repl: make REPL support multiline template literals

Let REPL enter multiline mode if user's input contains unterminated
template literals.

PR-URL: https://github.com/iojs/io.js/pull/333
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

lib/repl.js

@@ -87,6 +87,8 @@ function REPLServer(prompt, stream, eval_, useGlobal, ignoreUndefined) {
   self.useGlobal = !!useGlobal;
   self.ignoreUndefined = !!ignoreUndefined;
 
+  self._inTemplateLiteral = false;
+
   // just for backwards compat, see github.com/joyent/node/pull/7127
   self.rli = this;
 
@@ -102,7 +104,7 @@ function REPLServer(prompt, stream, eval_, useGlobal, ignoreUndefined) {
       });
     } catch (e) {
       debug('parse error %j', code, e);
-      if (isRecoverableError(e))
+      if (isRecoverableError(e, self))
         err = new Recoverable(e);
       else
         err = e;
@@ -226,7 +228,13 @@ function REPLServer(prompt, stream, eval_, useGlobal, ignoreUndefined) {
     debug('line %j', cmd);
     sawSIGINT = false;
     var skipCatchall = false;
-    cmd = trimWhitespace(cmd);
+
+    // leading whitespaces in template literals should not be trimmed.
+    if (self._inTemplateLiteral) {
+      self._inTemplateLiteral = false;
+    } else {
+      cmd = trimWhitespace(cmd);
+    }
 
     // Check to see if a REPL keyword was used. If it returns true,
     // display next prompt and return.
@@ -928,10 +936,17 @@ REPLServer.prototype.convertToContext = function(cmd) {
 
 // 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) {
-  return e &&
-      e.name === 'SyntaxError' &&
-      /^(Unexpected end of input|Unexpected token :)/.test(e.message);
+function isRecoverableError(e, self) {
+  if (e && e.name === 'SyntaxError') {
+    var message = e.message;
+    if (message === 'Unterminated template literal' ||
+        message === 'Missing } in template expression') {
+      self._inTemplateLiteral = true;
+      return true;
+    }
+    return /^(Unexpected end of input|Unexpected token :)/.test(message);
+  }
+  return false;
 }
 
 function Recoverable(err) {

test/parallel/test-repl.js

@@ -104,6 +104,17 @@ function error_test() {
     // But passing the same string to eval() should throw
     { client: client_unix, send: 'eval("function test_func() {")',
       expect: /^SyntaxError: Unexpected end of input/ },
+    // Can handle multiline template literals
+    { client: client_unix, send: '`io.js',
+      expect: prompt_multiline },
+    // Special REPL commands still available
+    { client: client_unix, send: '.break',
+      expect: prompt_unix },
+    // Template expressions can cross lines
+    { client: client_unix, send: '`io.js ${"1.0"',
+      expect: prompt_multiline },
+    { client: client_unix, send: '+ ".2"}`',
+      expect: `'io.js 1.0.2'\n${prompt_unix}` },
     // Floating point numbers are not interpreted as REPL commands.
     { client: client_unix, send: '.1234',
       expect: '0.1234' },