KT-8708 Function to strip leading whitespace (stripMargin, trimMargin, stripIndent?)

libraries/stdlib/test/text/StringTest.kt

@@ -1,6 +1,9 @@
 package test.text
 
-import kotlin.test.*
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+import kotlin.test.fails
 import org.junit.Test as test
 
 // could not be local inside isEmptyAndBlank, because non-toplevel declarations is not yet supported for JS
@@ -555,5 +558,114 @@ class StringTest {
         assertEquals("-test", "test".replaceFirst("", "-"))
     }
 
+    test fun trimMargin() {
+        // WARNING
+        // DO NOT REFORMAT AS TESTS MAY FAIL DUE TO INDENTATION CHANGE
 
+        assertEquals("ABC\n123\n456", """ABC
+                                      |123
+                                      |456""".trimMargin())
+
+        assertEquals("  ABC\n  123\n  456", """ABC
+                                      |123
+                                      |456""".trimMargin(newIndent = "  "))
+
+        assertEquals("ABC \n123\n456", """ABC${" "}
+                                      |123
+                                      |456""".trimMargin())
+
+        assertEquals(" ABC\n123\n456", """ ABC
+                                        >>123
+                                        ${"\t"}>>456""".trimMargin(">>"))
+
+        assertEquals("", "".trimMargin())
+
+        assertEquals("", """
+                            """.trimMargin())
+
+        assertEquals("", """
+                            |""".trimMargin())
+
+        assertEquals("", """
+                            |
+                            """.trimMargin())
+
+        assertEquals("    a", """
+            |    a
+        """.trimMargin())
+
+        assertEquals("    a", """
+            |    a""".trimMargin())
+
+        assertEquals("    a", """ |    a
+        """.trimMargin())
+
+        assertEquals("    a", """ |    a""".trimMargin())
+
+        assertEquals("\u0000|ABC", "${"\u0000"}|ABC".trimMargin())
+    }
+
+    test fun trimIndent() {
+        // WARNING
+        // DO NOT REFORMAT AS TESTS MAY FAIL DUE TO INDENTATION CHANGE
+
+        assertEquals("123", """
+        123
+        """.trimIndent())
+
+        assertEquals("123\n   456", """
+        123
+           456
+           """.trimIndent())
+
+        assertEquals("   123\n456", """
+           123
+        456
+        """.trimIndent())
+
+        assertEquals("     123\n  456", """
+           123
+        456
+        """.trimIndent(newIndent = "  "))
+
+        assertEquals("   123\n456", """
+           123
+        456""".trimIndent())
+
+        assertEquals("    ", """
+${"    "}
+        """.trimIndent())
+
+        val deindented = """
+                                                            ,.
+                      ,.                     _       oo.   `88P
+                     ]88b              ,o.  d88.    ]88b     '
+                      888   _          Y888o888     d88P     _     _
+                      888 ,888          `Y88888o_  ,888    d88b   d88._____
+                      888,888P ,oooooo.   ;888888b.]88P    888'   d888888888p
+                      888888P d88888888.  J88b'YPP ]88b   ,888    d888P'''888.
+                      8888P' ]88P   `888  d88[     d88P   ]88b    888'    Y88b
+                      8888p  ]88b    888  888      d88[    888    888.    `888
+                     ,88888b  888[   888  888.     d88[    888.   Y88b     Y88[
+                     d88PY88b `888L,d88P  Y88b     Y88b    ]88b   `888     888'
+                     888  Y88b  Y88888P    888.     888.    888.   Y88b   `88P
+                    d88P   888   `'P'      Y888.    `888.   `88P   `Y8P     '
+                    Y8P'    '               `YP      Y8P'     '
+
+                    ____       dXp   _    _        _________
+                  ddXXXXXp     XXP  ,XX  dXb      Yo.XXXXXX      ,oooooo.
+                  X'L_oXXP     XX'   XX[ dXb      dXb            YPPPPXXX'
+                  XYXXXXX     ]XX    dXb dXb      dX8Xooooo         dXXP
+                  XXb`YYXXo.   YXXo_ dXP dXP      YXb''''''       ,XXP'
+                  `XX   `YYXb   `YXXXXP  XX[      ]XX            ,XX'
+                   YXb     YXb     `''   XXXXooL  `XX._____      `XXXXXXXXooooo.
+                   `XP      '             ''''''   YPXXXXXX'       ''''''`''YPPP
+        """.trimIndent()
+
+        assertEquals(23, deindented.lines().size())
+        val indents = deindented.lines().map { "^\\s*".toRegex().match(it)!!.value.length() }
+        assertEquals(0, indents.min())
+        assertEquals(42, indents.max())
+        assertEquals(1, deindented.lines().count { it.isEmpty() })
+    }
 }