module-lang 0.2.0

Installation

[dependencies]
module-lang = "0.2"

Or from the terminal:

cargo add module-lang

Usage

Build a graph with one module per source file, define the items each exports, wire the imports between them, and resolve a name to the payload it refers to. The payload type is yours — a definition id, an AST node, a type — written here as &str for illustration.

use intern_lang::Interner;
use module_lang::{ModuleGraph, ResolveError, Visibility};
use source_lang::SourceMap;

// Two files, each a module: `app` uses an item exported by `util`.
let mut sources = SourceMap::new();
let app_src = sources.add("app.lang", "use util.helper;")?;
let util_src = sources.add("util.lang", "pub fn helper() {}")?;

let mut names = Interner::new();
let helper = names.intern("helper");

let mut graph: ModuleGraph<&str> = ModuleGraph::new();
let app = graph.add_module(names.intern("app"), app_src);
let util = graph.add_module(names.intern("util"), util_src);

graph.define(util, helper, Visibility::Public, "fn helper")?;
graph.import(app, util, helper)?;

// The import resolves through to the definition in `util`.
assert_eq!(graph.resolve(app, helper), Ok(&"fn helper"));

// A name nobody declared is a defined error, never a panic.
let missing = names.intern("nope");
assert!(matches!(graph.resolve(app, missing), Err(ResolveError::Unresolved { .. })));
# Ok::<(), Box<dyn std::error::Error>>(())

Visibility gates crossing a module boundary, not seeing a module's own names. A module reaches its own private items; an import from elsewhere does not:

use intern_lang::Interner;
use module_lang::{ModuleGraph, ResolveError, Visibility};
use source_lang::SourceMap;

let mut sources = SourceMap::new();
let mut names = Interner::new();
let mut graph: ModuleGraph<()> = ModuleGraph::new();

let lib = graph.add_module(names.intern("lib"), sources.add("lib", "")?);
let app = graph.add_module(names.intern("app"), sources.add("app", "")?);
let secret = names.intern("secret");

graph.define(lib, secret, Visibility::Private, ())?;
assert!(graph.resolve(lib, secret).is_ok());           // visible at home

graph.import(app, lib, secret)?;
assert!(matches!(                                       // not through an import
    graph.resolve(app, secret),
    Err(ResolveError::Private { .. }),
));
# Ok::<(), Box<dyn std::error::Error>>(())

Imports chain — a module may re-export what it imported — and a chain that loops back is reported as a cycle in bounded time rather than recursing without end:

use intern_lang::Interner;
use module_lang::{ModuleGraph, ResolveError, Visibility};
use source_lang::SourceMap;

let mut sources = SourceMap::new();
let mut names = Interner::new();
let mut graph: ModuleGraph<()> = ModuleGraph::new();

let a = graph.add_module(names.intern("a"), sources.add("a", "")?);
let b = graph.add_module(names.intern("b"), sources.add("b", "")?);
let x = names.intern("x");

// a imports x from b, b imports x from a: a closed loop with no definition.
graph.import(a, b, x)?;
graph.import(b, a, x)?;
assert!(matches!(graph.resolve(a, x), Err(ResolveError::ImportCycle { .. })));
# Ok::<(), Box<dyn std::error::Error>>(())

See docs/API.md for the full reference.

How it works

A ModuleGraph holds one module per source file, each carrying the SourceId it was read from and a flat namespace of names. A name is declared at most once per module — a second definition or a colliding import is a defined error. Names live in a BTreeMap keyed on the interned Symbol, so a lookup compares integers in O(log items) and iteration is deterministic.

Resolution treats a module's own names as fully visible, public or private. Crossing a module boundary through an import is where visibility applies: an import reaches a name in another module only if it is public. The walk along an import chain is iterative and tracks the (module, name) pairs it has seen, so a loop is reported as a cycle rather than overflowing the stack, and a local hit allocates nothing.

Status

v0.2.0 lands the resolution core: ModuleGraph with stable ModuleIds, define/import/resolve, visibility, and import-cycle detection, wiring symbol-lang for the name key and source-lang for the file each module came from. Every invariant is property-tested against a naive reference resolver and verified on Linux, macOS, and Windows. The public API is not yet frozen — it stabilises at 1.0.0; until then a minor release may make a breaking change, each documented in the CHANGELOG.

Contributing

See dev/DIRECTIVES.md for engineering standards and the definition of done. Before a PR: cargo fmt --all, cargo clippy --all-targets --all-features -- -D warnings, and cargo test --all-features must be clean.