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chains: refactor block formatting

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This commit is contained in:
Nick Cameron 2018-07-10 12:24:45 +12:00
parent 914e750c9e
commit 92701552bc
1 changed files with 94 additions and 115 deletions
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209
src/chains.rs
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@ -71,10 +71,7 @@ use macros::convert_try_mac;
use rewrite::{Rewrite, RewriteContext};
use shape::Shape;
use spanned::Spanned;
use utils::{
first_line_width, last_line_extendable, last_line_width, mk_sp, trimmed_last_line_width,
wrap_str,
};
use utils::{first_line_width, last_line_extendable, last_line_width, mk_sp, wrap_str};
use std::borrow::Cow;
use std::cmp::min;
@ -99,11 +96,13 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
}
// An expression plus trailing `?`s to be formatted together.
#[derive(Debug)]
struct ChainItem {
expr: ast::Expr,
tries: usize,
}
#[derive(Debug)]
struct Chain {
parent: ChainItem,
// TODO do we need to clone the exprs?
@ -136,82 +135,89 @@ impl Chain {
}
Chain {
parent: children.pop().unwrap(),
children: children.into_iter().rev().collect(),
parent: children.remove(0),
children,
}
}
}
fn rewrite_chain_block(mut chain: Chain, context: &RewriteContext, shape: Shape) -> Option<String> {
let last = chain.children.pop().unwrap();
fn rewrite_chain_block(chain: Chain, context: &RewriteContext, shape: Shape) -> Option<String> {
debug!("rewrite_chain_block {:?} {:?}", chain, shape);
// Parent is the first item in the chain, e.g., `foo` in `foo.bar.baz()`.
let parent_rewrite = chain.parent.expr
// Root is the parent plus any other chain items placed on the first line to
// avoid an orphan. E.g.,
// ```
// foo.bar
// .baz()
// ```
// If `bar` were not part of the root, then baz would be orphaned and 'float'.
let mut root_rewrite = chain.parent.expr
.rewrite(context, shape)
.map(|parent_rw| parent_rw + &"?".repeat(chain.parent.tries))?;
let parent_rewrite_contains_newline = parent_rewrite.contains('\n');
let is_small_parent = shape.offset + parent_rewrite.len() <= context.config.tab_spaces();
let parent_is_block = is_block_expr(context, &chain.parent.expr, &parent_rewrite);
// Decide how to layout the rest of the chain. `extend` is true if we can
// put the first non-parent item on the same line as the parent.
let other_child_shape = if parent_is_block {
let mut children: &[_] = &chain.children;
let mut root_ends_with_block = is_block_expr(context, &chain.parent.expr, &root_rewrite);
let tab_width = context.config.tab_spaces().saturating_sub(shape.offset);
while root_rewrite.len() <= tab_width && !root_rewrite.contains('\n') {
let item = &children[0];
let shape = shape.offset_left(root_rewrite.len())?;
match rewrite_chain_subexpr(&item.expr, context, shape) {
Some(rewrite) => {
root_rewrite.push_str(&rewrite);
root_rewrite.push_str(&"?".repeat(item.tries));
}
None => break,
}
root_ends_with_block = is_block_expr(context, &item.expr, &root_rewrite);
children = &children[1..];
if children.is_empty() {
return Some(root_rewrite);
}
}
// Separate out the last item in the chain for special treatment below.
let last = &children[children.len() - 1];
children = &children[..children.len() - 1];
// Decide how to layout the rest of the chain.
let child_shape = if root_ends_with_block {
shape
} else {
shape.block_indent(context.config.tab_spaces())
}.with_max_width(context.config);
let extend = parent_is_block || (is_small_parent && !parent_rewrite_contains_newline && is_continuable(&chain.parent.expr));
let first_child_shape = if extend {
let offset = trimmed_last_line_width(&parent_rewrite) + chain.parent.tries;
other_child_shape.offset_left(offset)?
} else {
other_child_shape
};
debug!(
"child_shapes {:?} {:?}",
first_child_shape, other_child_shape
);
let mut rewrites: Vec<String> = Vec::with_capacity(chain.children.len());
let mut is_block_like = Vec::with_capacity(chain.children.len());
is_block_like.push(true);
for (i, item) in chain.children.iter().enumerate() {
let shape = if *is_block_like.last().unwrap() && !(extend && i == 0) {
first_child_shape
} else {
other_child_shape
};
let rewrite = rewrite_chain_subexpr(&item.expr, context, shape)?;
let mut rewrites: Vec<String> = Vec::with_capacity(children.len());
rewrites.push(root_rewrite);
let mut is_block_like = Vec::with_capacity(children.len());
is_block_like.push(root_ends_with_block);
for item in children {
let rewrite = rewrite_chain_subexpr(&item.expr, context, child_shape)?;
is_block_like.push(is_block_expr(context, &item.expr, &rewrite));
rewrites.push(format!("{}{}", rewrite, "?".repeat(item.tries)));
}
// Total of all items excluding the last.
let extend_last_subexpr = if is_small_parent {
rewrites.len() == 1 && last_line_extendable(&rewrites[0])
} else {
rewrites.is_empty() && last_line_extendable(&parent_rewrite)
};
let extend_last_subexpr = last_line_extendable(&rewrites[rewrites.len() - 1]);
let almost_total = if extend_last_subexpr {
last_line_width(&parent_rewrite)
last_line_width(&rewrites[rewrites.len() - 1])
} else {
rewrites.iter().fold(0, |a, b| a + b.len()) + parent_rewrite.len()
rewrites.iter().fold(0, |a, b| a + b.len())
} + last.tries;
let one_line_budget = if rewrites.is_empty() {
let one_line_budget = if rewrites.len() == 1 {
shape.width
} else {
min(shape.width, context.config.width_heuristics().chain_width)
};
let all_in_one_line = !parent_rewrite_contains_newline
&& rewrites.iter().all(|s| !s.contains('\n'))
let all_in_one_line = rewrites.iter().all(|s| !s.contains('\n'))
&& almost_total < one_line_budget;
let last_shape = if is_block_like[rewrites.len()] {
first_child_shape
let last_shape = if all_in_one_line {
shape.sub_width(last.tries)?
} else {
other_child_shape
}.sub_width(shape.rhs_overhead(context.config) + last.tries)?;
child_shape.sub_width(shape.rhs_overhead(context.config) + last.tries)?
};
// Rewrite the last child. The last child of a chain requires special treatment. We need to
// know whether 'overflowing' the last child make a better formatting:
@ -246,46 +252,54 @@ fn rewrite_chain_block(mut chain: Chain, context: &RewriteContext, shape: Shape)
// })
// ```
// `rewrite_last` rewrites the last child on its own line. We use a closure here instead of
// directly calling `rewrite_chain_subexpr()` to avoid exponential blowup.
let (last_subexpr_str, fits_single_line) = if all_in_one_line || extend_last_subexpr {
let mut last_subexpr_str = None;
let mut fits_single_line = false;
if all_in_one_line || extend_last_subexpr {
// First we try to 'overflow' the last child and see if it looks better than using
// vertical layout.
shape.offset_left(almost_total).map(|shape| {
if let Some(shape) = last_shape.offset_left(almost_total) {
if let Some(rw) = rewrite_chain_subexpr(&last.expr, context, shape) {
// We allow overflowing here only if both of the following conditions match:
// 1. The entire chain fits in a single line except the last child.
// 2. `last_child_str.lines().count() >= 5`.
let line_count = rw.lines().count();
let fits_single_line = almost_total + first_line_width(&rw) <= one_line_budget;
let could_fit_single_line = almost_total + first_line_width(&rw) <= one_line_budget;
if fits_single_line && line_count >= 5 {
(Some(rw), true)
last_subexpr_str = Some(rw);
fits_single_line = true;
} else {
// We could not know whether overflowing is better than using vertical layout,
// just by looking at the overflowed rewrite. Now we rewrite the last child
// on its own line, and compare two rewrites to choose which is better.
match rewrite_chain_subexpr(&last.expr, context, last_shape) {
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)
Some(ref new_rw) if !could_fit_single_line => {
last_subexpr_str = Some(new_rw.clone());
}
Some(ref new_rw) if new_rw.lines().count() >= line_count => {
last_subexpr_str = Some(rw);
fits_single_line = could_fit_single_line;
}
new_rw @ Some(..) => {
last_subexpr_str = new_rw;
}
_ => {
last_subexpr_str = Some(rw);
fits_single_line = could_fit_single_line;
}
new_rw @ Some(..) => (new_rw, false),
_ => (Some(rw), fits_single_line),
}
}
} else {
(rewrite_chain_subexpr(&last.expr, context, last_shape), false)
}
})?
} else {
(rewrite_chain_subexpr(&last.expr, context, last_shape), false)
};
rewrites.push(last_subexpr_str?);
}
}
last_subexpr_str = last_subexpr_str.or_else(|| rewrite_chain_subexpr(&last.expr, context, last_shape));
rewrites.push(format!("{}{}", last_subexpr_str?, "?".repeat(last.tries)));
// We should never look at this, since we only look at the block-ness of the
// previous item in the chain.
is_block_like.push(false);
let connector = if fits_single_line && !parent_rewrite_contains_newline {
let connector = if fits_single_line && all_in_one_line {
// Yay, we can put everything on one line.
Cow::from("")
} else {
@ -293,44 +307,10 @@ fn rewrite_chain_block(mut chain: Chain, context: &RewriteContext, shape: Shape)
if *context.force_one_line_chain.borrow() {
return None;
}
other_child_shape.indent.to_string_with_newline(context.config)
child_shape.indent.to_string_with_newline(context.config)
};
let first_connector = if is_small_parent
|| fits_single_line
|| last_line_extendable(&parent_rewrite)
{
""
} else {
&connector
};
let result = if is_small_parent && rewrites.len() > 1 {
let second_connector = if fits_single_line
|| rewrites[1] == "?"
|| last_line_extendable(&rewrites[0])
{
""
} else {
&connector
};
format!(
"{}{}{}{}{}",
parent_rewrite,
first_connector,
rewrites[0],
second_connector,
join_rewrites(&rewrites[1..], &is_block_like[2..], &connector),
)
} else {
format!(
"{}{}{}",
parent_rewrite,
first_connector,
join_rewrites(&rewrites, &is_block_like[1..], &connector),
)
};
let result = format!("{}{}", result, "?".repeat(last.tries));
let result = join_rewrites(&rewrites, &is_block_like, &connector);
Some(result)
}
@ -424,7 +404,6 @@ fn rewrite_chain_visual(mut chain: Chain, context: &RewriteContext, shape: Shape
let mut last_subexpr_str = None;
let mut fits_single_line = false;
if all_in_one_line {
// First we try to 'overflow' the last child and see if it looks better than using
// vertical layout.
@ -517,7 +496,9 @@ fn join_rewrites_vis(rewrites: &[String], connector: &str) -> String {
// parens, braces, and brackets in its idiomatic formatting.
fn is_block_expr(context: &RewriteContext, expr: &ast::Expr, repr: &str) -> bool {
match expr.node {
ast::ExprKind::Mac(..) | ast::ExprKind::Call(..) => {
ast::ExprKind::Mac(..)
| ast::ExprKind::Call(..)
| ast::ExprKind::MethodCall(..) => {
context.use_block_indent() && repr.contains('\n')
}
ast::ExprKind::Struct(..)
@ -533,11 +514,9 @@ fn is_block_expr(context: &RewriteContext, expr: &ast::Expr, repr: &str) -> bool
| ast::ExprKind::Binary(_, _, ref expr)
| ast::ExprKind::Index(_, ref expr)
| ast::ExprKind::Unary(_, ref expr)
| ast::ExprKind::Closure(_, _, _, _, ref expr, _) => is_block_expr(context, expr, repr),
ast::ExprKind::MethodCall(_, ref exprs) => {
// TODO maybe should be like Call
is_block_expr(context, exprs.last().unwrap(), repr)
}
| ast::ExprKind::Closure(_, _, _, _, ref expr, _)
| ast::ExprKind::Try(ref expr)
| ast::ExprKind::Yield(Some(ref expr)) => is_block_expr(context, expr, repr),
_ => false,
}
}