Kotlin string concatenation - preserving indents with multiline strings

This is a common problem in practice, not trimIndent()'s problem. @gidds has explained it very clearly. If you want to achieve what you want, you can use trimMargin().

fun main(args: Array<String>) { val myString = """ hello world """.trimIndent() println(""" |teststring2 |$myString """.trimMargin()) } 

Output:

teststring2 hello world 

Here's the first string literal.  (To avoid confusion, I'll use underscores to represent spaces.)

____hello ____world 

Its trimIndent() call will remove the spaces, leaving it with no indentation, like this:

hello world 

The second string looks like this:

________teststring2 ________$myString 

Then the $myString will be substituted precisely with the contents of the first:

________teststring2 ________hello world 

Note that the indentation that was before $myString remains, giving the spaces you see before the "hello"; but there's no indentation within myString, so you don't see any before "world".

Now, trimIndent() removes “a common minimal indent of all the input lines”.  But there's no common indent here, because of the last line.  So the second trimIndent() call does nothing.

As to what to do, there are probably several options.  If you don't want any indents, then the most obvious would be to remove all indents, not just common ones.  (I don't think there's a dedicated function in the standard library, but it should be easy enough to write one.  For example, you could do a regular expression replace of "^ *" with "".)