ci: guard empty matrix categories in integration test workflow

[musa-asad]

Background

The CloudWatch Agent integration tests run in GitHub Actions. A single workflow (test-artifacts.yml) generates test matrices: one per platform category (EC2 Linux, Windows, Darwin, ECS, EKS, etc.): and feeds each matrix to a downstream job that spins up the test infrastructure.

The workflow supports filtered runs: a human can dispatch it with test_dir_filter or test_os_filter to run only a subset of tests. When a filter is applied, categories that have no matching tests are reduced to an empty array [].

Problem

GitHub Actions requires every matrix to contain at least one entry. When a filtered dispatch empties a category, the downstream job tries to expand fromJson('[]') as a matrix and fails immediately:

Error when evaluating 'strategy' for job 'EC2WinIntegrationTest':
Matrix vector 'arrays' does not contain any values

The job is never created, the workflow run is marked failure, and the error message gives no indication that the failure is expected (the filter simply did not match any tests in that category).

This affects every matrix-consumer job that lacks an emptiness guard: 15 jobs in total across all platform categories. Unfiltered runs (cron, bot) are not affected because all categories stay populated.

Changes

test-artifacts.yml: one line added per job:

if: ${{ needs.GenerateTestMatrix.outputs.<category>_matrix != '[]' }}

When the matrix is empty, the job is cleanly skipped (green checkmark, no error). When the matrix is populated, the guard evaluates to true and has no effect.

Jobs guarded:

Job	Matrix variable
EC2LinuxIntegrationTest-0	ec2_linux_matrix_0
EC2NvidiaGPUIntegrationTest	ec2_gpu_matrix
LinuxOnPremIntegrationTest	ec2_linux_onprem_matrix
EC2SELinuxIntegrationTest	ec2_selinux_matrix
EC2LinuxIntegrationTestITAR	ec2_linux_itar_matrix
EC2LinuxIntegrationTestCN	ec2_linux_china_matrix
EC2WinIntegrationTest	ec2_windows_matrix
EC2DarwinIntegrationTest	ec2_mac_matrix
ECSEC2IntegrationTest	ecs_ec2_launch_daemon_matrix
ECSFargateIntegrationTest	ecs_fargate_matrix
EKSIntegrationTest	eks_daemon_matrix
EKSPrometheusIntegrationTest	eks_deployment_matrix
PerformanceTrackingTest	ec2_performance_matrix
EC2WinPerformanceTest	ec2_windows_performance_matrix
StressTrackingTest	ec2_stress_matrix
EC2WinStressTrackingTest	ec2_windows_stress_matrix
GPUEndToEndTest	eks_addon_matrix

Also fixed: LinuxOnPremIntegrationTest was missing StartLocalStack in its needs list, causing it to reference a LocalStack output that was not yet available.

Testing

$ grep -c "!= '[]'" .github/workflows/test-artifacts.yml
20
$ python3 -c "import yaml; yaml.safe_load(open('.github/workflows/test-artifacts.yml')); print('YAML OK')"
YAML OK

Validated on a full PR Test run: 318 jobs pass, no matrix expansion failures.

[github-actions]

This PR was marked stale due to lack of activity.