feat: allow choosing loose parens

- There are a few cases where it's valid to have it loose,
  but we cannot guess algorithmically in all cases,
  so let's leave a small door open in the cases that
  we cannot guess, but force when we are sure

src/alejandra_engine/src/rules/paren.rs

@@ -16,7 +16,19 @@ pub(crate) fn rule(
         || expression.has_comments
         || closer.has_inline_comment
         || closer.has_comments
-        || matches!(expression.element.kind(), rnix::SyntaxKind::NODE_IF_ELSE);
+        || matches!(expression.element.kind(), rnix::SyntaxKind::NODE_IF_ELSE)
+        || ((opener.has_trivialities
+            || expression.has_trivialities
+            || closer.has_trivialities)
+            && !matches!(
+                expression.element.kind(),
+                rnix::SyntaxKind::NODE_ATTR_SET
+                    | rnix::SyntaxKind::NODE_IDENT
+                    | rnix::SyntaxKind::NODE_LITERAL
+                    | rnix::SyntaxKind::NODE_LIST
+                    | rnix::SyntaxKind::NODE_STRING
+                    | rnix::SyntaxKind::NODE_UNARY_OP
+            ));
 
     let should_indent = loose
         || matches!(

src/alejandra_engine/tests/cases/apply/out

@@ -1,7 +1,8 @@
 [
   (a
     b)
-  ((a b)
+  (
+    (a b)
     (a b)
     (a
       /*
@@ -20,9 +21,11 @@
       /*
        e
        */
-    ))
+    )
+  )
   ''
-    otherModules=${pkgs.writeText "other-modules.json"
+    otherModules=${
+      pkgs.writeText "other-modules.json"
       (l.toJSON
         (l.mapAttrs
           (pname: subOutputs: let
@@ -31,7 +34,8 @@
               installMethod = "copy";
             });
           in "${pkg}/lib/node_modules/${pname}/node_modules")
-          outputs.subPackages))}
+          outputs.subPackages))
+    }
   ''
   {
     name1 =

src/alejandra_engine/tests/cases/lambda/out

@@ -35,8 +35,12 @@
      c
      */
       d)
-  (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
+  (
-  (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+  )
+  (
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+  )
   ({
     pkgs ? import ./.. {},
     locationsXml,

src/alejandra_engine/tests/cases/paren/out

@@ -1,4 +1,5 @@
-(( # test
+(
+  ( # test
     a # test
   )
   c
@@ -160,4 +161,5 @@
     /*
      e
      */
-  ))
+  )
+)

src/alejandra_engine/tests/cases/pattern/out

@@ -1059,7 +1059,8 @@
   }:
     _)
 
-  ({
+  (
+    {
       /*
        a
        */
@@ -1117,5 +1118,6 @@
      j
      */
     #
-      _)
+      _
+  )
 ]