fix vs suggestion: Type-aware decision — auto-fix when the transformation preserves the expression's return type, suggestion otherwise
• Chain building: Generates correct optional chain output with ?. placement, preserving type arguments, call arguments, element access, and comments
• Options support: All 8 options from the original rule (checkAny, checkUnknown, checkString, checkNumber, checkBoolean, checkBigInt, requireNullish, allowPotentiallyUnsafeFixesThatModifyTheReturnTypeIKnowWhatImDoing)

Related Links

• Original rule: https://typescript-eslint.io/rules/prefer-optional-chain
• Related Issue: [Tracking]: typescript-eslint rule #37

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

[gemini-code-assist]

Summary of Changes

Hello @fansenze, 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 introduces a new linting rule, @typescript-eslint/prefer-optional-chain, to encourage more concise and readable code by transforming lengthy logical expressions into optional chaining. The rule analyzes complex logical structures involving nullish checks and property accesses, offering automated fixes or suggestions to simplify them into the modern optional chaining syntax. This enhancement improves code clarity and maintainability for TypeScript projects.

Highlights

• Rule Porting: The @typescript-eslint/prefer-optional-chain rule has been ported from TypeScript-ESLint to Go, enforcing the use of optional chaining (?.) over verbose logical ANDs (&&), negated logical ORs (||), or empty object coalescing patterns ((foo || {}).bar).
• Operand Analysis: The implementation includes sophisticated operand gathering and classification, flattening &&/|| chains and categorizing each operand by its type (boolean, null/undefined equality, typeof, negation).
• Node Comparison and Chain Building: The rule intelligently detects subset/prefix relationships between AST nodes to identify valid optional chain candidates, supporting type parameters, type references, and qualified names. It also correctly generates optional chain output, preserving type arguments, call arguments, element access, and comments.
• DeMorgan Inversion: For || chains, the rule correctly inverts comparison operators during classification and restores original operators for output generation, ensuring semantic correctness.
• Fix vs. Suggestion Logic: The rule makes a type-aware decision to auto-fix when the transformation preserves the expression's return type, otherwise providing a suggestion to avoid unintended side effects.
• Comprehensive Options Support: All eight options from the original rule are supported, including checkAny, checkUnknown, checkString, checkNumber, checkBoolean, checkBigInt, requireNullish, and allowPotentiallyUnsafeFixesThatModifyTheReturnTypeIKnowWhatImDoing.

Changelog

• go.work.sum
  • Updated hashes for golang.org/x/crypto to v0.47.0.
  • Added hash for golang.org/x/mod v0.31.0.
  • Updated hashes for golang.org/x/net to v0.49.0.
  • Added hash for golang.org/x/sys v0.30.0.
  • Updated hashes for golang.org/x/telemetry to v0.0.0-20260109210033-bd525da824e2.
  • Updated hashes for golang.org/x/tools to v0.40.0.
• internal/config/config.go
  • Imported the new prefer_optional_chain rule.
  • Registered @typescript-eslint/prefer-optional-chain in the global rule registry.
• internal/plugins/typescript/rules/prefer_optional_chain/analyze_chain.go
  • Added new file containing the ChainAnalyzer struct and its methods for analyzing logical chains, reporting issues, and building optional chain fix code.
  • Includes logic for determining fix safety (shouldUseFix), handling requireNullish option, and checking for vacuous strict guards.
• internal/plugins/typescript/rules/prefer_optional_chain/base_cases_test.go
  • Added new file providing base case structures and helper functions (rawBaseCases, generateInvalidBaseCases, generateValidBaseCases) for generating comprehensive test scenarios for the prefer-optional-chain rule.
• internal/plugins/typescript/rules/prefer_optional_chain/compare_nodes.go
  • Added new file defining NodeComparisonResult and compareNodesUncached function for deep comparison of AST nodes, crucial for identifying subset and equality relationships in chained expressions.
  • Includes isChainPrefix and isParenthesizedOptionalChain helpers for accurate node comparison.
• internal/plugins/typescript/rules/prefer_optional_chain/gather_logical_operands.go
  • Added new file implementing OperandAnalyzer to gather and classify operands within logical expressions.
  • Defines OperandValidity, NullishComparisonType, and Operand structs to categorize different types of nullish checks and truthiness conditions.
• internal/plugins/typescript/rules/prefer_optional_chain/prefer_optional_chain.go
  • Added new file defining the PreferOptionalChainRule and its options.
  • Sets up rule listeners for BinaryExpression, PropertyAccessExpression, and ElementAccessExpression to detect and process patterns suitable for optional chaining.
• internal/plugins/typescript/rules/prefer_optional_chain/prefer_optional_chain.md
  • Added new documentation file detailing the prefer-optional-chain rule, including examples of incorrect and correct code, and explanations for all supported options.
• internal/plugins/typescript/rules/prefer_optional_chain/prefer_optional_chain_test.go
  • Added new file containing extensive test cases for the prefer-optional-chain rule, combining generated base cases and hand-written edge cases to ensure robust coverage.
• packages/rslint-test-tools/rstest.config.mts
  • Added the new test file prefer-optional-chain/prefer-optional-chain.test.ts to the test configuration.
• packages/rslint-test-tools/tests/typescript-eslint/rules/prefer-optional-chain/prefer-optional-chain.test.ts
  • Updated existing TypeScript test cases to include new scenarios for type parameter chains and complex !== undefined checks, aligning with the Go implementation's test structures.

Activity

• Tests have been updated to cover the new rule's functionality and various edge cases.
• Documentation for the new rule has been added, explaining its purpose, usage, and configuration options.

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[gemini-code-assist]

Code Review

This is an impressive and comprehensive port of the @typescript-eslint/prefer-optional-chain rule. The implementation covers a wide range of complex scenarios, including different logical operators, comparison types, type-aware checks, and even DeMorgan's law for || chains. The test suite is extensive and provides great confidence in the rule's correctness. I've found a few areas for potential improvement regarding code clarity and a couple of possible bugs, which I've detailed in the specific comments. Overall, this is a high-quality contribution.