Improve printing of destructuring with local open.

CHANGES.md

@@ -8,6 +8,7 @@
   (@anmonteiro, [#2774](https://github.com/reasonml/reason/pull/2774))
 - Print poly variants as normal variansts (@Sander Spies) [#2708](https://github.com/reasonml/reason/pull/2708)
 - Improve printing of anonymous function return type
+- Improve printing of destructuring with local open. [#2684](https://github.com/reasonml/reason/pull/2684)
 
 ## 3.12.0
 

src/reason-parser/reason_pprint_ast.ml

@@ -5312,6 +5312,34 @@ let printer = object(self:'self)
          forms of explicit polymorphic annotations in the parse tree, and how
          we must recover them here.
        *)
+      | [], (Ppat_open (lid, {ppat_desc = Ppat_record(l, closed); _})) ->
+        (*
+         Special case handling for:
+
+         let Foo.{
+           destruct1,
+           destruct2,
+           destruct3,
+           destruct4,
+           destruct5,
+         } = bar;
+        *)
+
+        let upUntilEqual =
+          let pat = self#patternRecord l closed in
+          label
+            (label ~space:true
+              (atom prefixText)
+              (label
+                (self#longident_loc lid)
+                (atom ("."))
+              )
+            )
+            pat
+        in
+        let appTerms = self#unparseExprApplicationItems expr in
+        let includingEqual = makeList ~postSpace:true [upUntilEqual; atom "="] in
+        formatAttachmentApplication applicationFinalWrapping (Some (true, includingEqual)) appTerms
       | [], (Ppat_constraint(p, ty)) -> (
           (* Locally abstract forall types are *seriously* mangled by the parsing
              stage, and we have to be very smart about how to recover it.

test/general-syntax-re.t/input.re

@@ -1246,6 +1246,14 @@ let testCallNamedArgs = (foo: ((~a: int, ~b: int=?) => int), a, b) =>
 let Foo.{name} = bar;
 let Foo.Bar.{name} = bar;
 
+let Foo.{
+  destruct1,
+  destruct2,
+  destruct3,
+  destruct4,
+  destruct5,
+} = fooBar;
+
 let Foo.[ name ] = bar;
 let Foo.Bar.[ name ] = bar;
 
@@ -1284,3 +1292,10 @@ let x = 1.123g;
 
 let x = switch () { | _ => .};
 
+let%foo Foo.{
+  destruct1,
+  destruct2,
+  destruct3,
+  destruct4,
+  destruct5,
+} = fooBar;

test/general-syntax-re.t/run.t

@@ -1432,6 +1432,14 @@ Format general implementation syntax
   let Foo.{name} = bar;
   let Foo.Bar.{name} = bar;
 
+  let Foo.{
+    destruct1,
+    destruct2,
+    destruct3,
+    destruct4,
+    destruct5,
+  } = fooBar;
+
   let Foo.[name] = bar;
   let Foo.Bar.[name] = bar;
 
@@ -1472,3 +1480,11 @@ Format general implementation syntax
     switch () {
     | _ => .
     };
+
+  let%foo Foo.{
+    destruct1,
+    destruct2,
+    destruct3,
+    destruct4,
+    destruct5,
+  } = fooBar;