While loops 🔁

src/eval/mod.rs

@@ -118,6 +118,7 @@ impl Eval for Expr {
             Self::Binary(v) => v.eval(ctx),
             Self::Let(v) => v.eval(ctx),
             Self::If(v) => v.eval(ctx),
+            Self::While(v) => v.eval(ctx),
             Self::For(v) => v.eval(ctx),
         }
     }
@@ -403,26 +404,58 @@ impl Eval for ExprIf {
 
     fn eval(&self, ctx: &mut EvalContext) -> Self::Output {
         let condition = self.condition.eval(ctx);
-
+        if let Value::Bool(condition) = condition {
-        if let Value::Bool(boolean) = condition {
+            if condition {
-            return if boolean {
                 self.if_body.eval(ctx)
             } else if let Some(expr) = &self.else_body {
                 expr.eval(ctx)
             } else {
                 Value::None
-            };
+            }
-        } else if condition != Value::Error {
+        } else {
+            if condition != Value::Error {
                 ctx.diag(error!(
                     self.condition.span(),
                     "expected boolean, found {}",
                     condition.type_name(),
                 ));
             }
-
             Value::Error
         }
     }
+}
+
+impl Eval for ExprWhile {
+    type Output = Value;
+
+    fn eval(&self, ctx: &mut EvalContext) -> Self::Output {
+        let mut output = vec![];
+        loop {
+            let condition = self.condition.eval(ctx);
+            if let Value::Bool(condition) = condition {
+                if condition {
+                    match self.body.eval(ctx) {
+                        Value::Template(v) => output.extend(v),
+                        Value::Str(v) => output.push(TemplateNode::Str(v)),
+                        Value::Error => return Value::Error,
+                        _ => {}
+                    }
+                } else {
+                    return Value::Template(output);
+                }
+            } else {
+                if condition != Value::Error {
+                    ctx.diag(error!(
+                        self.condition.span(),
+                        "expected boolean, found {}",
+                        condition.type_name(),
+                    ));
+                }
+                return Value::Error;
+            }
+        }
+    }
+}
 
 impl Eval for ExprFor {
     type Output = Value;
@@ -438,7 +471,8 @@ impl Eval for ExprFor {
                     $(ctx.scopes.def_mut($binding.as_str(), $value);)*
 
                     match self.body.eval(ctx) {
-                        Value::Template(new) => output.extend(new),
+                        Value::Template(v) => output.extend(v),
+                        Value::Str(v) => output.push(TemplateNode::Str(v)),
                         Value::Error => {
                             ctx.scopes.pop();
                             return Value::Error;

src/eval/value.rs

@@ -586,7 +586,11 @@ primitive! { Color: "color", Value::Color }
 primitive! { String: "string", Value::Str }
 primitive! { ValueArray: "array", Value::Array }
 primitive! { ValueDict: "dictionary", Value::Dict }
-primitive! { ValueTemplate: "template", Value::Template }
+primitive! {
+    ValueTemplate: "template",
+    Value::Template,
+    Value::Str(v) => vec![TemplateNode::Str(v)],
+}
 primitive! { ValueFunc: "function", Value::Func }
 primitive! { ValueArgs: "arguments", Value::Args }
 

src/parse/mod.rs

@@ -71,7 +71,7 @@ fn node(p: &mut Parser, at_start: &mut bool) -> Option<Node> {
         Token::UnicodeEscape(t) => Node::Text(unicode_escape(p, t)),
 
         // Hashtag + keyword / identifier.
-        Token::Ident(_) | Token::Let | Token::If | Token::For => {
+        Token::Ident(_) | Token::Let | Token::If | Token::While | Token::For => {
             *at_start = false;
             let stmt = token == Token::Let;
             let group = if stmt { Group::Stmt } else { Group::Expr };
@@ -191,6 +191,7 @@ fn primary(p: &mut Parser) -> Option<Expr> {
         // Keywords.
         Some(Token::Let) => expr_let(p),
         Some(Token::If) => expr_if(p),
+        Some(Token::While) => expr_while(p),
         Some(Token::For) => expr_for(p),
 
         // Structures.
@@ -382,6 +383,25 @@ fn expr_if(p: &mut Parser) -> Option<Expr> {
     expr_if
 }
 
+/// Parse a while expresion.
+fn expr_while(p: &mut Parser) -> Option<Expr> {
+    let start = p.start();
+    p.assert(Token::While);
+
+    let mut expr_while = None;
+    if let Some(condition) = expr(p) {
+        if let Some(body) = body(p) {
+            expr_while = Some(Expr::While(ExprWhile {
+                span: p.span(start),
+                condition: Box::new(condition),
+                body: Box::new(body),
+            }));
+        }
+    }
+
+    expr_while
+}
+
 /// Parse a for expression.
 fn expr_for(p: &mut Parser) -> Option<Expr> {
     let start = p.start();

src/pretty.rs

@@ -221,6 +221,7 @@ impl Pretty for Expr {
             Self::Call(v) => v.pretty(p),
             Self::Let(v) => v.pretty(p),
             Self::If(v) => v.pretty(p),
+            Self::While(v) => v.pretty(p),
             Self::For(v) => v.pretty(p),
         }
     }
@@ -413,6 +414,15 @@ impl Pretty for ExprIf {
     }
 }
 
+impl Pretty for ExprWhile {
+    fn pretty(&self, p: &mut Printer) {
+        p.push_str("while ");
+        self.condition.pretty(p);
+        p.push(' ');
+        self.body.pretty(p);
+    }
+}
+
 impl Pretty for ExprFor {
     fn pretty(&self, p: &mut Printer) {
         p.push_str("for ");
@@ -718,9 +728,10 @@ mod tests {
 
         // Keywords.
         roundtrip("#let x = 1 + 2");
+        test_parse("#if x [y] #else [z]", "#if x [y] else [z]");
+        roundtrip("#while x {y}");
         roundtrip("#for x in y {z}");
         roundtrip("#for k, x in y {z}");
-        test_parse("#if x [y] #else [z]", "#if x [y] else [z]");
     }
 
     #[test]

src/syntax/expr.rs

@@ -19,19 +19,21 @@ pub enum Expr {
     Template(ExprTemplate),
     /// A grouped expression: `(1 + 2)`.
     Group(ExprGroup),
-    /// A block expression: `{ #let x = 1; x + 2 }`.
+    /// A block expression: `{ let x = 1; x + 2 }`.
     Block(ExprBlock),
     /// A unary operation: `-x`.
     Unary(ExprUnary),
     /// A binary operation: `a + b`.
     Binary(ExprBinary),
-    /// An invocation of a function: `foo(...)`, `#[foo ...]`.
+    /// An invocation of a function: `foo(...)`.
     Call(ExprCall),
-    /// A let expression: `#let x = 1`.
+    /// A let expression: `let x = 1`.
     Let(ExprLet),
-    /// An if expression: `#if x { y } #else { z }`.
+    /// An if expression: `if x { y } else { z }`.
     If(ExprIf),
-    /// A for expression: `#for x #in y { z }`.
+    /// A while expression: `while x { y }`.
+    While(ExprWhile),
+    /// A for expression: `for x in y { z }`.
     For(ExprFor),
 }
 
@@ -51,6 +53,7 @@ impl Expr {
             Self::Call(v) => v.span,
             Self::Let(v) => v.span,
             Self::If(v) => v.span,
+            Self::While(v) => v.span,
             Self::For(v) => v.span,
         }
     }
@@ -62,6 +65,7 @@ impl Expr {
             | Expr::Call(_)
             | Expr::Let(_)
             | Expr::If(_)
+            | Expr::While(_)
             | Expr::For(_)
         )
     }
@@ -154,7 +158,7 @@ pub struct ExprGroup {
     pub expr: Box<Expr>,
 }
 
-/// A block expression: `{ #let x = 1; x + 2 }`.
+/// A block expression: `{ let x = 1; x + 2 }`.
 #[derive(Debug, Clone, PartialEq)]
 pub struct ExprBlock {
     /// The source code location.
@@ -365,7 +369,7 @@ pub enum Associativity {
     Right,
 }
 
-/// An invocation of a function: `foo(...)`, `#[foo ...]`.
+/// An invocation of a function: `foo(...)`.
 #[derive(Debug, Clone, PartialEq)]
 pub struct ExprCall {
     /// The source code location.
@@ -407,7 +411,7 @@ impl ExprArg {
     }
 }
 
-/// A let expression: `#let x = 1`.
+/// A let expression: `let x = 1`.
 #[derive(Debug, Clone, PartialEq)]
 pub struct ExprLet {
     /// The source code location.
@@ -418,7 +422,7 @@ pub struct ExprLet {
     pub init: Option<Box<Expr>>,
 }
 
-/// An if expression: `#if x { y } #else { z }`.
+/// An if expression: `if x { y } else { z }`.
 #[derive(Debug, Clone, PartialEq)]
 pub struct ExprIf {
     /// The source code location.
@@ -431,7 +435,18 @@ pub struct ExprIf {
     pub else_body: Option<Box<Expr>>,
 }
 
-/// A for expression: `#for x #in y { z }`.
+/// A while expression: `while x { y }`.
+#[derive(Debug, Clone, PartialEq)]
+pub struct ExprWhile {
+    /// The source code location.
+    pub span: Span,
+    /// The condition which selects whether to evaluate the body.
+    pub condition: Box<Expr>,
+    /// The expression to evaluate while the condition is true.
+    pub body: Box<Expr>,
+}
+
+/// A for expression: `for x in y { z }`.
 #[derive(Debug, Clone, PartialEq)]
 pub struct ExprFor {
     /// The source code location.
@@ -447,9 +462,9 @@ pub struct ExprFor {
 /// A pattern in a for loop.
 #[derive(Debug, Clone, PartialEq)]
 pub enum ForPattern {
-    /// A value pattern: `#for v #in array`.
+    /// A value pattern: `for v in array`.
     Value(Ident),
-    /// A key-value pattern: `#for k, v #in dict`.
+    /// A key-value pattern: `for k, v in dict`.
     KeyValue(Ident, Ident),
 }
 

src/syntax/visit.rs

@@ -61,6 +61,7 @@ visit! {
             Expr::Call(e) => v.visit_call(e),
             Expr::Let(e) => v.visit_let(e),
             Expr::If(e) => v.visit_if(e),
+            Expr::While(e) => v.visit_while(e),
             Expr::For(e) => v.visit_for(e),
         }
     }
@@ -132,6 +133,11 @@ visit! {
         }
     }
 
+    fn visit_while(v, node: &ExprWhile) {
+        v.visit_expr(&node.condition);
+        v.visit_expr(&node.body);
+    }
+
     fn visit_for(v, node: &ExprFor) {
         v.visit_expr(&node.iter);
         v.visit_expr(&node.body);

tests/typ/control/for-invalid.typ

@@ -1,32 +0,0 @@
-// Test invalid for loop syntax.
-
----
-// Error: 5-5 expected identifier
-#for
-
-// Error: 7-7 expected keyword `in`
-#for v
-
-// Error: 10-10 expected expression
-#for v in
-
-// Error: 15-15 expected body
-#for v in iter
-
----
-// Should output `v in iter`.
-// Error: 5 expected identifier
-#for
-v in iter {}
-
-// Should output `A thing`.
-// Error: 7-10 expected identifier, found string
-A#for "v" thing.
-
-// Should output `in iter`.
-// Error: 6-9 expected identifier, found string
-#for "v" in iter {}
-
-// Should output `+ b in iter`.
-// Error: 7 expected keyword `in`
-#for a + b in iter {}

tests/typ/control/for-value.typ

@@ -1,20 +0,0 @@
-// Test return value of for loops.
-
----
-// Template body yields template.
-// Should output `234`.
-#for v in (1, 2, 3, 4) [#if v >= 2 [{v}]]
-
----
-// Block body yields template.
-// Should output `[1st, 2nd, 3rd, 4th, 5th, 6th]`.
-{
-    "[" + for v in (1, 2, 3, 4, 5, 6) {
-        (if v > 1 [, ]
-            + [{v}]
-            + if v == 1 [st]
-            + if v == 2 [nd]
-            + if v == 3 [rd]
-            + if v >= 4 [th])
-     } + "]"
-}

tests/typ/control/for.typ

@@ -1,11 +1,10 @@
 // Test for loops.
-// Ref: false
 
 ---
+// Empty array.
+#for x in () [Nope]
+
 // Array.
-
-#for x in () {}
-
 #let sum = 0
 #for x in (1, 2, 3, 4, 5) {
     sum += x
@@ -13,14 +12,12 @@
 
 #test(sum, 15)
 
----
+// Dictionary is not traversed in insertion order.
-// Dictionary.
+// Should output `age: 1, name: Typst,`.
-// Ref: true
+#for k, v in (name: "Typst", age: 2) [
-(\ #for k, v in (name: "Typst", age: 2) [
+    {k}: {v}, \
-    #h(0.5cm) {k}: {v}, \
+]
-])
 
----
 // String.
 {
     let out = ""
@@ -36,6 +33,33 @@
 }
 
 ---
+// Block body.
+// Should output `[1st, 2nd, 3rd, 4th, 5th, 6th]`.
+{
+    "[" + for v in (1, 2, 3, 4, 5, 6) {
+        (if v > 1 [, ]
+            + [{v}]
+            + if v == 1 [st]
+            + if v == 2 [nd]
+            + if v == 3 [rd]
+            + if v >= 4 [th])
+     } + "]"
+}
+
+// Template body.
+// Should output `234`.
+#for v in (1, 2, 3, 4, 5, 6, 7) [#if v >= 2 and v <= 5 { repr(v) }]
+
+---
+// Value of for loops.
+// Ref: false
+#test(type(for v in () {}), "template")
+#test(type(for v in () []), "template")
+
+---
+// Error: 14-19 unknown variable
+#let error = error
+
 // Uniterable expression.
 // Error: 11-15 cannot loop over boolean
 #for v in true {}
@@ -44,9 +68,7 @@
 // Error: 11-18 cannot add integer and string
 #for v in 1 + "2" {}
 
-// Error: 14-17 cannot apply '-' to string
+// A single error stops iteration.
-#let error = -""
+#test(error, for v in (1, 2, 3) {
-#let result = for v in (1, 2, 3) {
     if v < 2 [Ok] else {error}
-}
+})
-#test(result, error)

tests/typ/control/if-invalid.typ

@@ -1,28 +0,0 @@
-// Test invalid if syntax.
-
----
-// Error: 4 expected expression
-#if
-
-// Error: 4 expected expression
-{if}
-
-// Error: 6 expected body
-#if x
-
-// Error: 1-6 unexpected keyword `else`
-#else {}
-
----
-// Should output `x`.
-// Error: 4 expected expression
-#if
-x {}
-
-// Should output `something`.
-// Error: 6 expected body
-#if x something
-
-// Should output `A thing.`
-// Error: 20 expected body
-A#if false {} #else thing

tests/typ/control/if-value.typ

@@ -1,21 +0,0 @@
-// Test return value of if expressions.
-// Ref: false
-
----
-{
-    let x = 1
-    let y = 2
-    let z
-
-    // Returns if branch.
-    z = if x < y { "ok" }
-    test(z, "ok")
-
-    // Returns else branch.
-    z = if x > y { "bad" } else { "ok" }
-    test(z, "ok")
-
-    // Missing else evaluates to none.
-    z = if x > y { "bad" }
-    test(z, none)
-}

tests/typ/control/if.typ

@@ -3,35 +3,61 @@
 ---
 // Test condition evaluation.
 #if 1 < 2 [
-    Ok.
+    One.
 ]
 
 #if true == false [
-    Bad, but we {dont-care}!
+    {Bad}, but we {dont-care}!
 ]
 
 ---
-// Brace in condition.
+// Braced condition.
 #if {true} [
-    Ok.
+    One.
+]
+
+// Template in condition.
+#if [] != none [
+    Two.
 ]
 
 // Multi-line condition with parens.
 #if (
     1 + 1
       == 1
-) {
+) [
-    nope
+    Nope.
-} #else {
+] #else {
-    "Ok."
+    "Three."
 }
 
 // Multiline.
 #if false [
     Bad.
 ] #else {
-    let pt = "."
+    let point = "."
-    "Ok" + pt
+    "Four" + point
+}
+
+---
+// Value of if expressions.
+// Ref: false
+{
+    let x = 1
+    let y = 2
+    let z
+
+    // Returns if branch.
+    z = if x < y { "ok" }
+    test(z, "ok")
+
+    // Returns else branch.
+    z = if x > y { "bad" } else { "ok" }
+    test(z, "ok")
+
+    // Missing else evaluates to none.
+    z = if x > y { "bad" }
+    test(z, none)
 }
 
 ---

tests/typ/control/invalid.typ

@@ -0,0 +1,100 @@
+// Test invalid control syntax.
+
+---
+// Error: 5 expected identifier
+#let
+
+// Error: 5 expected identifier
+{let}
+
+// Error: 6-9 expected identifier, found string
+#let "v"
+
+// Should output `1`.
+// Error: 7 expected semicolon or line break
+#let v 1
+
+// Error: 9 expected expression
+#let v =
+
+// Should output `= 1`.
+// Error: 6-9 expected identifier, found string
+#let "v" = 1
+
+---
+// Error: 4 expected expression
+#if
+
+// Error: 4 expected expression
+{if}
+
+// Error: 6 expected body
+#if x
+
+// Error: 1-6 unexpected keyword `else`
+#else {}
+
+// Should output `x`.
+// Error: 4 expected expression
+#if
+x {}
+
+// Should output `something`.
+// Error: 6 expected body
+#if x something
+
+// Should output `A thing.`
+// Error: 20 expected body
+A#if false {} #else thing
+
+---
+// Error: 7 expected expression
+#while
+
+// Error: 7 expected expression
+{while}
+
+// Error: 9 expected body
+#while x
+
+// Should output `x`.
+// Error: 7 expected expression
+#while
+x {}
+
+// Should output `something`.
+// Error: 9 expected body
+#while x something
+
+---
+// Error: 5 expected identifier
+#for
+
+// Error: 5 expected identifier
+{for}
+
+// Error: 7 expected keyword `in`
+#for v
+
+// Error: 10 expected expression
+#for v in
+
+// Error: 15 expected body
+#for v in iter
+
+// Should output `v in iter`.
+// Error: 5 expected identifier
+#for
+v in iter {}
+
+// Should output `A thing`.
+// Error: 7-10 expected identifier, found string
+A#for "v" thing
+
+// Should output `in iter`.
+// Error: 6-9 expected identifier, found string
+#for "v" in iter {}
+
+// Should output `+ b in iter`.
+// Error: 7 expected keyword `in`
+#for a + b in iter {}

tests/typ/control/let-invalid.typ

@@ -1,20 +0,0 @@
-// Test invalid let binding syntax.
-
----
-// Error: 5 expected identifier
-#let
-
-// Error: 6-9 expected identifier, found string
-#let "v"
-
-// Should output `1`.
-// Error: 7 expected semicolon or line break
-#let v 1
-
-// Error: 9 expected expression
-#let v =
-
----
-// Should output `= 1`.
-// Error: 6-9 expected identifier, found string
-#let "v" = 1

tests/typ/control/let-terminated.typ

@@ -1,28 +0,0 @@
-// Test termination of let statements.
-
----
-// Terminated by line break.
-#let v1 = 1
-One
-
-// Terminated by semicolon.
-#let v2 = 2; Two
-
-// Terminated by semicolon and line break.
-#let v3 = 3;
-Three
-
-// Terminated because expression ends.
-// Error: 12 expected semicolon or line break
-#let v4 = 4 Four
-
-// Terminated by semicolon even though we are in a paren group.
-// Error: 2:19 expected expression
-// Error: 1:19 expected closing paren
-#let v5 = (1, 2 + ; Five
-
-#test(v1, 1)
-#test(v2, 2)
-#test(v3, 3)
-#test(v4, 4)
-#test(v5, (1, 2))

tests/typ/control/let.typ

@@ -1,7 +1,8 @@
 // Test let bindings.
-// Ref: false
 
 ---
+// Ref: false
+
 // Automatically initialized with none.
 #let x
 #test(x, none)
@@ -9,3 +10,32 @@
 // Manually initialized with one.
 #let x = 1
 #test(x, 1)
+
+---
+// Termination.
+
+// Terminated by line break.
+#let v1 = 1
+One
+
+// Terminated by semicolon.
+#let v2 = 2; Two
+
+// Terminated by semicolon and line break.
+#let v3 = 3;
+Three
+
+// Terminated because expression ends.
+// Error: 12 expected semicolon or line break
+#let v4 = 4 Four
+
+// Terminated by semicolon even though we are in a paren group.
+// Error: 2:19 expected expression
+// Error: 1:19 expected closing paren
+#let v5 = (1, 2 + ; Five
+
+#test(v1, 1)
+#test(v2, 2)
+#test(v3, 3)
+#test(v4, 4)
+#test(v5, (1, 2))

tests/typ/control/while.typ

@@ -0,0 +1,46 @@
+// Test while expressions.
+
+---
+// Should output `2 4 6 8 10`.
+#let i = 0
+#while i < 10 [
+    { i += 2 }
+    #i
+]
+
+// Should output `Hi`.
+#let iter = true
+#while iter {
+    iter = false
+    "Hi."
+}
+
+#while false {
+    dont-care
+}
+
+---
+// Value of while loops.
+// Ref: false
+#test(type(while false {}), "template")
+#test(type(while false []), "template")
+
+---
+// Error: 14-19 unknown variable
+#let error = error
+
+// Condition must be boolean.
+// Error: 8-14 expected boolean, found template
+#while [nope] [nope]
+
+// Make sure that we don't complain twice.
+// Error: 8-15 unknown variable
+#while nothing {}
+
+// A single error stops iteration.
+#let i = 0
+#test(error, while i < 10 {
+    i += 1
+    if i < 5 [nope] else { error }
+})
+#test(i, 5)

tests/typ/spacing.typ

@@ -19,9 +19,17 @@ A #if true{"B"} C \
 A#if false [] #else [B]C \
 A#if true [B] #else [] C \
 
+---
+// Spacing around while loop.
+
+#let c = true; A#while c [{c = false}B]C \
+#let c = true; A#while c [{c = false}B] C \
+#let c = true; A #while c { c = false; "B" }C \
+#let c = true; A #while c { c = false; "B" } C \
+
 ---
 // Spacing around for loop.
 
 A#for _ in (none,) [B]C  \
 A#for _ in (none,) [B] C \
-A #for _ in (none,) [B]C \
+A #for _ in (none,) {"B"}C \

tools/test-helper/extension.js

@@ -92,9 +92,9 @@ function getWebviewContent(pngSrc, refSrc, stdout, stderr) {
         <style>
         body, html {
             width: 100%;
-            text-align: center;
             margin: 0;
             padding: 0;
+            text-align: center;
         }
         img {
             width: 80%;
@@ -102,7 +102,10 @@ function getWebviewContent(pngSrc, refSrc, stdout, stderr) {
             object-fit: contain;
         }
         pre {
+            display: inline-block;
             font-family: var(--vscode-editor-font-family);
+            text-align: left;
+            width: 80%;
         }
         </style>
     </head>