Comments in scala repl paste mode

Question
1

Does the scala repl support comments in :paste mode?

I’m just starting out with scala and was suprised by this interaction:

scala> :paste
// Entering paste mode (ctrl-D to finish)

// This is a comment
val x = 1

// Exiting paste mode, now interpreting.

scala> x
       ^
       error: not found: value x

If I do the same thing without the comment before the val x = 1 line, x is defined as expected. Not sure why there’s no error message when the comment is there.

I am running scala version:
Scala code runner version 2.13.2 – Copyright 2002-2020, LAMP/EPFL and Lightbend, Inc.

1 Like
2

Are you sure there is a proper end of line between the comment and the val?

3

Yes, I’m sure. At least without somehow inspecting the actual bytes that scala is receiving from my terminal I’m sure. I’m hitting return after the comment.

The same behaviour happens with a file. In which case we can do a hexdump:

$ xxd PasteTest.scala 
00000000: 2f2f 2054 6869 7320 6973 2061 2063 6f6d  // This is a com
00000010: 6d65 6e74 0a76 616c 2078 203d 2031 0a    ment.val x = 1.

We can see the newline character in the file. (Byte 0x0a, the convention for Linux, right?).

scala> :paste PasteTest.scala
Pasting file PasteTest.scala...

scala> x
       ^
       error: not found: value x

Maybe there’s something screwed with my setup. Not sure, but I doubt it.

So in general it should be working ok? We would expect :paste mode to handle comments at the start of the file?

1 Like
4

Scala 2.13.2 comes with a new line reader. This looks like a bug in it to me. I reported it here: https://github.com/scala/bug/issues/11991

2 Likes
5

Thanks for reporting it!

6

Nice catch! Definitely a blocker for 2.13.3.