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feat: weak_space and weak_line #11

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15 changes: 15 additions & 0 deletions src/alloc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,11 @@ pub trait DocAllocator<'a> {
self.ascii_text(" ")
}

#[inline]
fn weak_space(&'a self) -> DocBuilder<'a, Self> {
DocBuilder(self, Doc::WeakSpace.into())
}

/// A line acts like a `\n` but behaves like `space` if it is grouped on a single line.
#[inline]
fn line(&'a self) -> DocBuilder<'a, Self> {
Expand Down Expand Up @@ -108,6 +113,16 @@ pub trait DocAllocator<'a> {
self.line_().group()
}

#[inline]
fn weak_line(&'a self) -> DocBuilder<'a, Self> {
DocBuilder(self, Doc::WeakLine.into()).flat_alt(self.space())
}

#[inline]
fn weak_line_(&'a self) -> DocBuilder<'a, Self> {
DocBuilder(self, Doc::WeakLine.into()).flat_alt(self.nil())
}

/// Equivalent to `self.nil().flat_alt(doc.pretty(self))`
#[inline]
fn if_group_flat(&'a self, doc: impl Pretty<'a, Self>) -> DocBuilder<'a, Self> {
Expand Down
16 changes: 15 additions & 1 deletion src/doc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,9 +33,11 @@ where
Fail,

// Texts
WeakSpace,
HardLine,
WeakLine,
Text(Text<'a>),
TextWithLen(usize, T), // Stores the length of a string document that is not just ascii
HardLine,

// Structural
Append(T, T), // Sequencing
Expand Down Expand Up @@ -129,7 +131,9 @@ where
Doc::Nil => f.write_str("Nil"),
Doc::Fail => f.write_str("Fail"),

Doc::WeakSpace => f.write_str("WeakSpace"),
Doc::HardLine => f.write_str("HardLine"),
Doc::WeakLine => f.write_str("WeakLine"),
Doc::TextWithLen(_, d) => d.fmt(f),
Doc::Text(s) => s.fmt(f),

Expand Down Expand Up @@ -401,11 +405,21 @@ macro_rules! impl_doc_methods {
Doc::HardLine.into()
}

#[inline]
pub fn weak_line() -> Self {
Doc::WeakLine.into()
}

#[inline]
pub fn space() -> Self {
Doc::Text(Text::Borrowed(" ")).into()
}

#[inline]
pub fn weak_space() -> Self {
Doc::WeakSpace.into()
}

/// Make the parent group break
#[inline]
pub fn expand_parent() -> Self {
Expand Down
127 changes: 108 additions & 19 deletions src/render/fit.rs
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Original file line number Diff line number Diff line change
@@ -1,19 +1,20 @@
use crate::{visitor::visit_sequence_rev, Doc, DocPtr, Render};
use crate::{render::write::write_spaces, visitor::visit_sequence_rev, Doc, DocPtr, Render};

use super::write::{write_newline, BufferWrite};
use super::write::BufferWrite;

pub fn print_doc<'a, W, T>(doc: &Doc<'a, T>, width: usize, out: &mut W) -> Result<(), W::Error>
where
T: DocPtr<'a> + 'a,
W: ?Sized + Render,
{
Printer {
pos: 0,
cmds: vec![Cmd {
indent: 0,
mode: Mode::Break,
doc,
}],
pos: 0,
pending_indent: Some(0),
fit_docs: vec![],
line_suffixes: vec![],
width,
Expand Down Expand Up @@ -52,8 +53,9 @@ struct Printer<'d, 'a, T>
where
T: DocPtr<'a> + 'a,
{
pos: usize,
cmds: Vec<Cmd<'d, 'a, T>>,
pos: usize,
pending_indent: Option<usize>,
fit_docs: Vec<FitCmd<'d, 'a, T>>,
line_suffixes: Vec<&'d Doc<'a, T>>,
width: usize,
Expand Down Expand Up @@ -92,10 +94,14 @@ where
Doc::Nil => break,
Doc::Fail => return Err(out.fail_doc()),

Doc::WeakSpace => {
if self.pending_indent.is_none() {
fits &= self.write_str(out, " ", 1)?;
}
break;
}
Doc::Text(ref s) => {
out.write_str_all(s)?;
self.pos += s.len();
fits &= self.pos <= self.width;
fits &= self.write_str(out, s, s.len())?;
break;
}

Expand All @@ -105,9 +111,7 @@ where
Doc::Text(ref s) => s,
_ => unreachable!(),
};
out.write_str_all(str)?;
self.pos += len;
fits &= self.pos <= self.width;
fits &= self.write_str(out, str, len)?;
break;
}

Expand All @@ -122,12 +126,38 @@ where
// The next document may have different indentation so we should use it if
// we can
if let Some(next) = self.cmds.pop() {
write_newline(next.indent, out)?;
self.pos = next.indent;
self.write_newline(out)?;
// write_spaces(next.indent, out)?;
// self.pos = next.indent;
self.pending_indent = Some(next.indent);
cmd = next;
} else {
self.write_newline(out)?;
// write_spaces(indent, out)?;
// self.pos = indent;
self.pending_indent = Some(indent);
break;
}
Comment on lines 128 to +140
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Contributor Author

@QuadnucYard QuadnucYard Oct 11, 2025

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here is the break. we need to work out new api for it.

}
Doc::WeakLine => {
// flush line suffixes
if self.line_suffixes.len() > ls_top {
self.cmds.push(cmd);
self.push_line_suffixes(ls_top, mode, indent);
break;
}

if self.pending_indent.is_some() {
// do not insert a newline if we are already in a fresh line
break;
}
if let Some(next) = self.cmds.pop() {
self.write_newline(out)?;
self.pending_indent = Some(next.indent);
cmd = next;
} else {
write_newline(indent, out)?;
self.pos = indent;
self.write_newline(out)?;
self.pending_indent = Some(indent);
break;
}
}
Expand All @@ -154,7 +184,7 @@ where
}
Doc::Align(ref inner) => {
// Align to the current position.
cmd.indent = self.pos;
cmd.indent = self.pending_indent.unwrap_or(0) + self.pos;
cmd.doc = inner;
}

Expand All @@ -170,7 +200,14 @@ where
};
}
Doc::Group(ref inner) => {
if mode == Mode::Break && self.fitting(inner, self.pos, indent, Mode::Flat)
if mode == Mode::Break
&& self.fitting(
inner,
self.pos,
indent,
Mode::Flat,
self.pending_indent,
)
{
cmd.mode = Mode::Flat;
}
Expand Down Expand Up @@ -208,7 +245,15 @@ where
}
}
Doc::PartialUnion(ref left, ref right) => {
if mode == Mode::Flat || self.fitting(left, self.pos, indent, Mode::Break) {
if mode == Mode::Flat
|| self.fitting(
left,
self.pos,
indent,
Mode::Break,
self.pending_indent,
)
{
cmd.doc = left;
} else {
cmd.doc = right;
Expand All @@ -235,6 +280,28 @@ where
Ok(fits)
}

fn write_str<W>(&mut self, out: &mut W, s: &str, len: usize) -> Result<bool, W::Error>
where
W: ?Sized + Render,
{
if let Some(indent) = self.pending_indent.take() {
write_spaces(indent, out)?;
self.pos = indent;
}
out.write_str_all(s)?;
self.pos += len;
Ok(self.pos <= self.width)
}

fn write_newline<W>(&mut self, out: &mut W) -> Result<(), W::Error>
where
W: ?Sized + Render,
{
out.write_str_all("\n")?;
self.pos = 0;
Ok(())
}

fn push_line_suffixes(&mut self, ls_top: usize, mode: Mode, indent: usize) {
self.line_suffixes
.drain(ls_top..)
Expand All @@ -243,7 +310,14 @@ where
}

#[cfg_attr(not(feature = "contextual"), allow(unused_variables))]
fn fitting(&mut self, next: &'d Doc<'a, T>, mut pos: usize, indent: usize, mode: Mode) -> bool {
fn fitting(
&mut self,
next: &'d Doc<'a, T>,
mut pos: usize,
indent: usize,
mode: Mode,
mut pending_indent: Option<usize>,
) -> bool {
// We start in "flat" mode and may fall back to "break" mode when backtracking.
let mut cmd_bottom = self.cmds.len();

Expand All @@ -268,22 +342,37 @@ where
Doc::Nil => break,
Doc::Fail => return false,

Doc::WeakSpace => {
if pending_indent.is_none() {
pos += 1;
if pos > self.width {
return false;
}
}
break;
}
Doc::Text(ref s) => {
if let Some(indent) = pending_indent.take() {
pos += indent;
}
pos += s.len();
if pos > self.width {
return false;
}
break;
}
Doc::TextWithLen(len, _) => {
if let Some(indent) = pending_indent.take() {
pos += indent;
}
pos += len;
if pos > self.width {
return false;
}
break;
}

Doc::HardLine => {
Doc::HardLine | Doc::WeakLine => {
// A hard_line only “fits” in break mode.
return mode == Mode::Break;
}
Expand Down
16 changes: 4 additions & 12 deletions src/render/write.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -100,22 +100,14 @@ impl Render for BufferWrite {
fn fail_doc(&self) -> Self::Error {}
}

pub(super) fn write_newline<W>(ind: usize, out: &mut W) -> Result<(), W::Error>
where
W: ?Sized + Render,
{
out.write_str_all("\n")?;
write_spaces(ind, out)
}

pub(super) fn write_spaces<W>(spaces: usize, out: &mut W) -> Result<(), W::Error>
where
W: ?Sized + Render,
{
let mut inserted = 0;
while inserted < spaces {
let insert = SPACES.len().min(spaces - inserted);
inserted += out.write_str(&SPACES[..insert])?;
let mut remaining = spaces;
while remaining > 0 {
let insert = SPACES.len().min(remaining);
remaining -= out.write_str(&SPACES[..insert])?;
}

Ok(())
Expand Down
51 changes: 51 additions & 0 deletions tests/render.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -352,3 +352,54 @@ fn pretty_cow() {

test_snapshot!(8, doc, @"abc 123");
}

#[test]
fn test_hard_line() {
let arena = Arena::new();
let doc = docs![&arena, "aaa", Doc::hard_line(), Doc::hard_line(), "bbb"].nest(2);

test_snapshot!(80, doc, @"aaa\n \n bbb");
}

#[test]
fn test_weak_space() {
let arena = Arena::new();
let doc = arena
.pretty((
Doc::weak_space(),
"aaa",
Doc::weak_space(),
Doc::weak_line(),
Doc::weak_space(),
"bbb",
))
.nest(2);

test_snapshot!(80, doc, @"aaa \n bbb");
}

#[test]
fn test_weak_line() {
let arena = Arena::new();
let doc = arena.pretty((
"(",
arena
.pretty((
Doc::weak_line(),
(
"aaa",
",",
Doc::weak_space(),
"// comment",
Doc::weak_line(),
),
Doc::weak_line(),
("bbb", ","),
))
.indent(2),
Doc::weak_line(),
")",
));

test_snapshot!(80, doc, @"(\n aaa, // comment\n bbb,\n)");
}
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