repl: implement reverse search

Add a reverse search that works similar to the ZSH one. It is
triggered with <ctrl> + r and <ctrl> + s. It skips duplicated history
entries and works with multiline statements. Matching entries indicate
the search parameter with an underscore and cancelling with <ctrl> + c
or escape brings back the original line.
Multiple matches in a single history entry work as well and are
matched in the order of the current search direction. The cursor is
positioned at the current match position of the history entry.
Changing the direction immediately checks for the next entry in the
expected direction from the current position on.
Entries are accepted as soon any button is pressed that doesn't
correspond with the reverse search.
The behavior is deactivated for simple terminals. They do not support
most ANSI escape codes that are necessary for this feature.

PR-URL: #31006
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

doc/api/repl.md

@@ -21,9 +21,11 @@ result. Input and output may be from `stdin` and `stdout`, respectively, or may
 be connected to any Node.js [stream][].
 
 Instances of [`repl.REPLServer`][] support automatic completion of inputs,
-simplistic Emacs-style line editing, multi-line inputs, ANSI-styled output,
-saving and restoring current REPL session state, error recovery, and
-customizable evaluation functions.
+completion preview, simplistic Emacs-style line editing, multi-line inputs,
+[ZSH][] like reverse-i-search, ANSI-styled output, saving and restoring current
+REPL session state, error recovery, and customizable evaluation functions.
+Terminals that do not support ANSI-styles and Emacs-style line editing
+automatically fall back to a limited feature set.
 
 ### Commands and Special Keys
 
@@ -232,6 +234,24 @@ undefined
 undefined
 ```
 
+### Reverse-i-search
+<!-- YAML
+added: REPLACEME
+-->
+
+The REPL supports bi-directional reverse-i-search similar to [ZSH][]. It is
+triggered with `<ctrl> + R` to search backwards and `<ctrl> + S` to search
+forwards.
+
+Duplicated history entires will be skipped.
+
+Entries are accepted as soon as any button is pressed that doesn't correspond
+with the reverse search. Cancelling is possible by pressing `escape` or
+`<ctrl> + C`.
+
+Changing the direction immediately searches for the next entry in the expected
+direction from the current position on.
+
 ### Custom Evaluation Functions
 
 When a new [`repl.REPLServer`][] is created, a custom evaluation function may be
@@ -695,6 +715,7 @@ a `net.Server` and `net.Socket` instance, see:
 For an example of running a REPL instance over [curl(1)][], see:
 <https://gist.github.com/TooTallNate/2053342>.
 
+[ZSH]: https://en.wikipedia.org/wiki/Z_shell
 [`'uncaughtException'`]: process.html#process_event_uncaughtexception
 [`--experimental-repl-await`]: cli.html#cli_experimental_repl_await
 [`ERR_DOMAIN_CANNOT_SET_UNCAUGHT_EXCEPTION_CAPTURE`]: errors.html#errors_err_domain_cannot_set_uncaught_exception_capture

lib/internal/repl/utils.js

@@ -24,6 +24,7 @@ const {
 
 const {
   clearLine,
+  clearScreenDown,
   cursorTo,
   moveCursor,
 } = require('readline');
@@ -42,7 +43,13 @@ const inspectOptions = {
   compact: true,
   breakLength: Infinity
 };
-const inspectedOptions = inspect(inspectOptions, { colors: false });
+// Specify options that might change the output in a way that it's not a valid
+// stringified object anymore.
+const inspectedOptions = inspect(inspectOptions, {
+  depth: 1,
+  colors: false,
+  showHidden: false
+});
 
 // If the error is that we've unexpectedly ended the input,
 // then let the user try to recover by adding more input.
@@ -393,8 +400,242 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
   return { showPreview, clearPreview };
 }
 
+function setupReverseSearch(repl) {
+  // Simple terminals can't use reverse search.
+  if (process.env.TERM === 'dumb') {
+    return { reverseSearch() { return false; } };
+  }
+
+  const alreadyMatched = new Set();
+  const labels = {
+    r: 'bck-i-search: ',
+    s: 'fwd-i-search: '
+  };
+  let isInReverseSearch = false;
+  let historyIndex = -1;
+  let input = '';
+  let cursor = -1;
+  let dir = 'r';
+  let lastMatch = -1;
+  let lastCursor = -1;
+  let promptPos;
+
+  function checkAndSetDirectionKey(keyName) {
+    if (!labels[keyName]) {
+      return false;
+    }
+    if (dir !== keyName) {
+      // Reset the already matched set in case the direction is changed. That
+      // way it's possible to find those entries again.
+      alreadyMatched.clear();
+    }
+    dir = keyName;
+    return true;
+  }
+
+  function goToNextHistoryIndex() {
+    // Ignore this entry for further searches and continue to the next
+    // history entry.
+    alreadyMatched.add(repl.history[historyIndex]);
+    historyIndex += dir === 'r' ? 1 : -1;
+    cursor = -1;
+  }
+
+  function search() {
+    // Just print an empty line in case the user removed the search parameter.
+    if (input === '') {
+      print(repl.line, `${labels[dir]}_`);
+      return;
+    }
+    // Fix the bounds in case the direction has changed in the meanwhile.
+    if (dir === 'r') {
+      if (historyIndex < 0) {
+        historyIndex = 0;
+      }
+    } else if (historyIndex >= repl.history.length) {
+      historyIndex = repl.history.length - 1;
+    }
+    // Check the history entries until a match is found.
+    while (historyIndex >= 0 && historyIndex < repl.history.length) {
+      let entry = repl.history[historyIndex];
+      // Visualize all potential matches only once.
+      if (alreadyMatched.has(entry)) {
+        historyIndex += dir === 'r' ? 1 : -1;
+        continue;
+      }
+      // Match the next entry either from the start or from the end, depending
+      // on the current direction.
+      if (dir === 'r') {
+        // Update the cursor in case it's necessary.
+        if (cursor === -1) {
+          cursor = entry.length;
+        }
+        cursor = entry.lastIndexOf(input, cursor - 1);
+      } else {
+        cursor = entry.indexOf(input, cursor + 1);
+      }
+      // Match not found.
+      if (cursor === -1) {
+        goToNextHistoryIndex();
+      // Match found.
+      } else {
+        if (repl.useColors) {
+          const start = entry.slice(0, cursor);
+          const end = entry.slice(cursor + input.length);
+          entry = `${start}\x1B[4m${input}\x1B[24m${end}`;
+        }
+        print(entry, `${labels[dir]}${input}_`, cursor);
+        lastMatch = historyIndex;
+        lastCursor = cursor;
+        // Explicitly go to the next history item in case no further matches are
+        // possible with the current entry.
+        if ((dir === 'r' && cursor === 0) ||
+            (dir === 's' && entry.length === cursor + input.length)) {
+          goToNextHistoryIndex();
+        }
+        return;
+      }
+    }
+    print(repl.line, `failed-${labels[dir]}${input}_`);
+  }
+
+  function print(outputLine, inputLine, cursor = repl.cursor) {
+    // TODO(BridgeAR): Resizing the terminal window hides the overlay. To fix
+    // that, readline must be aware of this information. It's probably best to
+    // add a couple of properties to readline that allow to do the following:
+    // 1. Add arbitrary data to the end of the current line while not counting
+    //    towards the line. This would be useful for the completion previews.
+    // 2. Add arbitrary extra lines that do not count towards the regular line.
+    //    This would be useful for both, the input preview and the reverse
+    //    search. It might be combined with the first part?
+    // 3. Add arbitrary input that is "on top" of the current line. That is
+    //    useful for the reverse search.
+    // 4. To trigger the line refresh, functions should be used to pass through
+    //    the information. Alternatively, getters and setters could be used.
+    //    That might even be more elegant.
+    // The data would then be accounted for when calling `_refreshLine()`.
+    // This function would then look similar to:
+    //   repl.overlay(outputLine);
+    //   repl.addTrailingLine(inputLine);
+    //   repl.setCursor(cursor);
+    // More potential improvements: use something similar to stream.cork().
+    // Multiple cursor moves on the same tick could be prevented in case all
+    // writes from the same tick are combined and the cursor is moved at the
+    // tick end instead of after each operation.
+    let rows = 0;
+    if (lastMatch !== -1) {
+      const line = repl.history[lastMatch].slice(0, lastCursor);
+      rows = repl._getDisplayPos(`${repl._prompt}${line}`).rows;
+      cursorTo(repl.output, promptPos.cols);
+    } else if (isInReverseSearch && repl.line !== '') {
+      rows = repl._getCursorPos().rows;
+      cursorTo(repl.output, promptPos.cols);
+    }
+    if (rows !== 0)
+      moveCursor(repl.output, 0, -rows);
+
+    if (isInReverseSearch) {
+      clearScreenDown(repl.output);
+      repl.output.write(`${outputLine}\n${inputLine}`);
+    } else {
+      repl.output.write(`\n${inputLine}`);
+    }
+
+    lastMatch = -1;
+
+    // To know exactly how many rows we have to move the cursor back we need the
+    // cursor rows, the output rows and the input rows.
+    const prompt = repl._prompt;
+    const cursorLine = `${prompt}${outputLine.slice(0, cursor)}`;
+    const cursorPos = repl._getDisplayPos(cursorLine);
+    const outputPos = repl._getDisplayPos(`${prompt}${outputLine}`);
+    const inputPos = repl._getDisplayPos(inputLine);
+    const inputRows = inputPos.rows - (inputPos.cols === 0 ? 1 : 0);
+
+    rows = -1 - inputRows - (outputPos.rows - cursorPos.rows);
+
+    moveCursor(repl.output, 0, rows);
+    cursorTo(repl.output, cursorPos.cols);
+  }
+
+  function reset(string) {
+    isInReverseSearch = string !== undefined;
+
+    // In case the reverse search ends and a history entry is found, reset the
+    // line to the found entry.
+    if (!isInReverseSearch) {
+      if (lastMatch !== -1) {
+        repl.line = repl.history[lastMatch];
+        repl.cursor = lastCursor;
+        repl.historyIndex = lastMatch;
+      }
+
+      lastMatch = -1;
+
+      // Clear screen and write the current repl.line before exiting.
+      cursorTo(repl.output, promptPos.cols);
+      if (promptPos.rows !== 0)
+        moveCursor(repl.output, 0, promptPos.rows);
+      clearScreenDown(repl.output);
+      if (repl.line !== '') {
+        repl.output.write(repl.line);
+        if (repl.line.length !== repl.cursor) {
+          const { cols, rows } = repl._getCursorPos();
+          cursorTo(repl.output, cols);
+          if (rows !== 0)
+            moveCursor(repl.output, 0, rows);
+        }
+      }
+    }
+
+    input = string || '';
+    cursor = -1;
+    historyIndex = repl.historyIndex;
+    alreadyMatched.clear();
+  }
+
+  function reverseSearch(string, key) {
+    if (!isInReverseSearch) {
+      if (key.ctrl && checkAndSetDirectionKey(key.name)) {
+        historyIndex = repl.historyIndex;
+        promptPos = repl._getDisplayPos(`${repl._prompt}`);
+        print(repl.line, `${labels[dir]}_`);
+        isInReverseSearch = true;
+      }
+    } else if (key.ctrl && checkAndSetDirectionKey(key.name)) {
+      search();
+    } else if (key.name === 'backspace' ||
+        (key.ctrl && (key.name === 'h' || key.name === 'w'))) {
+      reset(input.slice(0, input.length - 1));
+      search();
+      // Special handle <ctrl> + c and escape. Those should only cancel the
+      // reverse search. The original line is visible afterwards again.
+    } else if ((key.ctrl && key.name === 'c') || key.name === 'escape') {
+      lastMatch = -1;
+      reset();
+      return true;
+      // End search in case either enter is pressed or if any non-reverse-search
+      // key (combination) is pressed.
+    } else if (key.ctrl ||
+               key.meta ||
+               key.name === 'return' ||
+               key.name === 'enter' ||
+               typeof string !== 'string' ||
+               string === '') {
+      reset();
+    } else {
+      reset(`${input}${string}`);
+      search();
+    }
+    return isInReverseSearch;
+  }
+
+  return { reverseSearch };
+}
+
 module.exports = {
   isRecoverableError,
   kStandaloneREPL: Symbol('kStandaloneREPL'),
-  setupPreview
+  setupPreview,
+  setupReverseSearch
 };

lib/repl.js

@@ -102,6 +102,7 @@ const {
   isRecoverableError,
   kStandaloneREPL,
   setupPreview,
+  setupReverseSearch,
 } = require('internal/repl/utils');
 const {
   getOwnNonIndexProperties,
@@ -810,6 +811,8 @@ function REPLServer(prompt,
     }
   });
 
+  const { reverseSearch } = setupReverseSearch(this);
+
   const {
     clearPreview,
     showPreview
@@ -835,8 +838,10 @@ function REPLServer(prompt,
         self.clearLine();
       }
       clearPreview();
-      ttyWrite(d, key);
-      showPreview();
+      if (!reverseSearch(d, key)) {
+        ttyWrite(d, key);
+        showPreview();
+      }
       return;
     }
 
@@ -1081,6 +1086,9 @@ REPLServer.prototype.complete = function() {
   this.completer.apply(this, arguments);
 };
 
+// TODO: Native module names should be auto-resolved.
+// That improves the auto completion.
+
 // Provide a list of completions for the given leading text. This is
 // given to the readline interface for handling tab completion.
 //

test/parallel/test-repl-history-navigation.js

@@ -340,7 +340,7 @@ function runTest() {
         const output = chunk.toString();
 
         if (!opts.showEscapeCodes &&
-            output.charCodeAt(0) === 27 || /^[\r\n]+$/.test(output)) {
+            (output[0] === '\x1B' || /^[\r\n]+$/.test(output))) {
           return next();
         }