Warn if layout doesn't stabilize (#1684)

crates/typst/src/model/mod.rs

@@ -28,7 +28,7 @@ use std::mem::ManuallyDrop;
 
 use comemo::{Track, Tracked, TrackedMut, Validate};
 
-use crate::diag::{SourceDiagnostic, SourceResult};
+use crate::diag::{warning, SourceDiagnostic, SourceResult};
 use crate::doc::Document;
 use crate::eval::Tracer;
 use crate::World;
@@ -82,7 +82,20 @@ pub fn typeset(
         introspector = ManuallyDrop::new(Introspector::new(&document.pages));
         iter += 1;
 
-        if iter >= 5 || introspector.validate(&constraint) {
+        if introspector.validate(&constraint) {
+            break;
+        }
+
+        if iter >= 5 {
+            tracer.warn(
+                warning!(
+                    world.main().root().span(),
+                    "layout did not converge within 5 attempts",
+                )
+                .with_hint(
+                    "check if any states or queries are updating themselves".into(),
+                ),
+            );
             break;
         }
     }

tests/src/tests.rs

@@ -670,8 +670,14 @@ fn parse_part_metadata(source: &Source) -> TestPartMetadata {
         compare_ref = get_flag_metadata(line, "Ref").or(compare_ref);
         validate_hints = get_flag_metadata(line, "Hints").or(validate_hints);
 
-        fn num(s: &mut Scanner) -> usize {
-            s.eat_while(char::is_numeric).parse().unwrap()
+        fn num(s: &mut Scanner) -> isize {
+            let mut first = true;
+            let n = &s.eat_while(|c: char| {
+                let valid = first && c == '-' || c.is_numeric();
+                first = false;
+                valid
+            });
+            n.parse().unwrap_or_else(|e| panic!("{n} is not a number ({e})"))
         }
 
         let comments_until_code =
@@ -681,8 +687,15 @@ fn parse_part_metadata(source: &Source) -> TestPartMetadata {
             let first = num(s) - 1;
             let (delta, column) =
                 if s.eat_if(':') { (first, num(s) - 1) } else { (0, first) };
-            let line = (i + comments_until_code) + delta;
-            source.line_column_to_byte(line, column).unwrap()
+            let line = (i + comments_until_code)
+                .checked_add_signed(delta)
+                .expect("line number overflowed limits");
+            source
+                .line_column_to_byte(
+                    line,
+                    usize::try_from(column).expect("column number overflowed limits"),
+                )
+                .unwrap()
         };
 
         let error_factory: fn(Range<usize>, String) -> UserOutput = UserOutput::error;

tests/typ/meta/state.typ

@@ -46,3 +46,13 @@ Was: #locate(location => {
 #trait[Adventure]
 #trait[Fear]
 #trait[Anger]
+
+---
+// Make sure that a warning is produced if the layout fails to converge.
+// Warning: -3:1-6:1 layout did not converge within 5 attempts
+// Hint: -3:1-6:1 check if any states or queries are updating themselves
+#let s = state("x", 1)
+#locate(loc => {
+  s.update(s.final(loc) + 1)
+})
+#s.display()