Introduce {Flux,Stream}DistinctSort{,ed}{,WithComparator} Refaster rules

[Copilot]

Sorting data that will be largely discarded by a subsequent distinct operation wastes cycles. Applying distinct first reduces the element count before the expensive sort.

Changes

StreamRules.java

• StreamDistinctSorted: stream.sorted().distinct() → stream.distinct().sorted()
• StreamDistinctSortedWithComparator: stream.sorted(comparator).distinct() → stream.distinct().sorted(comparator)

ReactorRules.java

• FluxDistinctSort: flux.sort().distinct() → flux.distinct().sort()
• FluxDistinctSortWithComparator: flux.sort(comparator).distinct() → flux.distinct().sort(comparator)

Test coverage

Added test cases in StreamRulesTestInput/Output.java and ReactorRulesTestInput/Output.java

Example

// Before
Stream.of(1, 4, 3, 2, 4, 1)
    .sorted()      // Sorts 6 elements
    .distinct();   // Returns 4 elements

// After
Stream.of(1, 4, 3, 2, 4, 1)
    .distinct()    // Returns 4 elements
    .sorted();     // Sorts 4 elements

Warning

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• checkstyle.org
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Original prompt

---

This section details on the original issue you should resolve

<issue_title>Introduce sorting and distinct operation improvements</issue_title>
<issue_description>### Problem

Performing an expensive sort operation on data that will largely be discarded by the subsequent distinct operation should be avoided.

Description of the proposed new feature

• Support a stylistic preference.
• Avoid a common gotcha, or potential problem.
• Improve performance.

I would like to rewrite the following code:

stream.sorted().distinct()
// Rewrite to:
stream.distinct().sorted()

flux.sort().distinct()
// Rewrite to:
flux.distinct().sort()

Considerations

These rewrite rules can be implemented using Refaster by adding new rules to StreamRules and ReactorRules respectively.

Consider the overloads of the sort, sorted, and distinct APIs.

Participation

• I am willing to submit a pull request to implement this improvement.</issue_description>

<agent_instructions>- Introduce the requested Refaster rules in StreamRules.java and ReactorRules.java.

• Make sure to add test cases in the associated *TestInput.java and *TestOutput.java files.
• Carefully follow the existing programming style, with a focus on Javadoc style, use of generics, and test format and test data.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@mohamedsamehsalah Will assign to @Carlos-CBS. @mohamedsamehsalah Closed; Will assign internally. @mohamedsamehsalah Assigned to @ali-khaled-ali !

• Fixes Introduce sorting and distinct operation improvements #1828

---

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[Stephan202]

Added one commit with some tweaks. Thanks @copilot!

Suggested commit message:

Introduce `{Flux,Stream}DistinctSort{,ed}{,WithComparator}` Refaster rules (#1950)

While there, simplify some unrelated test cases.

Resolves #1828.

[github-actions]

Looks good. No mutations were possible for these changes.
Mutation testing report by Pitest. Review any surviving mutants by inspecting the line comments under Files changed.

[Stephan202]

To be merged after #1942.

[mohamedsamehsalah]

Thanks @Stephan202 and @copilot! 🚀

[mohamedsamehsalah]

😄 : I'd say "A for for effort" 👏

[github-actions]

Looks good. No mutations were possible for these changes.
Mutation testing report by Pitest. Review any surviving mutants by inspecting the line comments under Files changed.

[github-actions]

Looks good. No mutations were possible for these changes.
Mutation testing report by Pitest. Review any surviving mutants by inspecting the line comments under Files changed.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud