Receiving Transaction Receipt without Event Fired

Since Web3 1.0.0 (currently beta.27) you can integrate the process of

1. sending a transaction
2. handling the emitted events of the mined transaction

together nicely as the following

someContractInstance.methods[someMethodName](...args).send({ gas: someGasLimit })
  .on('transactionHash', function (txHash) {
	// after transaction sent and before transaction mined.
  })
  .on('receipt', function (receipt) {
	// after transaction mined.
	// if transaction fired some event, you can find the event return values in 
	console.log(receipt.events[someEventName].returnValues)
  })
  .on('error', console.error)

However, yesterday after I deployed a contract on a private network, I encountered the following error:

Error: Transaction was not mined within 50 blocks, please make sure your transaction was properly send. Be aware that it might still be mined!

With some debugging, I found out that receipt.events[someEventName] was null, which caused the problem.

However, the script did not raise some error like Cannot read property 'returnValues' of null (which I believe should be the correct and direct error message). Instead it stopped there, and triggered the on('receipt', ...) again, and until it repeated for 50 times, it raised the Transaction was not mined within 50 blocks error.

Since the on('receipt', ...) should not be triggered until the transaction is actually mined and executed, the event was not fired probably because the gas was used up before the miner reached the Event statement in the contract.

After I raised the gas limit, the problem solved, and indeed the receipt showed that I used 250,000 gas, which was higher than the 200,000 gas limit I set.