collect: fix lazy channel draining leaks and align collection edge-case behavior

[Copilot]

This follow-up addresses high-impact issues from the collection rollout: LazyCollection early-exit paths could leave upstream channel producers blocked, and several Collection behaviors were inconsistent with expected semantics (zip length handling, duplicates, where equality, splice bounds, and where-in ergonomics).

• LazyCollection: prevent blocked producers on early exits

  • Added channel draining in early-return/break paths for:
    • Every, First, FirstWhere, Some, Take, TakeWhile, Zip
  • Added internal drainChannel helper to consume remaining items when downstream stops early.

• Collection behavior alignment and edge-case fixes

  • Zip now truncates to the shorter input (no partial trailing pairs).
  • Duplicates now returns each duplicated value once.
  • Splice now treats negative deleteCount as 0.
  • Where equality/inequality now supports numerically equivalent simple mixed types (e.g. int field vs numeric string input).
  • WhereIn / WhereNotIn now accept variadic inputs while preserving compatibility with existing []interface{} calls.

• Performance and correctness refinements

  • Random now uses a shared RNG instance (mutex-protected) instead of per-call generator initialization.
  • Renamed lazy max/min locals to maxVal/minVal to avoid built-in name shadowing.
  • Corrected MapCollect doc comment grammar and GoDoc style.
  • Hardened comparable-type checks against nil-type reflection panics.

• Focused coverage additions

  • Added regression tests for lazy early-exit drain behavior.
  • Added closed-channel iterator test.
  • Updated tests for zip truncation, unique duplicate reporting, variadic WhereIn, numeric string/int equality in Where, and negative Splice deleteCount.

type Product struct{ Price int }
products := collect.Of([]Product{{Price: 100}})

products.Where("Price", "=", "100").Count() // now matches (1)

collect.New(1, 2).Zip(collect.New(3))       // now [[1, 3]]
collect.New(3, 3, 3).Duplicates().All()     // now [3]

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Collection Library: Address Review Comments and Improvements from PR #1134</issue_title>
<issue_description>## Overview

This issue tracks improvements and fixes needed for the Collection library that was merged in #1134. While the implementation is solid and provides comprehensive Laravel-style collection functionality, several issues were identified during review that should be addressed in follow-up PRs.

---

Critical Issues

1. Goroutine Leaks in LazyCollection

Files: support/collect/lazy_collection.go

Multiple methods in LazyCollection may leak goroutines by not draining channels after early returns/breaks:

• Zip (line 853-859): May leave ch2 goroutine running if ch1 completes first
• Take (line 669-676): Breaks early without draining input channel
• TakeWhile (line 694-700): Similar issue to Take
• Some (line 617-621): Returns early without consuming remaining items
• First (line 248-251): Returns early without draining channel
• FirstWhere (line 261-268): Same issue
• Every (line 210-218): Same issue

Fix: Drain channels after early returns to prevent blocking upstream goroutines:

// Example fix for Take
for item := range input {
    if taken >= n {
        // Drain remaining items to prevent blocking upstream
        go func() { for range input {} }()
        break
    }
    output <- item
    taken++
}

2. Performance Issues

Random() Generator Initialization (line 800)

• Initializes a new random generator on every call
• Fix: Use a global generator and reuse it

Unique() and Key Generation Performance (line 1058, 265, 735)

• Uses fmt.Sprintf("%v", ...) for key generation which is extremely slow for large structs
• Example: For a User struct with large fields, this allocates massive strings and uses reflection
• Affects: Unique, Duplicates, Diff, Intersect, GroupBy, and all methods using seen maps
• Fix: Accept a keyFunc parameter allowing users to provide efficient key extraction

---

Behavioral Issues

3. Zip Inconsistency (line 1239)

• Collection.Zip: includes partial pairs when lengths differ → [[1], [2, 3]] for [1,2] and [3]
• LazyCollection.Zip: stops at shorter collection → [] for same inputs
• Fix: Align both to Laravel style (stop at shorter collection)

4. Duplicates() Unexpected Behavior (line 272)

• Input: [3, 3, 3]
• Current output: [3, 3]
• Expected: [3] (each duplicate value once)
• Fix: Track which values have already been added to duplicates

5. Where Type Comparison Issues (line 1270)

type Product struct{ Price int }
c := Of([]Product{{Price: 100}})

c.Where("Price", ">", "50").Count()   // Returns 1 (works)
c.Where("Price", "=", "100").Count()  // Returns 0 (broken!)

• Comparison operators behave inconsistently with type mismatches
• Fix: Add proper type conversion or stricter type checking

---

API Design Issues

6. Pointer Returns (lines 858, 871, 961)

• Many methods return *T but it's unclear why
• Users can simply use pointer type for T if needed: Collection[*User]
• Affected: First, Last, Get, Random, etc.
• Consider: Change to return (T, bool) pattern or just T with zero value

7. WhereIn/WhereNotIn Usability (line 1172)

• Requires []any conversion which is cumbersome:

  c.WhereIn("ID", []any{1, 2, 3}) // Need to convert

• Other Where methods accept ...any which is easier:

  c.Where("ID", "=", 1) // No conversion needed

• Fix: Change signature to accept ...any instead of []any

8. Index Parameter Position (line 806)

• Currently inconsistent: some methods pass (item, index), others (index, item)
• Fix: Standardize to (item, index) everywhere for consistency with Go idioms

9. Mutability Inconsistency (line 1052)

• Some methods return new collections, others modify in place
• Transform modifies original, others don't
• Fix: Document which methods are mutating, consider making all immutable for safety

---

Edge Cases & Bugs

10. Splice Negative deleteCount (line 968)

• Doesn't validate negative deleteCount
• Results in element duplication instead of error
• Fix: Add validation: if deleteCount < 0 { deleteCount = 0 }

11. Slice Duplicate Check (line 896)

• Has duplicate check for start < 0
• Fix: Remove redundant check

12. Variable Naming Collision (line 613)

• Variable named max/min collides with Go built-in functions
• Fix: Rename to maxVal/minVal

13. Debug/Dump Missing Implementation (line 955)

• Methods exist but do nothing meaningful
• Fix: Implement proper debug output or remove if not needed

---

Additional Issues Identified

14. Thread Safety

• Collections are not thread-safe but this isn't documented
• Concurrent modificati...

• Fixes Collection Library: Address Review Comments and Improvements from PR #1134 goravel#883

---

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[codecov]

Codecov Report

❌ Patch coverage is 93.72385% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.27%. Comparing base (5457bef) to head (08402e7).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
support/collect/collection.go	85.43%	7 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1409      +/-   ##
==========================================
+ Coverage   66.42%   67.27%   +0.85%     
==========================================
  Files         344      344              
  Lines       25638    25574      -64     
==========================================
+ Hits        17030    17206     +176     
+ Misses       7872     7639     -233     
+ Partials      736      729       -7     

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[hwbrzzl]

@copilot CI failed

[Copilot]

@copilot CI failed

Investigated CI for this branch at commit c57f84d. There are two failures: (1) Check PR Title is failing because the PR title seen by the workflow is still "[WIP] Fix goroutine leaks in LazyCollection methods" (doesn’t match Conventional Commits), and (2) Test PR / windows (1.26) failed in process package (TestRunningPool_BasicFunctions_Windows/PIDs_returns_process_IDs, expected PID != 0), which appears unrelated to the collection changes. No code change in this PR is needed for the collection files; please update the PR title and rerun checks.