Fix let formatting (#1246)

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

@@ -791,7 +791,7 @@ internal class Builder(sourceText: String) {
   private fun formatLetParameterDefinition(node: Node): FormatNode {
     val nodes =
       formatGeneric(node.children) { prev, next ->
-        if (prev.isTerminal("(")) null else if (next.isTerminal(")")) Line else SpaceOrLine
+        if (prev.isTerminal("(") || next.isTerminal(")")) Line else SpaceOrLine
       }
     return Group(newId(), nodes)
   }

pkl-formatter/src/test/files/FormatterSnippetTests/input/expr-let.pkl

@@ -9,3 +9,9 @@ baz =
   let (someVariable = 10000000)
     let (someOtherVariable = 2000000)
       let (someAnotherVariable = 3000000) someVariable + someOtherVariable + someAnotherVariable
+
+qux = let ( // some comment
+    // another comment
+    bar = 5
+  )
+    bar

pkl-formatter/src/test/files/FormatterSnippetTests/input/when.pkl

@@ -7,3 +7,12 @@ foo {
     bar = 2
   }
 }
+
+bar {
+  when (new Listing {
+    1
+    2
+  }.contains(1)) {
+    "1"
+  }
+}

pkl-formatter/src/test/files/FormatterSnippetTests/output/expr-let.pkl

@@ -1,11 +1,13 @@
 foo =
-  let (vaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaariable =
+  let (
+    vaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaariable =
       10
   )
     1 * 1
 
 bar =
-  let (someVariable = new Listing {
+  let (
+    someVariable = new Listing {
       1
     }
   )
@@ -16,3 +18,10 @@ baz =
   let (someOtherVariable = 2000000)
   let (someAnotherVariable = 3000000)
     someVariable + someOtherVariable + someAnotherVariable
+
+qux =
+  let ( // some comment
+    // another comment
+    bar = 5
+  )
+    bar

pkl-formatter/src/test/files/FormatterSnippetTests/output/when.pkl

@@ -5,3 +5,14 @@ foo {
     bar = 2
   }
 }
+
+bar {
+  when (
+    new Listing {
+      1
+      2
+    }.contains(1)
+  ) {
+    "1"
+  }
+}