Support match_pattern_separator_break_point config option

src/expr.rs

@@ -25,7 +25,7 @@ use config::{Config, ControlBraceStyle, IndentStyle, MultilineStyle, Style};
 use items::{span_hi_for_arg, span_lo_for_arg};
 use lists::{definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting,
             struct_lit_shape, struct_lit_tactic, write_list, DefinitiveListTactic, ListFormatting,
-            ListItem, ListTactic, Separator, SeparatorTactic};
+            ListItem, ListTactic, Separator, SeparatorPlace, SeparatorTactic};
 use macros::{rewrite_macro, MacroPosition};
 use patterns::{can_be_overflowed_pat, TuplePatField};
 use rewrite::{Rewrite, RewriteContext};
@@ -473,6 +473,7 @@ where
         } else {
             SeparatorTactic::Vertical
         },
+        separator_place: SeparatorPlace::Back,
         shape: nested_shape,
         ends_with_newline: ends_with_newline,
         preserve_newline: false,
@@ -555,6 +556,7 @@ fn rewrite_closure_fn_decl(
         tactic: tactic,
         separator: ",",
         trailing_separator: SeparatorTactic::Never,
+        separator_place: SeparatorPlace::Back,
         shape: arg_shape,
         ends_with_newline: false,
         preserve_newline: true,
@@ -1578,6 +1580,7 @@ fn rewrite_match_arms(
         // We will add/remove commas inside `arm.rewrite()`, and hence no separator here.
         separator: "",
         trailing_separator: SeparatorTactic::Never,
+        separator_place: SeparatorPlace::Back,
         shape: arm_shape,
         ends_with_newline: true,
         preserve_newline: true,
@@ -1659,6 +1662,7 @@ fn rewrite_match_pattern(
         tactic: tactic,
         separator: " |",
         trailing_separator: SeparatorTactic::Never,
+        separator_place: context.config.match_pattern_separator_break_point(),
         shape: pat_shape,
         ends_with_newline: false,
         preserve_newline: false,
@@ -2161,6 +2165,7 @@ where
         } else {
             context.config.trailing_comma()
         },
+        separator_place: SeparatorPlace::Back,
         shape: shape,
         ends_with_newline: context.use_block_indent() && tactic == DefinitiveListTactic::Vertical,
         preserve_newline: false,
@@ -2761,6 +2766,7 @@ where
         tactic: tactic,
         separator: ",",
         trailing_separator: SeparatorTactic::Never,
+        separator_place: SeparatorPlace::Back,
         shape: shape,
         ends_with_newline: false,
         preserve_newline: false,

src/imports.rs

@@ -17,7 +17,7 @@ use Shape;
 use codemap::SpanUtils;
 use config::IndentStyle;
 use lists::{definitive_tactic, itemize_list, write_list, DefinitiveListTactic, ListFormatting,
-            ListItem, Separator, SeparatorTactic};
+            ListItem, Separator, SeparatorPlace, SeparatorTactic};
 use rewrite::{Rewrite, RewriteContext};
 use types::{rewrite_path, PathContext};
 use utils;
@@ -496,6 +496,7 @@ fn rewrite_use_list(
         } else {
             SeparatorTactic::Never
         },
+        separator_place: SeparatorPlace::Back,
         shape: nested_shape,
         ends_with_newline: ends_with_newline,
         preserve_newline: true,

src/items.rs

@@ -24,7 +24,7 @@ use config::{BraceStyle, Config, Density, IndentStyle, ReturnIndent, Style};
 use expr::{format_expr, is_empty_block, is_simple_block_stmt, rewrite_assign_rhs,
            rewrite_call_inner, ExprType};
 use lists::{definitive_tactic, itemize_list, write_list, DefinitiveListTactic, ListFormatting,
-            ListItem, ListTactic, Separator, SeparatorTactic};
+            ListItem, ListTactic, Separator, SeparatorPlace, SeparatorTactic};
 use rewrite::{Rewrite, RewriteContext};
 use types::join_bounds;
 use utils::{colon_spaces, contains_skip, end_typaram, first_line_width, format_abi,
@@ -481,6 +481,7 @@ impl<'a> FmtVisitor<'a> {
             tactic: DefinitiveListTactic::Vertical,
             separator: ",",
             trailing_separator: self.config.trailing_comma(),
+            separator_place: SeparatorPlace::Back,
             shape: shape,
             ends_with_newline: true,
             preserve_newline: true,
@@ -2267,6 +2268,7 @@ fn rewrite_args(
         } else {
             trailing_comma
         },
+        separator_place: SeparatorPlace::Back,
         shape: Shape::legacy(budget, indent),
         ends_with_newline: tactic.ends_with_newline(context.config.fn_args_layout()),
         preserve_newline: true,
@@ -2462,6 +2464,7 @@ where
         } else {
             context.config.trailing_comma()
         },
+        separator_place: SeparatorPlace::Back,
         shape: shape,
         ends_with_newline: tactic.ends_with_newline(context.config.generics_indent()),
         preserve_newline: true,
@@ -2574,6 +2577,7 @@ fn rewrite_where_clause_rfc_style(
         tactic: DefinitiveListTactic::Vertical,
         separator: ",",
         trailing_separator: comma_tactic,
+        separator_place: SeparatorPlace::Back,
         shape: clause_shape,
         ends_with_newline: true,
         preserve_newline: true,
@@ -2685,6 +2689,7 @@ fn rewrite_where_clause(
         tactic: tactic,
         separator: ",",
         trailing_separator: comma_tactic,
+        separator_place: SeparatorPlace::Back,
         shape: Shape::legacy(budget, offset),
         ends_with_newline: tactic.ends_with_newline(context.config.where_pred_indent()),
         preserve_newline: true,

src/lists.rs

@@ -61,6 +61,7 @@ pub struct ListFormatting<'a> {
     pub tactic: DefinitiveListTactic,
     pub separator: &'a str,
     pub trailing_separator: SeparatorTactic,
+    pub separator_place: SeparatorPlace,
     pub shape: Shape,
     // Non-expressions, e.g. items, will have a new line at the end of the list.
     // Important for comment styles.
@@ -70,6 +71,19 @@ pub struct ListFormatting<'a> {
     pub config: &'a Config,
 }
 
+impl<'a> ListFormatting<'a> {
+    pub fn needs_trailing_separator(&self) -> bool {
+        match self.trailing_separator {
+            // We always put separator in front.
+            SeparatorTactic::Always => true,
+            SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
+            SeparatorTactic::Never => {
+                self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
+            }
+        }
+    }
+}
+
 impl AsRef<ListItem> for ListItem {
     fn as_ref(&self) -> &ListItem {
         self
@@ -165,6 +179,32 @@ impl Separator {
     }
 }
 
+/// Where to put separator.
+#[derive(Eq, PartialEq, Debug, Copy, Clone)]
+pub enum SeparatorPlace {
+    Front,
+    Back,
+}
+
+impl_enum_serialize_and_deserialize!(SeparatorPlace, Front, Back);
+
+impl SeparatorPlace {
+    pub fn is_front(&self) -> bool {
+        *self == SeparatorPlace::Front
+    }
+
+    pub fn is_back(&self) -> bool {
+        *self == SeparatorPlace::Back
+    }
+
+    pub fn from_tactic(default: SeparatorPlace, tactic: DefinitiveListTactic) -> SeparatorPlace {
+        match tactic {
+            DefinitiveListTactic::Vertical => default,
+            _ => SeparatorPlace::Back,
+        }
+    }
+}
+
 pub fn definitive_tactic<I, T>(
     items: I,
     tactic: ListTactic,
@@ -214,11 +254,12 @@ where
 
     // Now that we know how we will layout, we can decide for sure if there
     // will be a trailing separator.
-    let mut trailing_separator = needs_trailing_separator(formatting.trailing_separator, tactic);
+    let mut trailing_separator = formatting.needs_trailing_separator();
     let mut result = String::new();
     let cloned_items = items.clone();
     let mut iter = items.into_iter().enumerate().peekable();
     let mut item_max_width: Option<usize> = None;
+    let mut sep_place = SeparatorPlace::from_tactic(formatting.separator_place, tactic);
 
     let mut line_len = 0;
     let indent_str = &formatting.shape.indent.to_string(formatting.config);
@@ -258,13 +299,16 @@ where
                     result.push('\n');
                     result.push_str(indent_str);
                     line_len = 0;
-                    if tactic == DefinitiveListTactic::Mixed && formatting.ends_with_newline {
+                    if formatting.ends_with_newline {
                         if last {
                             separate = true;
                         } else {
                             trailing_separator = true;
                         }
                     }
+                    sep_place = formatting.separator_place;
+                } else {
+                    sep_place = SeparatorPlace::Back;
                 }
 
                 if line_len > 0 {
@@ -314,6 +358,10 @@ where
             item_max_width = None;
         }
 
+        if separate && sep_place.is_front() && !first {
+            result.push_str(formatting.separator.trim());
+            result.push(' ');
+        }
         result.push_str(&inner_item[..]);
 
         // Post-comments
@@ -330,7 +378,7 @@ where
             result.push_str(&formatted_comment);
         }
 
-        if separate {
+        if separate && sep_place.is_back() {
             result.push_str(formatting.separator);
         }
 
@@ -642,17 +690,6 @@ where
     }
 }
 
-fn needs_trailing_separator(
-    separator_tactic: SeparatorTactic,
-    list_tactic: DefinitiveListTactic,
-) -> bool {
-    match separator_tactic {
-        SeparatorTactic::Always => true,
-        SeparatorTactic::Vertical => list_tactic == DefinitiveListTactic::Vertical,
-        SeparatorTactic::Never => false,
-    }
-}
-
 /// Returns the count and total width of the list items.
 fn calculate_width<I, T>(items: I) -> (usize, usize)
 where
@@ -762,6 +799,7 @@ pub fn struct_lit_formatting<'a>(
         } else {
             context.config.trailing_comma()
         },
+        separator_place: SeparatorPlace::Back,
         shape: shape,
         ends_with_newline: ends_with_newline,
         preserve_newline: true,

src/types.rs

@@ -23,7 +23,7 @@ use config::{IndentStyle, Style, TypeDensity};
 use expr::{rewrite_pair, rewrite_tuple, rewrite_unary_prefix, wrap_args_with_parens};
 use items::{format_generics_item_list, generics_shape_from_config};
 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, ListTactic, Separator,
-            SeparatorTactic};
+            SeparatorPlace, SeparatorTactic};
 use rewrite::{Rewrite, RewriteContext};
 use utils::{colon_spaces, extra_offset, format_mutability, last_line_width, mk_sp, wrap_str};
 
@@ -365,6 +365,7 @@ where
         } else {
             context.config.trailing_comma()
         },
+        separator_place: SeparatorPlace::Back,
         shape: list_shape,
         ends_with_newline: tactic.ends_with_newline(context.config.fn_call_style()),
         preserve_newline: true,

src/vertical.rs

@@ -20,7 +20,8 @@ use codemap::SpanUtils;
 use comment::{combine_strs_with_missing_comments, contains_comment};
 use expr::rewrite_field;
 use items::{rewrite_struct_field, rewrite_struct_field_prefix};
-use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, ListTactic, Separator};
+use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, ListTactic, Separator,
+            SeparatorPlace};
 use rewrite::{Rewrite, RewriteContext};
 use utils::{contains_skip, is_attributes_extendable, mk_sp};
 
@@ -257,6 +258,7 @@ fn rewrite_aligned_items_inner<T: AlignedItem>(
         tactic: tactic,
         separator: ",",
         trailing_separator: context.config.trailing_comma(),
+        separator_place: SeparatorPlace::Back,
         shape: item_shape,
         ends_with_newline: true,
         preserve_newline: true,

src/visitor.rs

@@ -24,7 +24,8 @@ use config::{BraceStyle, Config};
 use expr::{format_expr, ExprType};
 use items::{format_impl, format_trait, rewrite_associated_impl_type, rewrite_associated_type,
             rewrite_static, rewrite_type_alias};
-use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorTactic};
+use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
+            SeparatorTactic};
 use macros::{rewrite_macro, MacroPosition};
 use regex::Regex;
 use rewrite::{Rewrite, RewriteContext};
@@ -917,6 +918,7 @@ impl Rewrite for ast::MetaItem {
                     tactic: DefinitiveListTactic::Mixed,
                     separator: ",",
                     trailing_separator: SeparatorTactic::Never,
+                    separator_place: SeparatorPlace::Back,
                     shape: item_shape,
                     ends_with_newline: false,
                     preserve_newline: false,