REPL renders syntax highlighting colors INSIDE of strings when echoing evaluated values, happens after colon : and leading val

[bjornregnell]

Compiler version

3.0.0-RC1 and also in 3.0.0-RC2-bin-20210226-63a467b-NIGHTLY

Minimized code

If you enter this in REPL strange colors will emerge in echo: (see output png below)

scala> "a A"
val res0: String = a A

scala> "a: A"
val res1: String = a: A

scala> "a: A B C"                                                                                                              
val res2: String = a: A B C

scala> "a: A, B, C"                                                                                                            
val res3: String = a: A, B, C

scala> "val a: A, B, C"                                                                                                        
val res4: String = val a: A, B, C

Output

Expectation

Syntax highlighting should not be activated when rendering of characters inside string values when echoed.

[bjornregnell]

Perhaps related to #10615

[som-snytt]

The echoed text is no longer in double quotes. (This is finally addressed in the scala 2 PR for repl printing.)

[bjornregnell]

@som-snytt You mean this one? scala/scala#8885 (still open at time of writing)

The current Scala 2 REPL does correctly not try to syntax highlight inside arbitrary strings, so this is a regression in Scala 3.

[som-snytt]

Yes, example diff from the PR

val res1: String = muuh
val res1: String = "muuh"

In Scala 3, compare

scala> """"val x: Int = 42""""
val res0: String = "val x: Int = 42"

The PR adds the double quotes via replStringOf.

The highlighter highlights what you render. Note that Scala 2 colorization doesn't really compare.

Scala 3 invokes ScalaRunTime.replStringOf reflectively; fortunately, the PR preserves the API; it adds an overload that takes a flag for "verbose" case class rendering, which would be nice to add once that PR is merged, one of these years.

[som-snytt]

I goosed the Scala 2 PR again. I have no idea why they thought it was essential to put "val" in front of REPL output, but it doesn't matter whether strings are rendered with quotes. With quotes, Scala 3 colors are correct.

scala> "val a: B"
val res1: String = val a: B

scala> """"val a: B""""
val res2: String = "val a: B"

[bjornregnell]

I think the val makes sense from a learner's perspective. It makes it obvious what happens semantically in the REPL session. And with your nice quotes in output the code is even executable ;) which is even better. I think the quotes should always be there when rendering strings in the output so the code is executable. And it the string contains quotes it should be tripple-quoted if we buy that logic (that the output of a evaluated value is valid code).

[som-snytt]

This is the Scala 2 REPL PR:

scala> """"hello, world""""
val res1: String = "\"hello, world\""

scala> """"hello,
     | world""""
val res2: String =
"""\"hello,
world\""""

The escaping triple quotes for multiline, but uses ordinary escape for internal quote.

Edit: actually, the second example is wrong, it shouldn't do both! thanks for the heads up, @bjornregnell