Improve architecture detection efficiency and centralization in JupyterLab tests

[coderabbitai]

Problem Description

The current architecture detection implementation in tests/containers/workbenches/jupyterlab/jupyterlab_test.py is inefficient and lacks centralization:

Current Issues

1. Performance Inefficiency: The test_pdf_export method starts and stops a container solely for architecture detection (uname -m) on every test run
2. Code Duplication: Architecture detection logic will likely be duplicated across multiple test methods as more architecture-specific limitations are discovered
3. No Central Configuration: Architecture-specific feature limitations (like PDF export on s390x) are scattered throughout the codebase without a single authoritative source

Impact Analysis

• Unnecessary container overhead on every test execution
• Potential for inconsistent architecture handling across different tests
• Maintenance burden when adding new architecture-specific limitations
• Reduced test suite performance due to redundant container operations

Solution Options

Option 1: Helper Function with Session Caching

Create a helper function with pytest session-level caching:

@pytest.fixture(scope="session")
def container_architecture(jupyterlab_image):
    """Cache architecture detection per test session."""
    container = WorkbenchContainer(image=jupyterlab_image.name, user=4321, group_add=[0])
    container.start(wait_for_readiness=False)
    try:
        exit_code, arch_output = container.exec(["uname", "-m"])
        if exit_code == 0:
            return arch_output.decode().strip()
        return None
    finally:
        docker_utils.NotebookContainer(container).stop(timeout=0)

Option 2: Centralized Architecture Configuration

Create a configuration module for architecture-specific limitations:

# tests/containers/architecture_support.py
ARCHITECTURE_LIMITATIONS = {
    "s390x": {
        "pdf_export": False,
        "reason": "TexLive and Pandoc dependencies not available"
    }
}

def is_feature_supported(architecture: str, feature: str) -> bool:
    return ARCHITECTURE_LIMITATIONS.get(architecture, {}).get(feature, True)

Option 3: Hybrid Approach

Combine both solutions for maximum efficiency and maintainability:

• Session-cached architecture detection
• Centralized feature limitation configuration
• Helper functions for common architecture checks

Acceptance Criteria

Core Requirements

• Eliminate redundant container start/stop cycles for architecture detection
• Create centralized configuration for architecture-specific feature limitations
• Implement helper functions for common architecture checks
• Maintain backward compatibility with existing test behavior

Performance Requirements

• Architecture detection should occur only once per test session
• Test execution time should be reduced compared to current implementation
• Container resource usage should be minimized

Maintainability Requirements

• Single authoritative source for architecture limitations
• Easy addition of new architecture-specific constraints
• Clear documentation of architecture support matrix
• Consistent architecture handling across all test methods

Testing Requirements

• Verify architecture detection works correctly on x86_64, arm64, and s390x
• Ensure PDF export tests still skip appropriately on s390x
• Confirm no regression in existing test functionality
• Test session caching behavior

Implementation Guidance

Phase 1: Helper Functions

1. Create tests/containers/architecture_utils.py with detection helpers
2. Implement session-level caching for architecture detection
3. Update test_pdf_export to use new helper functions

Phase 2: Centralized Configuration

1. Create tests/containers/architecture_support.py configuration module
2. Define architecture limitation mappings
3. Implement feature support checking functions

Phase 3: Integration and Testing

1. Update all architecture-dependent tests to use new infrastructure
2. Add comprehensive test coverage for architecture detection utilities
3. Document architecture support matrix

Related Files

• tests/containers/workbenches/jupyterlab/jupyterlab_test.py (primary file)
• jupyter/utils/install_pdf_deps.sh (s390x PDF limitation source)
• Future test files that may need architecture-specific behavior

Context

• PR: Disable PDF export for s390x architecture in Jupyter Minimal images #1521 (Disable PDF export for s390x architecture in Jupyter Minimal images)
• Comment: Disable PDF export for s390x architecture in Jupyter Minimal images #1521 (comment)
• Requested by: @jiridanek