The TVM has a special function for dumping variables in debug - ~dump
Run ~dump(variable_name); to print a variable's contents.
Run ~dump(12345); to print the number 12345.
Example:
() recv_internal(int msg_value, cell in_msg, slice in_msg_body) impure {
;; let's say I want to print the value of the variable msg_value
~dump(msg_value);
}
Please note that this command will not run on mainnet, so do not deploy production contracts with it. My favorite way to test smart contracts locally is using ton-contract-executor - this awesome library run a local version of the TVM in web-assembly right inside Node.js, which is very convenient for writing JavaScript/TypeScript tests.
To enable debug prints in ton-contract-executor, when you create your contract instance pass debug: true in SmartContractConfig and print the logs after interacting with the contract:
import { SmartContract } from "ton-contract-executor";
const contract = await SmartContract.fromCell(codeCell, dataCell, {
debug: true // enable debug
});
const send = await contract.sendInternalMessage(...);
console.log(send.logs); // print the logs
