Add conditional value emitting

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

src/compiler/mod.rs

@@ -1,9 +1,9 @@
 use std::collections::BTreeMap;
 
-use crate::parser::TemplateAstExpr;
 use crate::input::NomoInput;
 use crate::lexer::TemplateToken;
 use crate::lexer::TokenOperator;
+use crate::parser::TemplateAstExpr;
 use crate::value::NomoValue;
 
 pub struct EmitMachine {
@@ -57,6 +57,7 @@ pub enum Instruction {
     LoadFromContextToSlot {
         name: NomoInput,
         slot: VariableSlot,
+        fail_on_not_found: bool,
     },
     EmitFromSlot {
         slot: VariableSlot,
@@ -424,6 +425,7 @@ fn emit_ast_expr(
         | TemplateAstExpr::Literal { .. }
         | TemplateAstExpr::FunctionCall { .. }
         | TemplateAstExpr::Operation { .. }
+        | TemplateAstExpr::ConditionalAccess { .. }
         | TemplateAstExpr::VariableAccess { .. } => eval.push(Instruction::Abort),
     }
 }
@@ -439,6 +441,14 @@ fn emit_expr_load(
             eval.push(Instruction::LoadFromContextToSlot {
                 name: template_token.source().clone(),
                 slot: emit_slot,
+                fail_on_not_found: true,
+            });
+        }
+        TemplateAstExpr::ConditionalAccess(template_token) => {
+            eval.push(Instruction::LoadFromContextToSlot {
+                name: template_token.source().clone(),
+                slot: emit_slot,
+                fail_on_not_found: false,
             });
         }
         TemplateAstExpr::Literal { source, value } => {
@@ -521,6 +531,7 @@ mod tests {
                     slot: VariableSlot {
                         index: 0,
                     },
+                    fail_on_not_found: true,
                 },
                 EmitFromSlot {
                     slot: VariableSlot {

src/compiler/snapshots/nomo__compiler__tests__check_if_else_if.snap

@@ -20,6 +20,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 1,
             },
+            fail_on_not_found: true,
         },
         JumpIfNotTrue {
             emit_slot: VariableSlot {
@@ -51,6 +52,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 3,
             },
+            fail_on_not_found: true,
         },
         JumpIfNotTrue {
             emit_slot: VariableSlot {

src/eval/mod.rs

@@ -93,15 +93,34 @@ pub fn execute(
         match instr {
             Instruction::NoOp => (),
             Instruction::AppendContent { content } => output.push_str(content),
-            Instruction::LoadFromContextToSlot { name, slot } => {
-                let value = scopes
-                    .get_scoped(name)
-                    .ok_or(EvaluationError::UnknownVariable(name.clone()))?;
+            Instruction::LoadFromContextToSlot {
+                name,
+                slot,
+                fail_on_not_found,
+            } => {
+                let value = scopes.get_scoped(name);
+
+                let value = if let Some(val) = value {
+                    val
+                } else {
+                    if *fail_on_not_found {
+                        return Err(EvaluationError::UnknownVariable(name.clone()));
+                    } else {
+                        &NomoValue::Undefined
+                    }
+                };
 
                 scopes.insert_into_slot(*slot, value.clone());
             }
             Instruction::EmitFromSlot { slot } => {
-                let value = scopes.get(slot).try_to_string().unwrap();
+                let value = scopes.get(slot);
+                let value = if let Some(value) = value.try_to_string() {
+                    value
+                } else if matches!(value, NomoValue::Undefined) {
+                    String::new()
+                } else {
+                    panic!("Unknown variable");
+                };
 
                 output.push_str(&value);
             }
@@ -286,4 +305,26 @@ mod tests {
         )
         "#);
     }
+
+    #[test]
+    fn check_conditional_access() {
+        let input = "Hello {{= unknown? }}";
+
+        let parsed = crate::lexer::parse(input.into()).unwrap();
+
+        let ast = crate::parser::parse(parsed.tokens()).unwrap();
+
+        let emit = crate::compiler::emit_machine(ast);
+
+        let context = Context::new();
+        let function_map = FunctionMap::default();
+
+        let output = execute(&function_map, &emit, &context);
+
+        insta::assert_debug_snapshot!(output, @r#"
+        Ok(
+            "Hello ",
+        )
+        "#);
+    }
 }

src/lexer/mod.rs

@@ -238,6 +238,7 @@ pub enum TokenOperator {
     GreaterOrEqual,
     Lesser,
     LesserOrEqual,
+    QuestionMark,
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -567,6 +568,7 @@ fn parse_operator<'input>(input: &mut Input<'input>) -> PResult<'input, Template
                 "=".value(TokenOperator::Equal),
                 cut_err(fail),
             )),
+            '?' => empty.value(TokenOperator::QuestionMark),
             _ => fail,
         },
     )
@@ -604,6 +606,7 @@ fn ident_terminator_check<'input>(input: &mut Input<'input>) -> PResult<'input,
 fn ident_terminator<'input>(input: &mut Input<'input>) -> PResult<'input, ()> {
     alt((
         eof.void(),
+        parse_operator.void(),
         one_of(('{', '}')).void(),
         one_of(('(', ',', ')')).void(),
         one_of((' ', '\t', '\r', '\n')).void(),
@@ -905,4 +908,26 @@ mod tests {
         )
         "#);
     }
+
+    #[test]
+    fn parse_question_mark() {
+        let input = "{{= foo? }}";
+        let output = parse(input.into());
+
+        insta::assert_debug_snapshot!(output, @r#"
+        Ok(
+            ParsedTemplate {
+                tokens: [
+                    [LeftDelim]"{{" (0..2),
+                    [WantsOutput]"=" (2..3),
+                    [Whitespace]" " (3..4),
+                    [Ident]"foo" (4..7),
+                    [Operator(QuestionMark)]"?" (7..8),
+                    [Whitespace]" " (8..9),
+                    [RightDelim]"}}" (9..11),
+                ],
+            },
+        )
+        "#);
+    }
 }

src/parser/mod.rs

@@ -2,11 +2,13 @@ use thiserror::Error;
 use winnow::Parser;
 use winnow::RecoverableParser;
 use winnow::combinator::Infix::Left;
+use winnow::combinator::Postfix;
 use winnow::combinator::alt;
 use winnow::combinator::cut_err;
 use winnow::combinator::delimited;
 use winnow::combinator::dispatch;
 use winnow::combinator::expression;
+use winnow::combinator::fail;
 use winnow::combinator::not;
 use winnow::combinator::opt;
 use winnow::combinator::peek;
@@ -248,6 +250,7 @@ pub enum TemplateAstExpr<'input> {
         value_expression: Box<TemplateAstExpr<'input>>,
     },
     ForElse,
+    ConditionalAccess(TemplateToken),
     VariableAccess(TemplateToken),
     IfConditional {
         expression: Box<TemplateAstExpr<'input>>,
@@ -685,8 +688,9 @@ fn parse_expression<'input>(
                         op: TokenOperator::$val,
                         lhs: Box::new(lhs),
                         rhs: Box::new(rhs)
-                    }))
-                ),*
+                    })),
+                )*
+                _ => fail
             }
         };
     }
@@ -707,6 +711,16 @@ fn parse_expression<'input>(
                 Left Lesser => 15,
                 Left LesserOrEqual => 15,
             ]
+        }).postfix(dispatch! { surrounded(ws, parse_operator);
+            TokenOperator::QuestionMark => Postfix(22, |input, rhs| {
+                match rhs {
+                    TemplateAstExpr::VariableAccess(access) => Ok(TemplateAstExpr::ConditionalAccess(access)),
+                    _ => Err(AstError::from_input(input)),
+                }
+
+
+            }),
+            _ => fail
         }),
     )
     .parse_next(input)
@@ -737,6 +751,7 @@ mod tests {
     use winnow::combinator::fail;
     use winnow::stream::TokenSlice;
 
+    use crate::lexer::TokenKind;
     use crate::parser::AstError;
     use crate::parser::AstFailure;
     use crate::parser::TemplateAst;
@@ -744,7 +759,6 @@ mod tests {
     use crate::parser::parse;
     use crate::parser::parse_block;
     use crate::parser::parse_end;
-    use crate::lexer::TokenKind;
 
     fn panic_pretty<'a>(
         input: &'_ str,
@@ -1046,4 +1060,15 @@ mod tests {
 
         insta::assert_debug_snapshot!(ast);
     }
+
+    #[test]
+    fn check_conditional_access() {
+        let input = "{{= foo? }}";
+
+        let parsed = crate::lexer::parse(input.into()).unwrap();
+
+        let ast = panic_pretty(input, parse(parsed.tokens()));
+
+        insta::assert_debug_snapshot!(ast);
+    }
 }

src/parser/snapshots/nomo__parser__tests__check_conditional_access.snap

@@ -0,0 +1,15 @@
+---
+source: src/parser/mod.rs
+expression: ast
+---
+TemplateAst {
+    root: [
+        Interpolation {
+            prev_whitespace_content: None,
+            expression: ConditionalAccess(
+                [Ident]"foo" (4..7),
+            ),
+            post_whitespace_content: None,
+        },
+    ],
+}

src/value.rs

@@ -31,6 +31,7 @@ pub enum NomoValue {
     Iterator {
         value: Box<dyn CloneIterator<Item = NomoValue>>,
     },
+    Undefined,
 }
 
 impl NomoValue {
@@ -241,6 +242,7 @@ impl NomoValue {
             NomoValue::SignedInteger { value } => Some(value.to_string()),
             NomoValue::Float { value } => Some(value.to_string()),
             NomoValue::Iterator { .. } => None,
+            NomoValue::Undefined => None,
         }
     }
 }
@@ -281,6 +283,7 @@ impl std::fmt::Debug for NomoValue {
                 .debug_struct("Iterator")
                 .field("value", &"Iterator")
                 .finish(),
+            Self::Undefined => f.debug_tuple("Undefined").finish(),
         }
     }
 }

tests/cases/condition.3-instructions.snap

@@ -22,6 +22,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 1,
             },
+            fail_on_not_found: true,
         },
         JumpIfNotTrue {
             emit_slot: VariableSlot {
@@ -56,6 +57,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 3,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {

tests/cases/identifiers.3-instructions.snap

@@ -4,12 +4,12 @@ expression: emit
 info:
   input: "{{= _name }}\n{{= a_name }}\n{{= name }}\n{{= _name1 }}\n{{= _namE }}\n{{= name1 }}"
   context:
-    name1: Foo
-    _name: Foo
-    _namE: Foo
     a_name: Foo
-    name: Foo
+    _name: Foo
     _name1: Foo
+    _namE: Foo
+    name1: Foo
+    name: Foo
 ---
 VMInstructions {
     labels: {},
@@ -19,6 +19,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 0,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {
@@ -33,6 +34,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 1,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {
@@ -47,6 +49,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 2,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {
@@ -61,6 +64,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 3,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {
@@ -75,6 +79,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 4,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {
@@ -89,6 +94,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 5,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {

tests/cases/if_else_if.3-instructions.snap

@@ -26,6 +26,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 1,
             },
+            fail_on_not_found: true,
         },
         JumpIfNotTrue {
             emit_slot: VariableSlot {
@@ -57,6 +58,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 3,
             },
+            fail_on_not_found: true,
         },
         JumpIfNotTrue {
             emit_slot: VariableSlot {

tests/cases/interpolation.3-instructions.snap

@@ -20,6 +20,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 0,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {

tests/cases/multiple.3-instructions.snap

@@ -21,6 +21,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 0,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {
@@ -35,6 +36,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 1,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {

tests/cases/simple_for.3-instructions.snap

@@ -39,6 +39,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 4,
             },
+            fail_on_not_found: true,
         },
         CreateIteratorFromSlotToSlot {
             iterator_slot: VariableSlot {
@@ -78,6 +79,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 6,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {
@@ -104,6 +106,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 11,
             },
+            fail_on_not_found: true,
         },
         CreateIteratorFromSlotToSlot {
             iterator_slot: VariableSlot {
@@ -143,6 +146,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 13,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {

tests/cases/trim_whitespace.3-instructions.snap

@@ -4,8 +4,8 @@ expression: emit
 info:
   input: "{{ if test -}}\n    Hello {{= stuff -}}\n{{- end }}"
   context:
-    stuff: Hemera
     test: true
+    stuff: Hemera
 ---
 VMInstructions {
     labels: {
@@ -22,6 +22,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 1,
             },
+            fail_on_not_found: true,
         },
         JumpIfNotTrue {
             emit_slot: VariableSlot {
@@ -42,6 +43,7 @@ VMInstructions {
             slot: VariableSlot {
                 index: 3,
             },
+            fail_on_not_found: true,
         },
         EmitFromSlot {
             slot: VariableSlot {