fix(cli-repl): properly handle \r\n newlines in input MONGOSH-998 (#1141)

Author: addaleax

packages/cli-repl/src/line-by-line-input.spec.ts

@@ -45,6 +45,12 @@ describe('LineByLineInput', () => {
       lineByLineInput.nextLine();
       expect(forwardedChunks).to.deep.equal(['ab', '\n', 'c']);
     });
+
+    it('groups \\r\\n together', () => {
+      stdinMock.emit('data', Buffer.from('ab\r\nc'));
+      lineByLineInput.nextLine();
+      expect(forwardedChunks).to.deep.equal(['ab', '\r\n', 'c']);
+    });
   });
 
   context('when block on newline is disabled', () => {

packages/cli-repl/src/line-by-line-input.ts

@@ -104,15 +104,27 @@ export class LineByLineInput extends Readable {
     return this._forwardWithoutBlocking(chunk);
   };
 
+  // eslint-disable-next-line complexity
   private _forwardAndBlockOnNewline(chunk: Buffer | null): void {
     const chars = chunk === null ? [null] : this._decoder.write(chunk);
     for (const char of chars) {
+      // Look up the last character we have queued up, if any:
+      const lastCharQueueEntry = this._charQueue.length ?
+        this._charQueue[this._charQueue.length - 1] : '';
+      const lastCharQueueChar = lastCharQueueEntry?.length ?
+        lastCharQueueEntry[lastCharQueueEntry.length - 1] : '';
+
       if (this._isCtrlC(char) || this._isCtrlD(char)) {
         this.push(char);
       } else if (
-        this._isRegularCharacter(char) &&
-        this._charQueue.length > 0 &&
-        this._isRegularCharacter(this._charQueue[this._charQueue.length - 1])) {
+        (
+          char === '\n' && lastCharQueueChar === '\r'
+        ) || (
+          this._isRegularCharacter(char) &&
+          lastCharQueueChar !== '' &&
+          this._isRegularCharacter(lastCharQueueChar)
+        )
+      ) {
         (this._charQueue[this._charQueue.length - 1] as string) += char as string;
       } else {
         this._charQueue.push(char);

packages/cli-repl/test/e2e.spec.ts

@@ -144,6 +144,16 @@ describe('e2e', function() {
       const result = await shell.executeLine('"a"+\n"<\\101>"');
       expect(result).to.match(/a<A>/);
     });
+    it('handles \\r\\n newline input properly', async() => {
+      shell.writeInput('34+55\r\n');
+      await promisify(setTimeout)(100);
+      shell.writeInput('_+55\r\n');
+      await promisify(setTimeout)(100);
+      shell.writeInput('_+89\r\n');
+      await eventually(() => {
+        shell.assertContainsOutput('233');
+      });
+    });
   });
 
   describe('set db', () => {