ProLeap ANTLR4-based parser for Visual Basic 6.0

This is a Visual Basic 6.0 parser based on an ANTLR4 grammar, which generates an Abstract Syntax Tree (AST) and Abstract Semantic Graph (ASG) for Visual Basic 6.0 code. The AST represents plain Visual Basic 6.0 source code in a syntax tree structure. The ASG is generated from the AST by semantic analysis and provides data and control flow information (e. g. variable access).

The parser is developed test-driven and has successfully been applied to large Visual Basic 6.0 projects. It is used by the ProLeap analyzer & transformer for Visual Basic 6.0.

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Example

Input: VB6 code

Private Sub Command1_Click ()
   Text1.Text = "Hello, world!"
End Sub

Output: Abstract Syntax Tree (AST)

(startRule
  (module
    (moduleBody
      (moduleBodyElement
        (subStmt
          (visibility Private) Sub
          (ambiguousIdentifier Command1_Click)
          (argList ( ))
          (block
            (blockStmt
              (letStmt
                (implicitCallStmt_InStmt
                  (iCS_S_MembersCall
                    (iCS_S_VariableOrProcedureCall
                      (ambiguousIdentifier Text1))
                    (iCS_S_MemberCall .
                      (iCS_S_VariableOrProcedureCall
                        (ambiguousIdentifier
                          (ambiguousKeyword Text)))))) =
                (valueStmt
                  (literal "Hello, world!"))))) End Sub)))) <EOF>)

Getting started

To include the parser in your Maven project build it and add the dependency:

<dependency>
  <groupId>io.github.uwol</groupId>
  <artifactId>proleap-vb6-parser</artifactId>
  <version>3.0.0</version>
</dependency>

Use the following code as a starting point for developing own code.

Simple: Generate an Abstract Semantic Graph (ASG) from VB6 code

// generate ASG from plain VB6 code
java.io.File inputFile = new java.io.File("src/test/resources/io/proleap/vb6/asg/HelloWorld.cls");
io.proleap.vb6.asg.metamodel.Program program = new io.proleap.vb6.asg.runner.impl.VbParserRunnerImpl().analyzeFile(inputFile);

// navigate on ASG
io.proleap.vb6.asg.metamodel.Module module = program.getClazzModule("HelloWorld");
io.proleap.vb6.asg.metamodel.Variable variableI = module.getVariable("I");
io.proleap.vb6.asg.metamodel.type.Type typeOfI = variableI.getType();

Complex: Generate an Abstract Semantic Graph (ASG) and traverse the Abstract Syntax Tree (AST)

// generate ASG from plain VB6 code
java.io.File inputFile = new java.io.File("src/test/resources/io/proleap/vb6/asg/HelloWorld.cls");
io.proleap.vb6.asg.metamodel.Program program = new io.proleap.vb6.asg.runner.impl.VbParserRunnerImpl().analyzeFile(inputFile);

// traverse the AST
io.proleap.vb6.VisualBasic6BaseVisitor<Boolean> visitor = new io.proleap.vb6.VisualBasic6BaseVisitor<Boolean>() {
  @Override
  public Boolean visitVariableSubStmt(final io.proleap.vb6.VisualBasic6Parser.VariableSubStmtContext ctx) {
    io.proleap.vb6.asg.metamodel.Variable variable = (io.proleap.vb6.asg.metamodel.Variable) program.getASGElementRegistry().getASGElement(ctx);
    String name = variable.getName();
    io.proleap.vb6.asg.metamodel.type.Type type = variable.getType();

    return visitChildren(ctx);
  }
};

for (final io.proleap.vb6.asg.metamodel.Module module : program.getModules()) {
  visitor.visit(module.getCtx());
}

Where to look next

• ANTLR4 Visual Basic 6.0 grammar
• Unit test code examples
• ProLeap analyzer & transformer for Visual Basic 6.0

How to cite

Please cite ProLeap Visual Basic 6.0 parser in your publications, if it helps your research. Here is an example BibTeX entry:

@misc{wolffgang2018vb6,
  title={ProLeap Visual Basic 6.0 parser},
  author={Wolffgang, Ulrich and others},
  year={2018},
  howpublished={\url{https://github.com/uwol/proleap-vb6-parser}},
}

Features

• The grammar is line-based and takes into account whitespace, so that member calls (e.g. A.B) are distinguished from contextual object calls in WITH statements (e.g. A .B).
• Keywords can be used as identifiers depending on the context, enabling e.g. A.Type, but not Type.B.
• The ANTLR4 grammar is derived from the Visual Basic 6.0 language reference and tested against MSDN VB6 statement examples as well as several Visual Basic 6.0 code repositories.
• Rigorous test-driven development.

Build process

The build process is based on Maven (version 3 or higher). Building requires a JDK 17 and generates a Maven JAR, which can be used in other Maven projects as a dependency.

• Clone or download the repository.
• In Eclipse import the directory as a an existing Maven project.
• To build, run:

$ mvn clean package

• The test suite executes AST and ASG tests against VB6 test code and MSDN statement examples. Unit tests and parse tree files were generated by class io.proleap.vb6.TestGenerator from those VB6 test files.
• You should see output like this:

[INFO] Scanning for projects...
...
-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running io.proleap.vb6.ast.calls.CallsTest
Parsing file Calls.cls.
Comparing parse tree with file Calls.cls.tree.
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 6.991 sec
Running io.proleap.vb6.ast.calls.Module1Test
...
Results :

Tests run: 215, Failures: 0, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

• To install the JAR in your local Maven repository:

$ mvn clean install

• To only run the tests:

$ mvn clean test

Release process

• Milestones of the grammar are published in the ANTLR grammars repo.

License

Licensed under the MIT License. See LICENSE for details.