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chains: split handling of chains in block and visual cases

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Just refactoring, lots of code dup here, but it should get better...
This commit is contained in:
Nick Cameron 2018-07-09 13:02:14 +12:00
parent 728b0182c5
commit a8d5f25572
1 changed files with 221 additions and 59 deletions
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280
src/chains.rs
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@ -84,6 +84,13 @@ use syntax::{ast, ptr};
pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -> Option<String> {
debug!("rewrite_chain {:?}", shape);
match context.config.indent_style() {
IndentStyle::Block => rewrite_chain_block(expr, context, shape),
IndentStyle::Visual => rewrite_chain_visual(expr, context, shape),
}
}
fn rewrite_chain_block(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -> Option<String> {
let total_span = expr.span;
let (parent, subexpr_list) = make_subexpr_list(expr, context);
@ -96,14 +103,7 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
let prefix_try_num = subexpr_list.iter().rev().take_while(|e| is_try(e)).count();
// Parent is the first item in the chain, e.g., `foo` in `foo.bar.baz()`.
let parent_shape = if is_block_expr(context, &parent, "\n") {
match context.config.indent_style() {
IndentStyle::Block => shape,
IndentStyle::Visual => shape.visual_indent(0),
}
} else {
shape
};
let parent_shape = shape;
let parent_rewrite = parent
.rewrite(context, parent_shape)
.map(|parent_rw| parent_rw + &"?".repeat(prefix_try_num))?;
@ -114,29 +114,14 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
// 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 (nested_shape, extend) = if !parent_rewrite_contains_newline && is_continuable(&parent) {
match context.config.indent_style() {
IndentStyle::Block => {
// TODO this is naive since if the first child is on the same line
// as the parent, then we should look at that, instead of the parent.
// Can we make the parent the first two things then?
let shape = if parent_is_block {
shape
} else {
chain_indent(context, shape.add_offset(parent_rewrite.len()))
};
(shape, is_small_parent)
}
// TODO is this right?
IndentStyle::Visual => (chain_indent(context, shape.add_offset(parent_rewrite.len())), true),
}
let shape = if parent_is_block {
shape
} else {
chain_indent(context, shape.add_offset(parent_rewrite.len()))
};
(shape, is_small_parent)
} else if parent_is_block {
match context.config.indent_style() {
// Try to put the first child on the same line with parent's last line
IndentStyle::Block => (parent_shape, true),
// The parent is a block, so align the rest of the chain with the closing
// brace.
IndentStyle::Visual => (parent_shape, false),
}
(parent_shape, true)
} else {
(
chain_indent(context, shape.add_offset(parent_rewrite.len())),
@ -147,21 +132,13 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
let other_child_shape = nested_shape.with_max_width(context.config);
let first_child_shape = if extend {
match context.config.indent_style() {
IndentStyle::Block => {
let offset = trimmed_last_line_width(&parent_rewrite) + prefix_try_num;
if parent_is_block {
parent_shape.offset_left(offset)?
} else {
parent_shape
.block_indent(context.config.tab_spaces())
.offset_left(offset)?
}
}
IndentStyle::Visual => {
let overhead = last_line_width(&parent_rewrite);
parent_shape.offset_left(overhead)?
}
let offset = trimmed_last_line_width(&parent_rewrite) + prefix_try_num;
if parent_is_block {
parent_shape.offset_left(offset)?
} else {
parent_shape
.block_indent(context.config.tab_spaces())
.offset_left(offset)?
}
} else {
other_child_shape
@ -179,9 +156,7 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
let mut is_block_like = Vec::with_capacity(subexpr_list.len());
is_block_like.push(true);
for (i, expr) in subexpr_list.iter().skip(1).rev().enumerate() {
// TODO should only use first_child_shape if expr is block like
let shape = if *is_block_like.last().unwrap() && !(extend && i == 0) {
// TODO change the name of the shapes
first_child_shape
} else {
other_child_shape
@ -303,7 +278,6 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
let first_connector = if is_small_parent
|| fits_single_line
|| last_line_extendable(&parent_rewrite)
|| context.config.indent_style() == IndentStyle::Visual
{
""
} else {
@ -314,7 +288,6 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
let second_connector = if fits_single_line
|| rewrites[1] == "?"
|| last_line_extendable(&rewrites[0])
|| context.config.indent_style() == IndentStyle::Visual
{
""
} else {
@ -337,11 +310,203 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
)
};
let result = format!("{}{}", result, "?".repeat(suffix_try_num));
if context.config.indent_style() == IndentStyle::Visual {
wrap_str(result, context.config.max_width(), shape)
} else {
Some(result)
Some(result)
}
fn rewrite_chain_visual(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -> Option<String> {
let total_span = expr.span;
let (parent, subexpr_list) = make_subexpr_list(expr, context);
// Bail out if the chain is just try sugar, i.e., an expression followed by
// any number of `?`s.
if chain_only_try(&subexpr_list) {
return rewrite_try(&parent, subexpr_list.len(), context, shape);
}
let suffix_try_num = subexpr_list.iter().take_while(|e| is_try(e)).count();
let prefix_try_num = subexpr_list.iter().rev().take_while(|e| is_try(e)).count();
// Parent is the first item in the chain, e.g., `foo` in `foo.bar.baz()`.
let parent_shape = if is_block_expr(context, &parent, "\n") {
shape.visual_indent(0)
} else {
shape
};
let parent_rewrite = parent
.rewrite(context, parent_shape)
.map(|parent_rw| parent_rw + &"?".repeat(prefix_try_num))?;
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, &parent, &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 (nested_shape, extend) = if !parent_rewrite_contains_newline && is_continuable(&parent) {
(shape.visual_indent(0), true)
} else if parent_is_block {
(parent_shape, false)
} else {
(
shape.visual_indent(0),
false,
)
};
let other_child_shape = nested_shape.with_max_width(context.config);
let first_child_shape = if extend {
let overhead = last_line_width(&parent_rewrite);
parent_shape.offset_left(overhead)?
} else {
other_child_shape
};
debug!(
"child_shapes {:?} {:?}",
first_child_shape, 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 mut rewrites: Vec<String> = Vec::with_capacity(subexpr_list.len());
let mut is_block_like = Vec::with_capacity(subexpr_list.len());
is_block_like.push(true);
for (i, expr) in subexpr_list.iter().skip(1).rev().enumerate() {
let shape = if *is_block_like.last().unwrap() && !(extend && i == 0) {
first_child_shape
} else {
other_child_shape
};
let rewrite = rewrite_chain_subexpr(expr, total_span, context, shape)?;
is_block_like.push(is_block_expr(context, expr, &rewrite));
rewrites.push(rewrite);
}
// 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 almost_total = if extend_last_subexpr {
last_line_width(&parent_rewrite)
} else {
rewrites.iter().fold(0, |a, b| a + b.len()) + parent_rewrite.len()
} + suffix_try_num;
let one_line_budget = if rewrites.is_empty() {
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'))
&& almost_total < one_line_budget;
let last_shape = if is_block_like[rewrites.len()] {
first_child_shape
} else {
other_child_shape
}.sub_width(shape.rhs_overhead(context.config) + suffix_try_num)?;
// 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:
//
// A chain with overflowing the last child:
// ```
// parent.child1.child2.last_child(
// a,
// b,
// c,
// )
// ```
//
// A chain without overflowing the last child (in vertical layout):
// ```
// parent
// .child1
// .child2
// .last_child(a, b, c)
// ```
//
// In particular, overflowing is effective when the last child is a method with a multi-lined
// block-like argument (e.g. closure):
// ```
// parent.child1.child2.last_child(|a, b, c| {
// let x = foo(a, b, c);
// let y = bar(a, b, c);
//
// // ...
//
// result
// })
// ```
// `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 rewrite_last = || rewrite_chain_subexpr(last_subexpr, total_span, context, last_shape);
let (last_subexpr_str, fits_single_line) = 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.
parent_shape.offset_left(almost_total).map(|shape| {
if let Some(rw) = rewrite_chain_subexpr(last_subexpr, total_span, 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;
if fits_single_line && line_count >= 5 {
(Some(rw), 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_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),
}
}
} else {
(rewrite_last(), false)
}
})?
} else {
(rewrite_last(), false)
};
rewrites.push(last_subexpr_str?);
// 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 {
// Yay, we can put everything on one line.
Cow::from("")
} else {
// Use new lines.
if *context.force_one_line_chain.borrow() {
return None;
}
nested_shape.indent.to_string_with_newline(context.config)
};
let result = if is_small_parent && rewrites.len() > 1 {
format!(
"{}{}{}",
parent_rewrite,
rewrites[0],
join_rewrites(&rewrites[1..], &is_block_like[2..], &connector),
)
} else {
format!(
"{}{}",
parent_rewrite,
join_rewrites(&rewrites, &is_block_like[1..], &connector),
)
};
let result = format!("{}{}", result, "?".repeat(suffix_try_num));
wrap_str(result, context.config.max_width(), shape)
}
// True if the chain is only `?`s.
@ -421,12 +586,9 @@ fn make_subexpr_list(expr: &ast::Expr, context: &RewriteContext) -> (ast::Expr,
}
fn chain_indent(context: &RewriteContext, shape: Shape) -> Shape {
match context.config.indent_style() {
IndentStyle::Visual => shape.visual_indent(0),
IndentStyle::Block => shape
.block_indent(context.config.tab_spaces())
.with_max_width(context.config),
}
IndentStyle::Block => shape
.block_indent(context.config.tab_spaces())
.with_max_width(context.config),
}
// Returns the expression's subexpression, if it exists. When the subexpr