[gcloud] Allow configuring the BigQuery emulator project id

[alimhin]

What

Adds BigQueryEmulatorContainer#withProjectId(String). The default stays test-project, so existing users are not affected. getProjectId() now returns the configured value.

Why

The project id is hardcoded (--project test-project). Tests that use a fixed project id in SQL, fixtures or application configuration cannot use the container as-is. Several projects end up rewriting it, for example:

• enrichmeai/culvert (project id and dataset as parameters)
• exasol/bigquery-virtual-schema (--project=test)
• flink-gcp/flink-connector-gcp (newContainer(project, dataset))

How to test

• New testCustomProjectId: starts the emulator with withProjectId("my_project"), checks getProjectId(), and creates a dataset under my_project.
• Without the --project change, that test fails with project my_project is not found.
• ./gradlew :testcontainers-gcloud:test --tests '*BigQueryEmulatorContainerTest*' passes (3/3), and spotlessCheck passes.

Docs

docs/modules/gcloud.md: mentions the default project id and adds a snippet for withProjectId.

Summary by CodeRabbit

• New Features
  • BigQuery emulator containers use test-project by default and support configuring a custom project ID.
  • Invalid project IDs—including null, empty, or whitespace-only values—are rejected.
• Documentation
  • BigQuery usage examples explain the default project ID and show how to configure a custom one.

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Reviewing files that changed from the base of the PR and between 928c1dd and d87fcca.

📒 Files selected for processing: 2

• modules/gcloud/src/main/java/org/testcontainers/gcloud/BigQueryEmulatorContainer.java
• modules/gcloud/src/test/java/org/testcontainers/gcloud/BigQueryEmulatorContainerTest.java

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📝 Walkthrough

BigQueryEmulatorContainer now supports a configurable project ID. It defaults to test-project, applies a configured ID to the emulator command, and returns the configured value. Documentation and tests cover custom IDs and invalid values.

Changes: BigQuery emulator project ID

Layer / File(s)	Summary
Store and apply project IDs modules/gcloud/src/main/java/org/testcontainers/gcloud/BigQueryEmulatorContainer.java	The container initializes its project ID to test-project, applies valid configured IDs to the emulator command, and returns the stored ID.
Document and verify custom IDs docs/modules/gcloud.md, modules/gcloud/src/test/java/org/testcontainers/gcloud/BigQueryEmulatorContainerTest.java	The documentation describes the default and links to custom project ID usage. Tests check dataset access with a custom ID and rejection of null, empty, and whitespace-only IDs.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Feature

Suggested reviewers: eddumelendez

Merge Risk: ⚪ Minimal · up to d87fc

The change lets users configure the BigQuery emulator project ID while preserving the required startup argument. No concrete merge-blocking issue remains, so the PR is ready to merge subject to normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 10.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: allowing configuration of the BigQuery emulator project ID.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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Inline comments:
Review comments at
@modules/gcloud/src/main/java/org/testcontainers/gcloud/BigQueryEmulatorContainer.java:
- Around line 41-43: Update BigQueryEmulatorContainer.withProjectId to reject
null or empty project IDs with IllegalArgumentException before assigning
projectId or configuring the command; preserve the existing behavior for valid
IDs.

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: Repository UI
• Review profile: CHILL
• Plan: Advanced
• Run ID: 420188cd-a0f8-4f70-8318-78c8839d879c

📥 Commits

Reviewing files that changed from the base of the PR and between 6cc7f8d and 928c1dd.

📒 Files selected for processing: 3

• docs/modules/gcloud.md
• modules/gcloud/src/main/java/org/testcontainers/gcloud/BigQueryEmulatorContainer.java
• modules/gcloud/src/test/java/org/testcontainers/gcloud/BigQueryEmulatorContainerTest.java

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