Support different modes for eval

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

@@ -1,3 +1,5 @@
+use typst::eval::EvalMode;
+
 use crate::prelude::*;
 
 /// Determines the type of a value.
@@ -196,7 +198,7 @@ pub fn assert_ne(
 /// ```example
 /// #eval("1 + 1") \
 /// #eval("(1, 2, 3, 4)").len() \
-/// #eval("[*Strong text*]")
+/// #eval("*Markup!*", mode: "markup") \
 /// ```
 ///
 /// Display: Evaluate
@@ -207,9 +209,18 @@ pub fn eval(
     ///
     /// The code in the string cannot interact with the file system.
     source: Spanned<String>,
+    /// The syntactical mode in which the string is parsed.
+    ///
+    /// ```example
+    /// #eval("= Heading", mode: "markup")
+    /// #eval("1_2^3", mode: "math")
+    /// ```
+    #[named]
+    #[default(EvalMode::Code)]
+    mode: EvalMode,
     /// The virtual machine.
     vm: &mut Vm,
 ) -> SourceResult<Value> {
     let Spanned { v: text, span } = source;
-    typst::eval::eval_string(vm.world(), &text, span)
+    typst::eval::eval_string(vm.world(), &text, mode, span)
 }

crates/typst/src/eval/mod.rs

@@ -74,8 +74,8 @@ use crate::model::{
 };
 use crate::syntax::ast::{self, AstNode};
 use crate::syntax::{
-    parse_code, FileId, PackageSpec, PackageVersion, Source, Span, Spanned, SyntaxKind,
-    SyntaxNode,
+    parse, parse_code, parse_math, FileId, PackageSpec, PackageVersion, Source, Span,
+    Spanned, SyntaxKind, SyntaxNode,
 };
 use crate::World;
 
@@ -144,10 +144,16 @@ pub fn eval(
 #[comemo::memoize]
 pub fn eval_string(
     world: Tracked<dyn World + '_>,
-    code: &str,
+    string: &str,
+    mode: EvalMode,
     span: Span,
 ) -> SourceResult<Value> {
-    let mut root = parse_code(code);
+    let mut root = match mode {
+        EvalMode::Code => parse_code(string),
+        EvalMode::Markup => parse(string),
+        EvalMode::Math => parse_math(string),
+    };
+
     root.synthesize(span);
 
     let errors = root.errors();
@@ -175,8 +181,15 @@ pub fn eval_string(
     let mut vm = Vm::new(vt, route.track(), id, scopes);
 
     // Evaluate the code.
-    let code = root.cast::<ast::Code>().unwrap();
-    let result = code.eval(&mut vm);
+    let result = match mode {
+        EvalMode::Code => root.cast::<ast::Code>().unwrap().eval(&mut vm),
+        EvalMode::Markup => {
+            root.cast::<ast::Markup>().unwrap().eval(&mut vm).map(Value::Content)
+        }
+        EvalMode::Math => {
+            root.cast::<ast::Math>().unwrap().eval(&mut vm).map(Value::Content)
+        }
+    };
 
     // Handle control flow.
     if let Some(flow) = vm.flow {
@@ -186,6 +199,17 @@ pub fn eval_string(
     result
 }
 
+/// In which mode to evaluate a string.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
+pub enum EvalMode {
+    /// Evaluate as code, as after a hashtag.
+    Code,
+    /// Evaluate as markup, like in a Typst file.
+    Markup,
+    /// Evaluate as math, as in an equation.
+    Math,
+}
+
 /// A virtual machine.
 ///
 /// Holds the state needed to [evaluate](eval) Typst sources. A new