VB6Parse

A complete, high-performance parser library for Visual Basic 6 code and project files.

Project Documentation & Resources
VB6 Library Reference
Code Coverage Report
Performance Benchmarks

Overview

VB6Parse is designed as a foundational library for tools that analyze, convert, or process Visual Basic 6 code. While capable of supporting real-time syntax highlighting and language servers, its primary focus is on offline analysis, legacy code utilities, and migration tools.

Key Features:

Fast, efficient parsing with minimal allocations
Full support for VB6 project files, modules, classes, forms, and resources
Concrete Syntax Tree (CST) with complete source fidelity
160+ built-in VB6 library functions and 42 statements
Comprehensive error handling with detailed failure information
Zero-copy tokenization and streaming parsing

Quick Start

Add VB6Parse to your Cargo.toml:

[dependencies]
vb6parse = "0.5.1"

Parse a VB6 Project File

use vb6parse::*;

let input = r#"Type=Exe
Reference=*\G{00020430-0000-0000-C000-000000000046}#2.0#0#...\stdole2.tlb#OLE Automation
Module=Module1; Module1.bas
Form=Form1.frm
"#;

// Decode source with Windows-1252 encoding (VB6 default)
let source = SourceFile::from_string("Project1.vbp", input);

// Parse the project
let result = ProjectFile::parse(&source);

// Handle results
let (project, failures) = result.unpack();

if let Some(project) = project {
    println!("Project type: {:?}", project.project_type);
    println!("Modules: {}", project.modules().count());
    println!("Forms: {}", project.forms().count());
}

// Print any parsing errors
for failure in failures {
    failure.print();
}

Parse a VB6 Module

use vb6parse::*;

let code = r#"Attribute VB_Name = "MyModule"
Public Sub HelloWorld()
    MsgBox "Hello, World!"
End Sub
"#;

let source = SourceFile::from_string("MyModule.bas", code);
let result = ModuleFile::parse(&source);

let (module, failures) = result.unpack();
if let Some(module) = module {
    println!("Module name: {}", module.name);
}

Tokenize VB6 Code

use vb6parse::*;
let mut source_stream = SourceStream::new("test.bas", "Dim x As Integer");
let (token_stream, _failures) = tokenize(&mut source_stream).unpack();

if let Some(tokens) = token_stream {
    for (text, token) in tokens {
        println!("{:?}: {:?}", text, token);
    }
}

Parse to Concrete Syntax Tree

use vb6parse::*;

let contents = "Sub Test()\n    x = 5\nEnd Sub";

let (tree_opt, _failures) = ConcreteSyntaxTree::from_text("test.bas", contents).unpack();

// Print the tree
if let Some(tree) = tree_opt {
    println!("{}", tree.debug_tree());
}

Navigating the CST

The CST provides rich navigation capabilities for traversing and querying the tree structure:

use vb6parse::*;
use vb6parse::parsers::SyntaxKind;

let source = "Sub Test()\n    Dim x As Integer\n    x = 42\nEnd Sub";
let cst = ConcreteSyntaxTree::from_text("test.bas", source).unwrap();
let root = cst.to_root_node();

// Basic navigation
let child_count = root.child_count();
let first = root.first_child();

// Find by kind
let sub_stmt = root.find(SyntaxKind::SubStatement); // First match
let all_dims = root.find_all(SyntaxKind::DimStatement); // All matches

// Filter children
let non_tokens: Vec<_> = root.non_token_children().collect();
let significant: Vec<_> = root.significant_children().collect();

// Custom search with predicates
let keywords = root.find_all_if(|n| n.kind().to_string().ends_with("Keyword"));
let complex = root.find_all_if(|n| !n.is_token() && n.children().len() > 5);

// Iterate all nodes depth-first
for node in root.descendants() {
    if node.is_significant() {
        println!("{:?}: {}", node.kind(), node.text());
    }

    // Convenience checkers
    if node.is_comment() || node.is_whitespace() {
        // Skip trivia
    }
}

Available Navigation Methods:

Both ConcreteSyntaxTree and CstNode provide:

Basic: child_count(), first_child(), last_child(), child_at()
By Kind: children_by_kind(), first_child_by_kind(), contains_kind()
Recursive: find(), find_all()
Filtering: non_token_children(), token_children(), significant_children()
Predicates: find_if(), find_all_if()
Traversal: descendants(), depth_first_iter()

CstNode also provides: is_whitespace(), is_newline(), is_comment(), is_trivia(), is_significant()

See also: examples/cst_navigation.rs for comprehensive examples.

API Surface

Top-Level Imports

For common use cases, import everything with:

use vb6parse::*;

This brings in:

I/O Layer: SourceFile, SourceStream
Lexer: tokenize(), Token, TokenStream
File Parsers: ProjectFile, ClassFile, ModuleFile, FormFile, FormResourceFile
Syntax Parsers: parse(), ConcreteSyntaxTree, SyntaxKind, SerializableTree
Error Handling: ErrorDetails, ParseResult, all error kind enums

Layer Modules (Advanced Usage)

For advanced use cases, access specific layers:

use vb6parse::io::{SourceFile, SourceStream, Comparator};
use vb6parse::lexer::{tokenize, Token, TokenStream};
use vb6parse::parsers::{parse, ConcreteSyntaxTree};
use vb6parse::language::controls::{Control, ControlKind};
use vb6parse::errors::{ProjectErrorKind, FormErrorKind};

Parsing Architecture

Bytes/String/File → SourceFile → SourceStream → TokenStream → CST → Object Layer
                    (Windows-1252) (Characters)   (Tokens)    (Tree) (Structured)

Layers:

I/O Layer (io): Character decoding and stream access
Lexer Layer (lexer): Tokenization with keyword lookup
Syntax Layer (syntax): VB6 language constructs and library functions
Parsers Layer (parsers): CST construction from tokens
Files Layer (files): High-level file format parsers
Language Layer (language): VB6 types, colors, controls
Errors Layer (errors): Comprehensive error types

Source Code Organization

src/
├── io/                          # I/O Layer - Character streams and decoding
│   ├── mod.rs                   # SourceFile, SourceStream
│   ├── comparator.rs            # Case-sensitive/insensitive comparison
│   └── decode.rs                # Windows-1252 decoding
│
├── lexer/                       # Lexer Layer - Tokenization
│   ├── mod.rs                   # tokenize() function, keyword lookup
│   └── token_stream.rs          # TokenStream implementation
│
├── syntax/                      # Syntax Layer - VB6 Language constructs
│   ├── library/                 # VB6 built-in library unit tests and documentation
│   │   ├── functions/           # 160+ VB6 functions (14 categories)
│   │   │   ├── array/           # Array, Filter, Join, Split, etc.
│   │   │   ├── conversion/      # CBool, CInt, CLng, Str, Val, etc.
│   │   │   ├── datetime/        # Date, Now, Time, Year, Month, etc.
│   │   │   ├── file_system/     # Dir, EOF, FileLen, LOF, etc.
│   │   │   ├── financial/       # FV, IPmt, IRR, NPV, PV, Rate, etc.
│   │   │   ├── interaction/     # MsgBox, InputBox, Shell, etc.
│   │   │   ├── math/            # Abs, Cos, Sin, Tan, Log, Sqr, etc.
│   │   │   ├── miscellaneous/   # Environ, RGB, QBColor, etc.
│   │   │   ├── string/          # Left, Right, Mid, Len, Trim, etc.
│   │   │   └── ...
│   │   └── statements/          # VB6 statement unit tests and documentation (7 categories)
│   │       ├── file_operations/ # Open, Close, Get, Put, etc.
│   │       ├── filesystem/      # FileCopy, Kill, MkDir, RmDir, etc.
│   │       ├── runtime_control/ # DoEvents, Stop, End, etc.
│   │       ├── runtime_state/   # Date, Time assignment, etc.
│   │       ├── string_manipulation/ # Mid statement, etc.
│   │       ├── system_interaction/  # Beep, etc.
│   │       └── ...
│   ├── statements/              # Statement parsing logic
│   │   ├── control_flow/        # If, Select Case, For, While parsers
│   │   ├── declarations/        # Dim, ReDim, Const, Enum parsers
│   │   └── objects/             # Set, With, RaiseEvent parsers
│   └── expressions/             # Expression parsing utilities
│
├── parsers/                     # Parsers Layer - CST construction
│   ├── cst/                     # Concrete Syntax Tree implementation
│   │   ├── mod.rs               # parse(), ConcreteSyntaxTree, CstNode
│   │   └── rowan_wrapper.rs     # Red-green tree wrapper
│   ├── parseresults.rs          # ParseResult<T, E> type
│   └── syntaxkind.rs            # SyntaxKind enum (all token types)
│
├── files/                       # Files Layer - VB6 file format parsers
│   ├── common/                  # Shared parsing utilities
│   │   ├── properties.rs        # Property bag, PropertyGroup
│   │   ├── attributes.rs        # Attribute statement parsing
│   │   └── references.rs        # Object reference parsing
│   ├── project/                 # VBP - Project files
│   │   ├── mod.rs               # ProjectFile struct and parser
│   │   ├── properties.rs        # Project properties
│   │   ├── references.rs        # Reference types
│   │   └── compilesettings.rs   # Compilation settings
│   ├── class/                   # CLS - Class modules
│   ├── module/                  # BAS - Code modules
│   ├── form/                    # FRM - Forms
│   └── resource/                # FRX - Form resources
│
├── language/                    # Language Layer - VB6 types and definitions
│   ├── color.rs                 # VB6 color constants and Color type
│   ├── controls/                # VB6 control definitions (50+ controls)
│   │   ├── mod.rs               # Control, ControlKind enums
│   │   ├── form.rs              # FormProperties
│   │   ├── textbox.rs           # TextBoxProperties
│   │   ├── label.rs             # LabelProperties
│   │   └── ...                  # 50+ control types
│   └── tokens.rs                # Token enum definition
│
├── errors/                      # Errors Layer - Error types
│   ├── mod.rs                   # ErrorDetails, error printing
│   ├── decode.rs                # SourceFileErrorKind
│   ├── tokenize.rs              # CodeErrorKind
│   ├── project.rs               # ProjectErrorKind
│   ├── class.rs                 # ClassErrorKind
│   ├── module.rs                # ModuleErrorKind
│   ├── form.rs                  # FormErrorKind
│   ├── property.rs              # PropertyError
│   └── resource.rs              # ResourceErrorKind
│
└── lib.rs                       # Public API surface

Common Tasks

1. Extract All Form Controls

use vb6parse::language::Control;
use vb6parse::*;

fn extract_controls(form_path: &str) -> Vec<String> {
    let source = SourceFile::from_file(form_path).unwrap();
    let result = FormFile::parse(&source);
    let (form, _) = result.unpack();

    let mut control_names = Vec::new();

    if let Some(formfile) = form {
        fn visit_control(control: &Control, names: &mut Vec<String>) {
            names.push(control.name().to_string());

            // Recursively visit children
            if let Some(children) = control.kind().children() {
                for child in children {
                    visit_control(child, names);
                }
            }
        }

        for control in formfile.form.children().unwrap() {
            visit_control(control, &mut control_names);
        }
    }

    control_names
}

2. Analyze Code Without Full Parsing

use vb6parse::*;

fn count_identifiers(code: &str, function_name: &str) -> usize {
    let mut source_stream = SourceStream::new("temp.bas", code);
    let result = tokenize(&mut source_stream);
    let (tokens, _) = result.unpack();

    tokens
        .map(|ts| {
            ts.filter(|(text, token)| {
                *token == language::Token::Identifier && text.eq_ignore_ascii_case(function_name)
            })
            .count()
        })
        .unwrap_or(0)
}

Advanced Topics

Error Handling

VB6Parse uses a custom ParseResult<T, E> type that separates successful results from recoverable errors:

use vb6parse::*;

let result = ProjectFile::parse(&source);

// Option 1: Unpack into result and failures
let (project_opt, failures) = result.unpack();

// Option 2: Check for failures first
if result.has_failures() {
    for failure in result.failures() {
        eprintln!("Error at line {}: {:?}", failure.error_offset, failure.kind);
    }
}

// Option 3: Convert to Result<T, Vec<ErrorDetails>>
let std_result = result.ok_or_errors();

See also:

src/parsers/parseresults.rs - ParseResult implementation
src/errors/mod.rs - Error types and ErrorDetails

Working with the CST

The Concrete Syntax Tree preserves all source information including whitespace and comments:

use vb6parse::*;

let tree = parse(token_stream);

// Navigate the tree
let root = tree.to_root_node();
for child in root.children() {
    println!("Node: {:?}", child.kind());
    println!("Text: {}", child.text());
}

// Serialize for debugging
let serializable = tree.to_serializable();
println!("{:#?}", serializable);

See also:

src/parsers/cst/mod.rs - CST documentation
examples/cst_parse.rs - CST parsing example
examples/debug_cst.rs - CST debugging

Character Encoding

VB6 uses Windows-1252 encoding. Always use decode_with_replacement() for file content:

use vb6parse::*;

// From bytes (e.g., file read)
let bytes = std::fs::read("file.bas")?;
let source = SourceFile::decode_with_replacement("file.bas", &bytes).unwrap();

// From UTF-8 string (testing/programmatic)
let source = SourceFile::from_string("test.bas", "Dim x As Integer");

See also:

src/io/decode.rs - Decoding implementation
examples/parse_class.rs - Byte-level parsing

VB6 Library Functions

VB6Parse includes full definitions for 160+ VB6 library functions organized into 14 categories:

// Access function metadata
use vb6parse::syntax::library::functions::string::left;
use vb6parse::syntax::library::functions::math::sin;
use vb6parse::syntax::library::functions::conversion::cint;

// Each module includes:
// - Full VB6 documentation
// - Function signatures
// - Parameter descriptions
// - Usage examples
// - Related functions

Categories:

Array manipulation (Array, Filter, Join, Split, UBound, LBound)
Conversion (CBool, CDate, CInt, CLng, CStr, Val, Str)
Date/Time (Date, Time, Now, Year, Month, Day, Hour, DateAdd, DateDiff)
File System (Dir, EOF, FileLen, FreeFile, LOF, Seek)
Financial (FV, IPmt, IRR, NPV, PV, Rate)
Formatting (Format, FormatCurrency, FormatDateTime, FormatNumber, FormatPercent)
Interaction (MsgBox, InputBox, Shell, CreateObject, GetObject)
Inspection (IsArray, IsDate, IsEmpty, IsNull, IsNumeric, TypeName, VarType)
Math (Abs, Atn, Cos, Exp, Log, Rnd, Sgn, Sin, Sqr, Tan)
String (Left, Right, Mid, Len, InStr, Replace, Trim, UCase, LCase)
And more...

See also: src/syntax/library/functions/

Form Resources (FRX Files)

Form resource files contain binary data for controls (images, icons, property blobs):

use vb6parse::*;

// Option 1: load bytes and hand to FormResourceFile to handle.
let bytes = std::fs::read("Form1.frx")?;
let result = FormResourceFile::parse("Form1.frx", bytes);

// Option 2: Load directly from file.
let result = FormResourceFile::from_file("Form1.frx")?;

let (resource, _failures) = result.unpack();
if let Some(resource) = resource {
    for (offset, data) in resource.iter_entries() {
        println!(
            "Resource at offset {}: {} bytes",
            offset,
            data.as_bytes().unwrap().len()
        );
    }
}

See also:

docs/technical/frx-format.html - FRX format specification
examples/debug_resource.rs - Resource file debugging

Testing

VB6Parse has comprehensive test coverage.

📊 View Test Coverage Report

Running Tests

# Clone test data (required for integration tests)
git submodule update --init --recursive

# Run all tests
cargo test

# Run only library tests
cargo test --lib

# Run only integration tests
cargo test --test '*'

# Run documentation tests
cargo test --doc

Snapshot Testing

Integration tests use insta for snapshot testing:

# Review snapshot changes
cargo insta review

# Accept all snapshots
cargo insta accept

Test data location: tests/data/ (git submodules of real VB6 projects)

See also:

Benchmarking

VB6Parse includes criterion benchmarks for performance testing:

# Run all benchmarks
cargo bench

# Run specific benchmark
cargo bench bulk_parser_load

# Generate HTML reports
# Results saved to target/criterion/

Benchmarks:

bulk_parser_load - Parsing multiple large VB6 projects
Token stream generation
CST construction

See also:

benches/ - Benchmark source code
📈 View Benchmark Results

Code Coverage

VB6Parse uses cargo-llvm-cov to track test coverage and ensure comprehensive testing across all modules.

Installation

# Install cargo-llvm-cov
cargo install cargo-llvm-cov

Running Coverage

# Generate coverage report (terminal output)
cargo llvm-cov

# Generate HTML report
cargo llvm-cov --html
# Open target/llvm-cov/html/index.html in your browser

# Generate coverage with open HTML report
cargo llvm-cov --open

# Generate detailed coverage for specific packages
cargo llvm-cov --package vb6parse

# Include tests in coverage
cargo llvm-cov --all-targets

# Generate LCOV format (for CI/CD integration)
cargo llvm-cov --lcov --output-path lcov.info

Coverage Reports

Coverage reports are saved to:

HTML reports: target/llvm-cov/html/
Terminal summary: Displays percentage coverage after running cargo llvm-cov
LCOV files: lcov.info (when using --lcov flag)

Current Coverage:

Library tests: 5,467 tests covering VB6 library functions
Integration tests: 31 tests with real-world VB6 projects
Documentation tests: 83 tests ensuring examples work
Coverage focus: Parsers, tokenization, error handling, and file format support

Contributing to VB6Parse

Contributions are welcome! Please see the CONTRIBUTING.md file for more information.

Development Setup

# Clone repository
git clone https://github.com/scriptandcompile/vb6parse
cd vb6parse

# Get test data
git submodule update --init --recursive

# Run tests
cargo test

# Run benchmarks
cargo bench

# Check for issues
cargo clippy

# Format code
cargo fmt

Code Organization Guidelines

Layer Separation: Keep clear boundaries between layers
Windows-1252 Handling: Always use SourceFile::decode_with_replacement()
Error Recovery: Parsers should recover from errors when possible
CST Fidelity: Preserve all source text including whitespace and comments
Documentation: Include doc tests for public APIs

Adding New Features

VB6 Library Functions:

Add to appropriate category in src/syntax/library/functions/
Include full VB6 documentation
Add comprehensive tests
Update category mod.rs

Control Types:

Add to src/language/controls/
Define properties struct
Add to ControlKind enum
Include property validation

Error Types:

Add to appropriate error module in src/errors/
Ensure Display implementation
Add context information

Performance Considerations

Use zero-copy where possible (string slices, not String)
Avoid unnecessary allocations (use iterators)
Leverage rowan's red-green tree for CST memory efficiency
Use phf crate for compile-time lookup tables

See also:

CHANGELOG.md - Version history

Supported File Types

Extension	Description	Status
`.vbp`	Project files	✅ Complete
`.cls`	Class modules	✅ Complete
`.bas`	Code modules	✅ Complete
`.frm`	Forms	⚠️ Partial (font, some icons, etc)
`.frx`	Form resources	⚠️ Partial (binary blobs loaded, not all mapped to properties)
`.ctl`	User controls	✅ Parsed as forms
`.dob`	User documents	✅ Parsed as forms
`.vbw`	IDE window state	❌ Not yet implemented
`.dsx`	Data environments	❌ Not yet implemented
`.dsr`	Data env. resources	❌ Not yet implemented
`.ttx`	Crystal reports	❌ Not yet implemented

Project Status

✅ Core Parsing: Fully implemented for VBP, CLS, BAS files
✅ Tokenization: Complete with keyword lookup
✅ CST Construction: Full syntax tree with source fidelity
✅ Error Handling: Comprehensive error types and recovery
✅ VB6 Library: 160+ functions, 42 statements documented
⚠️ FRX Resources: Binary loading complete, property mapping partial
⚠️ FRM Properties: Majority of FRM properties load properly, (icon, background, font mapping partial)
❌ AST: Not yet implemented (CST available)
✅ Testing: 5,500+ tests across unit, integration, and doc tests
✅ Benchmarking: Criterion-based performance testing
✅ Fuzz Testing: Coverage-guided fuzzing with cargo-fuzz
✅ Documentation: Comprehensive API docs and examples

Fuzz Testing

VB6Parse includes comprehensive fuzz testing using cargo-fuzz and libFuzzer to discover edge cases, crashes, and undefined behavior.

Available Fuzz Targets:

sourcefile_decode - Tests Windows-1252 decoding with arbitrary bytes
sourcestream - Tests low-level character stream operations
tokenize - Tests tokenization with malformed VB6 code
cst_parse - Tests Concrete Syntax Tree parsing with invalid syntax

Quick Start:

# Install cargo-fuzz (requires nightly)
cargo install cargo-fuzz

# Run a fuzzer for 60 seconds
cargo +nightly fuzz run sourcefile_decode -- -max_total_time=60

# List all fuzz targets
cargo +nightly fuzz list

Learn More: See fuzz/README.md for detailed usage.

Examples

All examples are located in the examples/ directory:

Example	Description
audiostation_parse.rs	Parse a complete real-world VB6 project
cst_navigation.rs	Navigate and query the Concrete Syntax Tree
cst_parse.rs	Parse tokens directly to CST
debug_cst.rs	Display CST debug representation
debug_resource.rs	Inspect FRX resource files
parse_class.rs	Parse class files from bytes
parse_control_only.rs	Parse individual form controls
parse_form.rs	Parse VB6 forms
parse_module.rs	Parse code modules
parse_project.rs	Parse project files
sourcestream.rs	Work with character streams
tokenstream.rs	Tokenize VB6 code

Run any example with:

cargo run --example parse_project

Resources

Documentation: docs.rs/vb6parse
Repository: github.com/scriptandcompile/vb6parse
Crates.io: crates.io/crates/vb6parse
License: MIT

Limitations

Encoding: Primarily designed for "predominantly English" source code with Windows-1252 encoding detection limitations
AST: Abstract Syntax Tree is not yet implemented (Concrete Syntax Tree is available)
FRX Mapping: Binary resources are loaded but not all are mapped to control properties
Real-time Use: While capable, not optimized for real-time highlighting or LSP (focus is on offline analysis)

License

MIT License - See LICENSE file for details.

Built with ❤️ by ScriptAndCompile

Name		Name	Last commit message	Last commit date
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.github		.github
benches		benches
docs		docs
examples		examples
fuzz		fuzz
scripts		scripts
snapshots		snapshots
src		src
tests		tests
.gitignore		.gitignore
.gitmodules		.gitmodules
CHANGELOG.md		CHANGELOG.md
CONTRIBUTING.md		CONTRIBUTING.md
Cargo.toml		Cargo.toml
LICENSE		LICENSE
README.md		README.md
deny.toml		deny.toml

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VB6Parse

Overview

Quick Start

Parse a VB6 Project File

Parse a VB6 Module

Tokenize VB6 Code

Parse to Concrete Syntax Tree

Navigating the CST

API Surface

Top-Level Imports

Layer Modules (Advanced Usage)

Parsing Architecture

Source Code Organization

Common Tasks

1. Extract All Form Controls

2. Analyze Code Without Full Parsing

Advanced Topics

Error Handling

Working with the CST

Character Encoding

VB6 Library Functions

Form Resources (FRX Files)

Testing

Running Tests

Snapshot Testing

Benchmarking

Code Coverage

Installation

Running Coverage

Coverage Reports

Contributing to VB6Parse

Development Setup

Code Organization Guidelines

Adding New Features

Performance Considerations

Supported File Types

Project Status

Fuzz Testing

Examples

Resources

Limitations

License

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