feat: add FitEntireBody as new match_arm_wrapping option, and rename NoBlockFirstLine to FitFirstLine (rust-lang#4896)

Author: ashvin021

Diff for: src/config/config_type.rs

@@ -435,7 +435,7 @@ macro_rules! create_config {
                         self.match_arm_wrapping.2 = if self.match_arm_blocks() {
                             MatchArmWrapping::Default
                         } else {
-                            MatchArmWrapping::NoBlockFirstLine
+                            MatchArmWrapping::FitFirstLine
                         };
                     }
                 }

Diff for: src/config/mod.rs

@@ -745,10 +745,7 @@ make_backup = false
                 match_arm_blocks = false
             "#;
             let config = Config::from_toml(toml, Path::new("")).unwrap();
-            assert_eq!(
-                config.match_arm_wrapping(),
-                MatchArmWrapping::NoBlockFirstLine
-            );
+            assert_eq!(config.match_arm_wrapping(), MatchArmWrapping::FitFirstLine);
         }
 
         #[test]
@@ -786,15 +783,12 @@ make_backup = false
             }
             let toml = r#"
                 unstable_features = true
-                match_arm_wrapping = "NoBlockFirstLine"
+                match_arm_wrapping = "FitFirstLine"
             "#;
             let mut config = Config::from_toml(toml, Path::new("")).unwrap();
             config.override_value("match_arm_blocks", "false");
             // no effect: the new option always takes precedence
-            assert_eq!(
-                config.match_arm_wrapping(),
-                MatchArmWrapping::NoBlockFirstLine
-            );
+            assert_eq!(config.match_arm_wrapping(), MatchArmWrapping::FitFirstLine);
         }
     }
 

Diff for: src/config/options.rs

@@ -450,9 +450,12 @@ pub enum MatchArmWrapping {
     Default,
     /// Same as Default, except don't block wrap match arms when the opening line of its body
     /// can't fit on the same line as the `=>`.
-    NoBlockFirstLine,
+    FitFirstLine,
     /// Always block wrap match arms
     Always,
     /// Preserve the block wrapping on match arms
     Preserve,
+    /// Same as Default, except wrap the match arm if the entire body cannot fit on the same line
+    /// as the `=>`.
+    FitEntireBody,
 }

Diff for: src/matches.rs

@@ -420,7 +420,7 @@ fn rewrite_match_body(
 
         let indent_str = shape.indent.to_string_with_newline(context.config);
         let (body_prefix, body_suffix) = match context.config.match_arm_wrapping() {
-            MatchArmWrapping::NoBlockFirstLine => ("", String::from(",")),
+            MatchArmWrapping::FitFirstLine => ("", String::from(",")),
             _ if !context.inside_macro() => {
                 let comma = if context.config.match_block_trailing_comma() {
                     ","
@@ -501,7 +501,9 @@ fn rewrite_match_body(
 
     match (orig_body, next_line_body) {
         (Some(ref orig_str), Some(ref next_line_str))
-            if prefer_next_line(orig_str, next_line_str, RhsTactics::Default) =>
+            if prefer_next_line(orig_str, next_line_str, RhsTactics::Default)
+                || (context.config.match_arm_wrapping() == MatchArmWrapping::FitEntireBody
+                    && orig_str.contains('\n')) =>
         {
             combine_next_line_body(next_line_str)
         }