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Provide the most specific implicit for IsEmpty on iterables #1355

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Merged
merged 1 commit into from
Aug 4, 2025
Merged

Provide the most specific implicit for IsEmpty on iterables #1355

merged 1 commit into from
Aug 4, 2025

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bdmendes
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@bdmendes bdmendes commented Aug 4, 2025 •
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Hi! I want to support this use case:

futMap must beEmpty.await

Since Matcher is not covariant, the rhs of must fails right now as IsEmpty[IterableOnce[?]] is not a IsEmpty[Map[K, V]]. I think this change is okay to fix it. Hoping it does not break binary compatibility.
This is a follow-up to #1345.

Summary by CodeRabbit

  • Tests

    • Added new test cases to ensure that empty generic containers (such as Option, Seq, Map, and Set) are correctly recognized as empty by the matcher.

  • Refactor

    • Generalized internal handling of empty checks to support all subtypes of generic collections.

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coderabbitai bot commented Aug 4, 2025 •
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Walkthrough

The changes generalize the IsEmpty typeclass instance for IterableOnce types by making it fully generic, and update its method signature accordingly. Additionally, new test cases are added to ensure that the beEmpty matcher correctly recognizes empty generic containers, increasing test coverage for various collection types.

Changes

Cohort / File(s) Change Summary
IsEmpty Typeclass Generalization
common/shared/src/main/scala/org/specs2/collection/IsEmpty.scala		 Generalized the IsEmpty instance for IterableOnce from a non-generic to a generic form, updating method signatures.
Matcher Test Coverage
tests/jvm/src/test/scala/org/specs2/matcher/AnyMatchersSpec.scala		 Added test cases to verify that beEmpty matcher works for empty generic containers (Option, Seq, Map, Set).

Sequence Diagram(s)

sequenceDiagram
  participant Test as Test Suite
  participant Matcher as beEmpty Matcher
  participant IsEmpty as IsEmpty Typeclass

  Test->>Matcher: assert(emptyContainer should beEmpty)
  Matcher->>IsEmpty: isEmpty(emptyContainer)
  IsEmpty-->>Matcher: Boolean result
  Matcher-->>Test: Assertion result
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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~7 minutes

Possibly related PRs

Suggested reviewers

  • etorreborre

Poem

In the warren of code, a hop and a leap,
Now IsEmpty is clever, its bounds not so steep.
With tests for all types—Option, Map, Set—
This bunny ensures no empty’s unmet!
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📥 Commits

Reviewing files that changed from the base of the PR and between 224cb5c and 1ed6a14.

📒 Files selected for processing (2)
  • common/shared/src/main/scala/org/specs2/collection/IsEmpty.scala (1 hunks)
  • tests/jvm/src/test/scala/org/specs2/matcher/AnyMatchersSpec.scala (1 hunks)
🔇 Additional comments (2)
common/shared/src/main/scala/org/specs2/collection/IsEmpty.scala (1)

41-42: LGTM! Well-targeted fix for type variance issue.

The change from IsEmpty[IterableOnce[?]] to IsEmpty[T <: IterableOnce[?]] correctly addresses the type compatibility issue described in the PR objectives. This more specific implicit should resolve the problem where futMap must beEmpty.await was failing due to Matcher type variance.

tests/jvm/src/test/scala/org/specs2/matcher/AnyMatchersSpec.scala (1)

49-52: Excellent test coverage for the generic IsEmpty fix.

These test cases properly verify that the generalized IsEmpty[T <: IterableOnce[?]] instance works correctly with explicit type annotations. The tests cover the main collection types and should catch any regressions in the type variance fix.

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etorreborre
etorreborre approved these changes Aug 4, 2025
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Nice generalization, thanks!

@etorreborre etorreborre merged commit 4e1659b into etorreborre:main Aug 4, 2025
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@bdmendes @etorreborre