From e48f45f76ee1c26c655ebc30c25622e0208f99d2 Mon Sep 17 00:00:00 2001
From: Michael Rose <michael_rose@gmx.de>
Date: Fri, 21 May 2021 11:47:49 +0200
Subject: [PATCH] fix(cli-repl): do not throw internal errors for invalid user
 code MONGOSH-777

---
 .../src/js-multiline-to-singleline.ts         | 22 +++++++++++++------
 packages/cli-repl/src/mongosh-repl.spec.ts    | 22 +++++++++++++++++++
 2 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/packages/cli-repl/src/js-multiline-to-singleline.ts b/packages/cli-repl/src/js-multiline-to-singleline.ts
index 7f53b8d5e9..69b5ac44a2 100644
--- a/packages/cli-repl/src/js-multiline-to-singleline.ts
+++ b/packages/cli-repl/src/js-multiline-to-singleline.ts
@@ -1,7 +1,7 @@
 import { transformSync } from '@babel/core';
 
 export function makeMultilineJSIntoSingleLine(src: string): string {
-  // We use babel without any actual transofmration steps, and only for ASI
+  // We use babel without any actual transformation steps, and only for ASI
   // effects here, e.g. turning `return\n42` into `return;\n42;`
   // since without the added semicolons semantics would be different.
   // This unfortunately modifies the code in some other ways as well, e.g.
@@ -9,12 +9,20 @@ export function makeMultilineJSIntoSingleLine(src: string): string {
   // important here than keeping aesthetics intact.
   // It would be nice to have a dedicated package at some point that does
   // ASI and *only* ASI and leaves the source intact otherwise.
-  const postASI = transformSync(src, {
-    retainLines: true,
-    compact: false,
-    code: true,
-    comments: false
-  })?.code ?? src;
+  let postASI: string;
+  try {
+    postASI = transformSync(src, {
+      retainLines: true,
+      compact: false,
+      code: true,
+      comments: false
+    })?.code ?? src;
+  } catch {
+    // The src might still be invalid, e.g. because a recoverable error was not fixed
+    // and is now an unrecoverable error. Best we can do is just keep the lines now.
+    postASI = src;
+  }
+
   const asSingleLine = postASI.split(/[\r\n]+/g)
     .map(line => line.trim())
     .join(' ')
diff --git a/packages/cli-repl/src/mongosh-repl.spec.ts b/packages/cli-repl/src/mongosh-repl.spec.ts
index aacfad15ac..fcbdbdb77f 100644
--- a/packages/cli-repl/src/mongosh-repl.spec.ts
+++ b/packages/cli-repl/src/mongosh-repl.spec.ts
@@ -308,6 +308,28 @@ describe('MongoshNodeRepl', () => {
       expect(output).not.to.include('Error');
     });
 
+    it('allows to enter and fix recoverable errors', async() => {
+      input.write('24 %\n');
+      await waitEval(bus);
+      expect(output).to.not.include('Error');
+
+      input.write('6\n');
+      await waitEval(bus);
+      expect(output).to.include(0);
+      expect(output).to.not.include('Error');
+    });
+
+    it('behaves correctly on non-recoverable multi-line errors', async() => {
+      input.write('24 %\n');
+      await waitEval(bus);
+      expect(output).to.not.include('Error');
+
+      input.write(';\n');
+      await waitEval(bus);
+      expect(output).to.not.include('MongoshInternalError');
+      expect(output).to.include('SyntaxError');
+    });
+
     it('pressing Ctrl+C twice exits the shell', async() => {
       input.write('\u0003');
       await tick();