How to insert double quotes into String with interpolation in scala

This is a bug in Scala:

escape does not work with string interpolation

but maybe you can use:

scala> import org.apache.commons.lang.StringEscapeUtils.escapeJava
import org.apache.commons.lang.StringEscapeUtils.escapeJava

scala> escapeJava("this is a string\nover two lines")
res1: java.lang.String = this is a string\nover two lines

You don't need to escape quotes in triple-quoted string, so s""""$value""""" will work. Admittedly, it doesn't look good either.

Another solution (also mentioned in the Scala tracker) is to use

case _ => s"${'"'}$value${'"'}"

Still ugly, but sometimes perhaps may be preferred over triple quotes.

It seems an escape sequence $" was suggested as a part of SIP-24 for 2.12:

case _ => s"$"$value$""

This SIP was never accepted, as it contained other more controversial suggestions. Currently there is an effort to get escape sequence $" implemented in 2.13 as Pre SIP/mini SIP $” escapes in interpolations.

For your use case, they make it easy to achieve nice syntax.

scala> implicit class `string quoter`(val sc: StringContext) {
     | def q(args: Any*): String = "\"" + sc.s(args: _*) + "\""
     | }
defined class string$u0020quoter

scala> q"hello,${" "*8}world"
res0: String = "hello,        world"

scala> "hello, world"
res1: String = hello, world       // REPL doesn't add the quotes, sanity check

scala> " hello, world "
res2: String = " hello, world "   // unless the string is untrimmed

Squirrel the implicit away in a package object somewhere.

You can name the interpolator something besides q, of course.

Last week, someone asked on the ML for the ability to use backquoted identifiers. Right now you can do res3 but not res4:

scala> val `"` = "\""
": String = "

scala> s"${`"`}"
res3: String = "

scala> s"hello, so-called $`"`world$`"`"
res4: String = hello, so-called "world"

Another idea that just occurred to me was that the f-interpolator already does some work to massage your string. For instance, it has to handle "%n" intelligently. It could, at the same time, handle an additional escape "%q" which it would not pass through to the underlying formatter.

That would look like:

scala> f"%qhello, world%q"
<console>:9: error: conversions must follow a splice; use %% for literal %, %n for newline

That's worth an enhancement request.

Update: just noticed that octals aren't deprecated in interpolations yet:

scala> s"\42hello, world\42"
res12: String = "hello, world"