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AGENTS.md

Guidance for AI coding agents working in this repository.

General Rules

  • Use English in repository files: code, comments, commit messages, PR titles, PR bodies, and technical docs.
  • Add comments only when they explain non-obvious intent or constraints.
  • Add tests when they verify real behavior or guard a regression; do not add placeholder tests.
  • Do not change public APIs or behavior tests unless the task explicitly requires it.

AI-Assisted Contributions

Follow AI-Assisted Contributions policy.

  • Do not publish an Issue, Pull Request, Discussion, or review comment unless a human has meaningfully reviewed the content and explicitly asked you to submit it.
  • Do not implement or submit a service-specific change based only on source-code analysis, a mock or emulator, a synthetic malformed response, or another service's implementation. Reproduce the problem against the actual service first.
  • If actual-service reproduction is unavailable, stop before changing code or opening a Pull Request. Raise the hypothesis in a Discussion unless a maintainer has explicitly accepted it as a hardening or maintenance goal.
  • A test against a fabricated response can verify implementation behavior, but it does not establish that the change solves a real-world problem.
  • In a Pull Request, disclose each materially contributing harness, model, and reasoning effort setting, along with AI's role and any assumptions or unknowns that affect review. Follow the AI Usage Statement requirements in CONTRIBUTING.md. Do not repeat routine validation output.

The human contributor remains responsible for every submitted claim and change.

Helper Functions

  • Extract a helper only when it owns a stable, cohesive responsibility, such as a non-trivial invariant or algorithm, shared protocol encoding with identical semantics, a state-machine transition, or a trait or interface boundary.
  • Do not introduce an intermediate type or helper merely to deduplicate a short condition, merge, forwarding step, request parameter, or error mapping. Prefer a few duplicated lines when they keep each operation easier to read and maintain in isolation.
  • Keep operation-specific validation, lowering, request construction, and response handling at the dispatch, request-builder, or response-processing boundary that owns the behavior. A reader should be able to see how one operation maps its options without following a chain of generic helpers.
  • Before sharing code, verify that the call sites have the same contract, inputs, failure semantics, and reasons to change. Similar syntax alone does not justify an abstraction.
  • Reuse an existing helper only when it already expresses the same contract. Do not broaden it with operation-specific branches merely to obtain reuse.

Documentation Style

  • Prefer active voice. Name the type or component that performs an action, for example, “RetryLayer retries failed operations.”
  • Use direct, present-tense sentences.
  • Lead with what a public type or method does, then explain important constraints, defaults, and behavior.
  • Describe API semantics precisely. Verify option types, capability requirements, error behavior, and overwrite or versioning semantics against the implementation.
  • Keep terminology consistent with the codebase, especially service, layer, operator, storage and operation.
  • Use parallel structure in lists and punctuate complete sentences consistently.

Documentation Architecture

OpenDAL splits documentation by audience. The website carries only content that holds for OpenDAL across languages; Rust-specific documentation lives in rustdoc.

  • core/core/src/docs/specs/ contains the living portable contracts, the one set of documents published to both destinations. Rustdoc publishes them under opendal::docs::specs; the website reads the same Markdown at /docs/specifications/.
  • core/core/src/docs/concepts.rs, core/core/src/docs/internals/, and core/core/src/docs/performance/ contain the Rust core guides: Rust types, traits, implementation architecture, runtime resources, and transport tuning. They are rustdoc-only; do not publish them on the website.
  • website/docs/ contains cross-language concepts and non-normative guidance, plus the per-language guides. Content there must hold for OpenDAL as a whole. Do not present Rust implementation detail as cross-language behavior, and do not claim every binding exposes a feature (layers, builders, concurrency controls) unless the bindings demonstrate it.
  • core/core/src/docs/rfcs/ contains immutable accepted design history. An accepted RFC records the proposal that reached consensus; update a specification, not the accepted RFC, when the current contract changes.
  • core/core/src/docs/upgrade.md contains upgrade procedures, and CHANGELOG.md contains the release changelog. Rustdoc exposes them through opendal::docs.
  • website/docusaurus.config.js and website/specifications.sidebars.js define website publication and navigation for the specifications. Do not add a website section that republishes rustdoc content, and do not copy specifications into website/docs/.

Public API documentation under core/core/src/types/ must explain the observable behavior, capability requirements, and relevant errors at the API site. Link to a specification only after the local API contract is self-contained.

Rust Workspace Commands

The Rust workspace for OpenDAL core lives under core/. There is no root Cargo.toml; run core cargo commands from core/.

cd core

# Check and build
cargo check
cargo build --locked
cargo build --all-features --locked

# Lint, matching Core CI
cargo clippy --workspace --all-targets --all-features -- -D warnings

# Lint a focused service/layer feature set
cargo clippy --all-targets --features=services-s3 -- -D warnings

# Unit tests, matching Core CI
cargo nextest run --workspace --no-fail-fast --all-features

# Doc tests and docs
cargo test --workspace --doc --all-features
cargo doc --lib --no-deps --all-features

# Behavior tests
OPENDAL_TEST=s3 cargo test behavior --features tests,services-s3

# Format core workspace
cargo fmt --all
cargo fmt --all -- --check

Repository-wide format checks run from the repository root:

./scripts/workspace.py cargo fmt -- --check
taplo format --check

Code generation and release helpers also run from the repository root:

just generate python
just generate java
just update-version
just release

Current Architecture

OpenDAL's Rust core has been split into a facade crate plus smaller core, service, and layer crates.

  • core/Cargo.toml: Rust workspace root and opendal facade package.
  • core/src/lib.rs: facade crate that re-exports opendal-core, wires optional service/layer crates, and registers enabled services for Operator::from_uri / Operator::via_iter.
  • core/core/: opendal-core, containing public core types, raw traits, shared layers, HTTP utilities, docs, RFCs, and the always-available memory service.
  • core/services/<service>/: standalone service crates named opendal-service-*.
  • core/layers/<layer>/: standalone layer crates named opendal-layer-*.
  • core/testkit/: behavior-test support.
  • core/tests/behavior/: core behavior test entrypoint.
  • integrations/: ecosystem integrations such as object_store, parquet, dav-server, unftp-sbe, and Spring.
  • bindings/: language bindings; each binding has its own build/test conventions.
  • website/: documentation website.
  • dev/: repository maintenance, code generation, and release tooling used by just.

Important consequences of the split:

  • Service and layer code no longer lives under core/src/services or core/src/layers.
  • Public API changes usually touch core/core/src/... and the facade exports in core/src/lib.rs.
  • Optional user-facing features are declared in core/Cargo.toml as services-* and layers-*, and usually map to optional opendal-service-* / opendal-layer-* dependencies.
  • The memory service is in core/core/src/services/memory; services-memory is a deprecated compatibility feature because memory is always enabled.

Service Implementation Pattern

Most services follow this shape under core/services/<name>/:

  • src/lib.rs: crate docs, module declarations, public builder/config exports, and service registration function.
  • src/backend.rs: builder and opendal_core::raw::Access implementation.
  • src/config.rs: serializable config and builder conversion.
  • src/core.rs: shared service client, request construction, and service-specific helpers.
  • src/error.rs: service-specific error parsing.
  • src/reader.rs, src/writer.rs, src/lister.rs, src/deleter.rs, src/copier.rs: operation implementations when the service needs them.
  • src/docs.md: service docs included into rustdoc.

When adding or changing a service:

  1. Put implementation in core/services/<service>/.
  2. Implement Builder and Access using opendal_core.
  3. Add or update the facade feature and optional dependency in core/Cargo.toml.
  4. Register the service in core/src/lib.rs when it should support URI/iterator construction.
  5. Add or update behavior-test setup under .github/services/<service>/ when real backend testing is needed.
  6. Run focused clippy/tests first, then broaden validation based on the blast radius.

Layer Implementation Pattern

Reusable layers live under core/layers/<layer>/ as opendal-layer-* crates. Core layers that are required by opendal-core itself live under core/core/src/layers/.

When adding or changing a public optional layer:

  1. Put reusable optional code in core/layers/<layer>/.
  2. Depend on opendal-core and implement Layer / LayeredAccess against opendal_core::raw.
  3. Add or update the corresponding layers-* feature and optional dependency in core/Cargo.toml.
  4. Re-export it from the facade when users should access it through opendal::layers.

Testing Expectations

  • Use cargo fmt --all -- --check for Rust formatting inside core/; use ./scripts/workspace.py cargo fmt -- --check for the repository-wide format check.
  • For core changes, cargo clippy --workspace --all-targets --all-features -- -D warnings is the CI-level lint gate.
  • For behavior changes, run the narrow behavior test, for example OPENDAL_TEST=s3 cargo test behavior --features tests,services-s3.
  • Behavior tests require backend credentials or fixture setup. Use .env.example, fixtures/, and .github/services/<service>/ as the source of truth for service-specific setup.
  • Integration crates under integrations/ have their own CI workflows and should be validated in their own directories when touched.
  • Binding changes should follow the binding's local README/build files and the matching .github/workflows/ci_bindings_*.yml.

Pull Requests

  • Before opening a PR, search for similar open PRs, issues, and in-progress branches that already address the same problem. Prefer contributing to or coordinating with existing work over opening a duplicate.
  • Always use .github/pull_request_template.md when creating a PR.
  • Keep PR titles and descriptions factual and concise.
  • Do not add AI-tool branding or co-author trailers.
  • If public APIs or user-facing behavior change, update docs and call out the user-facing impact in the PR template.

Important Notes

  • Minimum Rust version is 1.91, configured in core/Cargo.toml and checked by CI.
  • Use opendal_core::raw::Access, Layer, and LayeredAccess for internal implementations.
  • Use opendal_core::raw::oio::{ReadStream, Write, List, Delete} for operation bodies.
  • Use Operator and blocking::Operator as the public API entry points.

Security

Security model: SECURITY.md

Agents that scan this repository should consult SECURITY.md and the threat model it links (SECURITY-THREAT-MODEL.md) for the project's in-scope / out-of-scope declarations, adversary model, and known non-findings before reporting issues.