BigQuery: create() throws NullPointerException on a duplicate job id outside the US multi-region (java-bigquery#3034 not fixed by #3035)

Start in java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/BigQueryImpl.java around lines 609–611, then compare the fixed-id branch with the nearby idRandom null handling. Review testCreateJobTryGetNotRandom and add coverage for a null re-fetch; done means a regional duplicate produces the original Already Exists error instead of a NullPointerException.

Environment details

1. API: BigQuery (java-bigquery)
2. OS type and version: macOS 15 / Linux (not OS-specific)
3. Java version: 17
4. Version: google-cloud-bigquery 2.68.0, and present on current main
   (java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/BigQueryImpl.java
   lines 609–611)

Summary

BigQuery.create(JobInfo) with an explicit job id throws
NullPointerException: Cannot invoke "com.google.cloud.bigquery.Job.getStatistics()" because "job" is null
when the id already exists and the job lives outside the US multi-region while the JobId carries
no location — masking the real Already Exists: Job project:location.id error.

This is the failure googleapis/java-bigquery#3034 reported. That issue was closed by
googleapis/java-bigquery#3035, which does not cover this path:

• #3035's production change narrows the re-fetch from getJob(jobId) to
  getJob(jobId, JobOption.fields(JobField.STATISTICS)). Narrowing the requested fields cannot
  turn a null return into a job, and #3034's stack trace shows the receiver job itself was null.
• #3035's added test (testCreateJobTryGetNotRandom) mocks the RPC getJob returning a job,
  so only the found-job path is covered; the null return has no test.

The NPE therefore still reproduces, deterministically, on 2.68.0 — which contains #3035's change.

Root cause

jobs.get resolves a JobId that names no location against the US multi-region only. When the
duplicated job's location was inferred from the statement (a query or load touching a regional
dataset), the duplicate-id handler's re-fetch misses it, getJob returns null, and
job.getStatistics() throws. The idRandom branch a few lines below already handles exactly this
case with if (job == null) { throw createException; }; the fixed-id branch lacks the same guard.

Steps to reproduce

Run the code below against any project with a dataset outside the US multi-region (reproduced
against a us-central1 dataset). No location is set anywhere; the region comes from the query.

BigQuery bq = BigQueryOptions.newBuilder().setProjectId(project).build().getService();
String sql = "SELECT COUNT(*) FROM `" + project + "." + regionalDataset + ".INFORMATION_SCHEMA.TABLES`";
String id = "npe_repro_" + System.currentTimeMillis();

bq.create(JobInfo.of(JobId.newBuilder().setProject(project).setJob(id).build(),
        QueryJobConfiguration.of(sql)));                     // ok — server infers us-central1
bq.create(JobInfo.of(JobId.newBuilder().setProject(project).setJob(id).build(),
        QueryJobConfiguration.of(sql)));                     // NullPointerException

Control arm: setting the location on the second create's JobId makes the handler find the job
and return it — the intended duplicate-id behaviour — which isolates the defect to the
location-less re-fetch.

Stack trace

java.lang.NullPointerException: Cannot invoke "com.google.cloud.bigquery.Job.getStatistics()" because "job" is null
	at com.google.cloud.bigquery.BigQueryImpl.create(BigQueryImpl.java:611)
	at com.google.cloud.bigquery.BigQueryImpl.create(BigQueryImpl.java:511)

Expected behaviour and fix

When the re-fetch returns null, fall through to the original exception, as the idRandom branch
does. Verified against BigQuery with the guard patched in: the NPE becomes
BigQueryException: Already Exists: Job flink-gcp:us-central1.npe_repro_a_…, whose message names
the job's actual location. I can send the PR.