add support for Kotlin multi-dollar interpolation string (#7090)

Author: barbulescu

rewrite-kotlin/src/main/java/org/openrewrite/kotlin/internal/KotlinTreeParserVisitor.java

@@ -3132,15 +3132,24 @@ public J visitStringTemplateExpression(KtStringTemplateExpression expression, Ex
     }
 
     private static String getString(KtStringTemplateExpression expression, StringBuilder valueSb) {
-        PsiElement openQuote = expression.getFirstChild();
+        PsiElement openQuote;
+        String prefix;
+        if (expression.getInterpolationPrefix() == null) {
+            openQuote = expression.getFirstChild();
+            prefix = "";
+        } else {
+            openQuote = expression.getFirstChild().getNextSibling();
+            prefix = expression.getInterpolationPrefix().getInterpolationPrefix();
+        }
+
         PsiElement closingQuota = expression.getLastChild();
         if (openQuote == null || closingQuota == null ||
             openQuote.getNode().getElementType() != KtTokens.OPEN_QUOTE ||
             closingQuota.getNode().getElementType() != KtTokens.CLOSING_QUOTE) {
             throw new UnsupportedOperationException("This should never happen");
         }
 
-        return openQuote.getText() + valueSb + closingQuota.getText();
+        return prefix + openQuote.getText() + valueSb + closingQuota.getText();
     }
 
     @Override

rewrite-kotlin/src/test/java/org/openrewrite/kotlin/KotlinParserTest.java

@@ -63,4 +63,15 @@ class MyClass
         );
     }
 
+    @Test
+    void multiDollarStringInterpolation() {
+        rewriteRun(
+          kotlin(
+            """
+              val x = $$"$something"
+              """
+          )
+        );
+    }
+
 }