[Jest] Lazy core mocks (elastic#235003)

Closes elastic#235079

Lazily instantiate core mocks, to relieve memory pressure. This has the
benefit of tests using less memory usage, and thus us being able to run
them in parallel without upsizing our CI workers, and CPU time spent on
garbage collection goes down. Here's how it affects one of the alerting
plugin test files, significant improvements across the board:

```stdout
Benchmark diff: cwd -> f69f92
cwd: [Jest] Lazily instantiate mocks
f69f92: [Agent Builder] Setup doclinks structure (elastic#235804)
alerting-plugin-test
-
                         cwd            f69f92                    Δ                   CI 
 Duration         6.3s ±1.7%        7.0s ±1.8%       711ms (+11.3%)    95%, +7.9%–+14.8% 
 CPU Usage        6.5s ±2.0%        7.4s ±2.1%       852ms (+13.1%)    95%, +9.1%–+17.2% 
 Max RSS     857.90 MB ±1.3%   977.20 MB ±2.4%   119.30 MB (+13.9%)   95%, +10.3%–+17.6% 
 GC time         190ms ±4.4%       252ms ±3.4%        62ms (+32.6%)   95%, +23.8%–+42.0%
 ```
 
### How it works

Core mocks are instantiated using `lazyObject`. This is a helper utility that will be rewritten using a Babel plugin to create annotated getters that will only instantiate the mock when it is accessed.

### Why it helps

Core mocks are eagerly created, and this means that many objects will be allocated. Specifically, jest will keep mocks in a global registry to support `jest.clearAllMocks()`. This means only when a test file completes these functions will be garbage collected. Increased memory consumption has two consequences that are relevant in this context:

- they increase memory pressure, which means garbage collection has to run more frequently to prevent the process from running out of memory
- our CI workers (that run Jest tests) have 16gb of memory. running jest configs in parallel means that there currently is a risk that either the processes themselves run out of memory, or the agent will. if we reduce memory usage, we can run them in parallel.

---------

Co-authored-by: kibanamachine <[email protected]>

Author: dgieselaar

.github/CODEOWNERS

@@ -1796,6 +1796,7 @@ x-pack/platform/plugins/shared/ml/server/models/data_recognizer/modules/security
 /.eslintrc.js @elastic/kibana-operations
 /.eslintignore @elastic/kibana-operations
 /.ci/.storybook @elastic/kibana-operations
+/src/platform/packages/shared/kbn-lazy-object @elastic/kibana-operations @elastic/obs-ui-devex-team
 
 # QA - Appex QA
 .buildkite/scout_ci_config.yml @elastic/appex-qa

package.json

@@ -1587,6 +1587,7 @@
     "@kbn/json-ast": "link:packages/kbn-json-ast",
     "@kbn/kbn-genai-cli": "link:x-pack/solutions/observability/packages/kbn-genai-cli",
     "@kbn/kibana-manifest-schema": "link:packages/kbn-kibana-manifest-schema",
+    "@kbn/lazy-object": "link:src/platform/packages/shared/kbn-lazy-object",
     "@kbn/lint-packages-cli": "link:packages/kbn-lint-packages-cli",
     "@kbn/lint-ts-projects-cli": "link:packages/kbn-lint-ts-projects-cli",
     "@kbn/managed-vscode-config": "link:packages/kbn-managed-vscode-config",

packages/kbn-babel-preset/common_preset.js

@@ -14,8 +14,8 @@ module.exports = (api) => ({
     // our explicit plugin configs to a sub-preset
     {
       plugins: [
+        require.resolve('@kbn/lazy-object/src/plugin/lazy_babel_plugin'),
         require.resolve('babel-plugin-add-module-exports'),
-
         // The class properties proposal was merged with the private fields proposal
         // into the "class fields" proposal. Babel doesn't support this combined
         // proposal yet, which includes private field, so this transform is

src/core/packages/analytics/browser-internal/src/analytics_service.test.mocks.ts

@@ -9,8 +9,9 @@
 
 import type { AnalyticsClient } from '@elastic/ebt/client';
 import { Subject } from 'rxjs';
+import { lazyObject } from '@kbn/lazy-object';
 
-export const analyticsClientMock: jest.Mocked<AnalyticsClient> = {
+export const analyticsClientMock: jest.Mocked<AnalyticsClient> = lazyObject({
   optIn: jest.fn(),
   reportEvent: jest.fn(),
   registerEventType: jest.fn(),
@@ -20,7 +21,7 @@ export const analyticsClientMock: jest.Mocked<AnalyticsClient> = {
   telemetryCounter$: new Subject(),
   flush: jest.fn(),
   shutdown: jest.fn(),
-};
+});
 
 jest.doMock('@elastic/ebt/client', () => ({
   createAnalytics: () => analyticsClientMock,

src/core/packages/analytics/browser-internal/tsconfig.json

@@ -11,7 +11,8 @@
     "@kbn/core-injected-metadata-browser-internal",
     "@kbn/core-analytics-browser",
     "@kbn/core-base-browser-mocks",
-    "@kbn/core-injected-metadata-browser-mocks"
+    "@kbn/core-injected-metadata-browser-mocks",
+    "@kbn/lazy-object"
   ],
   "exclude": ["target/**/*"]
 }

src/core/packages/analytics/browser-mocks/src/analytics_service.mock.ts

@@ -11,35 +11,36 @@ import { Subject } from 'rxjs';
 import type { PublicMethodsOf } from '@kbn/utility-types';
 import type { AnalyticsServiceSetup, AnalyticsServiceStart } from '@kbn/core-analytics-browser';
 import type { AnalyticsService } from '@kbn/core-analytics-browser-internal';
+import { lazyObject } from '@kbn/lazy-object';
 
 type AnalyticsServiceContract = PublicMethodsOf<AnalyticsService>;
 
 const createAnalyticsServiceSetup = (): jest.Mocked<AnalyticsServiceSetup> => {
-  return {
+  return lazyObject({
     optIn: jest.fn(),
     reportEvent: jest.fn(),
     registerEventType: jest.fn(),
     registerContextProvider: jest.fn(),
     removeContextProvider: jest.fn(),
     registerShipper: jest.fn(),
     telemetryCounter$: new Subject(),
-  };
+  });
 };
 
 const createAnalyticsServiceStart = (): jest.Mocked<AnalyticsServiceStart> => {
-  return {
+  return lazyObject({
     optIn: jest.fn(),
     reportEvent: jest.fn(),
     telemetryCounter$: new Subject(),
-  };
+  });
 };
 
 const createAnalyticsServiceMock = (): jest.Mocked<AnalyticsServiceContract> => {
-  return {
+  return lazyObject({
     setup: jest.fn().mockImplementation(createAnalyticsServiceSetup),
     start: jest.fn().mockImplementation(createAnalyticsServiceStart),
     stop: jest.fn(),
-  };
+  });
 };
 
 export const analyticsServiceMock = {

src/core/packages/analytics/browser-mocks/tsconfig.json

@@ -13,7 +13,8 @@
   "kbn_references": [
     "@kbn/utility-types",
     "@kbn/core-analytics-browser",
-    "@kbn/core-analytics-browser-internal"
+    "@kbn/core-analytics-browser-internal",
+    "@kbn/lazy-object"
   ],
   "exclude": [
     "target/**/*",

src/core/packages/analytics/server-internal/src/analytics_service.test.mocks.ts

@@ -9,8 +9,9 @@
 
 import type { AnalyticsClient } from '@elastic/ebt/client';
 import { Subject } from 'rxjs';
+import { lazyObject } from '@kbn/lazy-object';
 
-export const analyticsClientMock: jest.Mocked<AnalyticsClient> = {
+export const analyticsClientMock: jest.Mocked<AnalyticsClient> = lazyObject({
   optIn: jest.fn(),
   reportEvent: jest.fn(),
   registerEventType: jest.fn(),
@@ -20,7 +21,7 @@ export const analyticsClientMock: jest.Mocked<AnalyticsClient> = {
   telemetryCounter$: new Subject(),
   shutdown: jest.fn(),
   flush: jest.fn(),
-};
+});
 
 jest.doMock('@elastic/ebt/client', () => ({
   createAnalytics: () => analyticsClientMock,

src/core/packages/analytics/server-internal/tsconfig.json

@@ -15,7 +15,8 @@
     "@kbn/core-base-server-internal",
     "@kbn/core-analytics-server",
     "@kbn/config-mocks",
-    "@kbn/core-base-server-mocks"
+    "@kbn/core-base-server-mocks",
+    "@kbn/lazy-object"
   ],
   "exclude": [
     "target/**/*",

src/core/packages/analytics/server-mocks/src/analytics_service.mock.ts

@@ -15,48 +15,49 @@ import type {
   AnalyticsServicePreboot,
 } from '@kbn/core-analytics-server';
 import type { AnalyticsService } from '@kbn/core-analytics-server-internal';
+import { lazyObject } from '@kbn/lazy-object';
 
 type AnalyticsServiceContract = PublicMethodsOf<AnalyticsService>;
 
 const createAnalyticsServicePreboot = (): jest.Mocked<AnalyticsServicePreboot> => {
-  return {
+  return lazyObject({
     optIn: jest.fn(),
     reportEvent: jest.fn(),
     registerEventType: jest.fn(),
     registerContextProvider: jest.fn(),
     removeContextProvider: jest.fn(),
     registerShipper: jest.fn(),
     telemetryCounter$: new Subject(),
-  };
+  });
 };
 
 const createAnalyticsServiceSetup = (): jest.Mocked<AnalyticsServiceSetup> => {
-  return {
+  return lazyObject({
     optIn: jest.fn(),
     reportEvent: jest.fn(),
     registerEventType: jest.fn(),
     registerContextProvider: jest.fn(),
     removeContextProvider: jest.fn(),
     registerShipper: jest.fn(),
     telemetryCounter$: new Subject(),
-  };
+  });
 };
 
 const createAnalyticsServiceStart = (): jest.Mocked<AnalyticsServiceStart> => {
-  return {
+  return lazyObject({
     optIn: jest.fn(),
     reportEvent: jest.fn(),
     telemetryCounter$: new Subject(),
-  };
+  });
 };
 
 const createAnalyticsServiceMock = (): jest.Mocked<AnalyticsServiceContract> => {
-  return {
+  return lazyObject({
     preboot: jest.fn().mockImplementation(createAnalyticsServicePreboot),
     setup: jest.fn().mockImplementation(createAnalyticsServiceSetup),
     start: jest.fn().mockImplementation(createAnalyticsServiceStart),
     stop: jest.fn(),
-  };
+  });
 };
 
 export const analyticsServiceMock = {