Finish chapter 5: Add ast_printer and test thr created functions

CHANGELOG.md

@@ -7,15 +7,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.0.2] - 2020-08-06
+
 ### Added
 
 - Completing chapter 5
-- Completed including chapter 5.3.3
 - Created `tools/generate_ast.py`, added Visitor class
+- Added the generated `expr.py`
+- Not implemented methods in ABC base classes will raise an `NotImplementedError` that
+  is ignored by coverage tests
 
 ### Fixed
 
-- CTRL-D now works on OSX terminal
+- CTRL-D now works in the OSX terminal
 - Refactor: Exit method is called in a single place
 
 ## [0.0.1] - 2020-08-01
@@ -30,5 +34,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `Token`, `Scanner`, `TokenType`
 - Support `strings`, `numbers` and `identifiers`
 
-[Unreleased]: https://github.com/RoelAdriaans/yaplox/compare/v0.0.1...HEAD
+[Unreleased]: https://github.com/RoelAdriaans/yaplox/compare/v0.0.2...HEAD
+[0.0.2]: https://github.com/RoelAdriaans/yaplox/releases/tag/v0.0.2
 [0.0.1]: https://github.com/RoelAdriaans/yaplox/releases/tag/v0.0.1

src/yaplox/ast_printer.py

@@ -0,0 +1,31 @@
+from yaplox.expr import Binary, Expr, ExprVisitor, Grouping, Literal, Unary
+
+
+class AstPrinter(ExprVisitor):
+    def print(self, expr: Expr) -> str:
+        return expr.accept(self)
+
+    def visit_grouping_expr(self, expr: Grouping):
+        return self._parenthesize("group", expr.expression)
+
+    def visit_literal_expr(self, expr: Literal):
+        if expr.value is None:
+            return "nil"
+        return str(expr.value)
+
+    def visit_unary_expr(self, expr: Unary):
+        return self._parenthesize(expr.operator.lexeme, expr.right)
+
+    def visit_binary_expr(self, expr: Binary):
+        return self._parenthesize(expr.operator.lexeme, expr.left, expr.right)
+
+    def _parenthesize(self, name: str, *args: Expr):
+        expressions = ["(", name]
+
+        for expr in args:
+            expressions.append(" ")
+            expressions.append(expr.accept(self))
+
+        expressions.append(")")
+
+        return "".join(expressions)

src/yaplox/expr.py

@@ -0,0 +1,72 @@
+# This file has been auto-generated by tools/generate_ast.py
+# Do not edit this file by hand. Or do, but it will be overwritten
+
+from abc import ABC, abstractmethod
+from typing import Any
+
+from yaplox.token import Token
+
+
+class ExprVisitor(ABC):
+    """This class is used as an Vistor for the Expr class"""
+
+    @abstractmethod
+    def visit_binary_expr(self, expr: "Binary"):
+        raise NotImplementedError
+
+    @abstractmethod
+    def visit_grouping_expr(self, expr: "Grouping"):
+        raise NotImplementedError
+
+    @abstractmethod
+    def visit_literal_expr(self, expr: "Literal"):
+        raise NotImplementedError
+
+    @abstractmethod
+    def visit_unary_expr(self, expr: "Unary"):
+        raise NotImplementedError
+
+
+class Expr(ABC):
+    @abstractmethod
+    def accept(self, visitor: ExprVisitor):
+        raise NotImplementedError
+
+
+class Binary(Expr):
+    def __init__(self, left: Expr, operator: Token, right: Expr):
+        self.left = left
+        self.operator = operator
+        self.right = right
+
+    def accept(self, visitor: ExprVisitor):
+        """ Create a accept method that calls the visitor. """
+        return visitor.visit_binary_expr(self)
+
+
+class Grouping(Expr):
+    def __init__(self, expression: Expr):
+        self.expression = expression
+
+    def accept(self, visitor: ExprVisitor):
+        """ Create a accept method that calls the visitor. """
+        return visitor.visit_grouping_expr(self)
+
+
+class Literal(Expr):
+    def __init__(self, value: Any):
+        self.value = value
+
+    def accept(self, visitor: ExprVisitor):
+        """ Create a accept method that calls the visitor. """
+        return visitor.visit_literal_expr(self)
+
+
+class Unary(Expr):
+    def __init__(self, operator: Token, right: Expr):
+        self.operator = operator
+        self.right = right
+
+    def accept(self, visitor: ExprVisitor):
+        """ Create a accept method that calls the visitor. """
+        return visitor.visit_unary_expr(self)

tests/test_ast_printer.py

@@ -0,0 +1,27 @@
+from yaplox import expr
+from yaplox.ast_printer import AstPrinter
+from yaplox.token import Token
+from yaplox.token_type import TokenType
+
+
+class TestAstPrinter:
+    def test_astrinter(self):
+        # This is the main/test function given in the chapter for the
+        # ast_printer in chapter A (Not Very) pretty printer.
+        # This code might be obsolete in the future, but it is a lot cleaner then
+        # creating a main function to test our code.
+        expression = expr.Binary(
+            expr.Unary(Token(TokenType.MINUS, "-", None, 1), expr.Literal(123)),
+            Token(TokenType.STAR, "*", None, 1),
+            expr.Grouping(expr.Literal(45.67)),
+        )
+
+        result = AstPrinter().print(expression)
+        assert result == "(* (- 123) (group 45.67))"
+
+    def test_astrinter_nill(self):
+        # Test a single edge case None
+        expression = expr.Literal(None)
+
+        result = AstPrinter().print(expression)
+        assert result == "nil"

tools/generate_ast.py

@@ -50,7 +50,14 @@ def _define_ast(self, base_name: str, types: List):
         ]
         lines.extend(self._define_visitor(base_name, types))
 
-        lines.extend([f"class {base_name}(ABC):", "    ...", ""])
+        lines.extend(
+            [
+                f"class {base_name}(ABC):",
+                "    @abstractmethod",
+                "    def accept(self, visitor: ExprVisitor):",
+                "        raise NotImplementedError",
+            ]
+        )
 
         for class_type in types:
             class_name = class_type.split(":")[0].strip()
@@ -73,7 +80,7 @@ def _define_visitor(self, base_name: str, types: List) -> List:
                 "    @abstractmethod",
                 f"    def visit_{class_name.lower()}_{base_name.lower()}"
                 f'(self, expr: "{class_name}"):',
-                "        pass",
+                "        raise NotImplementedError",
             ]
             vistor_lines.extend(lines)