repl: add repl.setupHistory for programmatic repl

Adds a `repl.setupHistory()` instance method so that
programmatic REPLs can also write history to a file.

This change also refactors all of the history file
management to `lib/internal/repl/history.js`, cleaning
up and simplifying `lib/internal/repl.js`.

PR-URL: https://github.com/nodejs/node/pull/25895
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

3 files changed, 160 insertions, 158 deletions

diff --git a/lib/internal/repl.js b/lib/internal/repl.js
index e58752e76e..321f4ab29e 100644
--- a/lib/internal/repl.js
+++ b/lib/internal/repl.js
@@ -1,24 +1,10 @@
 'use strict';
 
-const { Interface } = require('readline');
 const REPL = require('repl');
-const path = require('path');
-const fs = require('fs');
-const os = require('os');
-const util = require('util');
-const debug = util.debuglog('repl');
+
 module.exports = Object.create(REPL);
 module.exports.createInternalRepl = createRepl;
 
-// XXX(chrisdickinson): The 15ms debounce value is somewhat arbitrary.
-// The debounce is to guard against code pasted into the REPL.
-const kDebounceHistoryMS = 15;
-
-function _writeToOutput(repl, message) {
-  repl._writeToOutput(message);
-  repl._refreshLine();
-}
-
 function createRepl(env, opts, cb) {
   if (typeof opts === 'function') {
     cb = opts;
@@ -55,151 +41,9 @@ function createRepl(env, opts, cb) {
   if (!Number.isNaN(historySize) && historySize > 0) {
     opts.historySize = historySize;
   } else {
-    // XXX(chrisdickinson): set here to avoid affecting existing applications
-    // using repl instances.
     opts.historySize = 1000;
   }
 
   const repl = REPL.start(opts);
-  if (opts.terminal) {
-    return setupHistory(repl, env.NODE_REPL_HISTORY, cb);
-  }
-
-  repl._historyPrev = _replHistoryMessage;
-  cb(null, repl);
-}
-
-function setupHistory(repl, historyPath, ready) {
-  // Empty string disables persistent history
-  if (typeof historyPath === 'string')
-    historyPath = historyPath.trim();
-
-  if (historyPath === '') {
-    repl._historyPrev = _replHistoryMessage;
-    return ready(null, repl);
-  }
-
-  if (!historyPath) {
-    try {
-      historyPath = path.join(os.homedir(), '.node_repl_history');
-    } catch (err) {
-      _writeToOutput(repl, '\nError: Could not get the home directory.\n' +
-                     'REPL session history will not be persisted.\n');
-
-      debug(err.stack);
-      repl._historyPrev = _replHistoryMessage;
-      return ready(null, repl);
-    }
-  }
-
-  var timer = null;
-  var writing = false;
-  var pending = false;
-  repl.pause();
-  // History files are conventionally not readable by others:
-  // https://github.com/nodejs/node/issues/3392
-  // https://github.com/nodejs/node/pull/3394
-  fs.open(historyPath, 'a+', 0o0600, oninit);
-
-  function oninit(err, hnd) {
-    if (err) {
-      // Cannot open history file.
-      // Don't crash, just don't persist history.
-      _writeToOutput(repl, '\nError: Could not open history file.\n' +
-                           'REPL session history will not be persisted.\n');
-      debug(err.stack);
-
-      repl._historyPrev = _replHistoryMessage;
-      repl.resume();
-      return ready(null, repl);
-    }
-    fs.close(hnd, onclose);
-  }
-
-  function onclose(err) {
-    if (err) {
-      return ready(err);
-    }
-    fs.readFile(historyPath, 'utf8', onread);
-  }
-
-  function onread(err, data) {
-    if (err) {
-      return ready(err);
-    }
-
-    if (data) {
-      repl.history = data.split(/[\n\r]+/, repl.historySize);
-    } else {
-      repl.history = [];
-    }
-
-    fs.open(historyPath, 'r+', onhandle);
-  }
-
-  function onhandle(err, hnd) {
-    if (err) {
-      return ready(err);
-    }
-    fs.ftruncate(hnd, 0, (err) => {
-      repl._historyHandle = hnd;
-      repl.on('line', online);
-
-      // Reading the file data out erases it
-      repl.once('flushHistory', function() {
-        repl.resume();
-        ready(null, repl);
-      });
-      flushHistory();
-    });
-  }
-
-  // ------ history listeners ------
-  function online() {
-    repl._flushing = true;
-
-    if (timer) {
-      clearTimeout(timer);
-    }
-
-    timer = setTimeout(flushHistory, kDebounceHistoryMS);
-  }
-
-  function flushHistory() {
-    timer = null;
-    if (writing) {
-      pending = true;
-      return;
-    }
-    writing = true;
-    const historyData = repl.history.join(os.EOL);
-    fs.write(repl._historyHandle, historyData, 0, 'utf8', onwritten);
-  }
-
-  function onwritten(err, data) {
-    writing = false;
-    if (pending) {
-      pending = false;
-      online();
-    } else {
-      repl._flushing = Boolean(timer);
-      if (!repl._flushing) {
-        repl.emit('flushHistory');
-      }
-    }
-  }
-}
-
-
-function _replHistoryMessage() {
-  if (this.history.length === 0) {
-    _writeToOutput(
-      this,
-      '\nPersistent history support disabled. ' +
-        'Set the NODE_REPL_HISTORY environment\nvariable to ' +
-        'a valid, user-writable path to enable.\n'
-    );
-  }
-  this._historyPrev = Interface.prototype._historyPrev;
-  return this._historyPrev();
+  repl.setupHistory(opts.terminal ? env.NODE_REPL_HISTORY : '', cb);
 }
diff --git a/lib/internal/repl/history.js b/lib/internal/repl/history.js
new file mode 100644
index 0000000000..a0ae07441e
--- /dev/null
+++ b/lib/internal/repl/history.js
@@ -0,0 +1,153 @@
+'use strict';
+
+const { Interface } = require('readline');
+const path = require('path');
+const fs = require('fs');
+const os = require('os');
+const util = require('util');
+const debug = util.debuglog('repl');
+
+// XXX(chrisdickinson): The 15ms debounce value is somewhat arbitrary.
+// The debounce is to guard against code pasted into the REPL.
+const kDebounceHistoryMS = 15;
+
+module.exports = setupHistory;
+
+function _writeToOutput(repl, message) {
+  repl._writeToOutput(message);
+  repl._refreshLine();
+}
+
+function setupHistory(repl, historyPath, ready) {
+  // Empty string disables persistent history
+  if (typeof historyPath === 'string')
+    historyPath = historyPath.trim();
+
+  if (historyPath === '') {
+    repl._historyPrev = _replHistoryMessage;
+    return ready(null, repl);
+  }
+
+  if (!historyPath) {
+    try {
+      historyPath = path.join(os.homedir(), '.node_repl_history');
+    } catch (err) {
+      _writeToOutput(repl, '\nError: Could not get the home directory.\n' +
+        'REPL session history will not be persisted.\n');
+
+      debug(err.stack);
+      repl._historyPrev = _replHistoryMessage;
+      return ready(null, repl);
+    }
+  }
+
+  var timer = null;
+  var writing = false;
+  var pending = false;
+  repl.pause();
+  // History files are conventionally not readable by others:
+  // https://github.com/nodejs/node/issues/3392
+  // https://github.com/nodejs/node/pull/3394
+  fs.open(historyPath, 'a+', 0o0600, oninit);
+
+  function oninit(err, hnd) {
+    if (err) {
+      // Cannot open history file.
+      // Don't crash, just don't persist history.
+      _writeToOutput(repl, '\nError: Could not open history file.\n' +
+        'REPL session history will not be persisted.\n');
+      debug(err.stack);
+
+      repl._historyPrev = _replHistoryMessage;
+      repl.resume();
+      return ready(null, repl);
+    }
+    fs.close(hnd, onclose);
+  }
+
+  function onclose(err) {
+    if (err) {
+      return ready(err);
+    }
+    fs.readFile(historyPath, 'utf8', onread);
+  }
+
+  function onread(err, data) {
+    if (err) {
+      return ready(err);
+    }
+
+    if (data) {
+      repl.history = data.split(/[\n\r]+/, repl.historySize);
+    } else {
+      repl.history = [];
+    }
+
+    fs.open(historyPath, 'r+', onhandle);
+  }
+
+  function onhandle(err, hnd) {
+    if (err) {
+      return ready(err);
+    }
+    fs.ftruncate(hnd, 0, (err) => {
+      repl._historyHandle = hnd;
+      repl.on('line', online);
+
+      // Reading the file data out erases it
+      repl.once('flushHistory', function() {
+        repl.resume();
+        ready(null, repl);
+      });
+      flushHistory();
+    });
+  }
+
+  // ------ history listeners ------
+  function online(line) {
+    repl._flushing = true;
+
+    if (timer) {
+      clearTimeout(timer);
+    }
+
+    timer = setTimeout(flushHistory, kDebounceHistoryMS);
+  }
+
+  function flushHistory() {
+    timer = null;
+    if (writing) {
+      pending = true;
+      return;
+    }
+    writing = true;
+    const historyData = repl.history.join(os.EOL);
+    fs.write(repl._historyHandle, historyData, 0, 'utf8', onwritten);
+  }
+
+  function onwritten(err, data) {
+    writing = false;
+    if (pending) {
+      pending = false;
+      online();
+    } else {
+      repl._flushing = Boolean(timer);
+      if (!repl._flushing) {
+        repl.emit('flushHistory');
+      }
+    }
+  }
+}
+
+function _replHistoryMessage() {
+  if (this.history.length === 0) {
+    _writeToOutput(
+      this,
+      '\nPersistent history support disabled. ' +
+      'Set the NODE_REPL_HISTORY environment\nvariable to ' +
+      'a valid, user-writable path to enable.\n'
+    );
+  }
+  this._historyPrev = Interface.prototype._historyPrev;
+  return this._historyPrev();
+}
diff --git a/lib/repl.js b/lib/repl.js
index f1b269b801..1f89f43c24 100644
--- a/lib/repl.js
+++ b/lib/repl.js
@@ -82,6 +82,7 @@ const {
   startSigintWatchdog,
   stopSigintWatchdog
 } = internalBinding('util');
+const history = require('internal/repl/history');
 
 // Lazy-loaded.
 let processTopLevelAwait;
@@ -762,6 +763,10 @@ exports.start = function(prompt,
   return repl;
 };
 
+REPLServer.prototype.setupHistory = function setupHistory(historyFile, cb) {
+  history(this, historyFile, cb);
+};
+
 REPLServer.prototype.clearBufferedCommand = function clearBufferedCommand() {
   this[kBufferedCommandSymbol] = '';
 };