Add combined contract attribute

[robjtede]

Summary

• add a new #[contract(...)] attribute for grouping contract clauses in one macro invocation
• reuse the existing contract parser/codegen path for requires, ensures, invariant, and mode-prefixed clauses
• update the issue clippy reports unused imports when using both requires and ensures #9 regression to import only contract under deny(unused_imports)

Closes #9.

Validation

• cargo +1.65.0 test --test ui
• just clippy
• just test

Summary by CodeRabbit

• New Features

  • Added support for combining multiple contract conditions in a single #[contract(...)] attribute.
  • Supports mixing preconditions, postconditions, and debug-only postconditions.

• Documentation

  • Updated the unreleased changelog with combined contract attribute support.

• Tests

  • Added coverage for combined contracts and updated an existing example to use the new syntax.

[coderabbitai]

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 47ede8e7-7e59-464a-af45-5c5c8e6609cc

📥 Commits

Reviewing files that changed from the base of the PR and between 9efeb12 and 04c49d7.

📒 Files selected for processing (6)

• CHANGELOG.md
• src/implementation/contract.rs
• src/implementation/mod.rs
• src/lib.rs
• tests/issues.rs
• tests/ui/pass/combined_contract.rs

📝 Walkthrough

Walkthrough

Adds a public #[contract(...)] attribute that parses multiple contract clauses, integrates them into function generation, and validates the feature through issue and UI tests.

Changes

Combined contract attribute

Layer / File(s)	Summary
Contract attribute API and parsing src/lib.rs, src/implementation/mod.rs, src/implementation/contract.rs	Exposes #[contract(...)], parses comma-separated requires, ensures, and debug contract clauses, and generates the annotated function with those contracts.
Function contract construction src/implementation/mod.rs	Delegates initial contract construction through new_with_contracts.
Combined contract validation and release notes tests/issues.rs, tests/ui/pass/combined_contract.rs, CHANGELOG.md	Updates the issue regression test, adds a UI pass test covering multiple clauses, and documents the new attribute.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant AnnotatedFunction
  participant contract
  participant ContractClauses
  participant FuncWithContracts
  AnnotatedFunction->>contract: provide clauses and function tokens
  contract->>ContractClauses: parse combined clauses
  ContractClauses-->>contract: return contracts
  contract->>FuncWithContracts: generate contracted function

Loading

Possibly related PRs

• x52dev/contracts#115: Adds the UI test harness that runs the new combined-contract pass case.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: adding a combined contract attribute.
Linked Issues check	✅ Passed	The changes address issue #9 by enabling a combined contract form and updating the test to avoid unused imports.
Out of Scope Changes check	✅ Passed	The added parser, macro wiring, docs, and tests all support the new combined contract attribute and stay within scope.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex-add-combined-contract-attribute

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

tests/ui/pass/combined_contract.rs (1)

3-7: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Cover combined invariant clauses in the regression test.

This validates requires, ensures, and debug_ensures, but the new API also promises combined invariant clauses. Add one (for example, debug_invariant(x >= 0)) so both invariant parsing and its pre/post generation paths are covered.

Suggested addition

 #[contract(
     requires(x >= 0, "input is non-negative"),
+    debug_invariant(x >= 0),
     ensures(ret >= x),
     debug_ensures(ret == x + 1),
 )]

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@tests/ui/pass/combined_contract.rs` around lines 3 - 7, Add a combined
invariant clause, such as debug_invariant(x >= 0), to the contract attribute in
the combined contract regression test, alongside the existing requires, ensures,
and debug_ensures clauses. Keep the test’s current behavior unchanged while
covering invariant parsing and pre/post generation.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/implementation/contract.rs`:
- Line 20: Replace the infallible syn::parse_quote! call assigning func in the
contract macro with syn::parse2(...), propagating parse failures through
emit_error(err, toks) as done in the other contract macros. Preserve the
existing ItemFn result for valid input while returning a compile error instead
of panicking on invalid macro input.

---

Nitpick comments:
In `@tests/ui/pass/combined_contract.rs`:
- Around line 3-7: Add a combined invariant clause, such as debug_invariant(x >=
0), to the contract attribute in the combined contract regression test,
alongside the existing requires, ensures, and debug_ensures clauses. Keep the
test’s current behavior unchanged while covering invariant parsing and pre/post
generation.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 40c64443-cb14-425e-add1-e72d98cf9bb8

📥 Commits

Reviewing files that changed from the base of the PR and between 550c50d and 9efeb12.

📒 Files selected for processing (6)

• CHANGELOG.md
• src/implementation/contract.rs
• src/implementation/mod.rs
• src/lib.rs
• tests/issues.rs
• tests/ui/pass/combined_contract.rs