fix(config): handle null rules field in project config

[TabishB]

Summary

• Add null check when parsing rules field in project config
• YAML rules: with no value parses to null, and typeof null === 'object' in JavaScript
• Without this check, Object.entries(null) would throw an error

Test plan

• Added test case for rules: null scenario
• Verified test passes with the fix
• All existing tests still pass

🤖 Generated with Claude Code

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Fixed project configuration parsing to properly handle empty or null rules fields without validation errors.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds a null guard to the rules field parsing in project-config.ts to prevent false positives when the rules field is null, since typeof null === 'object'. A corresponding test case validates that empty rules fields are parsed gracefully with appropriate warnings.

Changes

Cohort / File(s)	Summary
Rules field null guard and test src/core/project-config.ts, test/core/project-config.test.ts	Added null check before type validation of rules field to prevent false positives when raw.rules is null. New test case validates parsing of empty rules field (rules: with no value) produces warning without aborting.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• feat(config): add project-level configuration via openspec/config.yaml #499: Both PRs modify src/core/project-config.ts and handle parsing/validation of the project "rules" field, with this PR adding a null guard and testing empty rules scenarios.

Poem

🐰 A null that hides in shadows deep,
Now caught before it makes us weep!
With gentle guard and test so neat,
Our rules field validation's sweet. ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a null guard for the rules field in project config to prevent errors from YAML parsing.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

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[vibe-kanban-cloud]

Review Complete

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[greptile-apps]

Greptile Summary

Added null check when parsing the rules field in project config to prevent Object.entries(null) from throwing an error when YAML parses rules: with no value as null.

• Fixed edge case where typeof null === 'object' in JavaScript could cause runtime error
• Added comprehensive test case validating the fix
• Config parsing now gracefully handles rules: null and continues processing other fields

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The change is a simple defensive null check that fixes a real edge case bug. The fix is minimal, well-tested, and follows JavaScript best practices for handling the quirk that typeof null === 'object'. The test case directly validates the bug scenario.
• No files require special attention

Important Files Changed

Filename	Overview
src/core/project-config.ts	Added null check to prevent Object.entries(null) error when parsing YAML rules field
test/core/project-config.test.ts	Added test case for rules: null scenario to validate the fix

Sequence Diagram

sequenceDiagram
    participant User
    participant readProjectConfig
    participant YAML Parser
    participant Validation Logic

    User->>readProjectConfig: Read config file
    readProjectConfig->>YAML Parser: Parse YAML content
    YAML Parser-->>readProjectConfig: Return parsed object (rules: null)
    
    readProjectConfig->>Validation Logic: Check raw.rules !== undefined
    Validation Logic-->>readProjectConfig: true
    
    readProjectConfig->>Validation Logic: Check typeof raw.rules === 'object'
    Validation Logic-->>readProjectConfig: true (typeof null === 'object')
    
    readProjectConfig->>Validation Logic: Check raw.rules !== null (NEW)
    Validation Logic-->>readProjectConfig: false (is null)
    
    readProjectConfig->>readProjectConfig: Skip Object.entries(null)
    readProjectConfig->>readProjectConfig: Log warning about invalid rules
    readProjectConfig-->>User: Return config with schema and context only

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