Router: Aggregator Batch Router V2

[mkflow27]

Add functionality See: balancer/balancer-deployments#316

[mkflow27]

AggregatorBatchRouter V2 vs Deprecated Version - Functional Differences Analysis

Overview

The new AggregatorBatchRouter V2 represents a streamlined, more focused version that removes complexity while improving core swap functionality.

Key Functional Differences

1. Removed Functions in V2

Function	Status	Purpose
multicall	Removed	Generic multicall for batching multiple operations
permitBatchAndCall	Removed	Complex permit functionality with Permit2 integration
getPermit2	Removed	Getter for Permit2 contract address
getSender	Removed	Getter for sender address
getWeth	Removed	Getter for WETH contract address

2. Enhanced Function Signatures

Swap Functions Comparison

Deprecated Version:

function swapExactIn(
    SwapPathExactAmountIn[] memory paths,
    uint256 deadline,
    bytes calldata userData
) external payable returns (...)

V2 Version:

function swapExactIn(
    SwapPathExactAmountIn[] memory paths,
    uint256 deadline,
    bool wethIsEth,  // NEW: Explicit ETH handling
    bytes calldata userData
) external payable returns (...)

3. Enhanced ETH/WETH Handling

Feature	Deprecated	V2
ETH Handling	Implicit	Explicit wethIsEth parameter
WETH Wrapping	Automatic	User-controlled
ETH Unwrapping	Automatic	User-controlled

Benefits:

• Better control over ETH wrapping/unwrapping behavior
• More predictable ETH handling
• Reduced gas costs for non-ETH operations

4. Constructor Changes

Deprecated:

constructor(
    IVault vault,
    string routerVersion
)

V2:

constructor(
    IVault vault,
    IWETH weth,           // NEW: Explicit WETH dependency
    IPermit2 permit2,     // NEW: Explicit Permit2 dependency
    string routerVersion
)

Benefits:

• Clearer dependencies - WETH and Permit2 are explicit
• Better testability - Dependencies are injected
• Reduced coupling - No hidden dependencies

5. Query Functions

V2 introduces dedicated query functions:

Function	Purpose
querySwapExactIn()	Query exact input swap results
querySwapExactOut()	Query exact output swap results

Benefits:

• Separation of concerns - Queries vs execution
• Gas efficiency - No state changes during queries
• Better UX - Predictable query behavior

Architecture Improvements

Simplified Design Philosophy

Aspect	Deprecated	V2
Complexity	High (multicall, permits)	Low (focused on swaps)
Gas Efficiency	Variable	Optimized
Maintainability	Complex	Simple
Security Surface	Large	Minimal

Removed Complexity

• Multicall functionality - Removed generic batching
• Complex permit batching - Simplified to core swaps
• Internal state getters - Removed unnecessary getters

Added Clarity

• Explicit ETH handling - wethIsEth parameter
• Clear dependencies - Constructor requires all dependencies
• Focused functionality - Core swap operations only

Migration Impact

Breaking Changes

1. Function signatures changed - wethIsEth parameter added
2. Multicall removed - Need separate transactions
3. Permit batching removed - Simpler permit handling required

Benefits for Users

1. Lower gas costs - Removed unused functionality
2. Better ETH handling - Explicit control over WETH operations
3. Cleaner interfaces - Easier to understand and use
4. Improved security - Smaller attack surface

Summary

The V2 AggregatorBatchRouter follows a "less is more" philosophy:

• Focused on core functionality - Swaps only
• Optimized for gas efficiency - Removed unused features
• Improved security - Smaller attack surface
• Better developer experience - Cleaner, more predictable APIs
• Cost-effective - Lower gas costs for common operations

This represents a mature evolution of the contract, prioritizing reliability and efficiency over feature completeness.