Empty or singleton array/list expressions are considered "simple" (#1943

)

CHANGES.md

@@ -12,7 +12,9 @@
 
 #### Changes
 
-  + Variant expressions with no argument are considered "simple" (not inducing a break e.g. as an argument of an application) (#1968, @gpetiot)
+  + More expressions are considered "simple" (not inducing a break e.g. as an argument of an application):
+    - Variants with no argument (#1968, @gpetiot)
+    - Empty or singleton arrays/lists (#1943, @gpetiot)
 
   + Print odoc code block delimiters on their own line (#1980, @gpetiot)
 

lib/Ast.ml

@@ -314,6 +314,8 @@ module Exp = struct
         ({pexp_desc= Pexp_ident {txt= Lident "not"; _}; _}, [(_, e1)]) ->
         is_trivial e1
     | Pexp_variant (_, None) -> true
+    | Pexp_array [] | Pexp_list [] -> true
+    | Pexp_array [x] | Pexp_list [x] -> is_trivial x
     | _ -> false
 
   let rec exposed_left e =

test/passing/tests/js_source.ml

@@ -7603,3 +7603,15 @@ let x =
     ~f:(fun thing ->
       something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
 ;;
+
+let x =
+  foo [ A; B ] ~f:(fun thing ->
+    something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
+;;
+
+let x =
+  foo
+    [ [ A ]; B ]
+    ~f:(fun thing ->
+      something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
+;;

test/passing/tests/js_source.ml.ocp

@@ -9844,3 +9844,13 @@ let x =
   foo (`A `b) ~f:(fun thing ->
       something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
 ;;
+
+let x =
+  foo [ A; B ] ~f:(fun thing ->
+      something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
+;;
+
+let x =
+  foo [ [ A ]; B ] ~f:(fun thing ->
+      something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
+;;

test/passing/tests/js_source.ml.ref

@@ -9844,3 +9844,13 @@ let x =
   foo (`A `b) ~f:(fun thing ->
       something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
 ;;
+
+let x =
+  foo [ A; B ] ~f:(fun thing ->
+      something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
+;;
+
+let x =
+  foo [ [ A ]; B ] ~f:(fun thing ->
+      something that reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally needs wrapping)
+;;

test/passing/tests/source.ml.ref

@@ -8967,9 +8967,7 @@ let h ?l:(p = 1) ?y:u ?(x = 3) = 2
 let _ = function
   | a, s, ba1, ba2, ba3, bg ->
       ignore
-        ( Array.get x 1
-        + Array.get [||] 0
-        + Array.get [|1|] 1
+        ( Array.get x 1 + Array.get [||] 0 + Array.get [|1|] 1
         + Array.get [|1; 2|] 2 ) ;
       ignore [String.get s 1; String.get "" 2; String.get "123" 3] ;
       ignore (ba1.{0} + ba2.{1, 2} + ba3.{3, 4, 5}) ignore bg.{1, 2, 3, 4}