Transform multiline brace blocks to do/end blocks

fixtures/small/block_local_variables_expected.rb

@@ -1,10 +1,10 @@
 y = 12
-lambda { |x, ;y|
+lambda do |x, ;y|
   puts(x)
   puts(y)
   y = 19
   puts(y)
-}
+end
   .call(17)
 puts(y)
 

fixtures/small/blocks_with_only_comments_expected.rb

@@ -15,15 +15,15 @@ def foo
   end
 
   # More comments!!
-  commented_brace_block {
+  commented_brace_block do
     # Such plainness of the pre-baroque
     # Hardly involves the eye, until
     # It meets his left-hand gauntlet, still
     # Clasped empty in the other; and
     # One sees, with a sharp tender shock,
 
     # His hand withdrawn, holding her hand.
-  }
+  end
 
   method_call
 end

fixtures/small/brace_to_do_blocks_actual.rb

@@ -0,0 +1,12 @@
+things.map { |thing| stuff; thing ** 2 }
+
+things.map { |thing|
+    # A comment makes this multiline!
+    thing
+}
+
+class Foo
+  # !! `example_dsl [].map { |k| k; k+1 }` is not equivalent to 
+  # !! `example_dsl [].map do |k| k; k+1 end`
+  example_dsl [].map { |k| k; k+1 }
+end

fixtures/small/brace_to_do_blocks_expected.rb

@@ -0,0 +1,20 @@
+things.map do |thing|
+  stuff
+  thing ** 2
+end
+
+things.map do |thing|
+  # A comment makes this multiline!
+  thing
+end
+
+class Foo
+  # !! `example_dsl [].map { |k| k; k+1 }` is not equivalent to
+  # !! `example_dsl [].map do |k| k; k+1 end`
+  example_dsl(
+    [].map do |k|
+      k
+      k + 1
+    end
+  )
+end

fixtures/small/curly_line_breaking_expected.rb

@@ -1,5 +1,5 @@
 do_something { |a| [a] }
-do_something { |a|
+do_something do |a|
   [
     1,
     2,
@@ -105,4 +105,4 @@
     3,
     3
   ]
-}
+end

fixtures/small/method_chains_expected.rb

@@ -1,8 +1,8 @@
 returns_array
-  .map { |foo|
+  .map do |foo|
     thing = foo.idk
     thing.call
-  }
+  end
   .chain do |bar|
     bar.do_stuff!
   end
@@ -110,10 +110,10 @@ def example
   .foo
   .bar
   .baz
-  .map { |x|
+  .map do |x|
     multiline
     block
-  }
+  end
   .bacon
   .next_call(
     a: "",

fixtures/small/multiline_chain_in_block_expected.rb

@@ -1,8 +1,8 @@
-sig {
+sig do
   params(
     route: String
   ).void
-}
+end
 def ajax_get(route)
   super
 end

librubyfmt/src/format.rs

@@ -3072,7 +3072,20 @@ fn should_multiline_call_chain(ps: &mut dyn ConcreteParserState, method_call: &M
 }
 
 pub fn format_block(ps: &mut dyn ConcreteParserState, b: Block) {
-    match b {
+    let block = match b {
+        Block::DoBlock(..) => b,
+        Block::BraceBlock(bb) => {
+            // Transform multiline BraceBlocks into do/end blocks
+            if bb.2.len() > 1
+                || ps.will_render_as_multiline(Box::new(|ps| format_brace_block(ps, bb.clone())))
+            {
+                Block::DoBlock(bb.into_do_block())
+            } else {
+                Block::BraceBlock(bb)
+            }
+        }
+    };
+    match block {
         Block::BraceBlock(bb) => format_brace_block(ps, bb),
         Block::DoBlock(db) => format_do_block(ps, db),
     }

librubyfmt/src/ripper_tree_types.rs

@@ -1912,6 +1912,17 @@ pub struct BraceBlock(
     pub StartEnd,
 );
 
+impl BraceBlock {
+    pub fn into_do_block(self) -> DoBlock {
+        DoBlock(
+            do_block_tag,
+            self.1,
+            Box::new(BodyStmt(bodystmt_tag, self.2, None, None, None)),
+            self.3,
+        )
+    }
+}
+
 def_tag!(while_tag, "while");
 #[derive(Deserialize, Debug, Clone)]
 pub struct While(