VPL Parser

Lexing and parsing for the VPL streaming analytics language.

This crate transforms VPL source code into an Abstract Syntax Tree (AST) that can be executed by the runtime engine.

Features

• Complete VPL grammar support
• Detailed error messages with line/column information
• Syntax hints for common mistakes
• PEG-based parsing via Pest

Modules

• [pest_parser]: Main parser implementation using Pest PEG grammar
• [lexer]: Token definitions (used for syntax highlighting)
• [error]: Parse error types with location information
• [helpers]: Parsing utility functions
• [indent]: Indentation handling

Quick Start

use varpulis_parser::parse;

let source = r#"
    stream Readings = SensorReading
        .where(temperature > 100)
        .emit(alert("HighTemp", "Temperature exceeded threshold"))
"#;

match parse(source) {
    Ok(program) => {
        println!("Parsed {} statements", program.statements.len());
    }
    Err(e) => {
        eprintln!("Parse error: {}", e);
    }
}

Error Handling

Parse errors include detailed location information:

use varpulis_parser::{parse, ParseError};

let result = parse("stream X form Y");  // Typo: "form" instead of "from"
if let Err(ParseError::Located { line, column, message, hint, .. }) = result {
    println!("Error at {}:{}: {}", line, column, message);
    if let Some(h) = hint {
        println!("Hint: {}", h);
    }
}

Grammar

The VPL grammar is defined in varpulis.pest and supports:

• Stream declarations with filtering, selection, windowing, and aggregation
• Event type definitions
• SASE+ pattern declarations (sequences, Kleene closures, negation)
• User-defined functions
• Configuration blocks
• Control flow (if/elif/else, for, while)
• Expressions with operators and function calls

See Also

• varpulis_core: AST types produced by the parser
• varpulis_runtime: Executing parsed programs