fix: example command hanging in REPL when executing multi-line code

PR-URL: #2706
Resolves: #2273

---------

Signed-off-by: Snehil Shah <snehilshah.989@gmail.com>
Reviewed-by: Athan Reines <kgryte@gmail.com> 
Reviewed-by: Philipp Burckhardt <pburckhardt@outlook.com>

Author: Snehil-Shah

lib/node_modules/@stdlib/repl/lib/commands/example.js

@@ -57,6 +57,7 @@ function command( repl, cmds ) {
 	function onCommand( alias ) {
 		var aliases;
 		var entry;
+		var lines;
 		var out;
 		var len;
 		var N;
@@ -133,6 +134,7 @@ function command( repl, cmds ) {
 			}
 		}
 		if ( out ) {
+			lines = [];
 			out = out.split( RE_EOL );
 			len = out.length;
 			i = -1;
@@ -149,13 +151,27 @@ function command( repl, cmds ) {
 		* @private
 		* @param {string} cmd - command
 		* @param {boolean} success - boolean indicating whether the command successfully executed
+		* @returns {void}
 		*/
 		function next() {
+			var j;
 			i += 1;
 			if ( i < len ) {
 				// Forward the next line to the REPL readline interface in order to mimic user input...
 				if ( out[ i ] ) {
-					repl._rli.write( out[ i ]+'\n' );
+					lines.push( out[ i ] );
+
+					// If line is part of a multi-line input, wait for the next line...
+					if ( repl._multilineHandler.isMultilineInput( lines.join( '\n' ) ) ) {
+						return next();
+					}
+					for ( j = 0; j < lines.length; j++ ) {
+						repl._rli.write( lines[ j ] );
+						repl._rli.write( '\n', {
+							'name': 'return'
+						});
+					}
+					lines = [];
 					repl.once( 'drain', next );
 				} else {
 					nextTick( next );

lib/node_modules/@stdlib/repl/lib/multiline_handler.js

@@ -394,56 +394,6 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, '_triggerMultiline', funct
 	this._rli.line = this._rli.line.substring( 0, this._rli.cursor );
 });
 
-/**
-* Checks if the command is incomplete and a multi-line input.
-*
-* @private
-* @name _isMultilineInput
-* @memberof MultilineHandler.prototype
-* @type {Function}
-* @param {string} cmd - command
-* @returns {boolean} boolean indicating whether the command is a multi-line input
-*/
-setNonEnumerableReadOnly( MultilineHandler.prototype, '_isMultilineInput', function isMultilineInput( cmd ) {
-	var node;
-	var tmp;
-	var ast;
-
-	debug( 'Attempting to detect multi-line input...' );
-	if ( RE_WHITESPACE.test( cmd ) ) {
-		debug( 'Multi-line input not detected.' );
-		return false;
-	}
-	if ( RE_SINGLE_LINE_COMMENT.test( cmd ) || RE_MULTI_LINE_COMMENT.test( cmd ) ) { // eslint-disable-line max-len
-		debug( 'Multi-line input not detected.' );
-		return false;
-	}
-	// Check if the command has valid syntax...
-	tmp = processCommand( cmd );
-	if ( !( tmp instanceof Error ) ) {
-		debug( 'Multi-line input not detected.' );
-		return false;
-	}
-	if ( hasMultilineError( cmd, AOPTS ) ) {
-		debug( 'Detected multi-line input. Triggering multi-line mode...' );
-		return true;
-	}
-	// Still possible that a user is attempting to enter an object literal across multiple lines...
-	ast = parseLoose( cmd, AOPTS );
-
-	// Check for a trailing node which is being interpreted as a block statement, as this could be an object literal...
-	node = ast.body[ ast.body.length-1 ];
-	if ( node.type === 'BlockStatement' && node.end === ast.end ) {
-		tmp = cmd.slice( node.start, node.end );
-		if ( hasMultilineError( tmp, AOPTS ) ) {
-			debug( 'Detected multi-line input. Triggering multi-line mode...' );
-			return true;
-		}
-	}
-	debug( 'Multi-line input not detected.' );
-	return false;
-});
-
 /**
 * Resets input buffers.
 *
@@ -581,6 +531,55 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, 'isPasting', function isPa
 	return this._multiline.pasteMode;
 });
 
+/**
+* Checks if the command is incomplete and a multi-line input.
+*
+* @name isMultilineInput
+* @memberof MultilineHandler.prototype
+* @type {Function}
+* @param {string} cmd - command
+* @returns {boolean} boolean indicating whether the command is a multi-line input
+*/
+setNonEnumerableReadOnly( MultilineHandler.prototype, 'isMultilineInput', function isMultilineInput( cmd ) {
+	var node;
+	var tmp;
+	var ast;
+
+	debug( 'Attempting to detect multi-line input...' );
+	if ( RE_WHITESPACE.test( cmd ) ) {
+		debug( 'Multi-line input not detected.' );
+		return false;
+	}
+	if ( RE_SINGLE_LINE_COMMENT.test( cmd ) || RE_MULTI_LINE_COMMENT.test( cmd ) ) { // eslint-disable-line max-len
+		debug( 'Multi-line input not detected.' );
+		return false;
+	}
+	// Check if the command has valid syntax...
+	tmp = processCommand( cmd );
+	if ( !( tmp instanceof Error ) ) {
+		debug( 'Multi-line input not detected.' );
+		return false;
+	}
+	if ( hasMultilineError( cmd, AOPTS ) ) {
+		debug( 'Detected multi-line input. Triggering multi-line mode...' );
+		return true;
+	}
+	// Still possible that a user is attempting to enter an object literal across multiple lines...
+	ast = parseLoose( cmd, AOPTS );
+
+	// Check for a trailing node which is being interpreted as a block statement, as this could be an object literal...
+	node = ast.body[ ast.body.length-1 ];
+	if ( node.type === 'BlockStatement' && node.end === ast.end ) {
+		tmp = cmd.slice( node.start, node.end );
+		if ( hasMultilineError( tmp, AOPTS ) ) {
+			debug( 'Detected multi-line input. Triggering multi-line mode...' );
+			return true;
+		}
+	}
+	debug( 'Multi-line input not detected.' );
+	return false;
+});
+
 /**
 * Processes input line data.
 *
@@ -737,9 +736,10 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, 'beforeKeypress', function
 	case 'return':
 		cmd = copy( this._cmd );
 		cmd[ this._lineIndex ] = this._rli.line;
+		this._lines[ this._lineIndex ] = this._rli.line;
 
 		// If we are in paste mode or the command is incomplete, trigger multi-line mode...
-		if ( !this._multiline.pasteMode && !this._isMultilineInput( cmd.join( '\n' ) ) ) {
+		if ( !this._multiline.pasteMode && !this.isMultilineInput( cmd.join( '\n' ) ) ) {
 			this._ttyWrite.call( this._rli, data, key );
 			return;
 		}