hardhat_api: Implement hardhat_dropTransaction method

[dutterbutter]

Description:

The hardhat_dropTransaction endpoint needs to be implemented. The purpose of this endpoint is to remove a transaction from the mempool. Hardhat docs for reference, test implementations can be found here.

// Interface in the `trait`
#[rpc(name = "hardhat_dropTransaction")]
fn drop_transaction(&self, tx_hash: H256) -> BoxFuture<Result<bool>>;

// Actual code in the `impl`
fn drop_transaction(&self, tx_hash: H256) -> BoxFuture<Result<bool>> {
    // TODO: Solution here
}

JS implementation:

/**
 * Removes the given transaction from the mempool, if it exists.
 *
 * @param txHash Transaction hash to be removed from the mempool.
 * @returns `true` if successful, otherwise `false`.
 * @throws if the transaction was already mined.
 */
export async function dropTransaction(txHash: string): Promise<boolean> {
  const provider = await getHardhatProvider();

  assertTxHash(txHash);

  return (await provider.request({
    method: "hardhat_dropTransaction",
    params: [txHash],
  })) as boolean;
}

Expected response

Command returns proper response:

curl -X POST http://localhost:8011 \
     -H "Content-Type: application/json" \
     --data '{
       "jsonrpc": "2.0",
       "id": 1,
       "method": "hardhat_dropTransaction",
       "params": ["0x7fTf4C4Bf8Ecd85dEf3E1c5Df137a7512a6a57bd987f3b8e"]
     }'

Response:

{"jsonrpc":"2.0", "result":true, "id":1}

Requirements:

1. Implement the API:

   • The endpoint should return true if successful in removing the tx from the mempool, otherwise false.
   • Ensure the method executes the call reliably and efficiently.
   • Ensure errors are properly returned.

2. Unit Tests:

   • Write unit tests to verify the functionality of the dropTransaction method.
   • Ensure coverage for multiple edge-case scenarios.

3. Documentation:

   • Add inline Rust documentation (/// comments) detailing the method's purpose, return values, and any potential edge cases or error scenarios.
   • Update SUPPORTED_APIS.md with updated documentation and examples.
   • (Optional) Add request to test_endpoints.http for easier manual verification.

Task Checklist:

• Implement the dropTransaction method.
• Write unit tests for the dropTransaction method.
• Add inline documentation for the hardhat_dropTransaction endpoint.
• Update documentation for the hardhat_dropTransaction endpoint in SUPPORTED_APIS.md.

Additional Notes:

If you're an external contributor looking to take on this issue, please comment below to let us know you're working on it. If you need further clarification on the requirements or need assistance with anything related to the implementation, feel free to ask!