Add an option to format struct lits with either block or visual indent

src/config.rs

@@ -10,7 +10,7 @@
 
 extern crate toml;
 
-use {NewlineStyle, BraceStyle, ReturnIndent};
+use {NewlineStyle, BraceStyle, ReturnIndent, StructLitStyle};
 use lists::SeparatorTactic;
 use issues::ReportTactic;
 
@@ -26,6 +26,7 @@ pub struct Config {
     pub fn_args_paren_newline: bool,
     pub struct_trailing_comma: SeparatorTactic,
     pub struct_lit_trailing_comma: SeparatorTactic,
+    pub struct_lit_style: StructLitStyle,
     pub enum_trailing_comma: bool,
     pub report_todo: ReportTactic,
     pub report_fixme: ReportTactic,
@@ -35,6 +36,14 @@ pub struct Config {
 impl Config {
     pub fn from_toml(toml: &str) -> Config {
         let parsed = toml.parse().unwrap();
-        toml::decode(parsed).unwrap()
+        match toml::decode(parsed) {
+            Some(decoded) => decoded,
+            None => {
+                println!("Decoding config file failed. Config:\n{}", toml);
+                let parsed: toml::Value = toml.parse().unwrap();
+                println!("\n\nParsed:\n{:?}", parsed);
+                panic!();
+            }
+        }
     }
 }

src/default.toml

@@ -7,6 +7,7 @@ fn_brace_style = "SameLineWhere"
 fn_return_indent = "WithArgs"
 fn_args_paren_newline = true
 struct_trailing_comma = "Vertical"
+struct_lit_style = "BlockIndent"
 struct_lit_trailing_comma = "Vertical"
 enum_trailing_comma = true
 report_todo = "Always"

src/expr.rs

@@ -11,6 +11,7 @@
 use rewrite::{Rewrite, RewriteContext};
 use lists::{write_list, itemize_list, ListFormatting, SeparatorTactic, ListTactic};
 use string::{StringFormat, rewrite_string};
+use StructLitStyle;
 use utils::{span_after, make_indent};
 use visitor::FmtVisitor;
 
@@ -188,8 +189,15 @@ fn rewrite_struct_lit<'a>(context: &RewriteContext,
 
     let path_str = pprust::path_to_string(path);
     // Foo { a: Foo } - indent is +3, width is -5.
-    let indent = offset + path_str.len() + 3;
-    let budget = width - (path_str.len() + 5);
+    let (indent, budget) = match context.config.struct_lit_style {
+        StructLitStyle::VisualIndent => {
+            (offset + path_str.len() + 3, width - (path_str.len() + 5))
+        }
+        StructLitStyle::BlockIndent => {
+            let indent = context.block_indent + context.config.tab_spaces;
+            (indent, width - indent)
+        }
+    };
 
     let field_iter = fields.into_iter().map(StructLitField::Regular)
                            .chain(base.into_iter().map(StructLitField::Base));
@@ -243,12 +251,18 @@ fn rewrite_struct_lit<'a>(context: &RewriteContext,
                                v_width: budget,
                                ends_with_newline: true, };
     let fields_str = write_list(&items, &fmt);
-    Some(format!("{} {{ {} }}", path_str, fields_str))
 
-    // FIXME if the usual multi-line layout is too wide, we should fall back to
-    // Foo {
-    //     a: ...,
-    // }
+    match context.config.struct_lit_style {
+        StructLitStyle::BlockIndent if fields_str.contains('\n') => {
+            let inner_indent = make_indent(context.block_indent + context.config.tab_spaces);
+            let outer_indent = make_indent(context.block_indent);
+            Some(format!("{} {{\n{}{}\n{}}}", path_str, inner_indent, fields_str, outer_indent))
+        }
+        _ => Some(format!("{} {{ {} }}", path_str, fields_str)),
+    }
+
+    // FIXME if context.config.struct_lit_style == VisualIndent, but we run out
+    // of space, we should fall back to BlockIndent.
 }
 
 fn rewrite_field(context: &RewriteContext,

src/lib.rs

@@ -111,6 +111,19 @@ pub enum ReturnIndent {
 
 impl_enum_decodable!(ReturnIndent, WithArgs, WithWhereClause);
 
+// How to stle a struct literal.
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+pub enum StructLitStyle {
+    // First line on the same line as the opening brace, all lines aligned with
+    // the first line.
+    VisualIndent,
+    // First line is on a new line and all lines align with block indent.
+    BlockIndent,
+    // FIXME Maybe we should also have an option to align types.
+}
+
+impl_enum_decodable!(StructLitStyle, VisualIndent, BlockIndent);
+
 enum ErrorKind {
     // Line has exceeded character limit
     LineOverflow,

tests/config/reorder_imports.toml

@@ -8,6 +8,7 @@ fn_return_indent = "WithArgs"
 fn_args_paren_newline = true
 struct_trailing_comma = "Vertical"
 struct_lit_trailing_comma = "Vertical"
+struct_lit_style = "BlockIndent"
 enum_trailing_comma = true
 report_todo = "Always"
 report_fixme = "Never"

tests/config/small_tabs.toml

@@ -8,6 +8,7 @@ fn_return_indent = "WithArgs"
 fn_args_paren_newline = true
 struct_trailing_comma = "Vertical"
 struct_lit_trailing_comma = "Vertical"
+struct_lit_style = "BlockIndent"
 enum_trailing_comma = true
 report_todo = "Always"
 report_fixme = "Never"

tests/config/visual_struct_lits.toml

@@ -0,0 +1,15 @@
+max_width = 100
+ideal_width = 80
+leeway = 5
+tab_spaces = 4
+newline_style = "Unix"
+fn_brace_style = "SameLineWhere"
+fn_return_indent = "WithArgs"
+fn_args_paren_newline = true
+struct_trailing_comma = "Vertical"
+struct_lit_style = "VisualIndent"
+struct_lit_trailing_comma = "Vertical"
+enum_trailing_comma = true
+report_todo = "Always"
+report_fixme = "Never"
+reorder_imports = false

tests/source/struct_lits_visual.rs

@@ -0,0 +1,39 @@
+// rustfmt-config: visual_struct_lits.toml
+
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo {a: x };
+
+    Foo { a: foo() /* comment*/, /* comment*/ b: bar(), ..something };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: foo(), b: bar(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo { a:Bar,
+          b:foo() };
+
+    A { 
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+    first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item
+    };
+
+    Diagram { /*                 o        This graph demonstrates how                  
+               *                / \       significant whitespace is           
+               *               o   o      preserved.  
+               *              /|\   \
+               *             o o o   o */
+              graph: G, }
+}

tests/target/struct_lits.rs

@@ -6,30 +6,35 @@ fn main() {
     // Comment
     let y = Foo { a: x };
 
-    Foo { a: foo(), // comment
-          // comment
-          b: bar(),
-          ..something };
+    Foo {
+        a: foo(), // comment
+        // comment
+        b: bar(),
+        ..something
+    };
 
-    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: foo(),
-                                                                               b: bar(), };
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        a: foo(),
+        b: bar(),
+    };
 
     Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { // Comment
-                                                                                        a: foo(), /* C
-                                                                                                   * o
-                                                                                                   * m
-                                                                                                   * m
-                                                                                                   * e
-                                                                                                   * n
-                                                                                                   * t */
-                                                                                        // Comment
-                                                                                        b: bar(), /* C
-                                                                                                   * o
-                                                                                                   * m
-                                                                                                   * m
-                                                                                                   * e
-                                                                                                   * n
-                                                                                                   * t */ };
+        a: foo(), /* C
+                   * o
+                   * m
+                   * m
+                   * e
+                   * n
+                   * t */
+        // Comment
+        b: bar(), /* C
+                   * o
+                   * m
+                   * m
+                   * e
+                   * n
+                   * t */
+    };
 
     Foo { a: Bar, b: foo() };
 
@@ -39,12 +44,14 @@ fn main() {
         first: item(),
         // Praesent et diam eget libero egestas mattis sit amet vitae augue.
         // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
-        second: Item, };
+        second: Item,
+    };
 
     Diagram { //                 o        This graph demonstrates how
               //                / \       significant whitespace is
               //               o   o      preserved.
               //              /|\   \
               //             o o o   o
-              graph: G, }
+        graph: G,
+    }
 }

tests/target/struct_lits_visual.rs

@@ -0,0 +1,52 @@
+// rustfmt-config: visual_struct_lits.toml
+
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo { a: x };
+
+    Foo { a: foo(), // comment
+          // comment
+          b: bar(),
+          ..something };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: foo(),
+                                                                               b: bar(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { // Comment
+                                                                                        a: foo(), /* C
+                                                                                                   * o
+                                                                                                   * m
+                                                                                                   * m
+                                                                                                   * e
+                                                                                                   * n
+                                                                                                   * t */
+                                                                                        // Comment
+                                                                                        b: bar(), /* C
+                                                                                                   * o
+                                                                                                   * m
+                                                                                                   * m
+                                                                                                   * e
+                                                                                                   * n
+                                                                                                   * t */ };
+
+    Foo { a: Bar, b: foo() };
+
+    A { // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit
+        // amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante
+        // hendrerit. Donec et mollis dolor.
+        first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item, };
+
+    Diagram { //                 o        This graph demonstrates how
+              //                / \       significant whitespace is
+              //               o   o      preserved.
+              //              /|\   \
+              //             o o o   o
+              graph: G, }
+}