feat(pyth-evm-js): add transaction filler for automatic Pyth price data bundling

[devin-ai-integration]

Add Transaction Filler for Automatic Pyth Price Data Bundling

Summary

This PR extends the Pyth EVM JS SDK to support automatic transaction filling with Pyth price data. The new functionality detects Pyth getPrice* method calls in transactions using trace calls, extracts price feed IDs, fetches updates from the Hermes price service, and bundles them with the original transaction using multicall.

Key Features

• Automatic Detection: Uses debug_traceCall to detect Pyth price feed usage in transactions
• Price Feed Extraction: Extracts price feed IDs from detected getPrice* method calls
• Price Update Fetching: Retrieves latest price updates from Hermes price service
• Multicall Bundling: Bundles price updates with original transaction using Multicall3
• Iterative Approach: Continues until no new price feeds are detected (handles nested dependencies)
• Dual API: Supports both functional (fillTransactionWithPythData) and class-based (TransactionFiller) approaches

Detected Methods

The implementation automatically detects these Pyth methods:

• getPrice(bytes32 id)
• getPriceUnsafe(bytes32 id)
• getPriceNoOlderThan(bytes32 id, uint256 age)
• getEmaPrice(bytes32 id)
• getEmaPriceUnsafe(bytes32 id)
• getEmaPriceNoOlderThan(bytes32 id, uint256 age)

Usage Example

import { fillTransactionWithPythData } from "@pythnetwork/pyth-evm-js";
import { createPublicClient, http } from "viem";
import { mainnet } from "viem/chains";

const client = createPublicClient({
  chain: mainnet,
  transport: http("https://eth.drpc.org"),
});

const result = await fillTransactionWithPythData({
  pythContractAddress: "0x4305FB66699C3B2702D4d05CF36551390A4c69C6",
  priceServiceEndpoint: "https://hermes.pyth.network",
  viemClient: client,
}, {
  to: "0xe0a80d35bB6618CBA260120b279d357978c42BCE",
  data: "0xa824bf67000000000000000000000000c1d023141ad6935f81e5286e577768b75c9ff8e90000000000000000000000000000000000000000000000000000000000000001",
});

Files Added/Modified

• src/TransactionFiller.ts - Main implementation with TransactionFiller class and utility functions
• src/examples/TransactionFillerExample.ts - Comprehensive example demonstrating usage
• src/index.ts - Export new functionality
• package.json - Add viem dependency and example script, bump version to 1.84.0
• README_TRANSACTION_FILLER.md - Detailed documentation

Testing Transparency

What I Actually Checked

✅ Lint and Format: All ESLint warnings fixed, pre-commit hooks pass
✅ Build Success: TypeScript compilation successful with pnpm run build
✅ Example Execution: Successfully ran pnpm run example-transaction-filler
✅ Mock Trace Logic: Verified trace parsing and price feed extraction logic
✅ API Consistency: Both functional and class-based APIs work correctly
✅ Error Handling: Graceful handling of failed trace calls and missing price feeds

What I Did Not Check

❌ Real Network Integration: Did not test with actual blockchain trace calls (used mock implementation)
❌ Hermes Service Integration: Did not test actual price update fetching from live Hermes endpoint
❌ Multicall Contract Interaction: Did not verify actual multicall transaction execution
❌ Edge Cases: Did not test with complex nested transaction scenarios
❌ Performance: Did not test with large numbers of price feeds or iterations

Implementation Notes

• Uses simplified viem type definitions to avoid complex dependency management
• Includes mock trace implementation for testing and demonstration
• Follows existing SDK patterns and conventions
• Maintains backward compatibility with existing SDK functionality
• Implements proper TypeScript typing throughout

Reviewer Checklist

• Verify the example runs successfully: pnpm run example-transaction-filler
• Check that lint passes: pnpm run fix:lint
• Confirm build succeeds: pnpm run build
• Review API design for consistency with existing SDK patterns
• Test with actual viem client and trace calls if needed
• Validate price feed ID extraction logic
• Confirm multicall bundling approach

---

Link to Devin run: https://app.devin.ai/sessions/13fbfcfa51014db0ac022798616aaf67
Requested by: Ali ([email protected])

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