refactor: replace strings.Index with strings.Cut for improved readallity

[ReneWerner87]

No description provided.

[coderabbitai]

Walkthrough

This pull request refactors string handling operations across multiple files, replacing index-based detection and slicing with modern Go string utilities (strings.Cut, strings.Contains). All changes maintain existing functionality while improving code clarity and using idiomatic Go patterns.

Changes

Cohort / File(s)	Summary
Modern string utility refactoring (strings.Cut) middleware/basicauth/basicauth.go, middleware/cors/utils.go, req.go	Replaced index-based string splitting with strings.Cut for extracting delimited components (credentials, schemes, query parameters). Improves readability and uses idiomatic Go string handling.
String presence detection (strings.Contains) client/core.go	Changed port detection from strings.Index() to strings.Contains() for checking colon presence in addresses. Semantically equivalent but more explicit intent.
Inline optimization helpers.go	Inlined temporary variable assignment by directly comparing result of strings.IndexByte() to -1, reducing intermediate variable assignment. No behavioral change.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

• Consistent refactoring pattern: All changes follow repetitive, well-defined patterns (index → strings.Cut, index → strings.Contains)
• No behavioral changes: String operations remain functionally identical, reducing cognitive load
• Error handling continuity: Changes in basicauth.go preserve existing error paths via strings.Cut's success/failure pattern

Possibly related PRs

• #3922: Parallel refactoring effort modifying the same files (helpers.go, req.go) with similar string utility improvements and index-to-Cut conversions.

Suggested reviewers

• gaby
• sixcolors
• efectn

Poem

🐰 String cuts, so clean and neat,
Index slicing, now obsolete!
Contains and Cut, the modern way,
Refactored code, hip-hip-hooray! ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	No pull request description was provided by the author, failing to meet the repository's required template structure and content guidelines.	Add a comprehensive description following the template, including purpose, type of change, and relevant checklist items for this refactoring effort.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main refactoring work across multiple files, replacing strings.Index calls with strings.Cut for better readability.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix_modernizer_hints

---

📜 Recent review details

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 312d2e6 and c5e5b0c.

📒 Files selected for processing (5)

• client/core.go (1 hunks)
• helpers.go (1 hunks)
• middleware/basicauth/basicauth.go (1 hunks)
• middleware/cors/utils.go (1 hunks)
• req.go (3 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

**/*.go

📄 CodeRabbit inference engine (AGENTS.md)

Prefer github.com/gofiber/utils/v2 helpers (for example, utils.Trim) when performing common operations such as string manipulation, whenever it is practical and appropriate for the surrounding code

Files:

• helpers.go
• middleware/basicauth/basicauth.go
• req.go
• client/core.go
• middleware/cors/utils.go

🧠 Learnings (1)

📓 Common learnings

Learnt from: CR
Repo: gofiber/fiber PR: 0
File: AGENTS.md:0-0
Timestamp: 2025-12-07T15:07:23.885Z
Learning: Applies to **/*.go : Prefer `github.com/gofiber/utils/v2` helpers (for example, `utils.Trim`) when performing common operations such as string manipulation, whenever it is practical and appropriate for the surrounding code

🧬 Code graph analysis (1)

req.go (1)

error.go (1)

• ErrRangeMalformed (32-32)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (5)

• GitHub Check: lint
• GitHub Check: unit (1.25.x, macos-latest)
• GitHub Check: unit (1.25.x, windows-latest)
• GitHub Check: repeated
• GitHub Check: Compare

🔇 Additional comments (7)

middleware/cors/utils.go (1)

10-12: LGTM! Clean refactor to strings.Cut.

The scheme extraction logic is now clearer and more idiomatic. Using strings.Cut with the ok flag provides better semantics than manual index-based slicing.

middleware/basicauth/basicauth.go (1)

94-101: LGTM! Improved credential parsing.

The refactor to strings.Cut makes the username/password extraction clearer and more robust. The error handling with the ok flag is appropriate.

helpers.go (1)

211-211: LGTM! Clean inline refactor.

Removing the temporary variable i is a minor simplification that maintains the same logic while reducing code.

client/core.go (1)

36-39: LGTM! More semantic port detection.

Using strings.Contains instead of strings.Index makes the intent clearer—we only care whether a colon exists, not its position.

req.go (3)

324-328: LGTM! Improved header parsing.

The refactor correctly handles comma-separated values in the X-Forwarded-Host header, extracting the first value when multiple are present. The logic is clear and handles both cases appropriately.

---

648-653: LGTM! Consistent header value extraction.

The scheme parsing now uses strings.Cut to handle comma-separated proxy headers consistently with the Host() method. The logic correctly prioritizes the first value when multiple are present.

---

762-770: LGTM! Robust range header parsing.

The refactor to strings.Cut improves the Range header parsing logic:

• Line 762 cleanly splits on the first "="
• Line 763 validates the format by rejecting missing or duplicate "=" characters
• Lines 766 and 770 use the split values appropriately

The validation logic correctly identifies malformed Range headers while maintaining the same behavior as the previous implementation.

---

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[gemini-code-assist]

Summary of Changes

Hello @ReneWerner87, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on a targeted refactoring effort to enhance the clarity and conciseness of string manipulation operations throughout the codebase. By migrating from strings.Index and manual slicing to the strings.Cut function, the changes aim to improve code readability and reduce potential errors associated with manual index handling, resulting in a more robust and maintainable codebase.

Highlights

• Refactoring to strings.Cut: Replaced multiple instances of strings.Index and manual string slicing with the more idiomatic and readable strings.Cut function across several files.
• Improved Readability: The use of strings.Cut simplifies string parsing logic, making the code easier to understand and maintain by directly returning the 'before' and 'after' parts, along with a boolean indicating if the separator was found.
• Code Simplification: In client/core.go and helpers.go, strings.Index was replaced with strings.Contains or its return value was directly used, removing unnecessary variable assignments when only the presence of a character was needed.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.62%. Comparing base (312d2e6) to head (c5e5b0c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3956   +/-   ##
=======================================
  Coverage   91.62%   91.62%           
=======================================
  Files         119      119           
  Lines       10190    10190           
=======================================
  Hits         9337     9337           
  Misses        540      540           
  Partials      313      313           

Flag	Coverage Δ
unittests	91.62% <100.00%> (ø)

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[Copilot]

Pull request overview

This PR refactors string manipulation code to use strings.Cut for improved readability, replacing older patterns using strings.Index and strings.IndexByte. Note: The PR title contains a typo ("readallity" should be "readability").

Key changes:

• Replaces strings.Index with strings.Cut to split strings and extract substrings before/after delimiters
• Simplifies conditional logic by checking the boolean return value from strings.Cut instead of comparing index values to -1
• Improves variable naming by using descriptive names like before and after instead of array slicing operations

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
req.go	Refactored Host(), Scheme(), and Range() methods to use strings.Cut for parsing comma-separated headers and range specifications
middleware/cors/utils.go	Updated matchScheme() to use strings.Cut for extracting and comparing URL schemes
middleware/basicauth/basicauth.go	Simplified credential parsing using strings.Cut to split username and password
helpers.go	Removed unused variable assignment when checking for asterisk character
client/core.go	Replaced strings.Index with strings.Contains for port existence check

[gemini-code-assist]

Code Review

This pull request aims to improve readability by replacing strings.Index with strings.Cut. The changes in middleware/basicauth/basicauth.go, middleware/cors/utils.go, and req.go are excellent and achieve this goal effectively. I have a couple of suggestions for client/core.go and helpers.go to further improve consistency and readability in line with the PR's objective. Overall, this is a good refactoring effort.

[sixcolors]

I believe IndexByte is more performant than Contains when searching for a single byte.

[ReneWerner87]

I believe IndexByte is more performant than Contains when searching for a single byte.

Yes, I know that indexByte is faster. That was actually just to fix modernizer for now and is an excerpt from your adjustments in the pull request.

https://patch-diff.githubusercontent.com/raw/gofiber/fiber/pull/3946.diff

The performance acceleration comes from my other pull request
#3923