Add a helper for getting the location of a span in some textual source

src/front/wgsl/mod.rs

@@ -16,6 +16,7 @@ use crate::{
  proc::{
  ensure_block_returns, Alignment, Layouter, ResolveContext, ResolveError, TypeResolution,
  },
+ span::SourceLocation,
  span::Span as NagaSpan,
  Bytes, ConstantInner, FastHashMap, ScalarValue,
 };
@@ -29,7 +30,7 @@ use self::{
 };
 use codespan_reporting::{
  diagnostic::{Diagnostic, Label},
- files::{Files, SimpleFile},
+ files::SimpleFile,
  term::{
  self,
  termcolor::{ColorChoice, ColorSpec, StandardStream, WriteColor},
@@ -1365,19 +1366,11 @@ impl ParseError {
  writer.into_string()
  }
 
- /// Returns the 1-based line number and column of the first label in the
- /// error message.
- pub fn location(&self, source: &str) -> (usize, usize) {
- let files = SimpleFile::new("wgsl", source);
- match self.labels.get(0) {
- Some(label) => {
- let location = files
- .location((), label.0.start)
- .expect("invalid span location");
- (location.line_number, location.column_number)
- }
- None => (1, 1),
- }
+ /// Returns a [`SourceLocation`] for the first label in the error message.
+ pub fn location(&self, source: &str) -> Option<SourceLocation> {
+ self.labels
+ .get(0)
+ .map(|label| NagaSpan::new(label.0.start as u32, label.0.end as u32).location(source))
  }
 }
 

src/lib.rs

@@ -211,7 +211,7 @@ pub mod valid;
 
 pub use crate::arena::{Arena, Handle, Range, UniqueArena};
 
-pub use crate::span::{Span, SpanContext, WithSpan};
+pub use crate::span::{SourceLocation, Span, SpanContext, WithSpan};
 #[cfg(feature = "arbitrary")]
 use arbitrary::Arbitrary;
 #[cfg(feature = "deserialize")]

src/span.rs

@@ -59,6 +59,21 @@ impl Span {
  pub fn is_defined(&self) -> bool {
  *self != Self::default()
  }
+
+ /// Return a [`SourceLocation`] for this span in the provided source.
+ pub fn location(&self, source: &str) -> SourceLocation {
+ let prefix = &source[..self.start as usize];
+ let line_number = prefix.matches('\n').count() as u32 + 1;
+ let line_start = prefix.rfind('\n').map(|pos| pos + 1).unwrap_or(0);
+ let line_position = source[line_start..self.start as usize].chars().count() as u32 + 1;
+
+ SourceLocation {
+ line_number,
+ line_position,
+ offset: self.start,
+ length: self.end - self.start,
+ }
+ }
 }
 
 impl From<Range<usize>> for Span {
@@ -70,6 +85,25 @@ impl From<Range<usize>> for Span {
  }
 }
 
+/// A human-readable representation for a span, tailored for text source.
+///
+/// Corresponds to the positional members of [`GPUCompilationMessage`][gcm] from
+/// the WebGPU specification, except that `offset` and `length` are in bytes
+/// (UTF-8 code units), instead of UTF-16 code units.
+///
+/// [gcm]: https://www.w3.org/TR/webgpu/#gpucompilationmessage
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct SourceLocation {
+ /// 1-based line number.
+ pub line_number: u32,
+ /// 1-based column of the start of this span
+ pub line_position: u32,
+ /// 0-based Offset in code units (in bytes) of the start of the span.
+ pub offset: u32,
+ /// Length in code units (in bytes) of the span.
+ pub length: u32,
+}
+
 /// A source code span together with "context", a user-readable description of what part of the error it refers to.
 pub type SpanContext = (Span, String);
 
@@ -186,6 +220,22 @@ impl<E> WithSpan<E> {
  res.spans.extend(self.spans);
  res
  }
+
+ #[cfg(feature = "span")]
+ /// Return a [`SourceLocation`] for our first span, if we have one.
+ pub fn location(&self, source: &str) -> Option<SourceLocation> {
+ if self.spans.is_empty() {
+ return None;
+ }
+
+ Some(self.spans[0].0.location(source))
+ }
+
+ #[cfg(not(feature = "span"))]
+ /// Return a [`SourceLocation`] for our first span, if we have one.
+ pub fn location(&self, _source: &str) -> Option<SourceLocation> {
+ None
+ }
 }
 
 /// Convenience trait for [`Error`] to be able to apply spans to anything.
@@ -273,3 +323,107 @@ impl<T, E, E2> MapErrWithSpan<E, E2> for Result<T, WithSpan<E>> {
  self.map_err(|e| e.and_then(func).into_other::<E2>())
  }
 }
+
+#[test]
+fn span_location() {
+ let source = "12\n45\n\n89\n";
+ assert_eq!(
+ Span { start: 0, end: 1 }.location(source),
+ SourceLocation {
+ line_number: 1,
+ line_position: 1,
+ offset: 0,
+ length: 1
+ }
+ );
+ assert_eq!(
+ Span { start: 1, end: 2 }.location(source),
+ SourceLocation {
+ line_number: 1,
+ line_position: 2,
+ offset: 1,
+ length: 1
+ }
+ );
+ assert_eq!(
+ Span { start: 2, end: 3 }.location(source),
+ SourceLocation {
+ line_number: 1,
+ line_position: 3,
+ offset: 2,
+ length: 1
+ }
+ );
+ assert_eq!(
+ Span { start: 3, end: 5 }.location(source),
+ SourceLocation {
+ line_number: 2,
+ line_position: 1,
+ offset: 3,
+ length: 2
+ }
+ );
+ assert_eq!(
+ Span { start: 4, end: 6 }.location(source),
+ SourceLocation {
+ line_number: 2,
+ line_position: 2,
+ offset: 4,
+ length: 2
+ }
+ );
+ assert_eq!(
+ Span { start: 5, end: 6 }.location(source),
+ SourceLocation {
+ line_number: 2,
+ line_position: 3,
+ offset: 5,
+ length: 1
+ }
+ );
+ assert_eq!(
+ Span { start: 6, end: 7 }.location(source),
+ SourceLocation {
+ line_number: 3,
+ line_position: 1,
+ offset: 6,
+ length: 1
+ }
+ );
+ assert_eq!(
+ Span { start: 7, end: 8 }.location(source),
+ SourceLocation {
+ line_number: 4,
+ line_position: 1,
+ offset: 7,
+ length: 1
+ }
+ );
+ assert_eq!(
+ Span { start: 8, end: 9 }.location(source),
+ SourceLocation {
+ line_number: 4,
+ line_position: 2,
+ offset: 8,
+ length: 1
+ }
+ );
+ assert_eq!(
+ Span { start: 9, end: 10 }.location(source),
+ SourceLocation {
+ line_number: 4,
+ line_position: 3,
+ offset: 9,
+ length: 1
+ }
+ );
+ assert_eq!(
+ Span { start: 10, end: 11 }.location(source),
+ SourceLocation {
+ line_number: 5,
+ line_position: 1,
+ offset: 10,
+ length: 1
+ }
+ );
+}