From 750ca52debb5107e8970f0c4090a08c2c51a66b8 Mon Sep 17 00:00:00 2001
From: Sean Hagstrom <sean@seanhagstrom.com>
Date: Mon, 16 May 2022 19:18:41 +0100
Subject: [PATCH] improvement(formatter): format empty record patterns without
 spaces

---
 compiler/fmt/src/pattern.rs    | 20 +++++++------
 compiler/fmt/tests/test_fmt.rs | 55 ++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 9 deletions(-)

diff --git a/compiler/fmt/src/pattern.rs b/compiler/fmt/src/pattern.rs
index e4f53fc47c..4df623dd5c 100644
--- a/compiler/fmt/src/pattern.rs
+++ b/compiler/fmt/src/pattern.rs
@@ -85,20 +85,22 @@ impl<'a> Formattable for Pattern<'a> {
             RecordDestructure(loc_patterns) => {
                 buf.indent(indent);
                 buf.push_str("{");
-                buf.spaces(1);
 
-                let mut it = loc_patterns.iter().peekable();
+                if !loc_patterns.is_empty() {
+                    buf.spaces(1);
+                    let mut it = loc_patterns.iter().peekable();
+                    while let Some(loc_pattern) = it.next() {
+                        loc_pattern.format(buf, indent);
 
-                while let Some(loc_pattern) = it.next() {
-                    loc_pattern.format(buf, indent);
-
-                    if it.peek().is_some() {
-                        buf.push_str(",");
-                        buf.spaces(1);
+                        if it.peek().is_some() {
+                            buf.push_str(",");
+                            buf.spaces(1);
+                        }
                     }
+                    buf.spaces(1);
                 }
 
-                buf.push_str(" }");
+                buf.push_str("}");
             }
 
             RequiredField(name, loc_pattern) => {
diff --git a/compiler/fmt/tests/test_fmt.rs b/compiler/fmt/tests/test_fmt.rs
index 985d4cbc28..3f3c25033c 100644
--- a/compiler/fmt/tests/test_fmt.rs
+++ b/compiler/fmt/tests/test_fmt.rs
@@ -2727,6 +2727,61 @@ mod test_fmt {
     #[test]
     fn empty_record() {
         expr_formats_same("{}");
+        expr_formats_to("{ }", "{}");
+    }
+
+    #[test]
+    fn empty_record_patterns() {
+        expr_formats_to(
+            indoc!(
+                r#"
+                    f = \{  } -> "Hello World"
+
+                    f
+                "#
+            ),
+            indoc!(
+                r#"
+                    f = \{} -> "Hello World"
+
+                    f
+                "#
+            ),
+        );
+
+        expr_formats_to(
+            indoc!(
+                r#"
+                    f = \a, b -> {  }
+
+                    f
+                "#
+            ),
+            indoc!(
+                r#"
+                    f = \a, b -> {}
+
+                    f
+                "#
+            ),
+        );
+
+        expr_formats_to(
+            indoc!(
+                r#"
+                    { } <- f a b
+
+                    {}
+                "#
+            ),
+            indoc!(
+                r#"
+                    {} <- f a b
+
+                    {}
+                "#
+            ),
+        );
     }
 
     #[test]