docs: add Nested SelectExpr documentation for reusable DTOs

[arika0093]

Summary by CodeRabbit

• Documentation
  • Added comprehensive "Nested SelectExpr (beta)" guide covering usage patterns, multiple nesting and collection examples, mixing with Select, generated DTO examples, common pitfalls and mitigations (e.g., DTO declaration requirements), feature comparisons with regular Select, and version compatibility notes (recommended .NET 9+, beta API stability guidance).

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[coderabbitai]

Walkthrough

Adds documentation for the Nested SelectExpr feature (beta): a README reference under Customization/Documentation and a new detailed docs page describing usage, requirements, examples, comparisons, and caveats. No code or public API changes.

Changes

Cohort / File(s)	Change Summary
Documentation Updates README.md, docs/library/nested-selectexpr.md	Added a README entry referencing "Nested SelectExpr (beta)" under Customization and Documentation; introduced docs/library/nested-selectexpr.md covering beta status, .NET 9+ recommendation, required empty partial DTO declarations, basic and multiple nesting examples, mixing Select with SelectExpr, generated DTO examples, error scenarios, rationale, and comparisons with regular Select.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

• Check examples for syntax and clarity
• Verify beta/version notes and requirements are accurate
• Ensure README links point to the new doc file

Poem

🐰 I nibble notes and tidy hops,

Nested DTOs in tidy crops,
Beta blossoms, examples clear,
A little hop to bring them near,
📚✨

Pre-merge checks and finishing touches

✅ 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 and specifically describes the main change: adding documentation for Nested SelectExpr feature for reusable DTOs.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch docs/inside-selectexpr

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3fddaf5 and 224d24f.

📒 Files selected for processing (1)

• docs/library/nested-selectexpr.md (1 hunks)

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

• docs/library/nested-selectexpr.md

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[coderabbitai]

Actionable comments posted: 1

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (2)

README.md (2)

2-2: Add alt text to the Linqraft logo image.

The image lacks an alt attribute, which is required for accessibility and markdown compliance (MD045).

Apply this diff:

-# <img width="24" src="./assets/linqraft.png" /> Linqraft 
+# <img width="24" src="./assets/linqraft.png" alt="Linqraft" /> Linqraft 

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159-159: Add descriptive alt text to the GIF image.

The image has empty alt text. Provide a descriptive alternative text for accessibility and markdown compliance (MD045).

Apply this diff:

-![](./assets/replace-codefix-sample.gif)
+![Linqraft analyzer replacing Select with SelectExpr](./assets/replace-codefix-sample.gif)

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a34d686 and 3fddaf5.

📒 Files selected for processing (2)

• README.md (1 hunks)
• docs/library/nested-selectexpr.md (1 hunks)

🧰 Additional context used

🪛 markdownlint-cli2 (0.18.1)

docs/library/nested-selectexpr.md

2-2: Images should have alternate text (alt text)

(MD045, no-alt-text)

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159-159: Images should have alternate text (alt text)

(MD045, no-alt-text)

🔇 Additional comments (2)

README.md (1)

244-244: Documentation reference addition looks good.

The new Nested SelectExpr documentation reference is properly positioned within the Customization section and maintains consistency with the existing documentation structure.

docs/library/nested-selectexpr.md (1)

1-201: Comprehensive and well-structured documentation.

The documentation clearly explains the Nested SelectExpr feature with appropriate beta warnings, .NET version guidance, and strict requirements for empty partial class declarations. The progressive examples (basic usage → multiple nesting levels → mixing with Select → collection types) are well-designed, and the comparison table effectively communicates when to use this feature versus regular Select. The guidance on why empty partial declarations are required is especially helpful for users.