Disallow empty labels and references (#5776) (#6332)

Co-authored-by: Laurenz <laurmaedje@gmail.com>

crates/typst-eval/src/markup.rs

@@ -205,7 +205,9 @@ impl Eval for ast::Label<'_> {
     type Output = Value;
 
     fn eval(self, _: &mut Vm) -> SourceResult<Self::Output> {
-        Ok(Value::Label(Label::new(PicoStr::intern(self.get()))))
+        Ok(Value::Label(
+            Label::new(PicoStr::intern(self.get())).expect("unexpected empty label"),
+        ))
     }
 }
 
@@ -213,7 +215,8 @@ impl Eval for ast::Ref<'_> {
     type Output = Content;
 
     fn eval(self, vm: &mut Vm) -> SourceResult<Self::Output> {
-        let target = Label::new(PicoStr::intern(self.target()));
+        let target = Label::new(PicoStr::intern(self.target()))
+            .expect("unexpected empty reference");
         let mut elem = RefElem::new(target);
         if let Some(supplement) = self.supplement() {
             elem.push_supplement(Smart::Custom(Some(Supplement::Content(

crates/typst-ide/src/definition.rs

@@ -72,7 +72,8 @@ pub fn definition(
 
         // Try to jump to the referenced content.
         DerefTarget::Ref(node) => {
-            let label = Label::new(PicoStr::intern(node.cast::<ast::Ref>()?.target()));
+            let label = Label::new(PicoStr::intern(node.cast::<ast::Ref>()?.target()))
+                .expect("unexpected empty reference");
             let selector = Selector::Label(label);
             let elem = document?.introspector.query_first(&selector)?;
             return Some(Definition::Span(elem.span()));

crates/typst-library/src/foundations/label.rs

@@ -1,7 +1,8 @@
 use ecow::{eco_format, EcoString};
 use typst_utils::{PicoStr, ResolvedPicoStr};
 
-use crate::foundations::{func, scope, ty, Repr, Str};
+use crate::diag::StrResult;
+use crate::foundations::{bail, func, scope, ty, Repr, Str};
 
 /// A label for an element.
 ///
@@ -27,7 +28,8 @@ use crate::foundations::{func, scope, ty, Repr, Str};
 /// # Syntax
 /// This function also has dedicated syntax: You can create a label by enclosing
 /// its name in angle brackets. This works both in markup and code. A label's
-/// name can contain letters, numbers, `_`, `-`, `:`, and `.`.
+/// name can contain letters, numbers, `_`, `-`, `:`, and `.`. A label cannot
+/// be empty.
 ///
 /// Note that there is a syntactical difference when using the dedicated syntax
 /// for this function. In the code below, the `[<a>]` terminates the heading and
@@ -50,8 +52,11 @@ pub struct Label(PicoStr);
 
 impl Label {
     /// Creates a label from an interned string.
-    pub fn new(name: PicoStr) -> Self {
-        Self(name)
+    ///
+    /// Returns `None` if the given string is empty.
+    pub fn new(name: PicoStr) -> Option<Self> {
+        const EMPTY: PicoStr = PicoStr::constant("");
+        (name != EMPTY).then_some(Self(name))
     }
 
     /// Resolves the label to a string.
@@ -70,10 +75,14 @@ impl Label {
     /// Creates a label from a string.
     #[func(constructor)]
     pub fn construct(
-        /// The name of the label.
+        /// The name of the label. Must not be empty.
         name: Str,
-    ) -> Label {
-        Self(PicoStr::intern(name.as_str()))
+    ) -> StrResult<Label> {
+        if name.is_empty() {
+            bail!("label name must not be empty");
+        }
+
+        Ok(Self(PicoStr::intern(name.as_str())))
     }
 }
 

crates/typst-library/src/model/bibliography.rs

@@ -321,7 +321,11 @@ impl Bibliography {
         for d in data.iter() {
             let library = decode_library(d)?;
             for entry in library {
-                match map.entry(Label::new(PicoStr::intern(entry.key()))) {
+                let label = Label::new(PicoStr::intern(entry.key()))
+                    .ok_or("bibliography contains entry with empty key")
+                    .at(d.source.span)?;
+
+                match map.entry(label) {
                     indexmap::map::Entry::Vacant(vacant) => {
                         vacant.insert(entry);
                     }

crates/typst-syntax/src/ast.rs

@@ -724,6 +724,8 @@ node! {
 
 impl<'a> Ref<'a> {
     /// Get the target.
+    ///
+    /// Will not be empty.
     pub fn target(self) -> &'a str {
         self.0
             .children()

crates/typst-syntax/src/lexer.rs

@@ -185,7 +185,7 @@ impl Lexer<'_> {
             'h' if self.s.eat_if("ttp://") => self.link(),
             'h' if self.s.eat_if("ttps://") => self.link(),
             '<' if self.s.at(is_id_continue) => self.label(),
-            '@' => self.ref_marker(),
+            '@' if self.s.at(is_id_continue) => self.ref_marker(),
 
             '.' if self.s.eat_if("..") => SyntaxKind::Shorthand,
             '-' if self.s.eat_if("--") => SyntaxKind::Shorthand,

tests/suite/foundations/label.typ

@@ -92,3 +92,7 @@ _Visible_
 --- label-non-existent-error ---
 // Error: 5-10 sequence does not have field "label"
 #[].label
+
+--- label-empty ---
+// Error: 23-32 label name must not be empty
+= Something to label #label("")

tests/suite/model/bibliography.typ

@@ -75,6 +75,14 @@ Now we have multiple bibliographies containing @glacier-melt @keshav2007read
 // Error: 2-62 CSL style "Alphanumeric" is not suitable for bibliographies
 #bibliography("/assets/bib/works.bib", style: "alphanumeric")
 
+--- bibliography-empty-key ---
+#let src = ```yaml
+"":
+  type: Book
+```
+// Error: 15-30 bibliography contains entry with empty key
+#bibliography(bytes(src.text))
+
 --- issue-4618-bibliography-set-heading-level ---
 // Test that the bibliography block's heading is set to 2 by the show rule,
 // and therefore should be rendered like a level-2 heading. Notably, this

tests/suite/model/ref.typ

@@ -86,3 +86,14 @@ Text seen on #ref(<text>, form: "page", supplement: "Page").
 // Test reference with non-whitespace before it.
 #figure[] <1>
 #test([(#ref(<1>))], [(@1)])
+
+--- ref-to-empty-label-not-possible ---
+// @ without any following label should just produce the symbol in the output
+// and not produce a reference to a label with an empty name.
+@
+
+--- ref-function-empty-label ---
+// using ref() should also not be possible
+// Error: 6-7 unexpected less-than operator
+// Error: 7-8 unexpected greater-than operator
+#ref(<>)