Syster Base

Core library for SysML v2 and KerML parsing, AST, semantic analysis, and model interchange.

Features

• Parser: Lossless incremental parser using logos (lexer) and rowan (CST)
• AST: Typed wrappers over a lossless Concrete Syntax Tree
• Incremental Semantic Analysis: Salsa-powered query system with automatic memoization
• Name Resolution: Scope-aware resolver with import and alias handling
• IDE Features: Completion, hover, goto-definition, find-references, semantic tokens, and more
• Standard Library: Bundled SysML v2 standard library files
• Interchange (feature-gated): Export/import via XMI, YAML, JSON-LD, KPAR; programmatic model editing with ID round-trip

Architecture

Module Stack

Layers are listed in dependency order — each depends only on the layers below it.

ide           → IDE features (completion, hover, goto-def, references, …)
  ↓
hir           → Semantic model with Salsa queries
  ↓
project       → Workspace loading, stdlib resolution
  ↓
syntax        → AST types, formatter, Span/Position
  ↓
parser        → logos lexer, rowan CST, recursive-descent parser
  ↓
base          → Primitives (FileId, Name interning, TextRange)

interchange   → (feature-gated) Model, views, editing, render, format I/O

Parser Pipeline

Source Text
    ↓
Lexer (logos) → Token stream with SyntaxKind
    ↓
Parser → GreenNode tree (immutable, cheap to clone)
    ↓
SyntaxNode (rowan) → Lossless CST with parent pointers
    ↓
AST layer → Typed wrappers over SyntaxNode
    ↓
HIR extraction → HirSymbol[] per file

The CST preserves all whitespace and comments, enabling exact formatting and incremental reparsing.

Query Layers (Salsa)

file_text(file)           ← INPUT: raw source text
    │
    ▼
parse(file)               ← Parse into AST (memoized per-file)
    │
    ▼
file_symbols(file)        ← Extract HIR symbols (memoized per-file)
    │
    ▼
symbol_index              ← Workspace-wide name index
    │
    ▼
resolve_name(scope, name) ← Name resolution with imports
    │
    ▼
file_diagnostics(file)    ← Semantic errors

Key Types

Modules

Interchange Submodules

Enabled with cargo build --features interchange. See ARCHITECTURE.md for detailed diagrams.

Usage

use syster::hir::{RootDatabase, FileText, parse_file, file_symbols};
use syster::base::FileId;

// Create the Salsa database
let db = RootDatabase::new();

// Set file content (input query)
let file_id = FileId::new(0);
let file_text = FileText::new(&db, file_id, r#"
    package Vehicle {
        part def Car {
            attribute mass : Real;
        }
    }
"#.to_string());

// Parse (memoized — subsequent calls are instant)
let parse_result = parse_file(&db, file_text);
assert!(parse_result.is_ok());

// Extract symbols (also memoized)
if let Some(ast) = parse_result.get_ast() {
    let symbols = file_symbols(file_id, ast);
    // symbols contains: Vehicle (package), Car (part def), mass (attribute)
}

Using the IDE Layer

use syster::ide::AnalysisHost;

let mut host = AnalysisHost::new();
host.set_file_content("test.sysml", "package Test { part def A; }");

let analysis = host.analysis();  // read-only snapshot
let symbols = analysis.document_symbols(file_id);
let completions = analysis.completions(file_id, position);

Using the Interchange Layer

use syster::interchange::{Xmi, ModelFormat, ModelHost};

// Load from XMI
let model = Xmi.read(&xmi_bytes)?;

// Or build from SysML text
let host = ModelHost::from_text("package P { part def A; }")?;
for view in host.root_views() {
    println!("{:?}", view.name());
}

Performance

The architecture provides significant performance benefits:

• Incremental parsing: rowan green nodes are immutable and shared — only changed subtrees are re-parsed
• Memoized queries: Salsa caches all query results; invalidation is automatic and minimal
• O(1) comparisons: Interned FileId and Name enable constant-time equality
• Reduced allocations: String interning shares storage across the codebase
• Incremental rendering: render_dirty() patches only changed model regions

Building

# Core library only
cargo build
cargo test

# With interchange support (decompiler, XMI, YAML, JSON-LD, KPAR)
cargo build --features interchange
cargo test --features interchange

Testing

# All tests (lib + integration, with interchange)
cargo test --features interchange

# Library tests only (425 tests — parser, HIR, IDE, interchange internals)
cargo test --features interchange --lib

# Integration tests only (226 tests — editing, roundtrip, decompiler coverage)
cargo test --test test_editing_integration --features interchange

# Run a specific integration test by name
cargo test --test test_editing_integration --features interchange decompile_drops_anonymous_usage

# Run a group of tests by prefix
cargo test --test test_editing_integration --features interchange decompile_

# Core tests without interchange
cargo test

Linting & Formatting

# Format code
cargo fmt

# Check formatting (CI)
cargo fmt -- --check

# Clippy with interchange
cargo clippy --all-targets --features interchange -- -D warnings

# Full validation pipeline (format + lint + test)
make run-guidelines

License

MIT