[PLUGIN-1736] Initialize dq_failure before use in send-to-error-and-continue directive

[DJSagarAhire]

This PR adds an initialization to the dq_failure transitory variable used in the send-to-error Wrangler directive. Without this initialization, if the dq_failure variable is used in Wrangler without it ever being incremented, the directive fails as the variable is not found.

[itsankit-google]

JIRA also mentions another issue: Even though send-to-error condition is false, record was send to error port.

Please add unit tests.

[itsankit-google]

Please add a comment why this variable is being initialized here.

[DJSagarAhire]

Done.

[itsankit-google]

Why can't we add an else condition here:

wrangler/wrangler-core/src/main/java/io/cdap/directives/row/SendToErrorAndContinue.java

Lines 117 to 128 in ddff013

	if (result.getBoolean()) {
	if (metric != null && context != null) {
	context.getMetrics().count(metric, 1);
	}
	if (message == null) {
	message = condition;
	}
	if (context != null) {
	context.getTransientStore().increment(TransientVariableScope.LOCAL, "dq_failure", 1);
	}
	throw new ReportErrorAndProceed(message, 1);
	}

And check if the variable dq_failure does not exist then initialize it?

[DJSagarAhire]

@itsankit-google I feel it's better to initialize the variable at the very beginning where it will be picked up regardless of what happens in subsequently used directives rather than rely on some potentially brittle condition. Lmk if you agree.

[itsankit-google]

@itsankit-google I feel it's better to initialize the variable at the very beginning where it will be picked up regardless of what happens in subsequently used directives rather than rely on some potentially brittle condition. Lmk if you agree.

According to the documentation, we don't expect the variable to be used unless SendToErrorAndContinue directive is used. Otherwise the same goes with dq_total variable if without using SendToErrorAndContinue directive, the recipe tries to access dq_total variable they can still get a NPE.

[itsankit-google]

@itsankit-google I feel it's better to initialize the variable at the very beginning where it will be picked up regardless of what happens in subsequently used directives rather than rely on some potentially brittle condition. Lmk if you agree.

Also I didn't understand how is this condition brittle and depending on subsequently used directive, can you please give an example?

[DJSagarAhire]

@itsankit-google I feel it's better to initialize the variable at the very beginning where it will be picked up regardless of what happens in subsequently used directives rather than rely on some potentially brittle condition. Lmk if you agree.

Also I didn't understand how is this condition brittle and depending on subsequently used directive, can you please give an example?

Never mind, I figured that referring to the variables without using Send-To-Error-And-Continue is an error anyway, so I made the change.