refactor: update jest transformer configuration in kbn-test

The whole point of this change is to make babel-jest transform options
shared and reusable by other packages' jest.config transforms that need
to add their own custom stuff. For example here
ecs_data_quality_dashboard
makes use of that to add @emotion/babel-preset-css-prop that is needed
to properly compile emotion css prop in jest tests.

packages/kbn-test/jest-preset.js

@@ -98,7 +98,7 @@ module.exports = {
 
   // A map from regular expressions to paths to transformers
   transform: {
-    '^.+\\.(js|tsx?)$': '<rootDir>/packages/kbn-test/src/jest/transforms/babel.js',
+    '^.+\\.(js|tsx?)$': '<rootDir>/packages/kbn-test/src/jest/transforms/babel/index.js',
     '^.+\\.(txt|html)?$': '<rootDir>/packages/kbn-test/src/jest/transforms/raw.js',
     '^.+\\.peggy?$': '<rootDir>/packages/kbn-test/src/jest/transforms/peggy.js',
   },

packages/kbn-test/src/jest/transforms/babel/index.js

@@ -0,0 +1,13 @@
+/*
+ * 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".
+ */
+
+const babelJest = require('babel-jest');
+const transformerConfig = require('./transformer_config');
+
+module.exports = babelJest.default.createTransformer(transformerConfig);

packages/kbn-test/src/jest/transforms/babel.js → packages/kbn-test/src/jest/transforms/babel/transformer_config.js

@@ -7,9 +7,7 @@
  * License v3.0 only", or the "Server Side Public License, v 1".
  */
 
-const babelJest = require('babel-jest');
-
-module.exports = babelJest.default.createTransformer({
+module.exports = {
   presets: [
     [
       require.resolve('@kbn/babel-preset/node_preset'),
@@ -21,11 +19,5 @@ module.exports = babelJest.default.createTransformer({
         },
       },
     ],
-    [
-      require.resolve('@emotion/babel-preset-css-prop'),
-      {
-        labelFormat: '[filename]--[local]',
-      },
-    ],
   ],
-});
+};

x-pack/solutions/security/packages/ecs_data_quality_dashboard/jest.config.js

@@ -5,6 +5,9 @@
  * 2.0.
  */
 
+// eslint-disable-next-line import/no-extraneous-dependencies
+const rootConfig = require('@kbn/test/jest-preset');
+
 module.exports = {
   coverageDirectory:
     '<rootDir>/target/kibana-coverage/jest/x-pack/solutions/security/packages/ecs_data_quality_dashboard_impl',
@@ -23,4 +26,9 @@ module.exports = {
   setupFilesAfterEnv: [
     '<rootDir>/x-pack/solutions/security/packages/ecs_data_quality_dashboard/setup_tests.ts',
   ],
+  transform: {
+    ...rootConfig.transform,
+    '^.+\\.(js|tsx?)$':
+      '<rootDir>/x-pack/solutions/security/packages/ecs_data_quality_dashboard/jest/babel-transformer.js',
+  },
 };

x-pack/solutions/security/packages/ecs_data_quality_dashboard/jest/babel-transformer.js

@@ -0,0 +1,25 @@
+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+// eslint-disable-next-line import/no-extraneous-dependencies
+const babelJest = require('babel-jest');
+
+// eslint-disable-next-line import/no-extraneous-dependencies
+const rootTransformerConfig = require('@kbn/test/src/jest/transforms/babel/transformer_config');
+
+module.exports = babelJest.default.createTransformer({
+  ...rootTransformerConfig,
+  presets: [
+    ...rootTransformerConfig.presets,
+    [
+      require.resolve('@emotion/babel-preset-css-prop'),
+      {
+        labelFormat: '[filename]--[local]',
+      },
+    ],
+  ],
+});