//! Lots of helpers for dealing with SWC, particularly from unist.
use micromark::{
mdast::Stop,
unist::{Point, Position},
Location,
};
use swc_common::{BytePos, Span, SyntaxContext, DUMMY_SP};
use swc_ecma_ast::{BinExpr, BinaryOp, Expr, Ident, MemberExpr, MemberProp};
use swc_ecma_visit::{noop_visit_mut_type, VisitMut};
/// Turn a unist position, into an SWC span, of two byte positions.
///
/// > 👉 **Note**: SWC byte positions are offset by one: they are `0` when they
/// > are missing or incremented by `1` when valid.
pub fn position_to_span(position: Option<&Position>) -> Span {
position.map_or(DUMMY_SP, |d| Span {
lo: point_to_bytepos(&d.start),
hi: point_to_bytepos(&d.end),
ctxt: SyntaxContext::empty(),
})
}
/// Turn an SWC span, of two byte positions, into a unist position.
///
/// This assumes the span comes from a fixed tree, or is a dummy.
///
/// > 👉 **Note**: SWC byte positions are offset by one: they are `0` when they
/// > are missing or incremented by `1` when valid.
pub fn span_to_position(span: &Span, location: Option<&Location>) -> Option<Position> {
let lo = span.lo.0 as usize;
let hi = span.hi.0 as usize;
if lo > 0 && hi > 0 {
if let Some(location) = location {
if let Some(start) = location.to_point(lo - 1) {
if let Some(end) = location.to_point(hi - 1) {
return Some(Position { start, end });
}
}
}
}
None
}
/// Turn a unist point into an SWC byte position.
///
/// > 👉 **Note**: SWC byte positions are offset by one: they are `0` when they
/// > are missing or incremented by `1` when valid.
pub fn point_to_bytepos(point: &Point) -> BytePos {
BytePos(point.offset as u32 + 1)
}
/// Turn an SWC byte position into a unist point.
///
/// This assumes the byte position comes from a fixed tree, or is a dummy.
///
/// > 👉 **Note**: SWC byte positions are offset by one: they are `0` when they
/// > are missing or incremented by `1` when valid.
pub fn bytepos_to_point(bytepos: &BytePos, location: Option<&Location>) -> Option<Point> {
let pos = bytepos.0 as usize;
if pos > 0 {
if let Some(location) = location {
return location.to_point(pos - 1);
}
}
None
}
/// Prefix an error message with an optional point.
pub fn prefix_error_with_point(reason: String, point: Option<&Point>) -> String {
if let Some(point) = point {
format!("{}: {}", point_to_string(point), reason)
} else {
reason
}
}
/// Serialize a unist position for humans.
pub fn position_to_string(position: &Position) -> String {
format!(
"{}-{}",
point_to_string(&position.start),
point_to_string(&position.end)
)
}
/// Serialize a unist point for humans.
pub fn point_to_string(point: &Point) -> String {
format!("{}:{}", point.line, point.column)
}
/// Visitor to fix SWC byte positions.
///
/// This assumes the byte position comes from an **unfixed** tree.
///
/// > 👉 **Note**: SWC byte positions are offset by one: they are `0` when they
/// > are missing or incremented by `1` when valid.
#[derive(Debug, Default, Clone)]
pub struct RewriteContext<'a> {
pub prefix_len: usize,
pub stops: &'a [Stop],
pub location: Option<&'a Location>,
}
impl<'a> VisitMut for RewriteContext<'a> {
noop_visit_mut_type!();
// Rewrite spans.
fn visit_mut_span(&mut self, span: &mut Span) {
let mut result = DUMMY_SP;
let lo_rel = span.lo.0 as usize;
let hi_rel = span.hi.0 as usize;
if lo_rel > self.prefix_len && hi_rel > self.prefix_len {
if let Some(lo_abs) =
Location::relative_to_absolute(self.stops, lo_rel - 1 - self.prefix_len)
{
if let Some(hi_abs) =
Location::relative_to_absolute(self.stops, hi_rel - 1 - self.prefix_len)
{
result = Span {
lo: BytePos(lo_abs as u32 + 1),
hi: BytePos(hi_abs as u32 + 1),
ctxt: SyntaxContext::empty(),
};
}
}
}
*span = result;
}
}
/// Generate an ident.
///
/// ```js
/// a
/// ```
pub fn create_ident(sym: &str) -> Ident {
Ident {
sym: sym.into(),
optional: false,
span: DUMMY_SP,
}
}
/// Generate an ident expression.
///
/// ```js
/// a
/// ```
pub fn create_ident_expression(sym: &str) -> Expr {
Expr::Ident(create_ident(sym))
}
/// Generate a binary expression.
///
/// ```js
/// a + b + c
/// a || b
/// ```
pub fn create_binary_expression(mut exprs: Vec<Expr>, op: BinaryOp) -> Expr {
exprs.reverse();
let mut left = None;
while let Some(right_expr) = exprs.pop() {
left = Some(if let Some(left_expr) = left {
Expr::Bin(BinExpr {
left: Box::new(left_expr),
right: Box::new(right_expr),
op,
span: swc_common::DUMMY_SP,
})
} else {
right_expr
});
}
left.expect("expected one or more expressions")
}
/// Generate a member expression.
///
/// ```js
/// a.b
/// a
/// ```
pub fn create_member_expression(name: &str) -> Expr {
let bytes = name.as_bytes();
let mut index = 0;
let mut start = 0;
let mut parts = vec![];
while index < bytes.len() {
if bytes[index] == b'.' {
parts.push(&name[start..index]);
start = index + 1;
}
index += 1;
}
if parts.len() > 1 {
let mut member = MemberExpr {
obj: Box::new(create_ident_expression(parts[0])),
prop: MemberProp::Ident(create_ident(parts[1])),
span: swc_common::DUMMY_SP,
};
let mut index = 2;
while index < parts.len() {
member = MemberExpr {
obj: Box::new(Expr::Member(member)),
prop: MemberProp::Ident(create_ident(parts[1])),
span: swc_common::DUMMY_SP,
};
index += 1;
}
Expr::Member(member)
} else {
create_ident_expression(name)
}
}
