parser.py

#!/usr/bin/env python3

# -----------------------------------------------------------------------------
# parser.py
#
# Author:       Ahmad Alhour (aalhour.com).
# Date:         July 13th, 2016.
# Description:  The Parser module. Implements syntax analysis and parsing rules
#               of the COOL CFG.
# -----------------------------------------------------------------------------

import ply.yacc as yacc
import pycoolc.ast as AST
from pycoolc.lexer import make_lexer


class PyCoolParser(object):
    """
    PyCoolParser class.

    Responsible for Syntax Analysis of COOL Programs. Implements the LALR(1) parsing algorithm.

    To use the parser, create an object from it and then call the parse() method passing in COOL Program(s) code as a
    string.

    PyCoolParser provides the following public APIs:
     * build(): Builds the parser.
     * parse(): Parses a COOL program source code passed as a string.
    """
    def __init__(self,
                 build_parser=True,
                 debug=False,
                 write_tables=True,
                 optimize=True,
                 outputdir="",
                 yacctab="pycoolc.yacctab",
                 debuglog=None,
                 errorlog=None):
        """
        Initializer.
        :param debug: Debug mode flag.
        :param optimize: Optimize mode flag.
        :param outputdir: Output directory of parser output; by default the .out file goes in the same directory.
        :param debuglog: Debug log file path; by default parser prints to stderr.
        :param errorlog: Error log file path; by default parser print to stderr.
        :param build_parser: If this is set to True the internal parser will be built right after initialization,
         which makes it convenient for direct use. If it's set to False, then an empty parser instance will be
         initialized and the parser object will have to be built by calling parser.build() after initialization.

        Example:
         parser = PyCoolParser(build_parser=False)
         ...
         parser.build()
         parser.parse(...)
         ...

        :return: None
        """
        # Initialize self.parser and self.tokens to None
        self.tokens = None
        self.lexer = None
        self.parser = None
        self.error_list = []

        # Save Flags - PRIVATE PROPERTIES
        self._debug = debug
        self._write_tables = write_tables
        self._optimize = optimize
        self._outputdir = outputdir
        self._yacctab = yacctab
        self._debuglog = debuglog
        self._errorlog = errorlog

        # Build parser if build_parser flag is set to True
        if build_parser is True:
            self.build(debug=debug, write_tables=write_tables, optimize=optimize, outputdir=outputdir,
                       yacctab=yacctab, debuglog=debuglog, errorlog=errorlog)

    # ################################# PRIVATE ########################################

    # ################################ PRECEDENCE RULES ################################

    # precedence rules
    precedence = (
        ('right', 'ASSIGN'),
        ('right', 'NOT'),
        ('nonassoc', 'LTEQ', 'LT', 'EQ'),
        ('left', 'PLUS', 'MINUS'),
        ('left', 'MULTIPLY', 'DIVIDE'),
        ('right', 'ISVOID'),
        ('right', 'INT_COMP'),
        ('left', 'AT'),
        ('left', 'DOT')
    )

    # ################### START OF FORMAL GRAMMAR RULES DECLARATION ####################

    def p_program(self, parse):
        """
        program : class_list
        """
        parse[0] = AST.Program(classes=parse[1])

    def p_class_list(self, parse):
        """
        class_list : class_list class SEMICOLON
                   | class SEMICOLON
        """
        if len(parse) == 3:
            parse[0] = (parse[1],)
        else:
            parse[0] = parse[1] + (parse[2],)

    def p_class(self, parse):
        """
        class : CLASS TYPE LBRACE features_list_opt RBRACE
        """
        parse[0] = AST.Class(name=parse[2], parent="Object", features=parse[4])

    def p_class_inherits(self, parse):
        """
        class : CLASS TYPE INHERITS TYPE LBRACE features_list_opt RBRACE
        """
        parse[0] = AST.Class(name=parse[2], parent=parse[4], features=parse[6])

    def p_feature_list_opt(self, parse):
        """
        features_list_opt : features_list
                          | empty
        """
        parse[0] = tuple() if parse.slice[1].type == "empty" else parse[1]

    def p_feature_list(self, parse):
        """
        features_list : features_list feature SEMICOLON
                      | feature SEMICOLON
        """
        if len(parse) == 3:
            parse[0] = (parse[1],)
        else:
            parse[0] = parse[1] + (parse[2],)

    def p_feature_method(self, parse):
        """
        feature : ID LPAREN formal_params_list RPAREN COLON TYPE LBRACE expression RBRACE
        """
        parse[0] = AST.ClassMethod(name=parse[1], formal_params=parse[3], return_type=parse[6], body=parse[8])

    def p_feature_method_no_formals(self, parse):
        """
        feature : ID LPAREN RPAREN COLON TYPE LBRACE expression RBRACE
        """
        parse[0] = AST.ClassMethod(name=parse[1], formal_params=tuple(), return_type=parse[5], body=parse[7])

    def p_feature_attr_initialized(self, parse):
        """
        feature : ID COLON TYPE ASSIGN expression
        """
        parse[0] = AST.ClassAttribute(name=parse[1], attr_type=parse[3], init_expr=parse[5])

    def p_feature_attr(self, parse):
        """
        feature : ID COLON TYPE
        """
        parse[0] = AST.ClassAttribute(name=parse[1], attr_type=parse[3], init_expr=None)

    def p_formal_list_many(self, parse):
        """
        formal_params_list  : formal_params_list COMMA formal_param
                            | formal_param
        """
        if len(parse) == 2:
            parse[0] = (parse[1],)
        else:
            parse[0] = parse[1] + (parse[3],)

    def p_formal(self, parse):
        """
        formal_param : ID COLON TYPE
        """
        parse[0] = AST.FormalParameter(name=parse[1], param_type=parse[3])

    def p_expression_object_identifier(self, parse):
        """
        expression : ID
        """
        parse[0] = AST.Object(name=parse[1])

    def p_expression_integer_constant(self, parse):
        """
        expression : INTEGER
        """
        parse[0] = AST.Integer(content=parse[1])

    def p_expression_boolean_constant(self, parse):
        """
        expression : BOOLEAN
        """
        parse[0] = AST.Boolean(content=parse[1])

    def p_expression_string_constant(self, parse):
        """
        expression : STRING
        """
        parse[0] = AST.String(content=parse[1])

    def p_expr_self(self, parse):
        """
        expression  : SELF
        """
        parse[0] = AST.Self()

    def p_expression_block(self, parse):
        """
        expression : LBRACE block_list RBRACE
        """
        parse[0] = AST.Block(expr_list=parse[2])

    def p_block_list(self, parse):
        """
        block_list : block_list expression SEMICOLON
                   | expression SEMICOLON
        """
        if len(parse) == 3:
            parse[0] = (parse[1],)
        else:
            parse[0] = parse[1] + (parse[2],)

    def p_expression_assignment(self, parse):
        """
        expression : ID ASSIGN expression
        """
        parse[0] = AST.Assignment(AST.Object(name=parse[1]), expr=parse[3])

    # ######################### METHODS DISPATCH ######################################

    def p_expression_dispatch(self, parse):
        """
        expression : expression DOT ID LPAREN arguments_list_opt RPAREN
        """
        parse[0] = AST.DynamicDispatch(instance=parse[1], method=parse[3], arguments=parse[5])

    def p_arguments_list_opt(self, parse):
        """
        arguments_list_opt : arguments_list
                           | empty
        """
        parse[0] = tuple() if parse.slice[1].type == "empty" else parse[1]

    def p_arguments_list(self, parse):
        """
        arguments_list : arguments_list COMMA expression
                       | expression
        """
        if len(parse) == 2:
            parse[0] = (parse[1],)
        else:
            parse[0] = parse[1] + (parse[3],)

    def p_expression_static_dispatch(self, parse):
        """
        expression : expression AT TYPE DOT ID LPAREN arguments_list_opt RPAREN
        """
        parse[0] = AST.StaticDispatch(instance=parse[1], dispatch_type=parse[3], method=parse[5], arguments=parse[7])

    def p_expression_self_dispatch(self, parse):
        """
        expression : ID LPAREN arguments_list_opt RPAREN
        """
        parse[0] = AST.DynamicDispatch(instance=AST.Self(), method=parse[1], arguments=parse[3])

    # ######################### PARENTHESIZED, MATH & COMPARISONS #####################

    def p_expression_math_operations(self, parse):
        """
        expression : expression PLUS expression
                   | expression MINUS expression
                   | expression MULTIPLY expression
                   | expression DIVIDE expression
        """
        if parse[2] == '+':
            parse[0] = AST.Addition(first=parse[1], second=parse[3])
        elif parse[2] == '-':
            parse[0] = AST.Subtraction(first=parse[1], second=parse[3])
        elif parse[2] == '*':
            parse[0] = AST.Multiplication(first=parse[1], second=parse[3])
        elif parse[2] == '/':
            parse[0] = AST.Division(first=parse[1], second=parse[3])

    def p_expression_math_comparisons(self, parse):
        """
        expression : expression LT expression
                   | expression LTEQ expression
                   | expression EQ expression
        """
        if parse[2] == '<':
            parse[0] = AST.LessThan(first=parse[1], second=parse[3])
        elif parse[2] == '<=':
            parse[0] = AST.LessThanOrEqual(first=parse[1], second=parse[3])
        elif parse[2] == '=':
            parse[0] = AST.Equal(first=parse[1], second=parse[3])

    def p_expression_with_parenthesis(self, parse):
        """
        expression : LPAREN expression RPAREN
        """
        parse[0] = parse[2]

    # ######################### CONTROL FLOW EXPRESSIONS ##############################

    def p_expression_if_conditional(self, parse):
        """
        expression : IF expression THEN expression ELSE expression FI
        """
        parse[0] = AST.If(predicate=parse[2], then_body=parse[4], else_body=parse[6])

    def p_expression_while_loop(self, parse):
        """
        expression : WHILE expression LOOP expression POOL
        """
        parse[0] = AST.WhileLoop(predicate=parse[2], body=parse[4])

    # ######################### LET EXPRESSIONS ########################################

    def p_expression_let(self, parse):
        """
         expression : let_expression
        """
        parse[0] = parse[1]

    def p_expression_let_simple(self, parse):
        """
        let_expression : LET ID COLON TYPE IN expression
                       | nested_lets COMMA LET ID COLON TYPE
        """
        parse[0] = AST.Let(instance=parse[2], return_type=parse[4], init_expr=None, body=parse[6])

    def p_expression_let_initialized(self, parse):
        """
        let_expression : LET ID COLON TYPE ASSIGN expression IN expression
                       | nested_lets COMMA LET ID COLON TYPE ASSIGN expression
        """
        parse[0] = AST.Let(instance=parse[2], return_type=parse[4], init_expr=parse[6], body=parse[8])

    def p_inner_lets_simple(self, parse):
        """
        nested_lets : ID COLON TYPE IN expression
                    | nested_lets COMMA ID COLON TYPE
        """
        parse[0] = AST.Let(instance=parse[1], return_type=parse[3], init_expr=None, body=parse[5])

    def p_inner_lets_initialized(self, parse):
        """
        nested_lets : ID COLON TYPE ASSIGN expression IN expression
                    | nested_lets COMMA ID COLON TYPE ASSIGN expression
        """
        parse[0] = AST.Let(instance=parse[1], return_type=parse[3], init_expr=parse[5], body=parse[7])

    # ######################### CASE EXPRESSION ########################################

    def p_expression_case(self, parse):
        """
        expression : CASE expression OF actions_list ESAC
        """
        parse[0] = AST.Case(expr=parse[2], actions=parse[4])

    def p_actions_list(self, parse):
        """
        actions_list : actions_list action
                     | action
        """
        if len(parse) == 2:
            parse[0] = (parse[1],)
        else:
            parse[0] = parse[1] + (parse[2],)

    def p_action_expr(self, parse):
        """
        action : ID COLON TYPE ARROW expression SEMICOLON
        """
        parse[0] = (parse[1], parse[3], parse[5])

    # ######################### UNARY OPERATIONS #######################################

    def p_expression_new(self, parse):
        """
        expression : NEW TYPE
        """
        parse[0] = AST.NewObject(parse[2])

    def p_expression_isvoid(self, parse):
        """
        expression : ISVOID expression
        """
        parse[0] = AST.IsVoid(parse[2])

    def p_expression_integer_complement(self, parse):
        """
        expression : INT_COMP expression
        """
        parse[0] = AST.IntegerComplement(parse[2])

    def p_expression_boolean_complement(self, parse):
        """
        expression : NOT expression
        """
        parse[0] = AST.BooleanComplement(parse[2])

    # ######################### THE EMPTY PRODUCTION ###################################

    def p_empty(self, parse):
        """
        empty :
        """
        parse[0] = None

    # ######################### PARSE ERROR HANDLER ####################################

    def p_error(self, parse):
        """
        Error rule for Syntax Errors handling and reporting.
        """
        if parse is None:
            print("Error! Unexpected end of input!")
        else:
            error = "Syntax error! Line: {}, position: {}, character: {}, type: {}".format(
                parse.lineno, parse.lexpos, parse.value, parse.type)
            self.error_list.append(error)
            self.parser.errok()

    # ################### END OF FORMAL GRAMMAR RULES SPECIFICATION ####################

    # #################################  PUBLIC  #######################################

    def build(self, **kwargs):
        """
        Builds the PyCoolParser instance with yaac.yaac() by binding the lexer object and its tokens list in the
        current instance scope.
        :param kwargs: yaac.yaac() config parameters, complete list:
            * debug: Debug mode flag.
            * optimize: Optimize mode flag.
            * debuglog: Debug log file path; by default parser prints to stderr.
            * errorlog: Error log file path; by default parser print to stderr.
            * outputdir: Output directory of parsing output; by default the .out file goes in the same directory.
        :return: None
        """
        # Parse the parameters
        if kwargs is None or len(kwargs) == 0:
            debug, write_tables, optimize, outputdir, yacctab, debuglog, errorlog = \
                self._debug, self._write_tables, self._optimize, self._outputdir, self._yacctab, self._debuglog, \
                self._errorlog
        else:
            debug = kwargs.get("debug", self._debug)
            write_tables = kwargs.get("write_tables", self._write_tables)
            optimize = kwargs.get("optimize", self._optimize)
            outputdir = kwargs.get("outputdir", self._outputdir)
            yacctab = kwargs.get("yacctab", self._yacctab)
            debuglog = kwargs.get("debuglog", self._debuglog)
            errorlog = kwargs.get("errorlog", self._errorlog)

        # Build PyCoolLexer
        self.lexer = make_lexer(debug=debug, optimize=optimize, outputdir=outputdir, debuglog=debuglog,
                                errorlog=errorlog)

        # Expose tokens collections to this instance scope
        self.tokens = self.lexer.tokens

        # Build yacc parser
        self.parser = yacc.yacc(module=self, write_tables=write_tables, debug=debug, optimize=optimize,
                                outputdir=outputdir, tabmodule=yacctab, debuglog=debuglog, errorlog=errorlog)

    def parse(self, program_source_code: str) -> AST.Program:
        """
        Parses a COOL program source code passed as a string.
        :param program_source_code: string.
        :return: Parser output.
        """
        if self.parser is None:
            raise ValueError("Parser was not build, try building it first with the build() method.")

        return self.parser.parse(program_source_code)


# -----------------------------------------------------------------------------
#
#                     Parser as a Standalone Python Program
#                     Usage: ./parser.py cool_program.cl
#
# -----------------------------------------------------------------------------


def make_parser(**kwargs) -> PyCoolParser:
    """
    Utility function.
    :return: PyCoolParser object.
    """
    a_parser = PyCoolParser(**kwargs)
    a_parser.build()
    return a_parser


if __name__ == '__main__':
    import sys

    parser = make_parser()

    if len(sys.argv) > 1:
        if not str(sys.argv[1]).endswith(".cl"):
            print("Cool program source code files must end with .cl extension.")
            print("Usage: ./parser.py program.cl")
            exit()

        input_file = sys.argv[1]
        with open(input_file, encoding="utf-8") as file:
            cool_program_code = file.read()

        parse_result = parser.parse(cool_program_code)
        print(parse_result)
    else:
        print("PyCOOLC Parser: Interactive Mode.\r\n")
        while True:
            try:
                s = input('COOL >>> ')
            except EOFError:
                break
            if not s:
                continue
            result = parser.parse(s)
            if result is not None:
                print(result)