Fix issue #3805 - wrap macro line with width of one char beyond max

Author: davidBar-On

src/macros.rs

@@ -1219,7 +1219,14 @@ impl MacroBranch {
         }
 
         // 5 = " => {"
-        let mut result = format_macro_args(context, self.args.clone(), shape.sub_width(5)?)?;
+        let old_body = context.snippet(self.body).trim();
+        let prefix_width = 5 + if context.config.format_macro_bodies() {
+            old_body.find(|ch| ch != '{').unwrap_or(old_body.len()) // " => {{..."
+        } else {
+            0
+        };
+        let mut result =
+            format_macro_args(context, self.args.clone(), shape.sub_width(prefix_width)?)?;
 
         if multi_branch_style {
             result += " =>";
@@ -1237,7 +1244,6 @@ impl MacroBranch {
         // `$$`). We'll try and format like an AST node, but we'll substitute
         // variables for new names with the same length first.
 
-        let old_body = context.snippet(self.body).trim();
         let (body_str, substs) = replace_names(old_body)?;
         let has_block_body = old_body.starts_with('{');
 

tests/source/issue-3805.rs

@@ -0,0 +1,43 @@
+// rustfmt-format_macro_matchers: true
+
+// From original issue example - Line length 101
+macro_rules! test {
+($aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeio:expr, $add:expr) => {{
+return;
+}};
+}
+
+// Line length 102
+macro_rules! test {
+($aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeiou:expr, $add:expr) => {{
+return;
+}};
+}
+
+// Line length 103
+macro_rules! test {
+($aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeioua:expr, $add:expr) => {{
+return;
+}};
+}
+
+// With extended macro body - Line length 101
+macro_rules! test {
+($aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeio:expr, $add:expr) => {{
+let VAR = "VALUE"; return VAR;
+}};
+}
+
+// With extended macro body - Line length 102
+macro_rules! test {
+($aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeiou:expr, $add:expr) => {{
+let VAR = "VALUE"; return VAR;
+}};
+}
+
+// With extended macro body - Line length 103
+macro_rules! test {
+($aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeioua:expr, $add:expr) => {{
+let VAR = "VALUE"; return VAR;
+}};
+}

tests/target/issue-3805.rs

@@ -0,0 +1,58 @@
+// rustfmt-format_macro_matchers: true
+
+// From original issue example - Line length 101
+macro_rules! test {
+    (
+        $aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeio:expr, $add:expr
+    ) => {{
+        return;
+    }};
+}
+
+// Line length 102
+macro_rules! test {
+    (
+        $aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeiou:expr, $add:expr
+    ) => {{
+        return;
+    }};
+}
+
+// Line length 103
+macro_rules! test {
+    (
+        $aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeioua:expr, $add:expr
+    ) => {{
+        return;
+    }};
+}
+
+// With extended macro body - Line length 101
+macro_rules! test {
+    (
+        $aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeio:expr, $add:expr
+    ) => {{
+        let VAR = "VALUE";
+        return VAR;
+    }};
+}
+
+// With extended macro body - Line length 102
+macro_rules! test {
+    (
+        $aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeiou:expr, $add:expr
+    ) => {{
+        let VAR = "VALUE";
+        return VAR;
+    }};
+}
+
+// With extended macro body - Line length 103
+macro_rules! test {
+    (
+        $aasdfghj:expr, $qwertyuiop:expr, $zxcvbnmasdfghjkl:expr, $aeiouaeiouaeioua:expr, $add:expr
+    ) => {{
+        let VAR = "VALUE";
+        return VAR;
+    }};
+}