Dynamic labels

library/src/base/string.rs

@@ -14,11 +14,17 @@ pub fn str(_: &Vm, args: &mut Args) -> SourceResult<Value> {
     Ok(Value::Str(match v {
         Value::Int(v) => format_str!("{}", v),
         Value::Float(v) => format_str!("{}", v),
+        Value::Label(label) => label.0.into(),
         Value::Str(v) => v,
         v => bail!(span, "cannot convert {} to string", v.type_name()),
     }))
 }
 
+/// Create a label from a string.
+pub fn label(_: &Vm, args: &mut Args) -> SourceResult<Value> {
+    Ok(Value::Label(Label(args.expect("string")?)))
+}
+
 /// Create blind text.
 pub fn lorem(_: &Vm, args: &mut Args) -> SourceResult<Value> {
     let words: usize = args.expect("number of words")?;

library/src/lib.rs

@@ -105,6 +105,7 @@ fn scope() -> Scope {
     std.def_fn("cmyk", base::cmyk);
     std.def_fn("repr", base::repr);
     std.def_fn("str", base::str);
+    std.def_fn("label", base::label);
     std.def_fn("regex", base::regex);
     std.def_fn("letter", base::letter);
     std.def_fn("roman", base::roman);

library/src/prelude.rs

@@ -16,7 +16,7 @@ pub use typst::geom::*;
 #[doc(no_inline)]
 pub use typst::model::{
     array, capability, castable, dict, dynamic, format_str, node, Args, Array, Cast,
-    Content, Dict, Finalize, Fold, Func, Node, NodeId, Resolve, Show, Smart, Str,
+    Content, Dict, Finalize, Fold, Func, Label, Node, NodeId, Resolve, Show, Smart, Str,
     StyleChain, StyleMap, StyleVec, Unlabellable, Value, Vm,
 };
 #[doc(no_inline)]

src/model/cast.rs

@@ -183,8 +183,9 @@ dynamic! {
 
 dynamic! {
     Selector: "selector",
-    Value::Func(func) => Self::Node(func.node()?, None),
     Value::Str(text) => Self::text(&text),
+    Value::Label(label) => Self::Label(label),
+    Value::Func(func) => Self::Node(func.node()?, None),
     @regex: Regex => Self::Regex(regex.clone()),
 }
 

src/model/content.rs

@@ -21,7 +21,7 @@ pub struct Content {
     obj: Arc<dyn Bounds>,
     guards: Vec<Guard>,
     span: Option<Span>,
-    label: Option<EcoString>,
+    label: Option<Label>,
 }
 
 impl Content {
@@ -54,7 +54,7 @@ impl Content {
     }
 
     /// Attach a label to the content.
-    pub fn labelled(mut self, label: EcoString) -> Self {
+    pub fn labelled(mut self, label: Label) -> Self {
         self.label = Some(label);
         self
     }
@@ -131,7 +131,7 @@ impl Content {
     }
 
     /// The content's label.
-    pub fn label(&self) -> Option<&EcoString> {
+    pub fn label(&self) -> Option<&Label> {
         self.label.as_ref()
     }
 
@@ -139,7 +139,7 @@ impl Content {
     pub fn field(&self, name: &str) -> Option<Value> {
         if name == "label" {
             return Some(match &self.label {
-                Some(label) => Value::Str(label.clone().into()),
+                Some(label) => Value::Label(label.clone()),
                 None => Value::None,
             });
         }
@@ -335,6 +335,16 @@ impl Debug for SequenceNode {
     }
 }
 
+/// A label for a node.
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct Label(pub EcoString);
+
+impl Debug for Label {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "<{}>", self.0)
+    }
+}
+
 /// A constructable, stylable content node.
 pub trait Node: 'static + Capable {
     /// Pack a node into type-erased content.

src/model/eval.rs

@@ -8,7 +8,7 @@ use comemo::{Track, Tracked};
 use unicode_segmentation::UnicodeSegmentation;
 
 use super::{
-    methods, ops, Arg, Args, Array, CapturesVisitor, Closure, Content, Dict, Func,
+    methods, ops, Arg, Args, Array, CapturesVisitor, Closure, Content, Dict, Func, Label,
     LangItems, Recipe, Scope, Scopes, Selector, StyleMap, Transform, Value,
 };
 use crate::diag::{
@@ -231,11 +231,16 @@ fn eval_markup(
                 let tail = eval_markup(vm, nodes)?;
                 seq.push(tail.styled_with_recipe(vm.world, recipe)?)
             }
-            ast::MarkupNode::Label(label) => {
-                if let Some(node) = seq.iter_mut().rev().find(|node| node.labellable()) {
-                    *node = mem::take(node).labelled(label.get().clone());
+            ast::MarkupNode::Expr(expr) => match expr.eval(vm)? {
+                Value::Label(label) => {
+                    if let Some(node) =
+                        seq.iter_mut().rev().find(|node| node.labellable())
+                    {
+                        *node = mem::take(node).labelled(label);
+                    }
                 }
-            }
+                value => seq.push(value.display().spanned(expr.span())),
+            },
             _ => seq.push(node.eval(vm)?),
         }
 
@@ -274,9 +279,8 @@ impl Eval for ast::MarkupNode {
             Self::List(v) => v.eval(vm)?,
             Self::Enum(v) => v.eval(vm)?,
             Self::Desc(v) => v.eval(vm)?,
-            Self::Label(_) => unimplemented!("handled above"),
             Self::Ref(v) => v.eval(vm)?,
-            Self::Expr(v) => v.eval(vm)?.display(),
+            Self::Expr(_) => unimplemented!("handled above"),
         }
         .spanned(self.span()))
     }
@@ -527,6 +531,7 @@ impl Eval for ast::Lit {
                 Unit::Percent => Ratio::new(v / 100.0).into(),
             },
             ast::LitKind::Str(v) => Value::Str(v.into()),
+            ast::LitKind::Label(v) => Value::Label(Label(v)),
         })
     }
 }

src/model/ops.rs

@@ -307,6 +307,7 @@ pub fn equal(lhs: &Value, rhs: &Value) -> bool {
         (Fraction(a), Fraction(b)) => a == b,
         (Color(a), Color(b)) => a == b,
         (Str(a), Str(b)) => a == b,
+        (Label(a), Label(b)) => a == b,
         (Content(a), Content(b)) => a == b,
         (Array(a), Array(b)) => a == b,
         (Dict(a), Dict(b)) => a == b,

src/model/realize.rs

@@ -78,6 +78,14 @@ fn try_apply(
             recipe.apply(world, target.clone().guarded(guard)).map(Some)
         }
 
+        Some(Selector::Label(label)) => {
+            if target.label() != Some(label) {
+                return Ok(None);
+            }
+
+            recipe.apply(world, target.clone().guarded(guard)).map(Some)
+        }
+
         Some(Selector::Regex(regex)) => {
             let Some(text) = item!(text_str)(&target) else {
                 return Ok(None);

src/model/styles.rs

@@ -7,7 +7,7 @@ use std::sync::Arc;
 
 use comemo::{Prehashed, Tracked};
 
-use super::{Args, Content, Dict, Func, NodeId, Regex, Smart, Value};
+use super::{Args, Content, Dict, Func, Label, NodeId, Regex, Smart, Value};
 use crate::diag::{SourceResult, Trace, Tracepoint};
 use crate::geom::{
     Abs, Align, Axes, Corners, Em, GenAlign, Length, Numeric, PartialStroke, Rel, Sides,
@@ -354,7 +354,9 @@ pub enum Selector {
     /// If there is a dictionary, only nodes with the fields from the
     /// dictionary match.
     Node(NodeId, Option<Dict>),
-    /// Matches text through a regular expression.
+    /// Matches nodes with a specific label.
+    Label(Label),
+    /// Matches text nodes through a regular expression.
     Regex(Regex),
 }
 
@@ -368,13 +370,17 @@ impl Selector {
     pub fn matches(&self, target: &Content) -> bool {
         match self {
             Self::Node(id, dict) => {
-                *id == target.id()
+                target.id() == *id
                     && dict
                         .iter()
                         .flat_map(|dict| dict.iter())
                         .all(|(name, value)| target.field(name).as_ref() == Some(value))
             }
-            Self::Regex(_) => target.id() == item!(text_id),
+            Self::Label(label) => target.label() == Some(label),
+            Self::Regex(regex) => {
+                target.id() == item!(text_id)
+                    && item!(text_str)(target).map_or(false, |text| regex.is_match(text))
+            }
         }
     }
 }

src/model/value.rs

@@ -6,7 +6,7 @@ use std::sync::Arc;
 
 use siphasher::sip128::{Hasher128, SipHasher};
 
-use super::{format_str, ops, Args, Array, Cast, Content, Dict, Func, Str};
+use super::{format_str, ops, Args, Array, Cast, Content, Dict, Func, Label, Str};
 use crate::diag::StrResult;
 use crate::geom::{Abs, Angle, Color, Em, Fr, Length, Ratio, Rel, RgbaColor};
 use crate::util::{format_eco, EcoString};
@@ -38,6 +38,8 @@ pub enum Value {
     Color(Color),
     /// A string: `"string"`.
     Str(Str),
+    /// A label: `<intro>`.
+    Label(Label),
     /// A content value: `[*Hi* there]`.
     Content(Content),
     /// An array of values: `(1, "hi", 12cm)`.
@@ -76,6 +78,7 @@ impl Value {
             Self::Fraction(_) => Fr::TYPE_NAME,
             Self::Color(_) => Color::TYPE_NAME,
             Self::Str(_) => Str::TYPE_NAME,
+            Self::Label(_) => Label::TYPE_NAME,
             Self::Content(_) => Content::TYPE_NAME,
             Self::Array(_) => Array::TYPE_NAME,
             Self::Dict(_) => Dict::TYPE_NAME,
@@ -130,6 +133,7 @@ impl Debug for Value {
             Self::Fraction(v) => Debug::fmt(v, f),
             Self::Color(v) => Debug::fmt(v, f),
             Self::Str(v) => Debug::fmt(v, f),
+            Self::Label(v) => Debug::fmt(v, f),
             Self::Content(_) => f.pad("[...]"),
             Self::Array(v) => Debug::fmt(v, f),
             Self::Dict(v) => Debug::fmt(v, f),
@@ -168,6 +172,7 @@ impl Hash for Value {
             Self::Fraction(v) => v.hash(state),
             Self::Color(v) => v.hash(state),
             Self::Str(v) => v.hash(state),
+            Self::Label(v) => v.hash(state),
             Self::Content(v) => v.hash(state),
             Self::Array(v) => v.hash(state),
             Self::Dict(v) => v.hash(state),
@@ -373,6 +378,7 @@ primitive! { Rel<Length>:  "relative length",
 primitive! { Fr: "fraction", Fraction }
 primitive! { Color: "color", Color }
 primitive! { Str: "string", Str }
+primitive! { Label: "label", Label }
 primitive! { Content: "content",
     Content,
     None => Content::empty(),

src/syntax/ast.rs

@@ -95,8 +95,6 @@ pub enum MarkupNode {
     Raw(Raw),
     /// A hyperlink: `https://typst.org`.
     Link(Link),
-    /// A label: `<label>`.
-    Label(Label),
     /// A reference: `@target`.
     Ref(Ref),
     /// A section heading: `= Introduction`.
@@ -126,7 +124,6 @@ impl AstNode for MarkupNode {
             SyntaxKind::Emph => node.cast().map(Self::Emph),
             SyntaxKind::Raw(_) => node.cast().map(Self::Raw),
             SyntaxKind::Link(_) => node.cast().map(Self::Link),
-            SyntaxKind::Label(_) => node.cast().map(Self::Label),
             SyntaxKind::Ref(_) => node.cast().map(Self::Ref),
             SyntaxKind::Heading => node.cast().map(Self::Heading),
             SyntaxKind::ListItem => node.cast().map(Self::List),
@@ -149,7 +146,6 @@ impl AstNode for MarkupNode {
             Self::Emph(v) => v.as_untyped(),
             Self::Raw(v) => v.as_untyped(),
             Self::Link(v) => v.as_untyped(),
-            Self::Label(v) => v.as_untyped(),
             Self::Ref(v) => v.as_untyped(),
             Self::Heading(v) => v.as_untyped(),
             Self::List(v) => v.as_untyped(),
@@ -313,21 +309,6 @@ impl Link {
     }
 }
 
-node! {
-    /// A label: `<label>`.
-    Label
-}
-
-impl Label {
-    /// Get the label.
-    pub fn get(&self) -> &EcoString {
-        match self.0.kind() {
-            SyntaxKind::Label(v) => v,
-            _ => panic!("label is of wrong kind"),
-        }
-    }
-}
-
 node! {
     /// A reference: `@target`.
     Ref
@@ -704,6 +685,7 @@ node! {
        | SyntaxKind::Float(_)
        | SyntaxKind::Numeric(_, _)
        | SyntaxKind::Str(_)
+       | SyntaxKind::Label(_)
 }
 
 impl Lit {
@@ -717,6 +699,7 @@ impl Lit {
             SyntaxKind::Float(v) => LitKind::Float(v),
             SyntaxKind::Numeric(v, unit) => LitKind::Numeric(v, unit),
             SyntaxKind::Str(ref v) => LitKind::Str(v.clone()),
+            SyntaxKind::Label(ref v) => LitKind::Label(v.clone()),
             _ => panic!("literal is of wrong kind"),
         }
     }
@@ -739,6 +722,8 @@ pub enum LitKind {
     Numeric(f64, Unit),
     /// A quoted string: `"..."`.
     Str(EcoString),
+    /// A label: `<intro>`.
+    Label(EcoString),
 }
 
 node! {

src/syntax/kind.rs

@@ -153,7 +153,7 @@ pub enum SyntaxKind {
     Raw(Arc<RawFields>),
     /// A hyperlink: `https://typst.org`.
     Link(EcoString),
-    /// A label: `<label>`.
+    /// A label: `<intro>`.
     Label(EcoString),
     /// A reference: `@target`.
     Ref(EcoString),

src/syntax/parsing.rs

@@ -232,7 +232,6 @@ fn markup_node(p: &mut Parser, at_start: &mut bool) {
         | SyntaxKind::Shorthand(_)
         | SyntaxKind::Link(_)
         | SyntaxKind::Raw(_)
-        | SyntaxKind::Label(_)
         | SyntaxKind::Ref(_) => p.eat(),
 
         // Math.
@@ -257,6 +256,7 @@ fn markup_node(p: &mut Parser, at_start: &mut bool) {
 
         // Hashtag + keyword / identifier.
         SyntaxKind::Ident(_)
+        | SyntaxKind::Label(_)
         | SyntaxKind::Let
         | SyntaxKind::Set
         | SyntaxKind::Show
@@ -617,7 +617,8 @@ fn literal(p: &mut Parser) -> bool {
             | SyntaxKind::Float(_)
             | SyntaxKind::Bool(_)
             | SyntaxKind::Numeric(_, _)
-            | SyntaxKind::Str(_),
+            | SyntaxKind::Str(_)
+            | SyntaxKind::Label(_),
         ) => {
             p.eat();
             true

src/syntax/tokens.rs

@@ -207,8 +207,8 @@ impl<'s> Tokens<'s> {
             }
             '`' => self.raw(),
             c if c.is_ascii_digit() => self.numbering(start),
-            '<' => self.label(),
-            '@' => self.reference(start),
+            '<' if self.s.at(is_id_continue) => self.label(),
+            '@' if self.s.at(is_id_continue) => self.reference(),
 
             // Escape sequences.
             '\\' => self.backslash(),
@@ -417,13 +417,8 @@ impl<'s> Tokens<'s> {
         }
     }
 
-    fn reference(&mut self, start: usize) -> SyntaxKind {
-        let label = self.s.eat_while(is_id_continue);
-        if !label.is_empty() {
-            SyntaxKind::Ref(label.into())
-        } else {
-            self.text(start)
-        }
+    fn reference(&mut self) -> SyntaxKind {
+        SyntaxKind::Ref(self.s.eat_while(is_id_continue).into())
     }
 
     fn math(&mut self, start: usize, c: char) -> SyntaxKind {
@@ -475,6 +470,9 @@ impl<'s> Tokens<'s> {
             '(' => SyntaxKind::LeftParen,
             ')' => SyntaxKind::RightParen,
 
+            // Labels.
+            '<' if self.s.at(is_id_continue) => self.label(),
+
             // Two-char operators.
             '=' if self.s.eat_if('=') => SyntaxKind::EqEq,
             '!' if self.s.eat_if('=') => SyntaxKind::ExclEq,
@@ -954,7 +952,7 @@ mod tests {
         t!(Code: "="        => Eq);
         t!(Code: "=="       => EqEq);
         t!(Code: "!="       => ExclEq);
-        t!(Code: "<"        => Lt);
+        t!(Code[" /"]: "<"  => Lt);
         t!(Code: "<="       => LtEq);
         t!(Code: ">"        => Gt);
         t!(Code: ">="       => GtEq);

tests/typ/style/label.typ

@@ -3,7 +3,7 @@
 ---
 // Test labelled headings.
 #show heading: set text(10pt)
-#show heading.where(label: "intro"): underline
+#show heading.where(label: <intro>): underline
 
 = Introduction <intro>
 The beginning.
@@ -13,7 +13,7 @@ The end.
 
 ---
 // Test label after expression.
-#show strong.where(label: "v"): set text(red)
+#show strong.where(label: <v>): set text(red)
 
 #let a = [*A*]
 #let b = [*B*]
@@ -22,22 +22,22 @@ The end.
 ---
 // Test labelled text.
 #show "t": it => {
-  set text(blue) if it.label == "last"
+  set text(blue) if it.label == <last>
   it
 }
 
 This is a thing [that <last>] happened.
 
 ---
-// Test abusing labels for styling.
-#show strong.where(label: "red"): set text(red)
-#show strong.where(label: "blue"): set text(blue)
+// Test abusing dynamic labels for styling.
+#show <red>: set text(red)
+#show <blue>: set text(blue)
 
-*A* *B* <red> *C* <blue> *D*
+*A* *B* <red> *C* #label("bl" + "ue") *D*
 
 ---
 // Test that label ignores parbreak.
-#show emph.where(label: "hide"): none
+#show <hide>: none
 
 _Hidden_
 <hide>
@@ -49,6 +49,10 @@ _Visible_
 
 ---
 // Test that label only works within one content block.
-#show strong.where(label: "strike"): strike
+#show <strike>: strike
 *This is* [<strike>] *protected.*
 *This is not.* <strike>
+
+---
+// Test that incomplete label is text.
+1 < 2 is #if 1 < 2 [not] a label.