Tweak repl to be a bit more useful (#19395)

* Tweak repl to be a bit more useful:

- Start it earlier so it can be used to diagnose server boot bugs
- Retain kbnServer, etc when repl is cleared (`.clear`)
- Change default print depth so it doesn't bomb when printing kbnServer
- Allow print depth to be changed as previous bullet may be annoying

src/cli/repl/__snapshots__/repl.test.js.snap

@@ -1,19 +1,11 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`repl it allows print depth to be specified 1`] = `"{ '0': { '1': { '2': [Object] } }, whoops: [Circular] }"`;
+
 exports[`repl it colorizes raw values 1`] = `"{ meaning: 42 }"`;
 
 exports[`repl it handles deep and recursive objects 1`] = `
-"{ '0': 
-   { '1': 
-      { '2': 
-         { '3': 
-            { '4': 
-               { '5': 
-                  { '6': 
-                     { '7': 
-                        { '8': 
-                           { '9': 
-                              { '10': { '11': { '12': { '13': { '14': { '15': [Object] } } } } } } } } } } } } } } },
+"{ '0': { '1': { '2': { '3': { '4': { '5': [Object] } } } } },
   whoops: [Circular] }"
 `;
 
@@ -53,17 +45,7 @@ Array [
   Array [
     "Promise Rejected: 
 ",
-    "{ '0': 
-   { '1': 
-      { '2': 
-         { '3': 
-            { '4': 
-               { '5': 
-                  { '6': 
-                     { '7': 
-                        { '8': 
-                           { '9': 
-                              { '10': { '11': { '12': { '13': { '14': { '15': [Object] } } } } } } } } } } } } } } },
+    "{ '0': { '1': { '2': { '3': { '4': { '5': [Object] } } } } },
   whoops: [Circular] }",
   ],
 ]
@@ -77,17 +59,7 @@ Array [
   Array [
     "Promise Resolved: 
 ",
-    "{ '0': 
-   { '1': 
-      { '2': 
-         { '3': 
-            { '4': 
-               { '5': 
-                  { '6': 
-                     { '7': 
-                        { '8': 
-                           { '9': 
-                              { '10': { '11': { '12': { '13': { '14': { '15': [Object] } } } } } } } } } } } } } } },
+    "{ '0': { '1': { '2': { '3': { '4': { '5': [Object] } } } } },
   whoops: [Circular] }",
   ],
 ]

src/cli/repl/index.js

@@ -20,6 +20,8 @@
 import repl from 'repl';
 import util from 'util';
 
+const PRINT_DEPTH = 5;
+
 /**
  * Starts an interactive REPL with a global `server` object.
  *
@@ -29,18 +31,27 @@ export function startRepl(kbnServer) {
   const replServer = repl.start({
     prompt: 'Kibana> ',
     useColors: true,
-    writer: promiseFriendlyWriter(() => replServer.displayPrompt()),
+    writer: promiseFriendlyWriter({
+      displayPrompt: () => replServer.displayPrompt(),
+      getPrintDepth: () => replServer.context.repl.printDepth,
+    }),
   });
 
-  replServer.context.kbnServer = kbnServer;
-  replServer.context.server = kbnServer.server;
-  replServer.context.repl = {
-    print(obj, depth = null) {
-      console.log(promisePrint(obj, () => replServer.displayPrompt(), depth));
-      return '';
-    },
+  const initializeContext = () => {
+    replServer.context.kbnServer = kbnServer;
+    replServer.context.server = kbnServer.server;
+    replServer.context.repl = {
+      printDepth: PRINT_DEPTH,
+      print(obj, depth = null) {
+        console.log(promisePrint(obj, () => replServer.displayPrompt(), () => depth));
+        return '';
+      },
+    };
   };
 
+  initializeContext();
+  replServer.on('reset', initializeContext);
+
   return replServer;
 }
 
@@ -54,12 +65,12 @@ function prettyPrint(text, o, depth) {
 
 // This lets us handle promises more gracefully than the default REPL,
 // which doesn't show the results.
-function promiseFriendlyWriter(displayPrompt) {
-  const PRINT_DEPTH = 15;
-  return (result) => promisePrint(result, displayPrompt, PRINT_DEPTH);
+function promiseFriendlyWriter({ displayPrompt, getPrintDepth }) {
+  return (result) => promisePrint(result, displayPrompt, getPrintDepth);
 }
 
-function promisePrint(result, displayPrompt, depth) {
+function promisePrint(result, displayPrompt, getPrintDepth) {
+  const depth = getPrintDepth();
   if (result && typeof result.then === 'function') {
     // Bit of a hack to encourage the user to wait for the result of a promise
     // by printing text out beside the current prompt.

src/cli/repl/repl.test.js

@@ -21,14 +21,29 @@ jest.mock('repl', () => ({ start: (opts) => ({ opts, context: {} }) }), { virtua
 
 describe('repl', () => {
   const originalConsoleLog = console.log;
+  let mockRepl;
 
   beforeEach(() => {
     global.console.log = jest.fn();
     require('repl').start = (opts) => {
-      return {
+      let resetHandler;
+      const replServer = {
         opts,
         context: { },
+        on: jest.fn((eventName, handler) => {
+          expect(eventName).toBe('reset');
+          resetHandler = handler;
+        }),
       };
+
+      mockRepl = {
+        replServer,
+        clear() {
+          replServer.context = {};
+          resetHandler(replServer.context);
+        },
+      };
+      return replServer;
     };
   });
 
@@ -79,6 +94,37 @@ describe('repl', () => {
       .toMatchSnapshot();
   });
 
+  test('it allows print depth to be specified', () => {
+    const { startRepl } = require('.');
+    const replServer = startRepl({});
+    const splosion = {};
+    let child = splosion;
+    for (let i = 0; i < 2000; ++i) {
+      child[i] = {};
+      child = child[i];
+    }
+    splosion.whoops = splosion;
+    replServer.context.repl.printDepth = 2;
+    expect(replServer.opts.writer(splosion))
+      .toMatchSnapshot();
+  });
+
+  test('resets context to original when reset', () => {
+    const { startRepl } = require('.');
+    const testServer = {
+      server: { },
+    };
+    const replServer = startRepl(testServer);
+    replServer.context.foo = 'bar';
+    expect(replServer.context.server).toBe(testServer.server);
+    expect(replServer.context.kbnServer).toBe(testServer);
+    expect(replServer.context.foo).toBe('bar');
+    mockRepl.clear();
+    expect(replServer.context.server).toBe(testServer.server);
+    expect(replServer.context.kbnServer).toBe(testServer);
+    expect(replServer.context.foo).toBeUndefined();
+  });
+
   test('it prints promise resolves', async () => {
     const { startRepl } = require('.');
     const replServer = startRepl({});

src/cli/serve/serve.js

@@ -217,6 +217,9 @@ export default function (program) {
       const KbnServer = require('../../server/kbn_server');
       try {
         kbnServer = new KbnServer(settings);
+        if (shouldStartRepl(opts)) {
+          startRepl(kbnServer);
+        }
         await kbnServer.ready();
       } catch (error) {
         const { server } = kbnServer;
@@ -248,10 +251,6 @@ export default function (program) {
         kbnServer.server.log(['info', 'config'], 'Reloaded logging configuration due to SIGHUP.');
       });
 
-      if (shouldStartRepl(opts)) {
-        startRepl(kbnServer);
-      }
-
       return kbnServer;
     });
 }