context-engine

Data labels used by a web system's runtime within a single processing cycle should have their session-context-dependent variations resolved outside of code (e.g., system_context["session.user"] rather than users[session[user_id]]). context-engine processes the data retrieval methods that application developers define as a DSL in YAML files, for each label. This allows server/store differences in system_context["session.user.preference"] and multi-tenant differences in context["session.user.tenant"] to be resolved appropriately through the methods defined in YAML.

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Version

Version	Status	Date	Description
0.1	Released	2026-2-12	-
0.1.6	Previous	2026-4-23	improve #57
0.1.7	Current	2026-9-29	improve #1

This project adheres to Semantic Versioning.

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Provided Functions

Mod	Description	fn
Context	operates context	new/get/set/delete/exists

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Why context-engine?

Before:

// Manual cache management
let session_key = format!("user:{}", id);
let user = redis.get(&session_key).or_else(|| {
    let user = db.query("SELECT id, email, name FROM users WHERE id=?", id)?;
    redis.set(&session_key, &user, 3600);
    Some(user)
})?;

After:

let user = state.get("session.user.name")?;

---

Quick Start

1. Add to dependencies.

# Cargo.toml
[dependencies]
context-engine = "0.1"

2. Write a yaml file.

# mine.yml
session:
  user:
    id:
      _get:
        store: Memory
        key: "request.authorization.user.id"
    name:
      _get:
        store: Db
        key: "users.${session.user.id}.name"

Case	Example
multi-tenant app	tenant.yml

3. Implement Store and StoreRegistry for your stores.

Trait	Description	Example
Store	get() set() delete()	TenantDbClient
Stores	maps YAML store names to Stores	MyStore

4. Precompile your yaml to a rs file.

cargo run --example precompile --features precompile -- examples/mine.yml src/dsl_compiled.rs
# -- <input.yml: required> <output.rs: optional>
# store: values are collected from the yaml in order of first appearance;
# the resulting order (and matching STORE_IDS constant) is printed and baked into the output.

5. Initialize Context with your registry.

use context_engine::{Context, Index};
use std::sync::Arc;

// Include the precompiled static data
include!("generated.rs");

let index = Arc::new(Index::new(
    Box::from(PATHS),
    Box::from(CHILDREN),
    Box::from(LEAVES),
    Box::from(INTERNING),
    Box::from(INTERNING_IDX),
));

let registry = MyRegistry::new();
let mut context = Context::new(index, &registry);

// --- setup completed ---

let user_name = context.get("session.user.name")?;

---

Architecture

┌─────────────┐        ┌─────────────────────────────────┐
│ DSL YAML    │------->│ Index (app global instance)     │
└─────────────┘compile └──────────┬──────────────────────┘
                                  │
                                  ▼
┌─────────────┐        ┌─────────────────────────────────┐
│ Application │<-------│ Context (request scope instance)│
└─────────────┘ provide└─────────────────────────────────┘
                                  ▲
                                  │
┌─────────────┐        ┌──────────┴──────────────────────┐
│ StoreImpls  │------->│ Stores (required to impl)       │
└─────────────┘register└─────────────────────────────────┘

See for details Architecture.md

Test

Passed unit and integration tests

# unit test
cargo test

# integration test (includes precompile path verification)
RUST_LOG=debug cargo run --example precompile --features precompile -- examples/tenant.yml src/dsl_compiled.rs && RUST_LOG=debug cargo run --example integration_tests --features precompile

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License

SPDX-License-Identifier: Apache-2.0 Copyright (c) 2026 Andyou andyou@animagram.jp