Implement {has}

src/internal/execute.rs

@@ -2,7 +2,7 @@ use core::fmt::Write;
 
 use crate::Value;
 
-use super::parse::{Ast, AstKind, For, Print, ValuePath};
+use super::parse::{Ast, AstKind, For, Has, Print, ValuePath};
 
 pub fn execute(ast: &Ast, value: &dyn Value) -> String {
 	let mut out = String::new();
@@ -17,6 +17,7 @@ pub fn execute_(out: &mut String, ast: &Ast, value: &dyn Value) {
 			AstKind::Text(t) => out.push_str(&t),
 			AstKind::Print(p) => print(out, p, value),
 			AstKind::For(f) => for_(out, f, value),
+			AstKind::Has(h) => has(out, h, value),
 			e => todo!("{e:?}"),
 		}
 	}
@@ -27,8 +28,6 @@ pub fn lookup<'a>(
 	path: &ValuePath,
 	value: &'a dyn Value,
 ) -> Option<&'a dyn Value> {
-	dbg!(value);
-	dbg!(path);
 	let mut value = value;
 	for name in &path.0 {
 		match value.lookup(name) {
@@ -65,3 +64,14 @@ pub fn for_(out: &mut String, f: &For, value: &dyn Value) {
 		idx += 1;
 	}
 }
+
+pub fn has(out: &mut String, f: &Has, value: &dyn Value) {
+	let value = match lookup(out, &f.expr, value) {
+		Some(v) => v,
+		None => return,
+	};
+
+	while let Some(value) = value.has() {
+		execute_(out, &f.body, value);
+	}
+}

src/internal/parse.rs

@@ -18,8 +18,8 @@ pub struct For {
 
 #[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct Has {
-	expr: Box<Expr>,
+	pub expr: Expr,
-	body: Ast,
+	pub body: Ast,
 }
 
 #[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
@@ -108,6 +108,8 @@ impl<'a> ParseState<'a> {
 			self.maybe_parse_print();
 		} else if remaining.starts_with("for") {
 			self.maybe_parse_for();
+		} else if remaining.starts_with("has") {
+			self.maybe_parse_has();
 		}
 	}
 
@@ -169,6 +171,47 @@ impl<'a> ParseState<'a> {
 		self.new_empty_text();
 	}
 
+	pub fn maybe_parse_has(&mut self) {
+		assert!(self.remaining().starts_with("has"));
+		self.current_byte_offset += "has".len();
+		self.skip_whitespace();
+		let path = match self.parse_path() {
+			None => return,
+			Some(vp) => vp,
+		};
+		self.skip_whitespace();
+		if !self.remaining().starts_with('}') {
+			return;
+		}
+		self.current_byte_offset += 1;
+
+		let mut inner = ParseState {
+			template: self.template,
+			last_byte_offset: self.last_byte_offset,
+			speculative_text_starts_at: self.current_byte_offset,
+			speculative_text_ends_at: self.current_byte_offset,
+			current_byte_offset: self.current_byte_offset,
+			ast: Ast::new(),
+		};
+		while inner.has_input() {
+			if inner.remaining().starts_with("{/has}") {
+				break;
+			}
+			inner.parse_one();
+		}
+		inner.text_might_end();
+		inner.add_current_text_to_ast();
+		self.current_byte_offset = inner.current_byte_offset;
+		if !self.remaining().starts_with("{/has}") {
+			return;
+		}
+		self.current_byte_offset += "{/has}".len();
+		let body = inner.ast;
+
+		self.push_node_and_text(AstKind::Has(Has { expr: path, body }));
+		self.new_empty_text();
+	}
+
 	pub fn parse_path(&mut self) -> Option<ValuePath> {
 		assert!(self.remaining().starts_with('.'));
 		self.current_byte_offset += 1;
@@ -225,7 +268,7 @@ pub fn parse(template: &str) -> Ast {
 mod test {
 	use crate::internal::parse::{AstKind, Print, ValuePath};
 
-	use super::{parse, Ast, For};
+	use super::{parse, Ast, For, Has};
 
 	fn go(tmpl: &str, rhs: Ast) {
 		let ast = parse(tmpl);
@@ -272,6 +315,17 @@ mod test {
 		);
 	}
 
+	#[test]
+	fn parse_has() {
+		go(
+			"{has .}{.}{/has}",
+			vec![AstKind::Has(Has {
+				expr: ValuePath(vec![]),
+				body: vec![AstKind::Print(Print(ValuePath(vec![])))],
+			})],
+		);
+	}
+
 	#[test]
 	fn parse_for_2() {
 		go(

src/lib.rs

@@ -192,6 +192,37 @@ impl<const N: usize> Value for [&dyn Value; N] {
 	}
 }
 
+impl<T> Value for Option<T>
+where
+	T: Value,
+{
+	fn print(&self, out: &mut String) {
+		if let Some(v) = self {
+			v.print(out)
+		}
+	}
+
+	fn lookup(&self, _: &str) -> Option<&dyn Value> {
+		None
+	}
+
+	fn has(&self) -> Option<&dyn Value> {
+		self.as_ref().map(|v| v as &dyn Value)
+	}
+
+	fn if_(&self) -> bool {
+		self.is_some()
+	}
+
+	fn for_(&self, index: usize) -> Option<&dyn Value> {
+		if index == 0 {
+			self.has()
+		} else {
+			None
+		}
+	}
+}
+
 mod build {}
 
 pub struct Newt {
@@ -275,4 +306,14 @@ mod test {
 			"Bob, Larry, ",
 		)
 	}
+
+	#[test]
+	fn print_has() {
+		go("{has .}{.}{/has}", &Some("Bob"), "Bob");
+	}
+
+	#[test]
+	fn print_has_none() {
+		go("{has .}{.}{/has}", &None::<&str>, "");
+	}
 }