ANTLR4：Python中的单元测试访问者类

几天前，我开始在自己的项目中使用ANTLR4，我很难看到如何对我的访问者类进行单元测试。我的规则文件非常简单：

grammar Mmk_Expr;
import Mmk_Common_Grammar, Mmk_Keywords;
prog: stat+;
stat : MMK_SOURCES '=' NEWLINE* (CPP NEWLINE)+         # Sources
     | MMK_HEADERS '=' NEWLINE* (HPP NEWLINE)+         # Headers
     | MMK_DEPEND_ON '=' NEWLINE* (DIR_PATH NEWLINE)+  # Depends
     | NEWLINE                                         # blank
     ;

在使用-visitor和-no侦听器选项运行ANTLR4之后，ANTLR生成了一个访问者：

# Generated from Mmk_Expr.g4 by ANTLR 4.8
from antlr4 import *
if __name__ is not None and "." in __name__:
    from .Mmk_ExprParser import Mmk_ExprParser
else:
    from Mmk_ExprParser import Mmk_ExprParser

# This class defines a complete generic visitor for a parse tree produced by Mmk_ExprParser.

class Mmk_ExprVisitor(ParseTreeVisitor):

    # Visit a parse tree produced by Mmk_ExprParser#prog.
    def visitProg(self, ctx:Mmk_ExprParser.ProgContext):
        return self.visitChildren(ctx)


    # Visit a parse tree produced by Mmk_ExprParser#Sources.
    def visitSources(self, ctx:Mmk_ExprParser.SourcesContext):
        return self.visitChildren(ctx)


    # Visit a parse tree produced by Mmk_ExprParser#Headers.
    def visitHeaders(self, ctx:Mmk_ExprParser.HeadersContext):
        return self.visitChildren(ctx)


    # Visit a parse tree produced by Mmk_ExprParser#Depends.
    def visitDepends(self, ctx:Mmk_ExprParser.DependsContext):
        return self.visitChildren(ctx)


    # Visit a parse tree produced by Mmk_ExprParser#blank.
    def visitBlank(self, ctx:Mmk_ExprParser.BlankContext):
        return self.visitChildren(ctx)



del Mmk_ExprParser

我继承了MMK_ExprVisitor并制作了MMK_EvalVisitor：

from Mmk_ExprVisitor import Mmk_ExprVisitor
from Mmk_ExprParser import Mmk_ExprParser
from typing import Dict, List

class Mmk_EvalVisitor(Mmk_ExprVisitor):
    def __init__(self):
        self.__expr: Dict[str, List[str]] = {}
        self.__name: str
        self.__sourceFiles: List[str] = []
        self.__headerFiles: List[str] = []
        self.__directories: List[str] = []

    def toDict(self):
        return self.__expr

    def visitSources(self, ctx: Mmk_ExprParser.SourcesContext):
        #print(ctx.MMK_SOURCES)
        self.__name = ctx.MMK_SOURCES().getText()
        for file in ctx.CPP():
            self.__sourceFiles.append(str(file))

        self.__expr[self.__name] = self.__sourceFiles

    def visitHeaders(self, ctx: Mmk_ExprParser.HeadersContext):
        self.__name = ctx.MMK_HEADERS().getText()
        for file in ctx.HPP():
            self.__headerFiles.append(str(file))
        
        self.__expr[self.__name] = self.__headerFiles
        return 0
   
    def visitDepends(self, ctx: Mmk_ExprParser.DependsContext):
        self.__name = ctx.MMK_DEPEND_ON().getText()
        for dirname in ctx.DIR_PATH():
            self.__directories.append(str(dirname))
        self.__expr[self.__name] = self.__directories
        return 0

我的单元测试如下所示：

import unittest

from antlr4 import CommonTokenStream, InputStream
from Mmk_ExprLexer import Mmk_ExprLexer
from Mmk_ExprParser import Mmk_ExprParser
from Mmk_EvalVisitor import Mmk_EvalVisitor

class Test_EvalVisitor(unittest.TestCase):
    def setup(self, inputText: str):
        input_stream = InputStream(inputText)
        lexer = Mmk_ExprLexer(input_stream)
        stream = CommonTokenStream(lexer)
        parser = Mmk_ExprParser(stream)
        return parser
    
    def test_visitSources(self):
        visitor = Mmk_EvalVisitor()
        expected = {"MMK_SOURCES": ["filename.cpp", "ofilename.cpp"]}
        parser = self.setup("\nMMK_SOURCES = filename.cpp \\"
                            "\n              ofilename.cpp \\")
        
        srcContext = parser.SourcesContext(parser, parser.prog())

        visitor.visitSources(srcContext)
        actual = visitor.toDict()
        self.assertDictEqual(expected, actual)

    def test_visitHeaders(self):
        visitor = Mmk_EvalVisitor()
        expected = {"MMK_HEADERS": ["filename.h", "ofilename.h"]}

        parser = self.setup("\nMMK_HEADERS = filename.h \\"
                            "\n              ofilename.h \\")

        HeadersContext = Mmk_ExprParser.HeadersContext(parser,parser.stat())

        visitor.visitHeaders(HeadersContext)

        actual = visitor.toDict()
        self.assertDictEqual(expected, actual)

        
if __name__ == '__main__':
    unittest.main()

但我的测试不会通过：

E
======================================================================
ERROR: test_visitHeaders (test_Mmk_Parser.Test_EvalVisitor)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/fredrik/bin/mymake/frontend/mmk_rules/test_Mmk_Parser.py", line 37, in test_visitHeaders
    visitor.visitHeaders(HeadersContext)
  File "/home/fredrik/bin/mymake/frontend/mmk_rules/Mmk_EvalVisitor.py", line 25, in visitHeaders
    self.__name = ctx.MMK_HEADERS().getText()
AttributeError: 'NoneType' object has no attribute 'getText'

======================================================================
ERROR: test_visitSources (test_Mmk_Parser.Test_EvalVisitor)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/fredrik/bin/mymake/frontend/mmk_rules/test_Mmk_Parser.py", line 24, in test_visitSources
    visitor.visitSources(srcContext)
  File "/home/fredrik/bin/mymake/frontend/mmk_rules/Mmk_EvalVisitor.py", line 18, in visitSources
    self.__name = ctx.MMK_SOURCES().getText()
AttributeError: 'NoneType' object has no attribute 'getText'

----------------------------------------------------------------------
Ran 2 tests in 0.007s

FAILED (errors=2)

在单元测试的设置中，我遗漏了什么？我相信我在设置AST时犯了一些错误，但我不知道该怎么做

先谢谢你