Format try shorthand

Author: marcusklaas

src/chains.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 /// Formatting of chained expressions, i.e. expressions which are chained by
-/// dots: struct and enum field access and method calls.
+/// dots: struct and enum field access, method calls, and try shorthand (?).
 ///
 /// Instead of walking these subexpressions one-by-one, as is our usual strategy
 /// for expression formatting, we collect maximal sequences of these expressions
@@ -81,7 +81,6 @@
 /// true, then we allow the last method call to spill over multiple lines without
 /// forcing the rest of the chain to be split.
 
-
 use Indent;
 use rewrite::{Rewrite, RewriteContext};
 use utils::{wrap_str, first_line_width};
@@ -109,8 +108,16 @@ pub fn rewrite_chain(expr: &ast::Expr,
     // put the first non-parent item on the same line as the parent.
     let (indent, extend) = if !parent_rewrite.contains('\n') && is_continuable(parent) ||
                               parent_rewrite.len() <= context.config.tab_spaces {
-        // Try and put at least the first two items on the same line.
-        (chain_indent(context, offset + Indent::new(0, parent_rewrite.len())), true)
+// <<<<<<< HEAD
+//         // Try and put at least the first two items on the same line.
+//         (chain_indent(context, offset + Indent::new(0, parent_rewrite.len())), true)
+// =======
+        let indent = if let ast::ExprKind::Try(..) = subexpr_list.last().unwrap().node {
+            parent_block_indent.block_indent(context.config)
+        } else {
+            offset + Indent::new(0, parent_rewrite.len())
+        };
+        (indent, true)
     } else if is_block_expr(parent, &parent_rewrite) {
         // The parent is a block, so align the rest of the chain with the closing
         // brace.
@@ -184,12 +191,27 @@ pub fn rewrite_chain(expr: &ast::Expr,
     wrap_str(format!("{}{}{}",
                      parent_rewrite,
                      first_connector,
-                     rewrites.join(&connector)),
+                     join_rewrites(&rewrites, &subexpr_list, &connector)),
              context.config.max_width,
              width,
              offset)
 }
 
+fn join_rewrites(rewrites: &[String], subexps: &[&ast::Expr], connector: &str) -> String {
+    let mut rewrite_iter = rewrites.iter();
+    let mut result = rewrite_iter.next().unwrap().clone();
+
+    for (rewrite, expr) in rewrite_iter.zip(subexps.iter()) {
+        match expr.node {
+            ast::ExprKind::Try(_) => (),
+            _ => result.push_str(connector),
+        };
+        result.push_str(&rewrite[..]);
+    }
+
+    result
+}
+
 // States whether an expression's last line exclusively consists of closing
 // parens, braces, and brackets in its idiomatic formatting.
 fn is_block_expr(expr: &ast::Expr, repr: &str) -> bool {
@@ -293,6 +315,16 @@ fn rewrite_method_call_with_overflow(expr_kind: &ast::ExprKind,
     }
 }
 
+fn pop_expr_chain(expr: &ast::Expr) -> Option<&ast::Expr> {
+    match expr.node {
+        ast::ExprKind::MethodCall(_, _, ref expressions) => Some(&expressions[0]),
+        ast::ExprKind::TupField(ref subexpr, _) |
+        ast::ExprKind::Field(ref subexpr, _) |
+        ast::ExprKind::Try(ref subexpr) => Some(subexpr),
+        _ => None,
+    }
+}
+
 // Rewrite the last element in the chain `expr`. E.g., given `a.b.c` we rewrite
 // `.c`.
 fn rewrite_chain_subexpr(expr: &ast::Expr,
@@ -328,6 +360,13 @@ fn rewrite_chain_subexpr(expr: &ast::Expr,
                 None
             }
         }
+        ast::ExprKind::Try(_) => {
+            if width >= 1 {
+                Some("?".into())
+            } else {
+                None
+            }
+        }
         _ => unreachable!(),
     }
 }

src/expr.rs

@@ -148,6 +148,7 @@ impl Rewrite for ast::Expr {
             ast::ExprKind::Closure(capture, ref fn_decl, ref body, _) => {
                 rewrite_closure(capture, fn_decl, body, self.span, context, width, offset)
             }
+            // ast::ExprKind::Try(..) |
             ast::ExprKind::Field(..) |
             ast::ExprKind::TupField(..) |
             ast::ExprKind::MethodCall(..) => rewrite_chain(self, context, width, offset),
@@ -199,21 +200,20 @@ impl Rewrite for ast::Expr {
                         rewrite_unary_prefix(context, delim, &**rhs, width, offset)
                     }
                     (Some(ref lhs), None) => {
-                        Some(format!("{}{}",
-                                     try_opt!(lhs.rewrite(context,
-                                                          try_opt!(width.checked_sub(delim.len())),
-                                                          offset)),
-                                     delim))
+                        rewrite_unary_suffix(context, delim, &**lhs, width, offset)
                     }
                     (None, None) => wrap_str(delim.into(), context.config.max_width, width, offset),
                 }
             }
+            ast::ExprKind::Try(ref expr) => {
+                rewrite_unary_suffix(context, "?", &**expr, width, offset)
+            }
             // We do not format these expressions yet, but they should still
             // satisfy our width restrictions.
             ast::ExprKind::InPlace(..) |
             ast::ExprKind::InlineAsm(..) |
-            // TODO(#867): Handle try shorthand
-            ast::ExprKind::Try(_) => {
+            // TODO(#848): Handle type ascription
+            ast::ExprKind::Type(_, _) => {
                 wrap_str(context.snippet(self.span),
                          context.config.max_width,
                          width,
@@ -1762,6 +1762,21 @@ pub fn rewrite_unary_prefix<R: Rewrite>(context: &RewriteContext,
         .map(|r| format!("{}{}", prefix, r))
 }
 
+// FIXME: this is probably not correct for multi-line Rewrites. we should
+// subtract suffix.len() from the last line budget, not the first!
+pub fn rewrite_unary_suffix<R: Rewrite>(context: &RewriteContext,
+                                        suffix: &str,
+                                        rewrite: &R,
+                                        width: usize,
+                                        offset: Indent)
+                                        -> Option<String> {
+    rewrite.rewrite(context, try_opt!(width.checked_sub(suffix.len())), offset)
+           .map(|mut r| {
+               r.push_str(suffix);
+               r
+           })
+}
+
 fn rewrite_unary_op(context: &RewriteContext,
                     op: &ast::UnOp,
                     expr: &ast::Expr,

tests/source/chains.rs

@@ -112,3 +112,12 @@ fn issue587() {
 
     std::mem::transmute(dl.symbol::<()>("init").unwrap())
 }
+
+fn try_shorthand() {
+    let x = expr?;
+    let y = expr.kaas()?.test();
+    let loooooooooooooooooooooooooooooooooooooooooong = does_this?.look?.good?.should_we_break?.after_the_first_question_mark?;
+    let yyyy = expr?.another?.another?.another?.another?.another?.another?.another?.another?.test();
+    let zzzz = expr?.another?.another?.another?.another?;
+    let aaa =  x ????????????  ?????????????? ???? ?????  ?????????????? ?????????  ?????????????? ??;
+}

tests/target/chains.rs

@@ -133,3 +133,16 @@ fn issue587() {
 
     std::mem::transmute(dl.symbol::<()>("init").unwrap())
 }
+
+fn try_shorthand() {
+    let x = expr?;
+    let y = expr.kaas()?.test();
+    let loooooooooooooooooooooooooooooooooooooooooong = does_this?
+                                                            .look?
+                                                            .good?
+                                                            .should_we_break?
+                                                            .after_the_first_question_mark?;
+    let yyyy = expr?.another?.another?.another?.another?.another?.another?.another?.another?.test();
+    let zzzz = expr?.another?.another?.another?.another?;
+    let aaa = x??????????????????????????????????????????????????????????????????????????;
+}