fix: wrap function without a body exceeding 100 characters (#6539)

src/items.rs

@@ -2500,6 +2500,7 @@ fn rewrite_fn_base(
         ret_str_len,
         fn_brace_style,
         multi_line_ret_str,
+        where_clause,
     );
 
     debug!(
@@ -2602,10 +2603,20 @@ fn rewrite_fn_base(
                 // the closing parenthesis of the param and the arrow '->' is considered.
                 let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
 
-                // If there is no where-clause, take into account the space after the return type
-                // and the brace.
+                // If there is no where-clause.
                 if where_clause.predicates.is_empty() {
-                    sig_length += 2;
+                    if context.config.style_edition() >= StyleEdition::Edition2027 {
+                        let line_ending_overhead = match fn_brace_style {
+                            FnBraceStyle::NextLine => 0, // No brace to account for
+                            FnBraceStyle::SameLine => 2, // Trailing space and brace, e.g. ` {`
+                            FnBraceStyle::None => 1,     // Trailing `;`
+                        };
+                        sig_length += line_ending_overhead;
+                    } else {
+                        // Take into account the space after the return type and the brace.
+                        // 2 = ' {'
+                        sig_length += 2;
+                    }
                 }
 
                 sig_length > context.config.max_width()
@@ -2747,8 +2758,13 @@ fn rewrite_fn_base(
 
     let ends_with_comment = last_line_contains_single_line_comment(&result);
     force_new_line_for_brace |= ends_with_comment;
-    force_new_line_for_brace |=
-        is_params_multi_lined && context.config.where_single_line() && !where_clause_str.is_empty();
+
+    // PreferSameLine should keep the brace on the same line as the last where predicate.
+    force_new_line_for_brace |= !where_clause_str.is_empty()
+        && context.config.where_single_line()
+        && is_params_multi_lined
+        && context.config.brace_style() != BraceStyle::PreferSameLine;
+
     Ok((result, ends_with_comment, force_new_line_for_brace))
 }
 
@@ -2889,6 +2905,7 @@ fn compute_budgets_for_params(
     ret_str_len: usize,
     fn_brace_style: FnBraceStyle,
     force_vertical_layout: bool,
+    where_clause: &ast::WhereClause,
 ) -> (usize, usize, Indent) {
     debug!(
         "compute_budgets_for_params {} {:?}, {}, {:?}",
@@ -2903,7 +2920,15 @@ fn compute_budgets_for_params(
         let overhead = if ret_str_len == 0 { 2 } else { 3 };
         let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
         match fn_brace_style {
-            FnBraceStyle::None => used_space += 1,     // 1 = `;`
+            _ if context.config.style_edition() >= StyleEdition::Edition2027
+                && where_clause.predicates.len() > 0 =>
+            {
+                // Don't add anything to `used_space` if we have a where clause.
+                // For all `FnBraceStyle` values if we have a where cluase that can't fit
+                // on the current line it'll be written to the next line.
+                // Therefore, we don't need to account for a trailing `;` or `{}`
+            }
+            FnBraceStyle::None => used_space += 1, // 1 = `;`
             FnBraceStyle::SameLine => used_space += 2, // 2 = `{}`
             FnBraceStyle::NextLine => (),
         }

tests/source/issue-6539/brace_next_line.rs

@@ -0,0 +1,73 @@
+// rustfmt-style_edition: 2027
+// rustfmt-brace_style: AlwaysNextLine
+// rustfmt-where_single_line: false
+
+// Top-level functions
+
+// Short function
+fn short_fn(a: f64, b: f64) -> f64;
+
+// Function with wrapping return type and no where clause
+fn fn_with_long_return_type(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>>;
+
+// Function with non-wrapping return type and where clause
+fn fn_with_short_where<T>(a: f64, b: T) -> f64 where T: Debug;
+
+// Function that wraps at a simple return type
+fn fn_with_wrapping_return_type<T>(aaaaaa: f64, bbbbbb: T, cccccc: f64, dddddd: f64, eeee: f64) -> f64;
+
+// Function that wraps at the where clause
+fn fn_with_wrapping_where_clause<T>(aaaaaa: f64, bbbbbb: T, cccccc: f64, dddddd: f64) -> f64 where T: Debug;
+
+// Function with both wrapping return type and wrapping where clause
+fn fn_with_long_return_and_where<T, U, 'a>(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+// Function with wrapping arguments, return type, and where clause
+fn fn_with_everything_long<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64, ffff: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+// Same variations with bodies
+fn short_fn_with_body(a: f64, b: f64) -> f64 {}
+
+fn fn_with_long_return_type_and_body(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> {}
+
+fn fn_with_short_where_and_body<T>(a: f64, b: T) -> f64 where T: Debug {}
+
+fn fn_with_wrapping_return_type_and_body<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64, ee: f64) -> f64 {}
+
+fn fn_with_wrapping_where_clause_and_body<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64) -> f64 where T: Debug {}
+
+fn fn_with_long_return_and_where_and_body<T, U, 'a>(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+fn fn_with_everything_long_and_body<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64, ffff: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+// Trait methods
+pub trait Trait {
+    fn short_method(a: f64, b: f64) -> f64;
+
+    fn method_with_long_return(&self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>>;
+
+    fn method_with_short_where<T>(&self, a: f64, b: T) -> f64 where T: Debug;
+
+    fn method_with_wrapping_return_type<T>(self, aaa: f64, bbb: T, ccc: f64, ddd: f64, ee: f64) -> f64;
+
+    fn method_with_wrapping_where_clause<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64) -> f64 where T: Debug;
+
+    fn method_with_long_return_and_where<T, U, 'a>(self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+    fn method_with_everything_long<T, U, 'a>(&self, aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+    // Same variations with bodies
+    fn short_method_with_body(a: f64, b: f64) -> f64 {}
+
+    fn method_with_long_return_and_body(&self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> {}
+
+    fn method_with_short_where_and_body<T>(&self, a: f64, b: T) -> f64 where T: Debug {}
+
+    fn method_with_wrapping_return_type_and_body<T>(aaaa: f64, bb: T, cc: f64, d: f64, e: f64) -> f64 {}
+
+    fn method_with_wrapping_where_clause_and_body<T>(aaa: f64, bb: T, cc: f64, d: f64) -> f64 where T: Debug {}
+
+    fn method_with_long_return_and_where_and_body<T, U, 'a>(self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+    fn method_with_everything_long_and_body<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+}

tests/source/issue-6539/brace_next_line_where_single_line.rs

@@ -0,0 +1,73 @@
+// rustfmt-style_edition: 2027
+// rustfmt-brace_style: AlwaysNextLine
+// rustfmt-where_single_line: true
+
+// Top-level functions
+
+// Short function
+fn short_fn(a: f64, b: f64) -> f64;
+
+// Function with wrapping return type and no where clause
+fn fn_with_long_return_type(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>>;
+
+// Function with non-wrapping return type and where clause
+fn fn_with_short_where<T>(a: f64, b: T) -> f64 where T: Debug;
+
+// Function that wraps at a simple return type
+fn fn_with_wrapping_return_type<T>(aaaaaa: f64, bbbbbb: T, cccccc: f64, dddddd: f64, eeee: f64) -> f64;
+
+// Function that wraps at the where clause
+fn fn_with_wrapping_where_clause<T>(aaaaaa: f64, bbbbbb: T, cccccc: f64, dddddd: f64) -> f64 where T: Debug;
+
+// Function with both wrapping return type and wrapping where clause
+fn fn_with_long_return_and_where<T, U, 'a>(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+// Function with wrapping arguments, return type, and where clause
+fn fn_with_everything_long<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64, ffff: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+// Same variations with bodies
+fn short_fn_with_body(a: f64, b: f64) -> f64 {}
+
+fn fn_with_long_return_type_and_body(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> {}
+
+fn fn_with_short_where_and_body<T>(a: f64, b: T) -> f64 where T: Debug {}
+
+fn fn_with_wrapping_return_type_and_body<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64, ee: f64) -> f64 {}
+
+fn fn_with_wrapping_where_clause_and_body<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64) -> f64 where T: Debug {}
+
+fn fn_with_long_return_and_where_and_body<T, U, 'a>(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+fn fn_with_everything_long_and_body<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64, ffff: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+// Trait methods
+pub trait Trait {
+    fn short_method(a: f64, b: f64) -> f64;
+
+    fn method_with_long_return(&self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>>;
+
+    fn method_with_short_where<T>(&self, a: f64, b: T) -> f64 where T: Debug;
+
+    fn method_with_wrapping_return_type<T>(self, aaa: f64, bbb: T, ccc: f64, ddd: f64, ee: f64) -> f64;
+
+    fn method_with_wrapping_where_clause<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64) -> f64 where T: Debug;
+
+    fn method_with_long_return_and_where<T, U, 'a>(self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+    fn method_with_everything_long<T, U, 'a>(&self, aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+    // Same variations with bodies
+    fn short_method_with_body(a: f64, b: f64) -> f64 {}
+
+    fn method_with_long_return_and_body(&self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> {}
+
+    fn method_with_short_where_and_body<T>(&self, a: f64, b: T) -> f64 where T: Debug {}
+
+    fn method_with_wrapping_return_type_and_body<T>(aaaa: f64, bb: T, cc: f64, d: f64, e: f64) -> f64 {}
+
+    fn method_with_wrapping_where_clause_and_body<T>(aaa: f64, bb: T, cc: f64, d: f64) -> f64 where T: Debug {}
+
+    fn method_with_long_return_and_where_and_body<T, U, 'a>(self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+    fn method_with_everything_long_and_body<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+}

tests/source/issue-6539/prefer_same_line.rs

@@ -0,0 +1,73 @@
+// rustfmt-style_edition: 2027
+// rustfmt-brace_style: PreferSameLine
+// rustfmt-where_single_line: false
+
+// Top-level functions
+
+// Short function
+fn short_fn(a: f64, b: f64) -> f64;
+
+// Function with wrapping return type and no where clause
+fn fn_with_long_return_type(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>>;
+
+// Function with non-wrapping return type and where clause
+fn fn_with_short_where<T>(a: f64, b: T) -> f64 where T: Debug;
+
+// Function that wraps at a simple return type
+fn fn_with_wrapping_return_type<T>(aaaaaa: f64, bbbbbb: T, cccccc: f64, dddddd: f64, eeee: f64) -> f64;
+
+// Function that wraps at the where clause
+fn fn_with_wrapping_where_clause<T>(aaaaaa: f64, bbbbbb: T, cccccc: f64, dddddd: f64) -> f64 where T: Debug;
+
+// Function with both wrapping return type and wrapping where clause
+fn fn_with_long_return_and_where<T, U, 'a>(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+// Function with wrapping arguments, return type, and where clause
+fn fn_with_everything_long<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64, ffff: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+// Same variations with bodies
+fn short_fn_with_body(a: f64, b: f64) -> f64 {}
+
+fn fn_with_long_return_type_and_body(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> {}
+
+fn fn_with_short_where_and_body<T>(a: f64, b: T) -> f64 where T: Debug {}
+
+fn fn_with_wrapping_return_type_and_body<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64, ee: f64) -> f64 {}
+
+fn fn_with_wrapping_where_clause_and_body<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64) -> f64 where T: Debug {}
+
+fn fn_with_long_return_and_where_and_body<T, U, 'a>(a: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+fn fn_with_everything_long_and_body<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64, ffff: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+// Trait methods
+pub trait Trait {
+    fn short_method(a: f64, b: f64) -> f64;
+
+    fn method_with_long_return(&self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>>;
+
+    fn method_with_short_where<T>(&self, a: f64, b: T) -> f64 where T: Debug;
+
+    fn method_with_wrapping_return_type<T>(self, aaa: f64, bbb: T, ccc: f64, ddd: f64, ee: f64) -> f64;
+
+    fn method_with_wrapping_where_clause<T>(aaaaaa: f64, bbbbbb: T, ccc: f64, ddd: f64) -> f64 where T: Debug;
+
+    fn method_with_long_return_and_where<T, U, 'a>(self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+    fn method_with_everything_long<T, U, 'a>(&self, aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator;
+
+    // Same variations with bodies
+    fn short_method_with_body(a: f64, b: f64) -> f64 {}
+
+    fn method_with_long_return_and_body(&self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> {}
+
+    fn method_with_short_where_and_body<T>(&self, a: f64, b: T) -> f64 where T: Debug {}
+
+    fn method_with_wrapping_return_type_and_body<T>(aaaa: f64, bb: T, cc: f64, d: f64, e: f64) -> f64 {}
+
+    fn method_with_wrapping_where_clause_and_body<T>(aaa: f64, bb: T, cc: f64, d: f64) -> f64 where T: Debug {}
+
+    fn method_with_long_return_and_where_and_body<T, U, 'a>(self) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+
+    fn method_with_everything_long_and_body<T, U, 'a>(aaaa: f64, bbbb: f64, cccc: f64, dddd: f64, eeee: f64) -> Result<HashMap<String, Vec<(SomeLongTypeName, AnotherLongTypeName, YetAnotherType)>>, Box<dyn Error + Send + Sync + 'static>> where T: Debug + Display + Clone + Send + Sync + 'static, U: Iterator<Item = &'a T> + ExactSizeIterator {}
+}