[9.2] [CI] Filter empty jest tests before grouping (#242440)

.buildkite/pipeline-utils/ci-stats/get_tests_from_config.ts

@@ -0,0 +1,58 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+import { readConfig } from 'jest-config';
+import { SearchSource } from 'jest';
+import Runtime from 'jest-runtime';
+import { resolve } from 'path';
+import { getKibanaDir, runBatchedPromises } from '#pipeline-utils';
+
+export async function getTestsFromJestConfig(configPath: string): Promise<string[]> {
+  try {
+    const emptyArgv = {
+      $0: '',
+      _: [],
+    };
+    const config = await readConfig(emptyArgv, configPath);
+    const searchSource = new SearchSource(
+      await Runtime.createContext(config.projectConfig, {
+        maxWorkers: 1,
+        watchman: false,
+        watch: false,
+        console: {
+          ...console,
+          warn() {
+            // ignore haste-map warnings
+          },
+        },
+      })
+    );
+
+    const results = await searchSource.getTestPaths(config.globalConfig, config.projectConfig);
+    return results.tests.map((t) => t.path);
+  } catch (error) {
+    console.error(
+      `Error while resolving test files from config: ${configPath} - validate your config.`
+    );
+    throw error;
+  }
+}
+
+export async function filterEmptyJestConfigs(
+  jestUnitConfigsWithEmpties: string[],
+  maxParallelism = 1
+): Promise<string[]> {
+  const promiseThunks = jestUnitConfigsWithEmpties.map((configPath) => async () => {
+    const kibanaRelativePath = resolve(getKibanaDir(), configPath);
+    const testFiles = await getTestsFromJestConfig(kibanaRelativePath);
+    return testFiles?.length > 0 ? [configPath] : [];
+  });
+  const nonEmptyConfigPaths = await runBatchedPromises(promiseThunks, maxParallelism);
+  // flat-mapping works better type-wise than filtering an Array<string | null>
+  return nonEmptyConfigPaths.flat();
+}

.buildkite/pipeline-utils/ci-stats/index.ts

@@ -12,3 +12,4 @@ export * from './on_complete';
 export * from './on_metrics_viable';
 export * from './on_start';
 export * from './pick_test_group_run_order';
+export * from './get_tests_from_config';