Adjust formatting of line comments in lets (#1256)

pkl-formatter/src/main/kotlin/org/pkl/formatter/Builder.kt

@@ -972,18 +972,22 @@ internal class Builder(sourceText: String, private val grammarVersion: GrammarVe
 
   private fun formatLetExpr(node: Node): FormatNode {
     val separator = if (node.isMultiline()) forceLine() else spaceOrLine()
+    val endsWithLet = node.children.last().type == NodeType.LET_EXPR
     val nodes =
       formatGenericWithGen(
         node.children,
         { _, next -> if (next.type == NodeType.LET_PARAMETER_DEFINITION) Space else separator },
-      ) { node, next ->
-        if (next == null) {
-          if (node.type == NodeType.LET_EXPR) {
+      ) { node, _ ->
+        when {
+          node.type == NodeType.LET_EXPR -> {
             // unpack the lets
             val group = formatLetExpr(node) as Group
             Nodes(group.nodes)
-          } else indent(format(node))
-        } else format(node)
+          }
+          endsWithLet -> format(node)
+          node.type.isExpression || node.type.isAffix -> indent(format(node))
+          else -> format(node)
+        }
       }
     return Group(newId(), nodes)
   }

pkl-formatter/src/test/files/FormatterSnippetTests/input/comment-interleaved.pkl

@@ -29,3 +29,46 @@ bar2 = ( // some comment
     foo, bar
     // another comment
   ) -> foo + bar
+
+bar3 =
+  let (bar = new Dynamic {})
+    // some coment
+    (bar) {
+      qux = 4
+    }
+
+bar4 =
+  // some coment
+  let (bar = new Dynamic {})
+    (bar) {
+      qux = 4
+    }
+
+bar5 =
+  let (bar = 4)
+  // some coment
+  let (qux = 5)
+    bar + qux
+
+bar6 =
+  let (bar = 4)
+    /* some comment */ bar + 5
+
+bar7 =
+  let (bar = 4) /* some comment */
+    bar + 5
+
+bar8 =
+  let (bar = 4)
+    // some comment
+    // another comment
+  let (foo = 5)
+    // some comment
+    // another comment
+      bar + foo
+
+bar9 =
+  let (bar = 4)
+    // some comment
+    // another comment
+    bar

pkl-formatter/src/test/files/FormatterSnippetTests/output/comment-interleaved.pkl

@@ -32,3 +32,46 @@ bar2 = ( // some comment
   bar
   // another comment
 ) -> foo + bar
+
+bar3 =
+  let (bar = new Dynamic {})
+    // some coment
+    (bar) {
+      qux = 4
+    }
+
+bar4 =
+  // some coment
+  let (bar = new Dynamic {})
+    (bar) {
+      qux = 4
+    }
+
+bar5 =
+  let (bar = 4)
+  // some coment
+  let (qux = 5)
+    bar + qux
+
+bar6 =
+  let (bar = 4)
+    /* some comment */ bar + 5
+
+bar7 =
+  let (bar = 4) /* some comment */
+    bar + 5
+
+bar8 =
+  let (bar = 4)
+  // some comment
+  // another comment
+  let (foo = 5)
+    // some comment
+    // another comment
+    bar + foo
+
+bar9 =
+  let (bar = 4)
+    // some comment
+    // another comment
+    bar