Neocarta Add Source Connector

Build a new connector under neocarta/connectors/ that satisfies the connector contract. This file is the operational loop for authoring one; the full prose standard lives in connector-contract.md (read it before designing a connector). The contract is also made executable in neocarta/connectors/_base.py (runtime-checkable SourceConnectorProtocol / FormatConnectorProtocol) and enforced per-connector by a test_conformance.py. Drive the whole loop with the driver: .claude/skills/neocarta-add-source-connector/scripts/driver.py, run through uv.

All paths below are relative to the repo root.

Scope: one connector, one PR

Building the connector library package and wiring it into the neocarta CLI are separate PRs. This skill covers only the library connector — the package under neocarta/connectors/, its tests, and its README. Do not add a CLI subcommand (neocarta/_cli/) in the same PR. CLI integration lands in a follow-up PR.

Prerequisites

The managed environment only — no system packages needed for scaffold/verify.

uv sync --all-groups

Running the integration tests (a real ingest into Neo4j) additionally needs Docker — the suite spins up a Neo4j testcontainer (tests/integration/conftest.py).

Run (agent path) — the driver

# See every connector and its detected kind (source/format):
uv run .claude/skills/neocarta-add-source-connector/scripts/driver.py list

# Scaffold a new flat source connector (creates package + conformance test):
uv run .claude/skills/neocarta-add-source-connector/scripts/driver.py scaffold salesforce

# A data-type sub-connector (sub-folder under a parent source):
uv run .claude/skills/neocarta-add-source-connector/scripts/driver.py scaffold salesforce/schema

# A format connector (adds the export() orchestrator):
uv run .claude/skills/neocarta-add-source-connector/scripts/driver.py scaffold acme_yaml --format

# Verify any connector against the contract (static checks + conformance pytest):
uv run .claude/skills/neocarta-add-source-connector/scripts/driver.py verify salesforce

<pkg> is a path under neocarta/connectors/. --class-name overrides the derived class name; --force overwrites a non-empty package dir.

scaffold writes a conformant skeleton: __init__.py, connector.py (all stage methods with the state-guard + deprecation-shim wiring already correct), extract.py, transform.py, README.md, and tests/unit/connectors/<pkg>/test_conformance.py. The skeleton passes verify as-is — you then fill the TODOs in extract/transform/load.

verify reports import + protocol conformance (source vs format, via issubclass), __all__ minimalism, README.md presence, inline-id-f-string and stray-print() warnings, then runs the connector's test_conformance.py. It exits non-zero on any FAIL. Warnings (e.g. an id f-string or a print()) don't fail the run but should be fixed.

Typical workflow

1. scaffold the package (flat, sub-connector, or --format).
2. Implement extract.py (populate the extractor cache, expose @property accessors, decorate extract_*_info methods with @log_stage), transform.py (build data_model objects via generate_id helpers), and the load() body (call self.loader.load_* for your node / relationship types). Fill _TRANSFORM_COUNTS so log_transform_counts reports per-type counts — see logging conventions in contract §16.
3. Fill in the README.md (see contract §12).
4. verify until green. Add behavior-specific unit tests beyond conformance.
5. Run the full unit suite + ruff (see Test), update CHANGELOG.md.

Test

make test-unit          # all unit tests
make fmt && make lint   # ruff format + lint — must be clean before PR
make test-it            # integration: real ingest into a Neo4j testcontainer (Docker)

Both the driver and the code it scaffolds are held to the project's select = ["ALL"] ruff rules — a freshly scaffolded connector is lint-clean and format-clean as generated, so make lint stays green before you've written any implementation. The stub extract() / export() bodies raise NotImplementedError until you implement them.

The connector contract

The full standard — connector kinds, directory layout, the public stage API, constructor-vs-method config, filtering, versioning, errors/warnings, loader scoping, lifecycle, __init__ exports, the required README, and id generation — lives in connector-contract.md. Read it before designing a connector. _base.py and every test_conformance.py cite it as the canonical reference.

Gotchas

• Per-call source args default to None in the skeleton (extract(self, source: str | None = None), ingest, run). This is deliberate: the conformance test calls connector.run() argless to assert the DeprecationWarning, mirroring how CSVConnector (whose inputs live on the constructor) is tested. Replace source with the real signature/type once the source inputs are known — but if you make an arg required, update the generated run test to pass one.
• Constructor vs method config (§4): long-lived resources on __init__, per-call inputs on extract/ingest.
• Sub-connector parent __init__.py: scaffolding foo/schema leaves a stub foo/__init__.py — add the from .schema import FooSchemaConnector re-export yourself (see bigquery/__init__.py).
• Filtering uses the shared enums (§5), not bespoke flags, unless the choice genuinely can't be expressed as a node/relationship type.
• Source connectors never expose version / SUPPORTED_VERSIONS or export — format-connector only.
• Don't re-export internals: keeping *Extractor/*Transformer/*Loader out of __all__ is enforced by both verify and the conformance test.
• Log, don't print() (§16): progress goes through the module logger (logging.getLogger(__name__)). Decorate the real extract_*_info methods with @log_stage, fill _TRANSFORM_COUNTS so log_transform_counts reports per-type counts, and let the loader log its own per-pattern write counts. Never log SQL, row values, or secrets — counts, labels, targets, and elapsed only. The scaffold generates this wiring, and verify warns on any stray print().

Troubleshooting

• verify FAIL: DID NOT WARN ... connector.run() / missing 1 required positional argument — your run()/ingest() require a positional the conformance test doesn't pass. Either default the arg to None or update the generated test to pass one.
• list shows (no exported connector) (e.g. databricks) — the package's __init__.py doesn't export a *Connector in __all__ yet (work in progress).
• verify FAIL: cannot import ... — missing optional dep for that source (e.g. google.cloud.bigquery). uv sync --all-groups pulls the lot.