repl: improve repl preview

This aligns the REPL preview with the one used in the Chrome
DevTools console. It will now preview the output for the input
including the completion suffix as input. When pressing enter while
previewing such data, it will automatically insert the suffix
before evaluating the input. When pressing escape, that behavior
is deactivated until the input is changed.

Signed-off-by: Ruben Bridgewater <ruben@bridgewater.de>

PR-URL: https://github.com/nodejs/node/pull/33282
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

1 files changed, 34 insertions, 10 deletions

diff --git a/lib/internal/repl/utils.js b/lib/internal/repl/utils.js
index 476760a08d5..a8b1e336d9a 100644
--- a/lib/internal/repl/utils.js
+++ b/lib/internal/repl/utils.js
@@ -138,6 +138,8 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
 
   let wrapped = false;
 
+  let escaped = null;
+
   function getPreviewPos() {
     const displayPos = repl._getDisplayPos(`${repl._prompt}${repl.line}`);
     const cursorPos = repl.line.length !== repl.cursor ?
@@ -146,7 +148,13 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
     return { displayPos, cursorPos };
   }
 
-  const clearPreview = () => {
+  function isCursorAtInputEnd() {
+    const { cursorPos, displayPos } = getPreviewPos();
+    return cursorPos.rows === displayPos.rows &&
+           cursorPos.cols === displayPos.cols;
+  }
+
+  const clearPreview = (key) => {
     if (inputPreview !== null) {
       const { displayPos, cursorPos } = getPreviewPos();
       const rows = displayPos.rows - cursorPos.rows + 1;
@@ -179,8 +187,23 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
         cursorTo(repl.output, pos.cursorPos.cols);
         moveCursor(repl.output, 0, -rows);
       }
+      if (!key.ctrl && !key.shift) {
+        if (key.name === 'escape') {
+          if (escaped === null && key.meta) {
+            escaped = repl.line;
+          }
+        } else if ((key.name === 'return' || key.name === 'enter') &&
+                   !key.meta &&
+                   escaped !== repl.line &&
+                   isCursorAtInputEnd()) {
+          repl._insertString(completionPreview);
+        }
+      }
       completionPreview = null;
     }
+    if (escaped !== repl.line) {
+      escaped = null;
+    }
   };
 
   function showCompletionPreview(line, insertPreview) {
@@ -317,13 +340,6 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
     }
 
     // Add the autocompletion preview.
-    // TODO(BridgeAR): Trigger the input preview after the completion preview.
-    // That way it's possible to trigger the input prefix including the
-    // potential completion suffix. To do so, we also have to change the
-    // behavior of `enter` and `escape`:
-    // Enter should automatically add the suffix to the current line as long as
-    // escape was not pressed. We might even remove the preview in case any
-    // cursor movement is triggered.
     const insertPreview = false;
     showCompletionPreview(repl.line, insertPreview);
 
@@ -397,9 +413,17 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
       moveCursor(repl.output, 0, -rows - 1);
     };
 
-    getInputPreview(line, inputPreviewCallback);
+    let previewLine = line;
+
+    if (completionPreview !== null &&
+        isCursorAtInputEnd() &&
+        escaped !== repl.line) {
+      previewLine += completionPreview;
+    }
+
+    getInputPreview(previewLine, inputPreviewCallback);
     if (wrapped) {
-      getInputPreview(line, inputPreviewCallback);
+      getInputPreview(previewLine, inputPreviewCallback);
     }
     wrapped = false;
   };