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Avoid trial and error in rewrite_chain whenever possible

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This commit is contained in:
Seiichi Uchida 2017-08-07 15:17:35 +09:00 committed by topecongiro
parent 7268a50e36
commit 04a6d16c7b
1 changed files with 48 additions and 154 deletions
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202
src/chains.rs
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@ -105,7 +105,7 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
let parent_shape = if is_block_expr(context, &parent, "\n") {
match context.config.chain_indent() {
IndentStyle::Visual => shape.visual_indent(0),
IndentStyle::Block => shape.block(),
IndentStyle::Block => shape,
}
} else {
shape
@ -133,13 +133,9 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
// brace.
IndentStyle::Visual => (parent_shape, false),
}
} else if parent_rewrite_contains_newline {
(chain_indent(context, parent_shape), false)
} else {
(
shape
.block_indent(context.config.tab_spaces())
.with_max_width(context.config),
chain_indent(context, shape.add_offset(parent_rewrite.len())),
false,
)
};
@ -166,8 +162,9 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
.into_iter()
.chain(iter::repeat(other_child_shape));
let subexpr_num = subexpr_list.len();
let last_subexpr = &subexpr_list[suffix_try_num];
let subexpr_list = &subexpr_list[suffix_try_num..subexpr_num - prefix_try_num];
let iter = subexpr_list.iter().rev().zip(child_shape_iter);
let iter = subexpr_list.iter().skip(1).rev().zip(child_shape_iter);
let mut rewrites = try_opt!(
iter.map(|(e, shape)| {
rewrite_chain_subexpr(e, total_span, context, shape)
@ -175,85 +172,46 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
);
// Total of all items excluding the last.
let rewrites_len = rewrites.len();
let almost_total = rewrites[0..(rewrites_len - 1)]
.iter()
.fold(0, |a, b| a + first_line_width(b)) + parent_rewrite.len();
let one_line_len =
rewrites.iter().fold(0, |a, r| a + first_line_width(r)) + parent_rewrite.len();
let one_line_budget = min(shape.width, context.config.chain_one_line_max());
let veto_single_line = if one_line_len > one_line_budget {
if rewrites.len() > 1 {
true
} else if rewrites.len() == 1 {
context.config.chain_split_single_child() || one_line_len > shape.width
} else {
false
}
} else if context.config.take_source_hints() && rewrites.len() > 1 {
// Look at the source code. Unless all chain elements start on the same
// line, we won't consider putting them on a single line either.
let last_span = context.snippet(mk_sp(subexpr_list[1].span.hi, total_span.hi));
let first_span = context.snippet(subexpr_list[1].span);
let last_iter = last_span.chars().take_while(|c| c.is_whitespace());
first_span.chars().chain(last_iter).any(|c| c == '\n')
let extend_last_subexr = last_line_extendable(&parent_rewrite) && rewrites.is_empty();
let almost_total = if extend_last_subexr {
last_line_width(&parent_rewrite)
} else {
false
rewrites.iter().fold(0, |a, b| a + b.len()) + parent_rewrite.len()
};
let mut fits_single_line = !veto_single_line && almost_total <= shape.width;
if fits_single_line {
let len = rewrites.len();
let (init, last) = rewrites.split_at_mut(len - 1);
fits_single_line = init.iter().all(|s| !s.contains('\n'));
if fits_single_line {
fits_single_line = match expr.node {
ref e @ ast::ExprKind::MethodCall(..) => {
if rewrite_method_call_with_overflow(
e,
&mut last[0],
almost_total,
total_span,
context,
shape,
) {
// If the first line of the last method does not fit into a single line
// after the others, allow new lines.
almost_total + first_line_width(&last[0]) < context.config.max_width()
} else {
false
let one_line_budget = if rewrites.is_empty() && !context.config.chain_split_single_child() {
shape.width
} else {
min(shape.width, context.config.chain_one_line_max())
};
let all_in_one_line = !parent_rewrite_contains_newline &&
rewrites.iter().all(|s| !s.contains('\n')) &&
almost_total < one_line_budget;
let rewrite_last = || rewrite_chain_subexpr(last_subexpr, total_span, context, nested_shape);
let (last_subexpr_str, fits_single_line) = try_opt!(if all_in_one_line || extend_last_subexr {
parent_shape.offset_left(almost_total).map(|shape| {
if let Some(rw) = rewrite_chain_subexpr(last_subexpr, total_span, context, shape) {
let line_count = rw.lines().count();
let fits_single_line = almost_total + first_line_width(&rw) <= one_line_budget;
if (line_count >= 5 && fits_single_line) || extend_last_subexr {
(Some(rw), true)
} else {
match rewrite_last() {
Some(ref new_rw) if !fits_single_line => (Some(new_rw.clone()), false),
Some(ref new_rw) if new_rw.lines().count() >= line_count => {
(Some(rw), fits_single_line)
}
new_rw @ Some(..) => (new_rw, false),
_ => (Some(rw), fits_single_line),
}
}
_ => !last[0].contains('\n'),
} else {
(rewrite_last(), false)
}
}
}
// Try overflowing the last element if we are using block indent and it goes multi line
// or it fits in a single line but goes over the max width.
if !fits_single_line && context.use_block_indent() {
let last_expr_index = rewrites.len() - 1;
let (init, last) = rewrites.split_at_mut(last_expr_index);
let almost_single_line = init.iter().all(|s| !s.contains('\n'));
if almost_single_line && last[0].contains('\n') {
let overflow_shape = Shape {
width: one_line_budget,
..parent_shape
};
fits_single_line = rewrite_last_child_with_overflow(
context,
&subexpr_list[0],
overflow_shape,
total_span,
almost_total,
one_line_budget,
&mut last[0],
);
}
}
})
} else {
Some((rewrite_last(), false))
});
rewrites.push(try_opt!(last_subexpr_str));
let connector = if fits_single_line && !parent_rewrite_contains_newline {
// Yay, we can put everything on one line.
@ -266,14 +224,14 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
format!("\n{}", nested_shape.indent.to_string(context.config))
};
let first_connector = choose_first_connector(
context,
&parent_rewrite,
&rewrites[0],
&connector,
&subexpr_list,
extend,
);
let first_connector = if is_small_parent || fits_single_line ||
last_line_extendable(&parent_rewrite) ||
context.config.chain_indent() == IndentStyle::Visual
{
""
} else {
connector.as_str()
};
let result = if is_small_parent && rewrites.len() > 1 {
let second_connector = choose_first_connector(
@ -301,11 +259,7 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
)
};
let result = format!("{}{}", result, repeat_try(suffix_try_num));
if context.config.chain_indent() == IndentStyle::Block {
Some(result)
} else {
wrap_str(result, context.config.max_width(), shape)
}
wrap_str(result, context.config.max_width(), shape)
}
fn is_extendable_parent(context: &RewriteContext, parent_str: &str) -> bool {
@ -323,26 +277,6 @@ fn chain_only_try(exprs: &[ast::Expr]) -> bool {
// Try to rewrite and replace the last non-try child. Return `true` if
// replacing succeeds.
fn rewrite_last_child_with_overflow(
context: &RewriteContext,
expr: &ast::Expr,
shape: Shape,
span: Span,
almost_total: usize,
one_line_budget: usize,
last_child: &mut String,
) -> bool {
if let Some(shape) = shape.shrink_left(almost_total) {
if let Some(ref mut rw) = rewrite_chain_subexpr(expr, span, context, shape) {
if almost_total + first_line_width(rw) <= one_line_budget && rw.lines().count() > 3 {
::std::mem::swap(last_child, rw);
return true;
}
}
}
false
}
fn repeat_try(try_count: usize) -> String {
iter::repeat("?").take(try_count).collect::<String>()
}
@ -420,46 +354,6 @@ fn chain_indent(context: &RewriteContext, shape: Shape) -> Shape {
}
}
fn rewrite_method_call_with_overflow(
expr_kind: &ast::ExprKind,
last: &mut String,
almost_total: usize,
total_span: Span,
context: &RewriteContext,
shape: Shape,
) -> bool {
if let &ast::ExprKind::MethodCall(ref segment, ref expressions) = expr_kind {
let shape = match shape.shrink_left(almost_total) {
Some(b) => b,
None => return false,
};
let types = match segment.parameters {
Some(ref params) => match **params {
ast::PathParameters::AngleBracketed(ref data) => &data.types[..],
_ => &[],
},
_ => &[],
};
let mut last_rewrite = rewrite_method_call(
segment.identifier,
types,
expressions,
total_span,
context,
shape,
);
if let Some(ref mut s) = last_rewrite {
::std::mem::swap(s, last);
true
} else {
false
}
} else {
unreachable!();
}
}
// Returns the expression's subexpression, if it exists. When the subexpr
// is a try! macro, we'll convert it to shorthand when the option is set.
fn pop_expr_chain(expr: &ast::Expr, context: &RewriteContext) -> Option<ast::Expr> {