Merge pull request #2667 from tspiteri/width-heuristics

Do not scale WidthHeuristics when max_width less than 100

src/config/config_type.rs

@@ -130,7 +130,7 @@ macro_rules! create_config {
             pub fn $i(&mut self, value: $ty) {
                 (self.0).$i.2 = value;
                 match stringify!($i) {
-                    "use_small_heuristics" => self.0.set_heuristics(),
+                    "max_width" | "use_small_heuristics" => self.0.set_heuristics(),
                     "license_template_path" => self.0.set_license_template(),
                     &_ => (),
                 }
@@ -292,7 +292,7 @@ macro_rules! create_config {
                 }
 
                 match key {
-                    "use_small_heuristics" => self.set_heuristics(),
+                    "max_width" | "use_small_heuristics" => self.set_heuristics(),
                     "license_template_path" => self.set_license_template(),
                     &_ => (),
                 }

src/config/options.rs

@@ -242,8 +242,14 @@ impl WidthHeuristics {
 
     // scale the default WidthHeuristics according to max_width
     pub fn scaled(max_width: usize) -> WidthHeuristics {
-        let mut max_width_ratio: f32 = max_width as f32 / 100.0; // 100 is the default width -> default ratio is 1
-        max_width_ratio = (max_width_ratio * 10.0).round() / 10.0; // round to the closest 0.1
+        const DEFAULT_MAX_WIDTH: usize = 100;
+        let max_width_ratio = if max_width > DEFAULT_MAX_WIDTH {
+            let ratio = max_width as f32 / DEFAULT_MAX_WIDTH as f32;
+            // round to the closest 0.1
+            (ratio * 10.0).round() / 10.0
+        } else {
+            1.0
+        };
         WidthHeuristics {
             fn_call_width: (60.0 * max_width_ratio).round() as usize,
             struct_lit_width: (18.0 * max_width_ratio).round() as usize,

tests/source/issue-2644.rs

@@ -0,0 +1,11 @@
+// rustfmt-max_width: 80
+fn foo(e: Enum) {
+    match e {
+        Enum::Var {
+            element1,
+            element2,
+        } => {
+            return;
+        }
+    }
+}

tests/source/width-heuristics.rs

@@ -0,0 +1,28 @@
+// rustfmt-max_width: 120
+
+// elems on multiple lines for max_width 100, but same line for max_width 120
+fn foo(e: Enum) {
+    match e {
+        Enum::Var {
+            elem1,
+            elem2,
+            elem3,
+        } => {
+            return;
+        }
+    }
+}
+
+// elems not on same line for either max_width 100 or 120
+fn bar(e: Enum) {
+    match e {
+        Enum::Var {
+            elem1,
+            elem2,
+            elem3,
+            elem4,
+        } => {
+            return;
+        }
+    }
+}

tests/target/issue-2644.rs

@@ -0,0 +1,8 @@
+// rustfmt-max_width: 80
+fn foo(e: Enum) {
+    match e {
+        Enum::Var { element1, element2 } => {
+            return;
+        }
+    }
+}

tests/target/width-heuristics.rs

@@ -0,0 +1,24 @@
+// rustfmt-max_width: 120
+
+// elems on multiple lines for max_width 100, but same line for max_width 120
+fn foo(e: Enum) {
+    match e {
+        Enum::Var { elem1, elem2, elem3 } => {
+            return;
+        }
+    }
+}
+
+// elems not on same line for either max_width 100 or 120
+fn bar(e: Enum) {
+    match e {
+        Enum::Var {
+            elem1,
+            elem2,
+            elem3,
+            elem4,
+        } => {
+            return;
+        }
+    }
+}