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>

1 files changed, 153 insertions, 0 deletions

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();
+}