repl: support mult-line string-keyed objects

lib/internal/repl/recoverable.js

@@ -0,0 +1,79 @@
+'use strict';
+
+const acorn = require('internal/deps/acorn/dist/acorn');
+const { tokTypes: tt } = acorn;
+
+// If the error is that we've unexpectedly ended the input,
+// then let the user try to recover by adding more input.
+// Note: `e` (the original exception) is not used by the current implemention,
+// but may be needed in the future.
+function isRecoverableError(e, code) {
+  let recoverable = false;
+
+  // Determine if the point of the any error raised is at the end of the input.
+  // There are two cases to consider:
+  //
+  //   1.  Any error raised after we have encountered the 'eof' token.
+  //       This prevents us from declaring partial tokens (like '2e') as
+  //       recoverable.
+  //
+  //   2.  Three cases where tokens can legally span lines.  This is
+  //       template, comment, and strings with a backslash at the end of
+  //       the line, indicating a continuation.  Note that we need to look
+  //       for the specific errors of 'unterminated' kind (not, for example,
+  //       a syntax error in a ${} expression in a template), and the only
+  //       way to do that currently is to look at the message.  Should Acorn
+  //       change these messages in the future, this will lead to a test
+  //       failure, indicating that this code needs to be updated.
+  //
+  acorn.plugins.replRecoverable = (parser) => {
+    parser.extend('nextToken', (nextToken) => {
+      return function() {
+        Reflect.apply(nextToken, this, []);
+
+        if (this.type === tt.eof) recoverable = true;
+      };
+    });
+
+    parser.extend('raise', (raise) => {
+      return function(pos, message) {
+        switch (message) {
+          case 'Unterminated template':
+          case 'Unterminated comment':
+            recoverable = true;
+            break;
+
+          case 'Unterminated string constant':
+            const token = this.input.slice(this.lastTokStart, this.pos);
+            // see https://www.ecma-international.org/ecma-262/#sec-line-terminators
+            recoverable = /\\(?:\r\n?|\n|\u2028|\u2029)$/.test(token);
+        }
+
+        Reflect.apply(raise, this, [pos, message]);
+      };
+    });
+  };
+
+  // For similar reasons as `defaultEval`, wrap expressions starting with a
+  // curly brace with parenthesis.  Note: only the open parenthesis is added
+  // here as the point is to test for potentially valid but incomplete
+  // expressions.
+  if (/^\s*\{/.test(code) && isRecoverableError(e, `(${code}`)) return true;
+
+  // Try to parse the code with acorn.  If the parse fails, ignore the acorn
+  // error and return the recoverable status.
+  try {
+    acorn.parse(code, { plugins: { replRecoverable: true } });
+
+    // Odd case: the underlying JS engine (V8, Chakra) rejected this input
+    // but Acorn detected no issue.  Presume that additional text won't
+    // address this issue.
+    return false;
+  } catch {
+    return recoverable;
+  }
+}
+
+module.exports = {
+  isRecoverableError
+};

lib/repl.js

@@ -73,6 +73,7 @@ const {
 } = require('internal/errors').codes;
 const { sendInspectorCommand } = require('internal/util/inspector');
 const { experimentalREPLAwait } = process.binding('config');
+const { isRecoverableError } = require('internal/repl/recoverable');
 
 // Lazy-loaded.
 let processTopLevelAwait;
@@ -227,7 +228,8 @@ function REPLServer(prompt,
       // It's confusing for `{ a : 1 }` to be interpreted as a block
       // statement rather than an object literal.  So, we first try
       // to wrap it in parentheses, so that it will be interpreted as
-      // an expression.
+      // an expression.  Note that if the above condition changes,
+      // lib/internal/repl/recoverable.js needs to be changed to match.
       code = `(${code.trim()})\n`;
       wrappedCmd = true;
     }
@@ -1505,76 +1507,6 @@ function regexpEscape(s) {
   return s.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, '\\$&');
 }
 
-// If the error is that we've unexpectedly ended the input,
-// then let the user try to recover by adding more input.
-function isRecoverableError(e, code) {
-  if (e && e.name === 'SyntaxError') {
-    var message = e.message;
-    if (message === 'Unterminated template literal' ||
-        message === 'Unexpected end of input') {
-      return true;
-    }
-
-    if (message === 'missing ) after argument list') {
-      const frames = e.stack.split(/\r?\n/);
-      const pos = frames.findIndex((f) => f.match(/^\s*\^+$/));
-      return pos > 0 && frames[pos - 1].length === frames[pos].length;
-    }
-
-    if (message === 'Invalid or unexpected token')
-      return isCodeRecoverable(code);
-  }
-  return false;
-}
-
-// Check whether a code snippet should be forced to fail in the REPL.
-function isCodeRecoverable(code) {
-  var current, previous, stringLiteral;
-  var isBlockComment = false;
-  var isSingleComment = false;
-  var isRegExpLiteral = false;
-  var lastChar = code.charAt(code.length - 2);
-  var prevTokenChar = null;
-
-  for (var i = 0; i < code.length; i++) {
-    previous = current;
-    current = code[i];
-
-    if (previous === '\\' && (stringLiteral || isRegExpLiteral)) {
-      current = null;
-    } else if (stringLiteral) {
-      if (stringLiteral === current) {
-        stringLiteral = null;
-      }
-    } else if (isRegExpLiteral && current === '/') {
-      isRegExpLiteral = false;
-    } else if (isBlockComment && previous === '*' && current === '/') {
-      isBlockComment = false;
-    } else if (isSingleComment && current === '\n') {
-      isSingleComment = false;
-    } else if (!isBlockComment && !isRegExpLiteral && !isSingleComment) {
-      if (current === '/' && previous === '/') {
-        isSingleComment = true;
-      } else if (previous === '/') {
-        if (current === '*') {
-          isBlockComment = true;
-          // Distinguish between a division operator and the start of a regex
-          // by examining the non-whitespace character that precedes the /
-        } else if ([null, '(', '[', '{', '}', ';'].includes(prevTokenChar)) {
-          isRegExpLiteral = true;
-        }
-      } else {
-        if (current.trim()) prevTokenChar = current;
-        if (current === '\'' || current === '"') {
-          stringLiteral = current;
-        }
-      }
-    }
-  }
-
-  return stringLiteral ? lastChar === '\\' : isBlockComment;
-}
-
 function Recoverable(err) {
   this.err = err;
 }

node.gyp

@@ -147,6 +147,7 @@
       'lib/internal/readline.js',
       'lib/internal/repl.js',
       'lib/internal/repl/await.js',
+      'lib/internal/repl/recoverable.js',
       'lib/internal/socket_list.js',
       'lib/internal/test/binding.js',
       'lib/internal/test/heap.js',

test/parallel/test-repl.js

@@ -162,13 +162,11 @@ const errorTests = [
   // Template expressions
   {
     send: '`io.js ${"1.0"',
-    expect: [
-      kSource,
-      kArrow,
-      '',
-      /^SyntaxError: /,
-      ''
-    ]
+    expect: '... '
+  },
+  {
+    send: '+ ".2"}`',
+    expect: '\'io.js 1.0.2\''
   },
   {
     send: '`io.js ${',
@@ -315,6 +313,15 @@ const errorTests = [
     send: '1 }',
     expect: '{ a: 1 }'
   },
+  // Multiline string-keyed object (e.g. JSON)
+  {
+    send: '{ "a": ',
+    expect: '... '
+  },
+  {
+    send: '1 }',
+    expect: '{ a: 1 }'
+  },
   // Multiline anonymous function with comment
   {
     send: '(function() {',