stemedb/CODING_GUIDELINES.md

Rust Coding Guidelines

Core Stack

Component	Required	Forbidden
Error handling	thiserror (lib), anyhow (bin)	.unwrap(), .expect(), panic!
Serialization	rkyv (zero-copy)	serde_json for hot paths
Hashing	blake3	sha256, md5
KV Store	sled (MVP), trait-abstracted	Direct rocksdb coupling
Async	tokio (if needed)	async-std
Logging	tracing	log, println!
Testing	proptest, rstest	Mocking core types

Error Handling

// Library errors: use thiserror
#[derive(Debug, thiserror::Error)]
pub enum StemeError {
    #[error("assertion not found: {0}")]
    NotFound(Hash),

    #[error("invalid signature for agent {agent}")]
    InvalidSignature { agent: AgentId },

    #[error("storage error: {0}")]
    Storage(#[from] sled::Error),
}

// Always add context
fn load_assertion(hash: &Hash) -> Result<Assertion, StemeError> {
    let bytes = self.store
        .get(hash)
        .context("failed to read from store")?
        .ok_or(StemeError::NotFound(*hash))?;
    // ...
}

Type Safety

Use newtypes for domain IDs:

// Good: Strong types
pub struct EntityId(pub String);
pub struct RelationId(pub String);
pub struct Hash(pub [u8; 32]);
pub struct AgentId(pub [u8; 32]);

// Bad: Stringly-typed
fn query(subject: String, predicate: String) -> ...

Formatting

• Use underscores in numbers: 1_000_000 not 1000000
• Use inline interpolation: println!("{hash:?}") not println!("{:?}", hash)
• Max line length: 100 characters
• Run cargo fmt before commit

Testing

#[cfg(test)]
mod tests {
    use super::*;
    use proptest::prelude::*;

    // Property test for critical invariants
    proptest! {
        #[test]
        fn assertion_round_trips(bytes in prop::collection::vec(any::<u8>(), 0..1000)) {
            let assertion = /* create from bytes */;
            let serialized = rkyv::to_bytes(&assertion)?;
            let deserialized = rkyv::from_bytes(&serialized)?;
            assert_eq!(assertion, deserialized);
        }
    }

    // Descriptive test names
    #[test]
    fn test_lens_consensus_returns_highest_vote_count() {
        // Arrange
        let assertions = vec![/* ... */];

        // Act
        let result = ConsensusLens.resolve(&assertions, &ctx);

        // Assert
        assert_eq!(result.value, expected);
    }
}

Module Structure

crates/stemedb-core/
  src/
    lib.rs           # Public API, re-exports
    assertion.rs     # Assertion struct
    types.rs         # EntityId, RelationId, Hash, etc.
    store.rs         # Storage trait
    error.rs         # StemeError
  tests/
    integration.rs   # Cross-module tests

Documentation

/// Resolves conflicting assertions using weighted voting.
///
/// # Arguments
/// * `candidates` - All assertions matching the query
/// * `context` - Query context including agent reputations
///
/// # Returns
/// The assertion with highest weighted support, or None if empty.
///
/// # Example
/// ```
/// let lens = ConsensusLens::default();
/// let result = lens.resolve(&assertions, &ctx);
/// ```
pub fn resolve(&self, candidates: &[Assertion], context: &QueryContext) -> Option<Assertion> {
    // ...
}

Clippy

Must pass with zero warnings:

cargo clippy --workspace -- -D warnings

Common fixes:

• needless_return: Remove explicit return when implicit works
• redundant_clone: Check if clone is actually needed
• missing_docs: Add doc comments to public items