From 555e77b47048edceb63d5b0ecacda26f6846e118 Mon Sep 17 00:00:00 2001
From: Kevin Newton <kddnewton@gmail.com>
Date: Sat, 16 Apr 2022 13:07:34 -0400
Subject: [PATCH] Empty HshPtn

---
 lib/syntax_tree/node.rb   |  6 ++++--
 lib/syntax_tree/parser.rb | 12 +++++++++---
 test/fixtures/hshptn.rb   |  4 ++++
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/lib/syntax_tree/node.rb b/lib/syntax_tree/node.rb
index 9e96bd96..afe50e4e 100644
--- a/lib/syntax_tree/node.rb
+++ b/lib/syntax_tree/node.rb
@@ -4536,6 +4536,7 @@ def deconstruct_keys(keys)
     def format(q)
       parts = keywords.map { |(key, value)| KeywordFormatter.new(key, value) }
       parts << KeywordRestFormatter.new(keyword_rest) if keyword_rest
+
       contents = -> do
         q.seplist(parts) { |part| q.format(part, stackable: false) }
       end
@@ -4546,8 +4547,9 @@ def format(q)
         return
       end
 
-      parent = q.parent
-      if PATTERNS.include?(parent.class)
+      if parts.empty?
+        q.text("{}")
+      elsif PATTERNS.include?(q.parent.class)
         q.text("{ ")
         contents.call
         q.text(" }")
diff --git a/lib/syntax_tree/parser.rb b/lib/syntax_tree/parser.rb
index 92a58ccb..c99eea4b 100644
--- a/lib/syntax_tree/parser.rb
+++ b/lib/syntax_tree/parser.rb
@@ -1501,13 +1501,19 @@ def on_heredoc_end(value)
     #     (nil | VarField) keyword_rest
     #   ) -> HshPtn
     def on_hshptn(constant, keywords, keyword_rest)
-      parts = [constant, keywords, keyword_rest].flatten(2).compact
+      parts = [constant, *keywords&.flatten(1), keyword_rest].compact
+      location =
+        if parts.empty?
+          find_token(LBrace).location.to(find_token(RBrace).location)
+        else
+          parts[0].location.to(parts[-1].location)
+        end
 
       HshPtn.new(
         constant: constant,
-        keywords: keywords,
+        keywords: keywords || [],
         keyword_rest: keyword_rest,
-        location: parts[0].location.to(parts[-1].location)
+        location: location
       )
     end
 
diff --git a/test/fixtures/hshptn.rb b/test/fixtures/hshptn.rb
index 2efe2fd3..857336d4 100644
--- a/test/fixtures/hshptn.rb
+++ b/test/fixtures/hshptn.rb
@@ -44,3 +44,7 @@
 case foo
 in Foo[**bar]
 end
+%
+case foo
+in {}
+end