kaby76 / antlr4templates

Third-party "dotnet new" templates for Antlr.

Antlr4Templates

This package is a third-party set of templates for generating Antlr4 programs using the Arithmetic.g4 grammar. A generated program contains:

• a grammar for expressions.
• a simple console program for parsing input.

To use this package, you will need to install NET 6. Older versions are supported if you modify the <TargetFramework> element in the generated .csproj file.

To install:

dotnet new -i Antlr4Templates

To create an Antlr C# program:

mkdir Foo
cd Foo
dotnet new csharp-combine
dotnet run

Available templates

• csharp-combine: unified Arithmetic grammar for C#.
• csharp-split: split Arithmetic grammar for C#.
• antlr4cs-combine: unified Arithmetic grammar for C# using the Antlr4cs fork.
• antlr4cs-split: split Arithmetic grammar for C# using the Antlr4cs fork.
• cpp-combine: unified Arithmetic grammar for C++.
• cpp-split: split Arithmetic grammar for C++.
• java-combine: unified Arithmetic grammar for Java.
• java-split: split Arithmetic grammar for Java.

To see the complete list of templates, type dotnet new --list | grep '[-]combine\|[-]split' in Bash.

These templates have been tested and work with MSYS2 for Windows 11 using NET6, and Linux. All apps are console programs that take no program arguments and output a parse for various strings, some that are not correct in order to demonstrate parse errors.

NB: Antlr4cs (in nuget here, here, and here; source here) is an obsolete fork of the "official" Antlr4 tool and runtime for CSharp. The Antlr4cs fork has many problems, and it is not being maintained:

• Build rule problems
  • CSC : warning CS2002: Source file 'C:\msys64\home\Kenne\te\obj\Debug\net6.0\ArithmeticBaseVisitor.cs' specified multiple times [C:\msys64\home\Kenne\te\te.csproj]
  • <CustomToolNamespace> element in .csproj is not displayed correctly in VS IDE settings.
• There is no lexer error listener override because it is not supported by the runtime. The source code was updated to be netstandard2.0 in Dec 2020, but it was not compiled and released since Dec 2018!

It is supported here only as a convenience.

To uninstall:

dotnet new -u Antlr4Templates

Alternative generator

If you are interested in generating a parser from a grammar, or for a target other than CSharp, use trgen.

antlr4templates's Issues

Got Antlr4.Runtime.InputMismatchException while adapting template example

Hi,

I was able to generate a template using dotnet new csharp-combine. I was able to build and run that example, and got the expected results from parsing the simple calculator language.

Now I have modified my own project using the template code to walk through the same sequence: read file, lex, parse, check errors.

I am getting an exception during the first call to the parser now:
Exception thrown: 'Antlr4.Runtime.InputMismatchException' in Antlr4.Runtime.Standard.dll

Looking at the documentation for this exception doesn't clarify much, it just says that the current input doesn't match the expected token.

If this was just my grammar resulting in a parse-error, I would think this would present as the flag had_error being true. Therefore, I assume this is a case of me misusing ANTLR, rather than anything being wrong in my grammar or my program source text being parsed.

Here is the function doing the work:

public Program Compile(string path)
        {
            var prog = new Program();

            String input = File.ReadAllText(path);
            var str = new AntlrInputStream(input);
            var lexer = new ML2Lexer(str);
            var tokens = new CommonTokenStream(lexer);
            var parser = new ML2Parser(tokens);
            var listener_lexer = new ML2ErrorListener<int>();
            var listener_parser = new ML2ErrorListener<IToken>();
            lexer.RemoveErrorListeners();
            parser.RemoveErrorListeners();
            lexer.AddErrorListener(listener_lexer);
            parser.AddErrorListener(listener_parser);
            
            parser.BuildParseTree = true;
            var tree = parser.program();

            if (listener_lexer.had_error || listener_parser.had_error)
            {
                Trace.WriteLine("Error in parse.");
            }
            else
            {
                Trace.WriteLine("Parse completed.");
            }

            Trace.WriteLine(tree.ToStringTree(parser));

            return prog;
        }

You can ignore the object Program since it's unused for now. The rest of the code, as far as I can see, follows the template example exactly, except that I am parsing a different grammar.

The exception happens at the line:
var tree = parser.program();

Do you have any suggestions for debugging this exception?