Add for loop

Signed-off-by: Marcel Müller <neikos@neikos.email>

Cargo.lock

@@ -371,6 +371,7 @@ dependencies = [
  "console",
  "globset",
  "once_cell",
+ "serde",
  "similar",
  "tempfile",
  "walkdir",
@@ -439,7 +440,6 @@ dependencies = [
  "criterion",
  "displaydoc",
  "insta",
- "nomo",
  "serde",
  "serde_json",
  "thiserror",

Cargo.toml

@@ -13,20 +13,21 @@ debug = true
 [dependencies]
 annotate-snippets = "0.12.13"
 displaydoc = "0.2.5"
-serde = { version = "1.0.228", features = ["derive"] }
+serde_json = { version = "1.0.149", optional = true }
-serde_json = "1.0.149"
 thiserror = "2.0.18"
 winnow = { version = "0.7.14", features = ["unstable-recover"] }
 
 [dev-dependencies]
 annotate-snippets = { version = "0.12.13", features = ["testing-colors"] }
 criterion = "0.8.2"
-insta = { version = "1.46.3", features = ["glob"] }
+insta = { version = "1.46.3", features = ["glob", "serde"] }
-nomo = { path = ".", features = ["serialize"] }
+serde = { version = "1.0.228", features = ["derive"] }
+serde_json = "1.0.149"
 
 [profile.dev.package]
 insta.opt-level = 3
 similar.opt-level = 3
 
 [features]
-serialize = []
+default = ["serde_json"]
+serde_json = ["dep:serde_json"]

src/emit/mod.rs

@@ -1,11 +1,11 @@
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 
 use crate::ast::TemplateAstExpr;
 use crate::input::NomoInput;
 
 pub struct EmitMachine {
     current_index: usize,
-    labels: HashMap<LabelSlot, usize>,
+    labels: BTreeMap<LabelSlot, usize>,
 }
 
 impl EmitMachine {
@@ -36,12 +36,12 @@ impl EmitMachine {
     }
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct VariableSlot {
     index: usize,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct LabelSlot {
     index: usize,
 }
@@ -70,11 +70,29 @@ pub enum Instruction {
         jump: LabelSlot,
     },
     NoOp,
+    CreateIteratorFromSlotToSlot {
+        iterator_slot: VariableSlot,
+        iterator_source_slot: VariableSlot,
+    },
+    AdvanceIteratorOrJump {
+        iterator_slot: VariableSlot,
+        value_slot: VariableSlot,
+        jump: LabelSlot,
+    },
+    GetIteratorEmptyOrJump {
+        iterator_slot: VariableSlot,
+        jump: LabelSlot,
+    },
+    PopScope,
+    LoadFromSlotToContext {
+        value_ident: NomoInput,
+        value_slot: VariableSlot,
+    },
 }
 
 #[derive(Debug, Clone)]
 pub struct VMInstructions {
-    pub labels: HashMap<LabelSlot, usize>,
+    pub labels: BTreeMap<LabelSlot, usize>,
     pub instructions: Vec<Instruction>,
 }
 
@@ -83,7 +101,7 @@ pub fn emit_machine(input: crate::ast::TemplateAst<'_>) -> VMInstructions {
 
     let mut machine = EmitMachine {
         current_index: 0,
-        labels: HashMap::new(),
+        labels: BTreeMap::new(),
     };
 
     for ast in input.root() {
@@ -221,13 +239,166 @@ fn emit_ast_expr(
                 eval.push(Instruction::NoOp);
             }
         }
+        TemplateAstExpr::ForChain {
+            for_block,
+            content,
+            else_block,
+            else_content,
+            end_block,
+        } => {
+            let post_for_whitespace_content;
+            let label_to_else_or_empty_index = machine.reserve_label();
+            let label_to_end_index = machine.reserve_label();
+            let label_start_loop = machine.reserve_label();
+            if let TemplateAstExpr::Block {
+                prev_whitespace_content,
+                expression,
+                post_whitespace_content,
+            } = &**for_block
+                && let TemplateAstExpr::For {
+                    value_ident,
+                    value_expression,
+                } = &**expression
+            {
+                if let Some(ws) = prev_whitespace_content {
+                    eval.push(Instruction::AppendContent {
+                        content: ws.source().clone(),
+                    });
+                }
+                post_for_whitespace_content = post_whitespace_content;
+
+                eval.push(Instruction::PushScope {
+                    inherit_parent: true,
+                });
+
+                let value_slot = machine.reserve_slot();
+                let iterator_source_slot = machine.reserve_slot();
+                let iterator_slot = machine.reserve_slot();
+
+                emit_expr_load(machine, eval, iterator_source_slot, value_expression);
+                eval.push(Instruction::CreateIteratorFromSlotToSlot {
+                    iterator_source_slot,
+                    iterator_slot,
+                });
+
+                eval.push(Instruction::GetIteratorEmptyOrJump {
+                    iterator_slot,
+                    jump: label_to_else_or_empty_index,
+                });
+
+                machine.assign_label(label_start_loop, eval.len());
+                eval.push(Instruction::AdvanceIteratorOrJump {
+                    iterator_slot,
+                    value_slot,
+                    jump: label_to_end_index,
+                });
+
+                eval.push(Instruction::LoadFromSlotToContext {
+                    value_slot,
+                    value_ident: value_ident.source(),
+                });
+            } else {
+                panic!("For block should be a for block");
+            };
+
+            if let Some(ws) = post_for_whitespace_content {
+                eval.push(Instruction::AppendContent {
+                    content: ws.source().clone(),
+                });
+            }
+
+            for content in content {
+                emit_ast_expr(machine, eval, content);
+            }
+
+            let end_of_content_jump = eval.len();
+            eval.push(Instruction::Jump {
+                jump: label_start_loop,
+            });
+
+            let has_else = else_block.is_some();
+
+            if let Some(TemplateAstExpr::Block {
+                prev_whitespace_content,
+                expression,
+                post_whitespace_content,
+            }) = else_block.as_deref()
+                && let TemplateAstExpr::ForElse = &**expression
+            {
+                if let Some(ws) = prev_whitespace_content {
+                    eval.insert(
+                        end_of_content_jump.saturating_sub(1),
+                        Instruction::AppendContent {
+                            content: ws.source().clone(),
+                        },
+                    );
+                }
+
+                machine.assign_label(label_to_else_or_empty_index, eval.len());
+
+                if let Some(ws) = post_whitespace_content {
+                    eval.push(Instruction::AppendContent {
+                        content: ws.source().clone(),
+                    });
+                }
+
+                for content in else_content
+                    .as_ref()
+                    .expect("If there is a for block, there should be for content (even if empty)")
+                {
+                    emit_ast_expr(machine, eval, content);
+                }
+            }
+
+            let post_end_whitespace_content;
+
+            if let TemplateAstExpr::Block {
+                prev_whitespace_content,
+                expression,
+                post_whitespace_content,
+            } = &**end_block
+                && let TemplateAstExpr::EndBlock = &**expression
+            {
+                post_end_whitespace_content = post_whitespace_content;
+
+                if let Some(ws) = prev_whitespace_content {
+                    if has_else {
+                        eval.push(Instruction::AppendContent {
+                            content: ws.source().clone(),
+                        });
+                    } else {
+                        eval.insert(
+                            end_of_content_jump.saturating_sub(1),
+                            Instruction::AppendContent {
+                                content: ws.source().clone(),
+                            },
+                        );
+                    }
+                }
+
+                if !has_else {
+                    machine.assign_label(label_to_else_or_empty_index, eval.len());
+                }
+
+                machine.assign_label(label_to_end_index, eval.len());
+
+                eval.push(Instruction::PopScope);
+
+                if let Some(ws) = post_end_whitespace_content {
+                    eval.push(Instruction::AppendContent {
+                        content: ws.source().clone(),
+                    });
+                }
+            } else {
+                panic!("End block should be an endblock");
+            }
+        }
 
         TemplateAstExpr::Block { .. }
         | TemplateAstExpr::EndBlock
         | TemplateAstExpr::IfConditional { .. }
         | TemplateAstExpr::ConditionalContent { .. }
         | TemplateAstExpr::ElseConditional { .. }
-        | TemplateAstExpr::ForChain { .. }
         | TemplateAstExpr::For { .. }
         | TemplateAstExpr::ForElse
         | TemplateAstExpr::Invalid { .. }

src/emit/snapshots/nomo__emit__tests__check_if_else_if.snap

@@ -4,15 +4,15 @@ expression: emit
 ---
 VMInstructions {
     labels: {
-        LabelSlot {
-            index: 4,
-        }: 14,
         LabelSlot {
             index: 0,
         }: 19,
         LabelSlot {
             index: 2,
         }: 7,
+        LabelSlot {
+            index: 4,
+        }: 14,
     },
     instructions: [
         LoadFromContextToSlot {

src/eval/mod.rs

@@ -6,7 +6,9 @@ use thiserror::Error;
 use crate::Context;
 use crate::emit::Instruction;
 use crate::emit::VMInstructions;
+use crate::emit::VariableSlot;
 use crate::input::NomoInput;
+use crate::value::NomoValue;
 
 #[derive(Debug, Error, Display)]
 pub enum EvaluationError {
@@ -21,10 +23,59 @@ pub enum EvaluationError {
     LabelNotFound,
 }
 
+struct Scope {
+    stack: Vec<HashMap<String, NomoValue>>,
+    slots: HashMap<VariableSlot, NomoValue>,
+}
+impl Scope {
+    fn insert_into_slot(&mut self, slot: VariableSlot, value: NomoValue) {
+        self.slots.insert(slot, value);
+    }
+
+    fn get(&self, slot: &VariableSlot) -> &NomoValue {
+        self.slots.get(slot).expect("All slot loads must be valid")
+    }
+
+    fn get_mut(&mut self, slot: &VariableSlot) -> &mut NomoValue {
+        self.slots
+            .get_mut(slot)
+            .expect("All slot loads must be valid")
+    }
+
+    fn push_scope(&mut self) {
+        self.stack.push(Default::default());
+    }
+
+    fn pop_scope(&mut self) {
+        self.stack.pop();
+    }
+
+    fn insert_into_scope(&mut self, ident: &NomoInput, value: NomoValue) {
+        self.stack
+            .last_mut()
+            .unwrap()
+            .insert(ident.to_string(), value);
+    }
+
+    fn get_scoped(&self, name: &NomoInput) -> Option<&NomoValue> {
+        self.stack
+            .iter()
+            .rev()
+            .find_map(|scope| scope.get(name.as_str()))
+    }
+}
+
+#[allow(
+    clippy::unnecessary_to_owned,
+    reason = "We cannot do the suggested way as the lifetimes would not match up"
+)]
 pub fn execute(vm: &VMInstructions, global_context: &Context) -> Result<String, EvaluationError> {
     let mut output = String::new();
 
-    let mut scopes: HashMap<crate::emit::VariableSlot, serde_json::Value> = HashMap::new();
+    let mut scopes = Scope {
+        stack: vec![global_context.values().clone()],
+        slots: HashMap::new(),
+    };
 
     let mut ip = 0;
     loop {
@@ -38,21 +89,22 @@ pub fn execute(vm: &VMInstructions, global_context: &Context) -> Result<String,
             Instruction::NoOp => (),
             Instruction::AppendContent { content } => output.push_str(content),
             Instruction::LoadFromContextToSlot { name, slot } => {
-                let value = global_context
+                let value = scopes
-                    .values
+                    .get_scoped(name)
-                    .get(name.as_str())
                     .ok_or(EvaluationError::UnknownVariable(name.clone()))?;
 
-                scopes.insert(*slot, value.clone());
+                scopes.insert_into_slot(*slot, value.clone());
             }
             Instruction::EmitFromSlot { slot } => {
-                let value = scopes.get(slot).unwrap().as_str().unwrap();
+                let value = scopes.get(slot).as_str().unwrap();
                 output.push_str(value);
             }
-            Instruction::PushScope { inherit_parent: _ } => todo!(),
+            Instruction::PushScope { inherit_parent: _ } => {
+                scopes.push_scope();
+            }
             Instruction::Abort => return Err(EvaluationError::ExplicitAbort),
             Instruction::JumpIfNotTrue { emit_slot, jump } => {
-                let dont_jump = scopes.get(emit_slot).unwrap().as_bool().unwrap();
+                let dont_jump = scopes.get(emit_slot).as_bool().unwrap();
                 if dont_jump {
                     // We are done
                 } else {
@@ -72,6 +124,59 @@ pub fn execute(vm: &VMInstructions, global_context: &Context) -> Result<String,
                 ip = *new_ip;
                 continue;
             }
+            Instruction::CreateIteratorFromSlotToSlot {
+                iterator_slot,
+                iterator_source_slot,
+            } => {
+                let value = scopes.get(iterator_source_slot).as_array().unwrap();
+                scopes.insert_into_slot(
+                    *iterator_slot,
+                    NomoValue::Iterator {
+                        value: Box::new(value.to_vec().into_iter()),
+                    },
+                );
+            }
+            Instruction::AdvanceIteratorOrJump {
+                iterator_slot,
+                value_slot,
+                jump,
+            } => {
+                let iterator = scopes.get_mut(iterator_slot).as_iterator_mut().unwrap();
+
+                if let Some(value) = iterator.next() {
+                    scopes.insert_into_slot(*value_slot, value);
+                } else {
+                    let Some(new_ip) = vm.labels.get(jump) else {
+                        return Err(EvaluationError::LabelNotFound);
+                    };
+
+                    ip = *new_ip;
+                }
+            }
+            Instruction::GetIteratorEmptyOrJump {
+                iterator_slot,
+                jump,
+            } => {
+                let iterator = scopes.get(iterator_slot).as_iterator().unwrap();
+                let (min, _) = iterator.size_hint();
+
+                if min == 0 {
+                    let Some(new_ip) = vm.labels.get(jump) else {
+                        return Err(EvaluationError::LabelNotFound);
+                    };
+
+                    ip = *new_ip;
+                }
+            }
+            Instruction::PopScope => scopes.pop_scope(),
+            Instruction::LoadFromSlotToContext {
+                value_ident,
+                value_slot,
+            } => {
+                let value = scopes.get(value_slot).clone();
+
+                scopes.insert_into_scope(value_ident, value);
+            }
         }
 
         ip += 1;

src/lib.rs

@@ -1,19 +1,19 @@
-use std::collections::BTreeMap;
 use std::collections::HashMap;
 
 use displaydoc::Display;
-use serde::Serialize;
 use thiserror::Error;
 
-use crate::emit::Instruction;
 use crate::emit::VMInstructions;
 use crate::input::NomoInput;
+use crate::value::NomoValue;
+use crate::value::NomoValueError;
 
 pub mod ast;
 pub mod emit;
 pub mod eval;
 pub mod input;
 pub mod parser;
+pub mod value;
 
 #[derive(Debug, Error, Display)]
 pub enum NomoError {
@@ -89,7 +89,7 @@ struct Template {
 }
 
 pub struct Context {
-    values: BTreeMap<String, serde_json::Value>,
+    values: HashMap<String, NomoValue>,
 }
 
 impl Default for Context {
@@ -101,23 +101,26 @@ impl Default for Context {
 impl Context {
     pub fn new() -> Context {
         Context {
-            values: BTreeMap::new(),
+            values: HashMap::new(),
         }
     }
 
     pub fn try_insert(
         &mut self,
         key: impl Into<String>,
-        value: impl Serialize,
+        value: impl TryInto<NomoValue, Error = NomoValueError>,
-    ) -> Result<(), serde_json::Error> {
+    ) -> Result<(), NomoValueError> {
-        self.values.insert(key.into(), serde_json::to_value(value)?);
+        self.values.insert(key.into(), value.try_into()?);
 
         Ok(())
     }
 
-    pub fn insert(&mut self, key: impl Into<String>, value: impl Serialize) {
+    pub fn insert(&mut self, key: impl Into<String>, value: impl Into<NomoValue>) {
-        self.try_insert(key, value)
+        self.values.insert(key.into(), value.into());
-            .expect("inserted value should serialize without error");
+    }
+
+    pub fn values(&self) -> &HashMap<String, NomoValue> {
+        &self.values
     }
 }
 

src/value.rs

@@ -0,0 +1,251 @@
+use std::borrow::Cow;
+use std::collections::BTreeMap;
+
+#[cfg(feature = "serde_json")]
+use displaydoc::Display;
+use thiserror::Error;
+
+#[derive(Clone)]
+pub enum NomoValue {
+    String {
+        value: Cow<'static, str>,
+    },
+    Array {
+        value: Vec<NomoValue>,
+    },
+    Bool {
+        value: bool,
+    },
+    Object {
+        value: BTreeMap<String, NomoValue>,
+    },
+    Integer {
+        value: u64,
+    },
+    SignedInteger {
+        value: i64,
+    },
+    Float {
+        value: f64,
+    },
+    Iterator {
+        value: Box<dyn CloneIterator<Item = NomoValue>>,
+    },
+}
+
+impl NomoValue {
+    pub fn as_str(&self) -> Option<&str> {
+        if let Self::String { value } = self {
+            Some(value)
+        } else {
+            None
+        }
+    }
+
+    pub fn as_array(&self) -> Option<&[NomoValue]> {
+        if let Self::Array { value } = self {
+            Some(value)
+        } else {
+            None
+        }
+    }
+
+    pub fn as_bool(&self) -> Option<bool> {
+        if let Self::Bool { value } = self {
+            Some(*value)
+        } else {
+            None
+        }
+    }
+
+    pub fn as_object(&self) -> Option<&BTreeMap<String, NomoValue>> {
+        if let Self::Object { value } = self {
+            Some(value)
+        } else {
+            None
+        }
+    }
+
+    pub fn as_integer(&self) -> Option<u64> {
+        if let Self::Integer { value } = self {
+            Some(*value)
+        } else {
+            None
+        }
+    }
+
+    pub fn as_float(&self) -> Option<f64> {
+        if let Self::Float { value } = self {
+            Some(*value)
+        } else {
+            None
+        }
+    }
+
+    pub fn as_iterator(&self) -> Option<&dyn CloneIterator<Item = NomoValue>> {
+        if let Self::Iterator { value } = self {
+            Some(value)
+        } else {
+            None
+        }
+    }
+
+    pub fn as_iterator_mut(&mut self) -> Option<&mut dyn CloneIterator<Item = NomoValue>> {
+        if let Self::Iterator { value } = self {
+            Some(value)
+        } else {
+            None
+        }
+    }
+}
+
+pub trait CloneIterator: Iterator<Item = NomoValue> {
+    fn clone_box(&self) -> Box<dyn CloneIterator<Item = NomoValue>>;
+}
+
+impl<I> CloneIterator for I
+where
+    I: Iterator<Item = NomoValue> + Clone + 'static,
+{
+    fn clone_box(&self) -> Box<dyn CloneIterator<Item = NomoValue>> {
+        Box::new(Clone::clone(self))
+    }
+}
+
+impl Clone for Box<dyn CloneIterator> {
+    fn clone(&self) -> Self {
+        self.clone_box()
+    }
+}
+
+impl std::fmt::Debug for NomoValue {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::String { value } => f.debug_struct("String").field("value", value).finish(),
+            Self::Array { value } => f.debug_struct("Array").field("value", value).finish(),
+            Self::Bool { value } => f.debug_struct("Bool").field("value", value).finish(),
+            Self::Object { value } => f.debug_struct("Object").field("value", value).finish(),
+            Self::Integer { value } => f.debug_struct("Integer").field("value", value).finish(),
+            Self::SignedInteger { value } => f
+                .debug_struct("SignedInteger")
+                .field("value", value)
+                .finish(),
+            Self::Float { value } => f.debug_struct("Float").field("value", value).finish(),
+            Self::Iterator { value: _ } => f
+                .debug_struct("Iterator")
+                .field("value", &"Iterator")
+                .finish(),
+        }
+    }
+}
+
+impl<R> From<&R> for NomoValue
+where
+    R: Into<NomoValue> + Clone,
+{
+    fn from(value: &R) -> Self {
+        value.clone().into()
+    }
+}
+
+impl From<String> for NomoValue {
+    fn from(val: String) -> Self {
+        NomoValue::String {
+            value: Cow::Owned(val),
+        }
+    }
+}
+
+impl From<&'static str> for NomoValue {
+    fn from(val: &'static str) -> Self {
+        NomoValue::String {
+            value: Cow::Borrowed(val),
+        }
+    }
+}
+
+impl<V> From<Vec<V>> for NomoValue
+where
+    V: Into<NomoValue>,
+{
+    fn from(val: Vec<V>) -> Self {
+        NomoValue::Array {
+            value: val.into_iter().map(Into::into).collect(),
+        }
+    }
+}
+
+impl<V> From<std::collections::VecDeque<V>> for NomoValue
+where
+    V: Into<NomoValue>,
+{
+    fn from(val: std::collections::VecDeque<V>) -> Self {
+        NomoValue::Array {
+            value: val.into_iter().map(Into::into).collect(),
+        }
+    }
+}
+
+impl<V> From<&[V]> for NomoValue
+where
+    V: Into<NomoValue> + Clone,
+{
+    fn from(value: &[V]) -> Self {
+        NomoValue::Array {
+            value: value.iter().cloned().map(Into::into).collect(),
+        }
+    }
+}
+
+impl<K, V> From<std::collections::HashMap<K, V>> for NomoValue
+where
+    K: Into<String>,
+    V: Into<NomoValue>,
+{
+    fn from(val: std::collections::HashMap<K, V>) -> Self {
+        NomoValue::Object {
+            value: val.into_iter().map(|(k, v)| (k.into(), v.into())).collect(),
+        }
+    }
+}
+
+#[cfg(feature = "serde_json")]
+#[derive(Debug, Error, Display)]
+/// Could not transform value to [`NomoValue`]
+pub struct NomoValueError;
+
+#[cfg(feature = "serde_json")]
+impl TryFrom<serde_json::Value> for NomoValue {
+    type Error = NomoValueError;
+    fn try_from(value: serde_json::Value) -> Result<Self, NomoValueError> {
+        match value {
+            serde_json::Value::Null => todo!(),
+            serde_json::Value::Bool(value) => Ok(NomoValue::Bool { value }),
+            serde_json::Value::Number(number) => {
+                if let Some(value) = number.as_u64() {
+                    return Ok(NomoValue::Integer { value });
+                }
+
+                if let Some(value) = number.as_f64() {
+                    return Ok(NomoValue::Float { value });
+                }
+
+                if let Some(value) = number.as_i64() {
+                    return Ok(NomoValue::SignedInteger { value });
+                }
+
+                Err(NomoValueError)
+            }
+            serde_json::Value::String(str) => Ok(NomoValue::String {
+                value: Cow::Owned(str),
+            }),
+            serde_json::Value::Array(values) => Ok(NomoValue::Array {
+                value: values
+                    .into_iter()
+                    .map(TryInto::try_into)
+                    .collect::<Result<_, _>>()?,
+            }),
+            serde_json::Value::Object(_map) => todo!(),
+        }
+    }
+}

tests/cases/1-parsed@simple_for.snap

@@ -0,0 +1,41 @@
+---
+source: tests/file_tests.rs
+expression: parsed
+info:
+  context:
+    values:
+      - one
+      - two
+input_file: tests/cases/simple_for.nomo
+---
+ParsedTemplate {
+    tokens: [
+        [LeftDelim]"{{" (0..2),
+        [Whitespace]" " (2..3),
+        [For]"for" (3..6),
+        [Whitespace]" " (6..7),
+        [Ident]"value" (7..12),
+        [Whitespace]" " (12..13),
+        [In]"in" (13..15),
+        [Whitespace]" " (15..16),
+        [Ident]"values" (16..22),
+        [Whitespace]" " (22..23),
+        [TrimWhitespace]"-" (23..24),
+        [RightDelim]"}}" (24..26),
+        [Whitespace]"\n    " (26..31),
+        [LeftDelim]"{{" (31..33),
+        [TrimWhitespace]"-" (33..34),
+        [WantsOutput]"=" (34..35),
+        [Whitespace]" " (35..36),
+        [Ident]"value" (36..41),
+        [Whitespace]" " (41..42),
+        [RightDelim]"}}" (42..44),
+        [Whitespace]"\n" (44..45),
+        [LeftDelim]"{{" (45..47),
+        [TrimWhitespace]"-" (47..48),
+        [Whitespace]" " (48..49),
+        [End]"end" (49..52),
+        [Whitespace]" " (52..53),
+        [RightDelim]"}}" (53..55),
+    ],
+}

tests/cases/2-ast@simple_for.snap

@@ -0,0 +1,44 @@
+---
+source: tests/file_tests.rs
+expression: ast
+info:
+  context:
+    values:
+      - one
+      - two
+input_file: tests/cases/simple_for.nomo
+---
+TemplateAst {
+    root: [
+        ForChain {
+            for_block: Block {
+                prev_whitespace_content: None,
+                expression: For {
+                    value_ident: [Ident]"value" (7..12),
+                    value_expression: VariableAccess(
+                        [Ident]"values" (16..22),
+                    ),
+                },
+                post_whitespace_content: None,
+            },
+            content: [
+                Interpolation {
+                    prev_whitespace_content: None,
+                    expression: VariableAccess(
+                        [Ident]"value" (36..41),
+                    ),
+                    post_whitespace_content: Some(
+                        [Whitespace]"\n" (44..45),
+                    ),
+                },
+            ],
+            else_block: None,
+            else_content: None,
+            end_block: Block {
+                prev_whitespace_content: None,
+                expression: EndBlock,
+                post_whitespace_content: None,
+            },
+        },
+    ],
+}

tests/cases/3-instructions@condition.snap

@@ -6,10 +6,10 @@ input_file: tests/cases/condition.nomo
 VMInstructions {
     labels: {
         LabelSlot {
-            index: 2,
+            index: 0,
         }: 7,
         LabelSlot {
-            index: 0,
+            index: 2,
         }: 7,
     },
     instructions: [

tests/cases/3-instructions@if_else_if.snap

@@ -5,15 +5,15 @@ input_file: tests/cases/if_else_if.nomo
 ---
 VMInstructions {
     labels: {
+        LabelSlot {
+            index: 0,
+        }: 14,
         LabelSlot {
             index: 2,
         }: 7,
         LabelSlot {
             index: 4,
         }: 14,
-        LabelSlot {
-            index: 0,
-        }: 14,
     },
     instructions: [
         LoadFromContextToSlot {

tests/cases/3-instructions@simple_for.snap

@@ -0,0 +1,87 @@
+---
+source: tests/file_tests.rs
+expression: emit
+info:
+  context:
+    values:
+      - one
+      - two
+input_file: tests/cases/simple_for.nomo
+---
+VMInstructions {
+    labels: {
+        LabelSlot {
+            index: 0,
+        }: 10,
+        LabelSlot {
+            index: 1,
+        }: 10,
+        LabelSlot {
+            index: 2,
+        }: 4,
+    },
+    instructions: [
+        PushScope {
+            inherit_parent: true,
+        },
+        LoadFromContextToSlot {
+            name: "values" (16..22),
+            slot: VariableSlot {
+                index: 4,
+            },
+        },
+        CreateIteratorFromSlotToSlot {
+            iterator_slot: VariableSlot {
+                index: 5,
+            },
+            iterator_source_slot: VariableSlot {
+                index: 4,
+            },
+        },
+        GetIteratorEmptyOrJump {
+            iterator_slot: VariableSlot {
+                index: 5,
+            },
+            jump: LabelSlot {
+                index: 0,
+            },
+        },
+        AdvanceIteratorOrJump {
+            iterator_slot: VariableSlot {
+                index: 5,
+            },
+            value_slot: VariableSlot {
+                index: 3,
+            },
+            jump: LabelSlot {
+                index: 1,
+            },
+        },
+        LoadFromSlotToContext {
+            value_ident: "value" (7..12),
+            value_slot: VariableSlot {
+                index: 3,
+            },
+        },
+        LoadFromContextToSlot {
+            name: "value" (36..41),
+            slot: VariableSlot {
+                index: 6,
+            },
+        },
+        EmitFromSlot {
+            slot: VariableSlot {
+                index: 6,
+            },
+        },
+        AppendContent {
+            content: "\n" (44..45),
+        },
+        Jump {
+            jump: LabelSlot {
+                index: 2,
+            },
+        },
+        PopScope,
+    ],
+}

tests/cases/3-instructions@trim_whitespace.snap

@@ -6,10 +6,10 @@ input_file: tests/cases/trim_whitespace.nomo
 VMInstructions {
     labels: {
         LabelSlot {
-            index: 2,
+            index: 0,
         }: 7,
         LabelSlot {
-            index: 0,
+            index: 2,
         }: 7,
     },
     instructions: [

tests/cases/4-output@simple_for.snap

@@ -0,0 +1,11 @@
+---
+source: tests/file_tests.rs
+expression: output
+info:
+  context:
+    values:
+      - one
+      - two
+input_file: tests/cases/simple_for.nomo
+---
+"one\ntwo\n"

tests/cases/simple_for.nomo

@@ -0,0 +1,7 @@
+{
+    "values": [ "one", "two" ]
+}
+---
+{{ for value in values -}}
+    {{-= value }}
+{{- end }}

tests/file_tests.rs

@@ -2,6 +2,11 @@ use std::collections::HashMap;
 
 use nomo::Context;
 
+#[derive(serde::Serialize)]
+struct Info {
+    context: HashMap<String, serde_json::Value>,
+}
+
 #[test]
 fn check_cases() {
     insta::glob!("cases/*.nomo", |path| {
@@ -9,7 +14,6 @@ fn check_cases() {
         settings.set_snapshot_path("cases");
         settings.set_snapshot_suffix(path.file_stem().unwrap().display().to_string());
         settings.set_prepend_module_to_snapshot(false);
-        let _guard = settings.bind_to_scope();
 
         let input = std::fs::read_to_string(path).unwrap();
 
@@ -21,14 +25,20 @@ fn check_cases() {
             HashMap::new()
         };
 
+        settings.set_info(&Info {
+            context: map.clone(),
+        });
+
         let mut context = Context::new();
 
         for (k, v) in map {
-            context.insert(k, v);
+            context.try_insert(k, v).unwrap();
         }
 
         let parsed = nomo::parser::parse(input.into()).unwrap();
 
+        let _guard = settings.bind_to_scope();
+
         insta::assert_debug_snapshot!("1-parsed", parsed);
 
         let ast = match nomo::ast::parse(parsed.tokens()) {