Add identifier not found error handling to evaluator

src/evaluator/environment/mod.rs

@@ -32,16 +32,13 @@ impl Environment {
         self.variables.insert(identifier, value);
     }
 
-    pub(super) fn get<T: AsRef<str>>(&self, identifier: T) -> Object {
+    pub(super) fn get<T: AsRef<str>>(&self, identifier: T) -> Option<Object> {
         match self.variables.get(identifier.as_ref()) {
-            Some(value) => value.clone(),
-            None => {
-                if let Some(sub_environment) = &self.sub_environment {
-                    return sub_environment.get(identifier);
-                }
-
-                Object::Null
-            }
+            Some(value) => Some(value.clone()),
+            None => match &self.sub_environment {
+                Some(sub_environment) => sub_environment.get(identifier),
+                None => None,
+            },
         }
     }
 }

src/evaluator/expression/identifier/mod.rs

@@ -0,0 +1,14 @@
+use crate::evaluator::Evaluator;
+use crate::evaluator::Object;
+
+impl Evaluator {
+    pub(super) fn evaluate_identifier_expression(
+        &self,
+        identifier: String,
+    ) -> anyhow::Result<Object> {
+        match self.environment.get(&identifier) {
+            Some(object) => Ok(object),
+            None => anyhow::bail!("Identifier not found: {}.", identifier),
+        }
+    }
+}

src/evaluator/expression/mod.rs

@@ -5,6 +5,7 @@ use crate::syntax_analysis::*;
 mod boolean;
 mod call;
 mod function;
+mod identifier;
 mod if_expression;
 mod infix;
 mod integer;
@@ -33,7 +34,9 @@ impl Evaluator {
                 consequence,
                 alternative,
             } => self.evaluate_if_expression(*condition, *consequence, *alternative),
-            Expression::Identifier { identifier } => Ok(self.environment.get(identifier)),
+            Expression::Identifier { identifier } => {
+                self.evaluate_identifier_expression(identifier)
+            }
             Expression::Function { parameters, block } => {
                 self.evaluate_function_expression(parameters, *block)
             }

src/tests/evaluation_error/identifier_not_found/mod.rs

@@ -0,0 +1,42 @@
+use super::*;
+
+#[template]
+#[rstest(
+    code,
+    snapshot_name,
+    case("foobar;", "identifier_not_found_case_1"),
+    case("let is_directory = false;\nis_file", "identifier_not_found_case_2"),
+    case("let a = 5;\na + b", "identifier_not_found_case_3"),
+    case(
+        "let double = fn(x) { x * 2 };\ndoubel(5)",
+        "identifier_not_found_case_4"
+    ),
+    case(
+        "let double = fn(x) { x * multiplier };\ndouble(5)",
+        "identifier_not_found_case_5"
+    ),
+    case(
+        "let identity = fn(x) { x };\nidentity(1);\nx",
+        "identifier_not_found_case_6"
+    ),
+    case("if (unknown) { 1 } else { 2 };", "identifier_not_found_case_7"),
+    case("let a = b;", "identifier_not_found_case_8"),
+    case("return missing;", "identifier_not_found_case_9"),
+    case("!undefined_boolean;", "identifier_not_found_case_10")
+)]
+fn identifier_not_found_cases(code: &str, snapshot_name: &str) {}
+
+#[apply(identifier_not_found_cases)]
+fn test_identifier_not_found_lexical_analysis(code: &str, snapshot_name: &str) {
+    assert_lexical_analysis!(code, snapshot_name);
+}
+
+#[apply(identifier_not_found_cases)]
+fn test_identifier_not_found_syntax_analysis(code: &str, snapshot_name: &str) {
+    assert_syntax_analysis!(code, snapshot_name);
+}
+
+#[apply(identifier_not_found_cases)]
+fn test_identifier_not_found_evaluation_error(code: &str, snapshot_name: &str) {
+    assert_evaluation_error!(code, snapshot_name);
+}

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_10_evaluation_error.snap

@@ -0,0 +1,7 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: error
+---
+Err(
+    "Identifier not found: undefined_boolean.",
+)

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_10_lexical_analysis.snap

@@ -0,0 +1,11 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: tokens
+---
+[
+    Not,
+    Identifier {
+        literal: "undefined_boolean",
+    },
+    SemiColon,
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_10_syntax_analysis.snap

@@ -0,0 +1,13 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: abstract_syntax_tree
+---
+[
+    Expression {
+        expression: NotPrefix {
+            right_hand: Identifier {
+                identifier: "undefined_boolean",
+            },
+        },
+    },
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_1_evaluation_error.snap

@@ -0,0 +1,7 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: error
+---
+Err(
+    "Identifier not found: foobar.",
+)

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_1_lexical_analysis.snap

@@ -0,0 +1,10 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: tokens
+---
+[
+    Identifier {
+        literal: "foobar",
+    },
+    SemiColon,
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_1_syntax_analysis.snap

@@ -0,0 +1,11 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: abstract_syntax_tree
+---
+[
+    Expression {
+        expression: Identifier {
+            identifier: "foobar",
+        },
+    },
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_2_evaluation_error.snap

@@ -0,0 +1,7 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: error
+---
+Err(
+    "Identifier not found: is_file.",
+)

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_2_lexical_analysis.snap

@@ -0,0 +1,16 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: tokens
+---
+[
+    Let,
+    Identifier {
+        literal: "is_directory",
+    },
+    Assign,
+    False,
+    SemiColon,
+    Identifier {
+        literal: "is_file",
+    },
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_2_syntax_analysis.snap

@@ -0,0 +1,19 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: abstract_syntax_tree
+---
+[
+    Statement {
+        statement: Let {
+            identifier: "is_directory",
+            expression: Boolean {
+                literal: false,
+            },
+        },
+    },
+    Expression {
+        expression: Identifier {
+            identifier: "is_file",
+        },
+    },
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_3_evaluation_error.snap

@@ -0,0 +1,7 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: error
+---
+Err(
+    "Identifier not found: b.",
+)

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_3_lexical_analysis.snap

@@ -0,0 +1,22 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: tokens
+---
+[
+    Let,
+    Identifier {
+        literal: "a",
+    },
+    Assign,
+    Integer {
+        literal: 5,
+    },
+    SemiColon,
+    Identifier {
+        literal: "a",
+    },
+    Plus,
+    Identifier {
+        literal: "b",
+    },
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_3_syntax_analysis.snap

@@ -0,0 +1,25 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: abstract_syntax_tree
+---
+[
+    Statement {
+        statement: Let {
+            identifier: "a",
+            expression: Integer {
+                literal: 5,
+            },
+        },
+    },
+    Expression {
+        expression: Infix {
+            left_hand: Identifier {
+                identifier: "a",
+            },
+            operator: Plus,
+            right_hand: Identifier {
+                identifier: "b",
+            },
+        },
+    },
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_4_evaluation_error.snap

@@ -0,0 +1,7 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: error
+---
+Err(
+    "Identifier not found: doubel.",
+)

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_4_lexical_analysis.snap

@@ -0,0 +1,35 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: tokens
+---
+[
+    Let,
+    Identifier {
+        literal: "double",
+    },
+    Assign,
+    Function,
+    OpeningRoundBracket,
+    Identifier {
+        literal: "x",
+    },
+    ClosingRoundBracket,
+    OpeningCurlyBracket,
+    Identifier {
+        literal: "x",
+    },
+    Multiply,
+    Integer {
+        literal: 2,
+    },
+    ClosingCurlyBracket,
+    SemiColon,
+    Identifier {
+        literal: "doubel",
+    },
+    OpeningRoundBracket,
+    Integer {
+        literal: 5,
+    },
+    ClosingRoundBracket,
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_4_syntax_analysis.snap

@@ -0,0 +1,43 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: abstract_syntax_tree
+---
+[
+    Statement {
+        statement: Let {
+            identifier: "double",
+            expression: Function {
+                parameters: [
+                    "x",
+                ],
+                block: Block {
+                    nodes: [
+                        Expression {
+                            expression: Infix {
+                                left_hand: Identifier {
+                                    identifier: "x",
+                                },
+                                operator: Multiply,
+                                right_hand: Integer {
+                                    literal: 2,
+                                },
+                            },
+                        },
+                    ],
+                },
+            },
+        },
+    },
+    Expression {
+        expression: Call {
+            function: Identifier {
+                identifier: "doubel",
+            },
+            arguments: [
+                Integer {
+                    literal: 5,
+                },
+            ],
+        },
+    },
+]

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_5_evaluation_error.snap

@@ -0,0 +1,7 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: error
+---
+Err(
+    "Identifier not found: multiplier.",
+)

src/tests/evaluation_error/identifier_not_found/snapshots/monkey_interpreter__tests__evaluation_error__identifier_not_found__test_identifier_not_found_case_5_lexical_analysis.snap

@@ -0,0 +1,35 @@
+---
+source: src/tests/evaluation_error/identifier_not_found/mod.rs
+expression: tokens
+---
+[
+    Let,
+    Identifier {
+        literal: "double",
+    },
+    Assign,
+    Function,
+    OpeningRoundBracket,
+    Identifier {
+        literal: "x",
+    },
+    ClosingRoundBracket,
+    OpeningCurlyBracket,
+    Identifier {
+        literal: "x",
+    },
+    Multiply,
+    Identifier {
+        literal: "multiplier",
+    },
+    ClosingCurlyBracket,
+    SemiColon,
+    Identifier {
+        literal: "double",
+    },
+    OpeningRoundBracket,
+    Integer {
+        literal: 5,
+    },
+    ClosingRoundBracket,
+]