[fix] Properly indent case/in statements (#887)

* Add test fixtures

* [fix] Properly indent case/in statements

Author: reese

fixtures/small/prism/case_match_nested_actual.rb

@@ -0,0 +1,23 @@
+module App
+  config = {db: {user: 'admin', password: 'abc123'}}
+
+  case config
+  in {db: {user:}}
+    puts "Connect with user '#{user}'"
+  in {connection: {username: }}
+    puts "Connect with user '#{username}'"
+  else
+    puts "Unrecognized structure of config"
+  end
+end
+
+class Foo
+  def bar(value)
+    case value
+    in 1
+      "one"
+    in 2
+      "two"
+    end
+  end
+end

fixtures/small/prism/case_match_nested_expected.rb

@@ -0,0 +1,23 @@
+module App
+  config = {db: {user: "admin", password: "abc123"}}
+
+  case config
+  in {db: {user:}}
+    puts "Connect with user '#{user}'"
+  in {connection: {username:}}
+    puts "Connect with user '#{username}'"
+  else
+    puts "Unrecognized structure of config"
+  end
+end
+
+class Foo
+  def bar(value)
+    case value
+    in 1
+      "one"
+    in 2
+      "two"
+    end
+  end
+end

fixtures/small/prism/case_match_trailing_comments_actual.rb

@@ -0,0 +1,11 @@
+case 1
+in 2 # Two
+in 3 # Three
+end
+
+case value
+in :a # comment a
+  do_a
+in :b # comment b
+  do_b
+end

fixtures/small/prism/case_match_trailing_comments_expected.rb

@@ -0,0 +1,15 @@
+case 1
+# Two
+in 2
+  # Three
+in 3
+end
+
+case value
+# comment a
+in :a
+  do_a
+  # comment b
+in :b
+  do_b
+end

librubyfmt/src/format_prism.rs

@@ -588,6 +588,11 @@ fn format_case_match_node<'src>(
     ps.emit_newline();
     ps.with_start_of_line(true, |ps| {
         for condition in case_match_node.conditions().iter() {
+            // We keep start_of_line false and handle indentation here
+            // so that format_node's trailing emit_newline doesn't insert
+            // a blank line between consecutive `in` clauses.
+            ps.at_offset(condition.location().start_offset());
+            ps.emit_indent();
             ps.with_start_of_line(false, |ps| format_node(ps, condition));
         }