[aaron-y-chen]

Summary

Client.getVariable(key) in the Java SDK is documented (KDoc and java.rst) to return null when the Variable does not exist, but it threw ApiError instead. A task reading an optional Variable failed rather than falling back to a default, and since ApiError carries no error type, callers could only tell "missing" apart from real failures by parsing the message.

The supervisor reports a missing Variable as ErrorResponse(VARIABLE_NOT_FOUND). getVariable now handles it with communicateOrNullIf, the same way getTaskStateStore handles TASK_STORE_NOT_FOUND: VARIABLE_NOT_FOUND returns null, and any other error still raises ApiError.

Behavior change

java-sdk 1.0.0-beta1 shipped with the throwing behavior. Code that catches ApiError to detect a missing Variable now gets null instead.

Testing

• CommsTest: VARIABLE_NOT_FOUND returns null; any other error response still raises ApiError.
• E2E: WriteAndDeleteVariable reads the Variable back after deleting it and fails unless the result is null. Verified locally: the Dag run fails without the fix (ApiError: [VARIABLE_NOT_FOUND]) and succeeds with it.

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[aaron-y-chen]

unrelated CI failure on bzip2/libbz2-1.0 in add-build-essential-extend