New context system (#3497)

6 files changed, 37 insertions, 0 deletions

diff --git a/crates/typst-syntax/src/ast.rs b/crates/typst-syntax/src/ast.rs
index 6dd9b5f6..df9cef0c 100644
--- a/crates/typst-syntax/src/ast.rs
+++ b/crates/typst-syntax/src/ast.rs
@@ -187,6 +187,8 @@ pub enum Expr<'a> {
     Set(SetRule<'a>),
     /// A show rule: `show heading: it => emph(it.body)`.
     Show(ShowRule<'a>),
+    /// A contextual expression: `context text.lang`.
+    Contextual(Contextual<'a>),
     /// An if-else conditional: `if x { y } else { z }`.
     Conditional(Conditional<'a>),
     /// A while loop: `while x { y }`.
@@ -264,6 +266,7 @@ impl<'a> AstNode<'a> for Expr<'a> {
             SyntaxKind::DestructAssignment => node.cast().map(Self::DestructAssign),
             SyntaxKind::SetRule => node.cast().map(Self::Set),
             SyntaxKind::ShowRule => node.cast().map(Self::Show),
+            SyntaxKind::Contextual => node.cast().map(Self::Contextual),
             SyntaxKind::Conditional => node.cast().map(Self::Conditional),
             SyntaxKind::WhileLoop => node.cast().map(Self::While),
             SyntaxKind::ForLoop => node.cast().map(Self::For),
@@ -326,6 +329,7 @@ impl<'a> AstNode<'a> for Expr<'a> {
             Self::DestructAssign(v) => v.to_untyped(),
             Self::Set(v) => v.to_untyped(),
             Self::Show(v) => v.to_untyped(),
+            Self::Contextual(v) => v.to_untyped(),
             Self::Conditional(v) => v.to_untyped(),
             Self::While(v) => v.to_untyped(),
             Self::For(v) => v.to_untyped(),
@@ -361,6 +365,7 @@ impl Expr<'_> {
                 | Self::Let(_)
                 | Self::Set(_)
                 | Self::Show(_)
+                | Self::Contextual(_)
                 | Self::Conditional(_)
                 | Self::While(_)
                 | Self::For(_)
@@ -1947,6 +1952,18 @@ impl<'a> ShowRule<'a> {
 }
 
 node! {
+    /// A contextual expression: `context text.lang`.
+    Contextual
+}
+
+impl<'a> Contextual<'a> {
+    /// The expression which depends on the context.
+    pub fn body(self) -> Expr<'a> {
+        self.0.cast_first_match().unwrap_or_default()
+    }
+}
+
+node! {
     /// An if-else conditional: `if x { y } else { z }`.
     Conditional
 }
diff --git a/crates/typst-syntax/src/highlight.rs b/crates/typst-syntax/src/highlight.rs
index 99fbf4fe..19d35d0a 100644
--- a/crates/typst-syntax/src/highlight.rs
+++ b/crates/typst-syntax/src/highlight.rs
@@ -230,6 +230,7 @@ pub fn highlight(node: &LinkedNode) -> Option<Tag> {
         SyntaxKind::Let => Some(Tag::Keyword),
         SyntaxKind::Set => Some(Tag::Keyword),
         SyntaxKind::Show => Some(Tag::Keyword),
+        SyntaxKind::Context => Some(Tag::Keyword),
         SyntaxKind::If => Some(Tag::Keyword),
         SyntaxKind::Else => Some(Tag::Keyword),
         SyntaxKind::For => Some(Tag::Keyword),
@@ -267,6 +268,7 @@ pub fn highlight(node: &LinkedNode) -> Option<Tag> {
         SyntaxKind::LetBinding => None,
         SyntaxKind::SetRule => None,
         SyntaxKind::ShowRule => None,
+        SyntaxKind::Contextual => None,
         SyntaxKind::Conditional => None,
         SyntaxKind::WhileLoop => None,
         SyntaxKind::ForLoop => None,
diff --git a/crates/typst-syntax/src/kind.rs b/crates/typst-syntax/src/kind.rs
index 536c9381..e5dd4e9b 100644
--- a/crates/typst-syntax/src/kind.rs
+++ b/crates/typst-syntax/src/kind.rs
@@ -159,6 +159,8 @@ pub enum SyntaxKind {
     Set,
     /// The `show` keyword.
     Show,
+    /// The `context` keyword.
+    Context,
     /// The `if` keyword.
     If,
     /// The `else` keyword.
@@ -232,6 +234,8 @@ pub enum SyntaxKind {
     SetRule,
     /// A show rule: `show heading: it => emph(it.body)`.
     ShowRule,
+    /// A contextual expression: `context text.lang`.
+    Contextual,
     /// An if-else conditional: `if x { y } else { z }`.
     Conditional,
     /// A while loop: `while x { y }`.
@@ -322,6 +326,7 @@ impl SyntaxKind {
                 | Self::Let
                 | Self::Set
                 | Self::Show
+                | Self::Context
                 | Self::If
                 | Self::Else
                 | Self::For
@@ -426,6 +431,7 @@ impl SyntaxKind {
             Self::Let => "keyword `let`",
             Self::Set => "keyword `set`",
             Self::Show => "keyword `show`",
+            Self::Context => "keyword `context`",
             Self::If => "keyword `if`",
             Self::Else => "keyword `else`",
             Self::For => "keyword `for`",
@@ -462,6 +468,7 @@ impl SyntaxKind {
             Self::LetBinding => "`let` expression",
             Self::SetRule => "`set` expression",
             Self::ShowRule => "`show` expression",
+            Self::Contextual => "`context` expression",
             Self::Conditional => "`if` expression",
             Self::WhileLoop => "while-loop expression",
             Self::ForLoop => "for-loop expression",
diff --git a/crates/typst-syntax/src/lexer.rs b/crates/typst-syntax/src/lexer.rs
index f0cf8846..cd1998a6 100644
--- a/crates/typst-syntax/src/lexer.rs
+++ b/crates/typst-syntax/src/lexer.rs
@@ -616,6 +616,7 @@ fn keyword(ident: &str) -> Option<SyntaxKind> {
         "let" => SyntaxKind::Let,
         "set" => SyntaxKind::Set,
         "show" => SyntaxKind::Show,
+        "context" => SyntaxKind::Context,
         "if" => SyntaxKind::If,
         "else" => SyntaxKind::Else,
         "for" => SyntaxKind::For,
diff --git a/crates/typst-syntax/src/parser.rs b/crates/typst-syntax/src/parser.rs
index 32e15cb7..567bcbd1 100644
--- a/crates/typst-syntax/src/parser.rs
+++ b/crates/typst-syntax/src/parser.rs
@@ -750,6 +750,7 @@ fn code_primary(p: &mut Parser, atomic: bool) {
         SyntaxKind::Let => let_binding(p),
         SyntaxKind::Set => set_rule(p),
         SyntaxKind::Show => show_rule(p),
+        SyntaxKind::Context => contextual(p, atomic),
         SyntaxKind::If => conditional(p),
         SyntaxKind::While => while_loop(p),
         SyntaxKind::For => for_loop(p),
@@ -889,6 +890,14 @@ fn show_rule(p: &mut Parser) {
     p.wrap(m, SyntaxKind::ShowRule);
 }
 
+/// Parses a contextual expression: `context text.lang`.
+fn contextual(p: &mut Parser, atomic: bool) {
+    let m = p.marker();
+    p.assert(SyntaxKind::Context);
+    code_expr_prec(p, atomic, 0);
+    p.wrap(m, SyntaxKind::Contextual);
+}
+
 /// Parses an if-else conditional: `if x { y } else { z }`.
 fn conditional(p: &mut Parser) {
     let m = p.marker();
diff --git a/crates/typst-syntax/src/set.rs b/crates/typst-syntax/src/set.rs
index 88a9b18b..906d5fac 100644
--- a/crates/typst-syntax/src/set.rs
+++ b/crates/typst-syntax/src/set.rs
@@ -102,6 +102,7 @@ pub const ATOMIC_CODE_PRIMARY: SyntaxSet = SyntaxSet::new()
     .add(SyntaxKind::Let)
     .add(SyntaxKind::Set)
     .add(SyntaxKind::Show)
+    .add(SyntaxKind::Context)
     .add(SyntaxKind::If)
     .add(SyntaxKind::While)
     .add(SyntaxKind::For)