[APM] Fix debug param issue (#19676)

* [APM] Fix debug param issue

* [APM] Fix _debug issue and add test

x-pack/plugins/apm/public/services/__test__/SessionStorageMock.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;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+export class SessionStorageMock {
+  store = {};
+
+  clear() {
+    this.store = {};
+  }
+
+  getItem(key) {
+    return this.store[key] || null;
+  }
+
+  setItem(key, value) {
+    this.store[key] = value.toString();
+  }
+
+  removeItem(key) {
+    delete this.store[key];
+  }
+}

x-pack/plugins/apm/public/services/__test__/rest.test.js

@@ -0,0 +1,79 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import * as kfetchModule from 'ui/kfetch';
+import { SessionStorageMock } from './SessionStorageMock';
+import { callApi } from '../rest';
+
+describe('rest', () => {
+  let kfetchSpy;
+
+  beforeEach(() => {
+    kfetchSpy = jest.spyOn(kfetchModule, 'kfetch').mockResolvedValue({
+      my_key: 'hello world'
+    });
+    global.sessionStorage = new SessionStorageMock();
+  });
+
+  afterEach(() => {
+    kfetchSpy.mockClear();
+  });
+
+  describe('callApi', () => {
+    describe('debug param', () => {
+      describe('when apm_debug is true', () => {
+        beforeEach(() => {
+          sessionStorage.setItem('apm_debug', 'true');
+        });
+
+        it('should add debug param for APM endpoints', async () => {
+          await callApi({ pathname: `/api/apm/status/server` });
+
+          expect(kfetchSpy).toHaveBeenCalledWith(
+            { pathname: '/api/apm/status/server', query: { _debug: true } },
+            { camelcase: true }
+          );
+        });
+
+        it('should not add debug param for non-APM endpoints', async () => {
+          await callApi({ pathname: `/api/kibana` });
+
+          expect(kfetchSpy).toHaveBeenCalledWith(
+            { pathname: '/api/kibana' },
+            { camelcase: true }
+          );
+        });
+      });
+    });
+
+    describe('camelcase', () => {
+      it('camelcase param should be true by default', async () => {
+        const res = await callApi({ pathname: `/api/kibana` });
+
+        expect(kfetchSpy).toHaveBeenCalledWith(
+          { pathname: '/api/kibana' },
+          { camelcase: true }
+        );
+
+        expect(res).toEqual({ myKey: 'hello world' });
+      });
+
+      it('should respect settings', async () => {
+        const res = await callApi(
+          { pathname: `/api/kibana` },
+          { camelcase: false }
+        );
+
+        expect(kfetchSpy).toHaveBeenCalledWith(
+          { pathname: '/api/kibana' },
+          { camelcase: false }
+        );
+
+        expect(res).toEqual({ my_key: 'hello world' });
+      });
+    });
+  });
+});

x-pack/plugins/apm/public/services/rest.js

@@ -7,25 +7,36 @@
 import 'isomorphic-fetch';
 import { camelizeKeys } from 'humps';
 import { kfetch } from 'ui/kfetch';
-import { memoize, isEmpty, first } from 'lodash';
+import { memoize, isEmpty, first, startsWith } from 'lodash';
 import chrome from 'ui/chrome';
 import { convertKueryToEsQuery } from './kuery';
 import { getFromSavedObject } from 'ui/index_patterns/static_utils';
 
-async function callApi(fetchOptions, kibanaOptions) {
+function fetchOptionsWithDebug(fetchOptions) {
+  const debugEnabled =
+    sessionStorage.getItem('apm_debug') === 'true' &&
+    startsWith(fetchOptions.pathname, '/api/apm');
+
+  if (!debugEnabled) {
+    return fetchOptions;
+  }
+
+  return {
+    ...fetchOptions,
+    query: {
+      ...fetchOptions.query,
+      _debug: true
+    }
+  };
+}
+
+export async function callApi(fetchOptions, kibanaOptions) {
   const combinedKibanaOptions = {
     camelcase: true,
     ...kibanaOptions
   };
 
-  const combinedFetchOptions = {
-    ...fetchOptions,
-    query: {
-      ...fetchOptions.query,
-      _debug: sessionStorage.getItem('apm_debug') || false
-    }
-  };
-
+  const combinedFetchOptions = fetchOptionsWithDebug(fetchOptions);
   const res = await kfetch(combinedFetchOptions, combinedKibanaOptions);
   return combinedKibanaOptions.camelcase ? camelizeKeys(res) : res;
 }