feat(dns): added support for a custom lookup function; (#5339)

[MitchLewis930]

PR_026

[greptile-apps]

Greptile Overview

Greptile Summary

This PR adds support for custom DNS lookup functions in axios HTTP adapter, allowing users to override DNS resolution behavior for Node.js environments.

Key Changes:

• Added family and lookup options to AxiosRequestConfig interface
• Created callbackify helper to convert async lookup functions to callback-based format
• Added utility functions (isAsyncFn, isGeneratorFn, etc.) to detect function types
• Implemented automatic IPv4/IPv6 family inference when lookup returns only an IP string
• Comprehensive test coverage for callback-based, async, and string-return lookup functions

Critical Issue:

• The IPv4/IPv6 family detection logic on line 160 of lib/adapters/http.js is inverted, which will cause incorrect address family assignment

Testing:

• Unit tests verify callback, async, and simplified string-return patterns
• TypeScript type definitions include both function signatures

Confidence Score: 2/5

• This PR contains a critical logic error in IPv4/IPv6 detection that will cause incorrect behavior
• The inverted family detection logic will assign family 6 to IPv4 addresses and family 4 to IPv6 addresses, causing connection failures or unexpected behavior. The feature is well-tested and the architecture is sound, but this bug must be fixed before merging.
• lib/adapters/http.js requires immediate attention to fix the IPv4/IPv6 detection logic on line 160

Important Files Changed

Filename	Overview
lib/adapters/http.js	Added custom DNS lookup support with async function conversion, but IPv4/IPv6 family detection logic is inverted
lib/helpers/callbackify.js	New helper to convert async functions to callback-based functions with optional value transformation
lib/utils.js	Added utility functions to detect async/generator functions and thenable objects

Sequence Diagram

sequenceDiagram
    participant User
    participant Axios
    participant httpAdapter
    participant callbackify
    participant lookup as Custom Lookup
    participant NodeHTTP as Node.js HTTP/HTTPS

    User->>Axios: axios.get(url, {lookup, family})
    Axios->>httpAdapter: httpAdapter(config)
    
    alt lookup is async function
        httpAdapter->>callbackify: callbackify(lookup, reducer)
        Note over callbackify: Converts async to callback
        callbackify-->>httpAdapter: callback-based lookup
    end
    
    httpAdapter->>httpAdapter: Build request options
    Note over httpAdapter: Add family & lookup to options
    
    httpAdapter->>NodeHTTP: http.request(options)
    
    alt DNS resolution needed
        NodeHTTP->>lookup: lookup(hostname, options, callback)
        
        alt Original async lookup
            lookup->>lookup: Resolve DNS async
            lookup-->>callbackify: Return [address, family] or string
            callbackify->>callbackify: Apply reducer transform
            callbackify-->>NodeHTTP: callback(null, address, family)
        else Original callback lookup
            lookup->>lookup: Resolve DNS
            lookup-->>NodeHTTP: callback(null, address, family)
        end
    end
    
    NodeHTTP->>NodeHTTP: Connect to resolved address
    NodeHTTP-->>httpAdapter: Response
    httpAdapter-->>Axios: Formatted response
    Axios-->>User: Response data

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[greptile-apps]

_{3 files reviewed, 2 comments}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

IPv4/IPv6 detection logic is inverted. IPv4 addresses contain dots (like 127.0.0.1), while IPv6 addresses use colons (like ::1). This will assign family 6 to IPv4 addresses and family 4 to IPv6 addresses.

Suggested change

	entry = [entry, entry.indexOf('.') < 0 ? 6 : 4]
	entry = [entry, entry.indexOf('.') < 0 ? 4 : 6]

Prompt To Fix With AI

This is a comment left during a code review.
Path: lib/adapters/http.js
Line: 160:160

Comment:
IPv4/IPv6 detection logic is inverted. IPv4 addresses contain dots (like `127.0.0.1`), while IPv6 addresses use colons (like `::1`). This will assign family 6 to IPv4 addresses and family 4 to IPv6 addresses.

```suggestion
          entry = [entry, entry.indexOf('.') < 0 ? 4 : 6]
```

How can I resolve this? If you propose a fix, please make it concise.

[greptile-apps]

Missing space after if keyword for consistency with the codebase style

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

Prompt To Fix With AI

This is a comment left during a code review.
Path: lib/adapters/http.js
Line: 159:159

Comment:
Missing space after `if` keyword for consistency with the codebase style

<sub>Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!</sub>

How can I resolve this? If you propose a fix, please make it concise.