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Merged
Lurk merged 2 commits into from
Jul 31, 2026
Merged

try_to_yamd #103

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c9a0d2c
try_to_yamd
Lurk Jul 30, 2026
67f2ccf
cover UnbalancedOpStream Display and root-frame mismatch
Lurk Jul 30, 2026
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1 change: 1 addition & 0 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,7 @@ pub mod op;
pub use nodes::Yamd;
pub use op::parse;
pub use op::to_yamd;
pub use op::{UnbalancedOpStream, try_to_yamd};

/// Deserialize a string into a Yamd struct
/// # Example
Expand Down
2 changes: 1 addition & 1 deletion src/op/mod.rs
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Expand Up @@ -43,7 +43,7 @@ mod strikethrough;
mod thematic_break;
mod title;
mod to_yamd;
pub use to_yamd::to_yamd;
pub use to_yamd::{UnbalancedOpStream, to_yamd, try_to_yamd};

/// Text content extracted from the source input.
///
Expand Down
77 changes: 56 additions & 21 deletions src/op/to_yamd.rs
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Expand Up @@ -5,6 +5,19 @@ use crate::nodes::{
};
use crate::op::{Content, Node, Op, OpKind};

/// Error returned by [`try_to_yamd`] when the op stream is not well-formed
/// (unbalanced Start/End pairs, or an End that doesn't match the frame it closes).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct UnbalancedOpStream;

impl std::fmt::Display for UnbalancedOpStream {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "op stream is not well-formed")
}
}

impl std::error::Error for UnbalancedOpStream {}

enum Frame {
Yamd {
metadata: Option<String>,
Expand Down Expand Up @@ -182,7 +195,16 @@ fn count_list_depth(stack: &[Frame]) -> usize {
/// let yamd = yamd::to_yamd(&ops, source);
/// assert_eq!(yamd.body.len(), 2);
/// ```
///
/// # Panics
///
/// Panics if `ops` is not well-formed. Use [`try_to_yamd`] to handle hand-built streams.
pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
try_to_yamd(ops, source).expect("op stream produced by parse() is always well-formed")
}

/// Fallible variant of [`to_yamd`]. Returns [`UnbalancedOpStream`] if `ops` is not well-formed.
pub fn try_to_yamd(ops: &[Op], source: &str) -> Result<Yamd, UnbalancedOpStream> {
let mut stack: Vec<Frame> = vec![Frame::Yamd {
metadata: None,
body: Vec::new(),
Expand Down Expand Up @@ -216,9 +238,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
},
OpKind::Value => {
let text = op.content.to_string(source);
let top = stack
.last_mut()
.expect("stack should not be empty on Value");
let top = stack.last_mut().ok_or(UnbalancedOpStream)?;
match top {
Frame::Heading { body, .. } => {
body.push(HeadingNodes::Text(text));
Expand Down Expand Up @@ -247,10 +267,10 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
}
}
OpKind::End(node) => {
let frame = stack.pop().expect("stack should not be empty on End");
let frame = stack.pop().ok_or(UnbalancedOpStream)?;
match (node, frame) {
(Node::Document, Frame::Document { children }) => {
let top = stack.last_mut().expect("stack underflow");
let top = stack.last_mut().ok_or(UnbalancedOpStream)?;
match top {
Frame::Collapsible { body, .. } => {
*body = children;
Expand All @@ -272,7 +292,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
push_yamd_node(&mut stack, Heading::new(level, body).into());
}
(Node::Paragraph, Frame::Paragraph { mut body }) => {
let top = stack.last_mut().expect("stack underflow");
let top = stack.last_mut().ok_or(UnbalancedOpStream)?;
match top {
Frame::Highlight { paragraphs, .. } => {
trim_trailing_newline_from_text(&mut body);
Expand All @@ -294,7 +314,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
}
(Node::Italic, Frame::Italic { text }) => {
let italic = Italic::new(text);
match stack.last_mut().expect("stack underflow") {
match stack.last_mut().ok_or(UnbalancedOpStream)? {
Frame::Paragraph { body } => body.push(italic.into()),
Frame::Bold { body } => body.push(italic.into()),
// coverage: defensive catchall; Italic's parent is always Paragraph or Bold
Expand All @@ -303,7 +323,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
}
(Node::Strikethrough, Frame::Strikethrough { text }) => {
let st = Strikethrough::new(text);
match stack.last_mut().expect("stack underflow") {
match stack.last_mut().ok_or(UnbalancedOpStream)? {
Frame::Paragraph { body } => body.push(st.into()),
Frame::Bold { body } => body.push(st.into()),
// coverage: defensive catchall; Strikethrough's parent is always Paragraph or Bold
Expand All @@ -317,7 +337,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
push_into_paragraph(&mut stack, Emphasis::new(text).into());
}
(Node::Title, Frame::Title { text }) => {
let top = stack.last_mut().expect("stack underflow");
let top = stack.last_mut().ok_or(UnbalancedOpStream)?;
match top {
Frame::Anchor { text: t, .. } => *t = text,
Frame::Image { alt, .. } => *alt = text,
Expand All @@ -326,7 +346,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
}
}
(Node::Destination, Frame::Destination { text }) => {
let top = stack.last_mut().expect("stack underflow");
let top = stack.last_mut().ok_or(UnbalancedOpStream)?;
match top {
Frame::Anchor { url, .. } => *url = text,
Frame::Image { src, .. } => *src = text,
Expand All @@ -336,7 +356,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
}
(Node::Anchor, Frame::Anchor { text, url }) => {
let anchor = Anchor::new(text, url);
let top = stack.last_mut().expect("stack underflow");
let top = stack.last_mut().ok_or(UnbalancedOpStream)?;
match top {
Frame::Paragraph { body } => body.push(anchor.into()),
Frame::Heading { body, .. } => body.push(anchor.into()),
Expand All @@ -346,7 +366,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
}
(Node::Image, Frame::Image { alt, src }) => {
let image = Image::new(alt, src);
let top = stack.last_mut().expect("stack underflow");
let top = stack.last_mut().ok_or(UnbalancedOpStream)?;
match top {
Frame::Images { images } => images.push(image),
_ => push_yamd_node(&mut stack, image.into()),
Expand All @@ -360,7 +380,7 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
push_yamd_node(&mut stack, Code::new(lang, code).into());
}
(Node::Modifier, Frame::Modifier { text }) => {
let top = stack.last_mut().expect("stack underflow");
let top = stack.last_mut().ok_or(UnbalancedOpStream)?;
match top {
Frame::Code { lang, .. } => *lang = text,
Frame::Highlight { title, .. } => *title = Some(text),
Expand Down Expand Up @@ -396,10 +416,10 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
push_yamd_node(&mut stack, Collapsible::new(title, body).into());
}
(Node::UnorderedList, Frame::UnorderedList { level, items }) => {
finish_list(&mut stack, List::new(ListTypes::Unordered, level, items));
finish_list(&mut stack, List::new(ListTypes::Unordered, level, items))?;
}
(Node::OrderedList, Frame::OrderedList { level, items }) => {
finish_list(&mut stack, List::new(ListTypes::Ordered, level, items));
finish_list(&mut stack, List::new(ListTypes::Ordered, level, items))?;
}
(Node::ListItem, Frame::ListItem { text, nested_list }) => {
let item = ListItem::new(text, nested_list);
Expand All @@ -417,10 +437,10 @@ pub fn to_yamd(ops: &[Op], source: &str) -> Yamd {
}
}

match stack.pop().expect("stack should have Yamd root") {
Frame::Yamd { metadata, body } => Yamd::new(metadata, body),
match stack.pop().ok_or(UnbalancedOpStream)? {
Frame::Yamd { metadata, body } => Ok(Yamd::new(metadata, body)),
// coverage: the root frame is invariantly Yamd; reaching this means stack corruption
_ => panic!("expected Yamd frame at bottom of stack"),
_ => Err(UnbalancedOpStream),
}
}

Expand Down Expand Up @@ -452,19 +472,20 @@ fn push_into_paragraph(stack: &mut [Frame], node: ParagraphNodes) {
}
}

fn finish_list(stack: &mut [Frame], list: List) {
match stack.last_mut().expect("stack underflow") {
fn finish_list(stack: &mut [Frame], list: List) -> Result<(), UnbalancedOpStream> {
match stack.last_mut().ok_or(UnbalancedOpStream)? {
Frame::ListItem { nested_list, .. } => *nested_list = Some(list),
_ => push_yamd_node(stack, list.into()),
}
Ok(())
}

#[cfg(test)]
mod tests {
use pretty_assertions::assert_eq;

use crate::nodes::*;
use crate::op::{parse, to_yamd};
use crate::op::{Node, Op, UnbalancedOpStream, parse, to_yamd, try_to_yamd};

#[test]
fn single_paragraph() {
Expand Down Expand Up @@ -1024,4 +1045,18 @@ end"#;
)
);
}

#[test]
fn unbalanced_op_stream_display() {
assert_eq!(
UnbalancedOpStream.to_string(),
"op stream is not well-formed"
);
}

#[test]
fn unclosed_frame_errors() {
let ops = vec![Op::new_start(Node::Heading, &[] as &[crate::lexer::Token])];
assert_eq!(try_to_yamd(&ops, ""), Err(UnbalancedOpStream));
}
}
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