Preserve function body braces

This is an alternative to reasonml#1826 implementing just the brace preservation
code, to make it easier to be reviewed.

I think this is now in a better place to get into the codebase given
that we have `Reason_attributes` outside of `Reason_pprint_ast` and that
we now remove our own attributes before printing to OCaml.

I think we can probably refactor this code further in future PRs, as
well as add other stylistic preservation changes.

Author: anmonteiro

formatTest/typeCheckedTests/expected_output/attributes.re

@@ -99,7 +99,11 @@ let x = [@attrEverything] (true && false);
 /**
  * How attribute parsings respond to other syntactic constructs.
  */
-let add = a => [@onRet] a;
+let add = a =>
+  [@onRet]
+  {
+    a;
+  };
 let add = a => [@onRet] a;
 let add = [@onEntireFunction] (a => a);
 
@@ -342,8 +346,18 @@ type classAttributesOnKeys = {
   .
   [@bs.set] key1: string,
   /* The follow two are the same */
-  [@bs.get null] key2: [@onType2] Js.t(int),
-  [@bs.get null] key3: [@onType2] Js.t(int),
+  [@bs.get
+    {
+      null;
+    }
+  ]
+  key2: [@onType2] Js.t(int),
+  [@bs.get
+    {
+      null;
+    }
+  ]
+  key3: [@onType2] Js.t(int),
   key4: Js.t([@justOnInt] int),
 };
 

formatTest/typeCheckedTests/expected_output/fastPipe.re

@@ -26,8 +26,9 @@ let c = true;
 let t3: bool = !a->b->c;
 
 /* parse fast pipe with  underscore application correct */
-let doStuff = (a: int, b: int, c: int): int =>
+let doStuff = (a: int, b: int, c: int): int => {
   a + 2 * b + 3 * c;
+};
 
 let (|.) = (a, f) => f(a);
 
@@ -69,18 +70,16 @@ let saveStatus = Pristine;
 
 let t7: string =
   <Foo>
-    {
-      (
-        switch (saveStatus) {
-        | Pristine => [0]
-        | Saved => [1]
-        | Saving => [2]
-        | Unsaved => [3]
-        }
-      )
-      ->Foo.map(Foo.plusOne)
-      ->Foo.toString
-    }
+    {(
+       switch (saveStatus) {
+       | Pristine => [0]
+       | Saved => [1]
+       | Saving => [2]
+       | Unsaved => [3]
+       }
+     )
+     ->Foo.map(Foo.plusOne)
+     ->Foo.toString}
   </Foo>;
 
 let genItems = f => List.map(f, items);
@@ -99,23 +98,19 @@ let foo = xs => List.concat([xs, xs]);
 
 let t10: string =
   <Foo>
-    {
-      blocks
-      ->foo
-      ->Foo.map(Foo.plusOne)
-      ->Foo.toString
-    }
+    {blocks
+     ->foo
+     ->Foo.map(Foo.plusOne)
+     ->Foo.toString}
   </Foo>;
 
 let t11: string =
   <Foo>
-    {
-      blocks
-      ->foo
-      ->Foo.map(Foo.plusOne)
-      ->Foo.map(Foo.plusOne)
-      ->Foo.toString
-    }
+    {blocks
+     ->foo
+     ->Foo.map(Foo.plusOne)
+     ->Foo.map(Foo.plusOne)
+     ->Foo.toString}
   </Foo>;
 
 let title = "los pilares de la tierra";
@@ -164,11 +159,9 @@ module FooLabeled = {
 
 let t14: string =
   <FooLabeled>
-    {
-      items
-      ->FooLabeled.map(~f=FooLabeled.plusOne)
-      ->FooLabeled.toString
-    }
+    {items
+     ->FooLabeled.map(~f=FooLabeled.plusOne)
+     ->FooLabeled.toString}
   </FooLabeled>;
 
 let c = (a, b) => a + b;

formatTest/typeCheckedTests/expected_output/jsx.re

@@ -102,29 +102,32 @@ module Namespace = {
 };
 
 module Optional1 = {
-  let createElement = (~required, ~children, ()) =>
+  let createElement = (~required, ~children, ()) => {
     switch (required) {
     | Some(a) => {displayName: a}
     | None => {displayName: "nope"}
     };
+  };
 };
 
 module Optional2 = {
   let createElement =
-      (~optional=?, ~children, ()) =>
+      (~optional=?, ~children, ()) => {
     switch (optional) {
     | Some(a) => {displayName: a}
     | None => {displayName: "nope"}
     };
+  };
 };
 
 module DefaultArg = {
   let createElement =
-      (~default=Some("foo"), ~children, ()) =>
+      (~default=Some("foo"), ~children, ()) => {
     switch (default) {
     | Some(a) => {displayName: a}
     | None => {displayName: "nope"}
     };
+  };
 };
 
 module LotsOfArguments = {
@@ -175,8 +178,9 @@ let notReallyJSX = (~foo, ~bar, children) => {
   displayName: "test",
 };
 
-let fakeRender = (el: component) =>
+let fakeRender = (el: component) => {
   el.displayName;
+};
 
 /* end of setup */
 
@@ -384,7 +388,7 @@ let asd2 = [@foo] [@JSX] video(~test=false, 10);
 let div = (~children) => 1;
 [@JSX] ((() => div)())(~children=[]);
 
-let myFun = () =>
+let myFun = () => {
   <>
     <Namespace.Foo
       intended=true
@@ -405,10 +409,13 @@ let myFun = () =>
       <Foo />
     </Namespace.Foo>
   </>;
+};
 
-let myFun = () => <> </>;
+let myFun = () => {
+  <> </>;
+};
 
-let myFun = () =>
+let myFun = () => {
   <>
     <Namespace.Foo
       intended=true
@@ -429,6 +436,7 @@ let myFun = () =>
       <Foo />
     </Namespace.Foo>
   </>;
+};
 
 /**
  * Children should wrap without forcing attributes to.

formatTest/typeCheckedTests/expected_output/oo.re

@@ -14,12 +14,18 @@ class virtual stack ('a) (init) = {
       Some(hd);
     | [] => None
     };
-  pub push = hd => v = [hd, ...v];
-  initializer (
-    print_string("initializing object")
-  );
-  pub explicitOverrideTest = a => a + 1;
-  pri explicitOverrideTest2 = a => a + 1;
+  pub push = hd => {
+    v = [hd, ...v];
+  };
+  initializer {
+    print_string("initializing object");
+  };
+  pub explicitOverrideTest = a => {
+    a + 1;
+  };
+  pri explicitOverrideTest2 = a => {
+    a + 1;
+  };
 };
 
 let tmp = {
@@ -50,10 +56,12 @@ class virtual stackWithAttributes ('a) (init) = {
       Some(hd);
     | [] => None
     };
-  pub push = hd => v = [hd, ...v];
-  initializer (
-    print_string("initializing object")
-  );
+  pub push = hd => {
+    v = [hd, ...v];
+  };
+  initializer {
+    print_string("initializing object");
+  };
 };
 
 class extendedStack ('a) (init) = {
@@ -67,9 +75,15 @@ class extendedStackAcknowledgeOverride
       (init) = {
   inherit (class stack('a))(init);
   val dummy = ();
-  pub implementMe = i => i + 1;
-  pub! explicitOverrideTest = a => a + 2;
-  pri! explicitOverrideTest2 = a => a + 2;
+  pub implementMe = i => {
+    i + 1;
+  };
+  pub! explicitOverrideTest = a => {
+    a + 2;
+  };
+  pri! explicitOverrideTest2 = a => {
+    a + 2;
+  };
 };
 
 let inst = (new extendedStack)([1, 2]);
@@ -133,8 +147,12 @@ let anonClosedObject: {
   x: int,
   y: int,
 } = {
-  pub x = 0;
-  pub y = 0
+  pub x = {
+    0;
+  };
+  pub y = {
+    0;
+  }
 };
 
 let onlyHasX = {pub x = 0};

formatTest/typeCheckedTests/expected_output/reasonComments.re

@@ -94,8 +94,9 @@ let myFunction = /* First arg */
       withFirstArg,
       /* Second Arg */
       andSecondArg,
-    ) =>
-  withFirstArg + andSecondArg; /* After Semi */
+    ) => {
+  withFirstArg + andSecondArg;
+}; /* After Semi */
 
 type point = {
   x: string, /* x field */
@@ -300,7 +301,11 @@ type intPair2 = (
   int,
 );
 
-let result = /**/ (2 + 3);
+let result =
+  /**/
+  {
+    2 + 3;
+  };
 
 /* This is not yet idempotent */
 /* { */
@@ -333,7 +338,9 @@ let blahCurriedX = x =>
   | Black(x) => 0 /* After black */
   | Green(x) => 0; /* After second green */ /* On next line after blahCurriedX def */
 
-let name_equal = (x, y) => x == y;
+let name_equal = (x, y) => {
+  x == y;
+};
 
 let equal = (i1, i2) =>
   i1.contents === i2.contents && true; /* most unlikely first */

formatTest/typeCheckedTests/expected_output/sequences.re

@@ -23,8 +23,16 @@ let twenty = 20;
  * printed in reduced form because sequences are a *parse* time construct.
  * To ensure these are parsed correctly, adding to an integer.
  */
-let result = 0 + twenty;
-let result = 0 + twenty;
+let result =
+  0
+  + {
+    twenty;
+  };
+let result =
+  0
+  + {
+    twenty;
+  };
 let result = 0 + twenty;
 
 let unitValue = ();
@@ -56,7 +64,9 @@ let cannotPunASingleFieldRecord = {
 };
 let fourty =
   20 + cannotPunASingleFieldRecord.number;
-let thisIsASequenceNotPunedRecord = number;
+let thisIsASequenceNotPunedRecord = {
+  number;
+};
 let fourty = 20 + thisIsASequenceNotPunedRecord;
 
 type recordType = {

formatTest/typeCheckedTests/expected_output/trailing.re

@@ -172,9 +172,9 @@ class virtual
   ];
   pub virtual implementMe:
     (int, int) => (int, int);
-  initializer (
-    print_string("initializing object")
-  );
+  initializer {
+    print_string("initializing object");
+  };
 };
 
 class extendedStack