initial attached comment detection

4 files changed, 104 insertions, 5 deletions

diff --git a/crates/typst-syntax/src/ast.rs b/crates/typst-syntax/src/ast.rs
index 1cd9cd42..85c4ca47 100644
--- a/crates/typst-syntax/src/ast.rs
+++ b/crates/typst-syntax/src/ast.rs
@@ -80,6 +80,19 @@ impl<'a> Markup<'a> {
     }
 }
 
+node! {
+    /// A comment: `// something`.
+    LineComment
+}
+
+impl<'a> LineComment<'a> {
+    /// The comment's contents, excluding the initial '//' marker.
+    pub fn content(self) -> &'a str {
+        let text = self.0.text();
+        text.strip_prefix("//").unwrap_or(text)
+    }
+}
+
 /// An expression in markup, math or code.
 #[derive(Debug, Copy, Clone, Hash)]
 pub enum Expr<'a> {
diff --git a/crates/typst-syntax/src/node.rs b/crates/typst-syntax/src/node.rs
index bc378e66..08cb346c 100644
--- a/crates/typst-syntax/src/node.rs
+++ b/crates/typst-syntax/src/node.rs
@@ -773,13 +773,17 @@ impl<'a> LinkedNode<'a> {
         self.parent.as_deref()
     }
 
-    /// Get the first previous non-trivia sibling node.
-    pub fn prev_sibling(&self) -> Option<Self> {
+    fn prev_sibling_inner(&self) -> Option<Self> {
         let parent = self.parent()?;
         let index = self.index.checked_sub(1)?;
         let node = parent.node.children().nth(index)?;
         let offset = self.offset - node.len();
-        let prev = Self { node, parent: self.parent.clone(), index, offset };
+        Some(Self { node, parent: self.parent.clone(), index, offset })
+    }
+
+    /// Get the first previous non-trivia sibling node.
+    pub fn prev_sibling(&self) -> Option<Self> {
+        let prev = self.prev_sibling_inner()?;
         if prev.kind().is_trivia() {
             prev.prev_sibling()
         } else {
@@ -787,6 +791,38 @@ impl<'a> LinkedNode<'a> {
         }
     }
 
+    /// Get the first sibling comment node at the line above this node.
+    /// This is done by moving backwards until the rightmost newline, and then
+    /// checking for comments before the previous newline.
+    pub fn prev_attached_comment(&self) -> Option<Self> {
+        if self.kind() == SyntaxKind::Parbreak
+            || self.kind() == SyntaxKind::Space && self.text().contains('\n')
+        {
+            // We hit a newline, so let's check for comments before the next
+            // newline.
+            let mut sibling_before_newline = self.prev_sibling_inner()?;
+            while sibling_before_newline.kind().is_trivia()
+                && !matches!(
+                    sibling_before_newline.kind(),
+                    SyntaxKind::Space | SyntaxKind::LineComment | SyntaxKind::Parbreak
+                )
+            {
+                sibling_before_newline = sibling_before_newline.prev_sibling_inner()?;
+            }
+            if sibling_before_newline.kind() == SyntaxKind::LineComment {
+                // Found a comment on the previous line
+                Some(sibling_before_newline)
+            } else {
+                // No comments on the previous line
+                None
+            }
+        } else {
+            self.prev_sibling_inner()
+                .as_ref()
+                .and_then(Self::prev_attached_comment)
+        }
+    }
+
     /// Get the next non-trivia sibling node.
     pub fn next_sibling(&self) -> Option<Self> {
         let parent = self.parent()?;
diff --git a/crates/typst/src/engine.rs b/crates/typst/src/engine.rs
index 2e2525b2..fed0e8de 100644
--- a/crates/typst/src/engine.rs
+++ b/crates/typst/src/engine.rs
@@ -7,10 +7,10 @@ use comemo::{Track, Tracked, TrackedMut, Validate};
 use ecow::EcoVec;
 use rayon::iter::{IndexedParallelIterator, IntoParallelIterator, ParallelIterator};
 
-use crate::diag::{SourceDiagnostic, SourceResult};
+use crate::diag::{Severity, SourceDiagnostic, SourceResult};
 use crate::foundations::{Styles, Value};
 use crate::introspection::Introspector;
-use crate::syntax::{FileId, Span};
+use crate::syntax::{ast, FileId, Span};
 use crate::World;
 
 /// Holds all data needed during compilation.
@@ -160,6 +160,19 @@ impl Sink {
     pub fn values(self) -> EcoVec<(Value, Option<Styles>)> {
         self.values
     }
+
+    /// Apply warning suppression.
+    pub fn suppress_warnings(&mut self, world: &dyn World) {
+        self.warnings.retain(|diag| {
+            // Only retain warnings which weren't locally suppressed where they
+            // were emitted or at any of their tracepoints.
+            diag.severity != Severity::Warning
+                || (!check_warning_suppressed(diag.span, world, &diag.message)
+                    && !diag.trace.iter().any(|tracepoint| {
+                        check_warning_suppressed(tracepoint.span, world, &diag.message)
+                    }))
+        });
+    }
 }
 
 #[comemo::track]
@@ -202,6 +215,41 @@ impl Sink {
     }
 }
 
+/// Checks if a given warning is suppressed given one span it has a tracepoint
+/// in. If one of the ancestors of the node where the warning occurred has a
+/// warning suppression decorator sibling right before it suppressing this
+/// particular warning, the warning is considered suppressed.
+fn check_warning_suppressed(
+    span: Span,
+    world: &dyn World,
+    _message: &ecow::EcoString,
+) -> bool {
+    let Some(file) = span.id() else {
+        // Don't suppress detached warnings.
+        return false;
+    };
+
+    // The source must exist if a warning occurred in the file,
+    // or has a tracepoint in the file.
+    let source = world.source(file).unwrap();
+    // The span must point to this source file, so we unwrap.
+    let mut node = &source.find(span).unwrap();
+
+    // Walk the parent nodes to check for a warning suppression.
+    while let Some(parent) = node.parent() {
+        if let Some(sibling) = parent.prev_attached_comment() {
+            if let Some(comment) = sibling.cast::<ast::LineComment>() {
+                let _text = comment.content();
+                // Find comment, return true if this warning was suppressed
+                todo!();
+            }
+        }
+        node = parent;
+    }
+
+    false
+}
+
 /// The route the engine took during compilation. This is used to detect
 /// cyclic imports and excessive nesting.
 pub struct Route<'a> {
diff --git a/crates/typst/src/lib.rs b/crates/typst/src/lib.rs
index e934ea37..e38abacc 100644
--- a/crates/typst/src/lib.rs
+++ b/crates/typst/src/lib.rs
@@ -86,6 +86,8 @@ pub fn compile(world: &dyn World) -> Warned<SourceResult<Document>> {
     let mut sink = Sink::new();
     let output = compile_inner(world.track(), Traced::default().track(), &mut sink)
         .map_err(deduplicate);
+
+    sink.suppress_warnings(world);
     Warned { output, warnings: sink.warnings() }
 }