Fix #4763: Comments at beginning or end of REPL input shouldn't throw errors (#4764)

Author: GeoffreyBooth

lib/coffeescript/repl.js

@@ -30,6 +30,14 @@ replDefaults =
     try
       # Tokenize the clean input.
       tokens = CoffeeScript.tokens input
+      # Filter out tokens generated just to hold comments.
+      if tokens.length >= 2 and tokens[0].generated and
+         tokens[0].comments?.length isnt 0 and tokens[0][1] is '' and
+         tokens[1][0] is 'TERMINATOR'
+        tokens = tokens[2...]
+      if tokens.length >= 1 and tokens[tokens.length - 1].generated and
+         tokens[tokens.length - 1].comments?.length isnt 0 and tokens[tokens.length - 1][1] is ''
+        tokens.pop()
       # Collect referenced variable names just like in `CoffeeScript.compile`.
       referencedVars = (token[1] for token in tokens when token[0] is 'IDENTIFIER')
       # Generate the AST of the tokens.

src/repl.coffee

@@ -77,6 +77,14 @@ testRepl "empty command evaluates to undefined", (input, output) ->
   input.emitLine ''
   eq 'undefined', output.lastWrite()
 
+testRepl "#4763: comment evaluates to undefined", (input, output) ->
+  input.emitLine '# comment'
+  eq 'undefined', output.lastWrite()
+
+testRepl "#4763: multiple comments evaluate to undefined", (input, output) ->
+  input.emitLine '### a ### ### b ### # c'
+  eq 'undefined', output.lastWrite()
+
 testRepl "ctrl-v toggles multiline prompt", (input, output) ->
   input.emit 'keypress', null, ctrlV
   eq '------> ', output.lastWrite(0)