Async-only chain-based variable lookup engine, support no_std with alloc.

varchain provides a flexible way to resolve variables from a prioritized chain of sources (e.g., in-memory maps, environment variables, network lookups) without enforcing a specific runtime.

• Async-Only: Designed for asynchronous contexts from the ground up, compatible with any runtime (Tokio, async-std, smol, etc.) or just core::future.
• Flexible Sources: Easy implementation of custom sources via the Source trait.
• Composability: Build lookup scopes by chaining multiple sources with strict precedence.

Check the examples directory for runnable code:

• HashMap Source: examples/hashmap.rs - Simple memory-based lookup.
• ahash Source: examples/ahash.rs - Use AHashMap for high-performance hashing.
• Closure Source: examples/closure.rs - Use functions for dynamic lookups.
• Chained Priority: examples/chain.rs - Demonstrate fallback and precedence.
• Custom Source: examples/custom_source.rs - Implement the Source trait for async backends.

[dependencies]
varchain = { version = "0.1", features = ["full"] }

Released under the MIT License © 2026 Canmi