feat: add Neo4j lineage exporter for dbt manifest metadata

README_neo4j.md

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+# Elementary Neo4j Lineage Exporter
+
+## Overview
+
+This utility exports dbt lineage data from Elementary's dbt manifest into Neo4j
+as a property graph. It enables downstream impact analysis, root cause detection,
+and lineage visualization directly in Neo4j.
+
+## Motivation
+
+Elementary already captures rich lineage metadata via dbt artifacts. This exporter
+makes that lineage available in Neo4j, enabling graph traversal queries for:
+
+- **Impact analysis** — which models are affected if a source schema changes?
+- **Root cause detection** — trace data quality issues upstream
+- **Lineage visualization** — explore your dbt DAG as a graph
+
+## Graph Model
+
+**Nodes** — each dbt model, source, seed, and snapshot becomes a `DbtNode`:
+- `unique_id` — dbt unique identifier (primary key)
+- `name` — model/source name
+- `resource_type` — model, source, seed, snapshot
+- `schema` — target schema in your warehouse
+- `database` — target database
+- `package_name` — dbt package
+- `description` — model documentation
+
+**Relationships** — `(upstream)-[:FEEDS_INTO]->(downstream)`
+
+## Installation
+
+```bash
+pip install neo4j
+```
+
+## Usage
+
+```python
+from elementary_neo4j.neo4j_config import Neo4jConfig
+from elementary_neo4j.neo4j_exporter import Neo4jLineageExporter
+
+config = Neo4jConfig(
+    uri="bolt://localhost:7687",
+    username="neo4j",
+    password="your-password"
+)
+
+exporter = Neo4jLineageExporter(config)
+result = exporter.export("path/to/manifest.json")
+print(result)
+# {"nodes_exported": 42, "dependencies_exported": 67}
+exporter.close()
+```
+
+## Environment Variables
+
+```bash
+export NEO4J_URI=bolt://localhost:7687
+export NEO4J_USERNAME=neo4j
+export NEO4J_PASSWORD=your-password
+export NEO4J_DATABASE=neo4j
+```
+
+Then use:
+```python
+config = Neo4jConfig.from_env()
+```
+
+## Example Neo4j Query
+
+Find all models impacted by a source change:
+```cypher
+MATCH (source:DbtNode {name: "raw_customers"})-[:FEEDS_INTO*]->(impacted)
+RETURN impacted.name, impacted.resource_type
+```
+
+## Running Tests
+
+```bash
+PYTHONPATH=. python -m pytest tests/test_neo4j_exporter.py -v --ignore=integration_tests
+```

elementary_neo4j/neo4j_config.py

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+from dataclasses import dataclass
+from typing import Optional
+
+
+@dataclass
+class Neo4jConfig:
+    uri: str
+    username: str
+    password: str
+    database: Optional[str] = "neo4j"
+
+    @classmethod
+    def from_env(cls) -> "Neo4jConfig":
+        import os
+        return cls(
+            uri=os.environ.get("NEO4J_URI", "bolt://localhost:7687"),
+            username=os.environ.get("NEO4J_USERNAME", "neo4j"),
+            password=os.environ.get("NEO4J_PASSWORD", ""),
+            database=os.environ.get("NEO4J_DATABASE", "neo4j"),
+        )

elementary_neo4j/neo4j_exporter.py

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+import json
+import logging
+from pathlib import Path
+from typing import Any, Dict, List, Optional
+
+from neo4j import GraphDatabase
+
+from elementary_neo4j.neo4j_config import Neo4jConfig
+
+logger = logging.getLogger(__name__)
+
+
+class Neo4jLineageExporter:
+    """
+    Exports dbt lineage from Elementary's dbt manifest into Neo4j.
+    Creates nodes for models, sources, and columns, and
+    relationships for dependencies between them.
+    """
+
+    def __init__(self, config: Neo4jConfig):
+        self.config = config
+        self.driver = GraphDatabase.driver(
+            config.uri,
+            auth=(config.username, config.password)
+        )
+
+    def close(self):
+        self.driver.close()
+
+    def load_manifest(self, manifest_path: str) -> Dict[str, Any]:
+        """Load dbt manifest.json from file path."""
+        path = Path(manifest_path)
+        if not path.exists():
+            raise FileNotFoundError(f"Manifest not found: {manifest_path}")
+        with open(path, "r") as f:
+            return json.load(f)
+
+    def extract_nodes(self, manifest: Dict[str, Any]) -> List[Dict]:
+        """Extract model and source nodes from manifest."""
+        nodes = []
+        for unique_id, node in manifest.get("nodes", {}).items():
+            if node.get("resource_type") in ("model", "seed", "snapshot"):
+                nodes.append({
+                    "unique_id": unique_id,
+                    "name": node.get("name"),
+                    "resource_type": node.get("resource_type"),
+                    "schema": node.get("schema"),
+                    "database": node.get("database"),
+                    "package_name": node.get("package_name"),
+                    "description": node.get("description", ""),
+                })
+        for unique_id, source in manifest.get("sources", {}).items():
+            nodes.append({
+                "unique_id": unique_id,
+                "name": source.get("name"),
+                "resource_type": "source",
+                "schema": source.get("schema"),
+                "database": source.get("database"),
+                "package_name": source.get("package_name"),
+                "description": source.get("description", ""),
+            })
+        return nodes
+
+    def extract_dependencies(self, manifest: Dict[str, Any]) -> List[Dict]:
+        """Extract upstream dependencies between nodes."""
+        dependencies = []
+        for unique_id, node in manifest.get("nodes", {}).items():
+            for upstream_id in node.get("depends_on", {}).get("nodes", []):
+                dependencies.append({
+                    "from_id": upstream_id,
+                    "to_id": unique_id,
+                })
+        return dependencies
+
+    def export_nodes(self, nodes: List[Dict]):
+        """Write nodes to Neo4j."""
+        with self.driver.session(database=self.config.database) as session:
+            for node in nodes:
+                session.run(
+                    """
+                    MERGE (n:DbtNode {unique_id: $unique_id})
+                    SET n.name = $name,
+                        n.resource_type = $resource_type,
+                        n.schema = $schema,
+                        n.database = $database,
+                        n.package_name = $package_name,
+                        n.description = $description
+                    """,
+                    **node
+                )
+        logger.info(f"Exported {len(nodes)} nodes to Neo4j")
+
+    def export_dependencies(self, dependencies: List[Dict]):
+        """Write dependency relationships to Neo4j."""
+        with self.driver.session(database=self.config.database) as session:
+            for dep in dependencies:
+                session.run(
+                    """
+                    MATCH (a:DbtNode {unique_id: $from_id})
+                    MATCH (b:DbtNode {unique_id: $to_id})
+                    MERGE (a)-[:FEEDS_INTO]->(b)
+                    """,
+                    **dep
+                )
+        logger.info(f"Exported {len(dependencies)} dependencies to Neo4j")
+
+    def export(self, manifest_path: str):
+        """Full export pipeline — nodes + dependencies."""
+        logger.info(f"Loading manifest from {manifest_path}")
+        manifest = self.load_manifest(manifest_path)
+        nodes = self.extract_nodes(manifest)
+        dependencies = self.extract_dependencies(manifest)
+        self.export_nodes(nodes)
+        self.export_dependencies(dependencies)
+        logger.info("Neo4j lineage export complete")
+        return {
+            "nodes_exported": len(nodes),
+            "dependencies_exported": len(dependencies)
+        }

tests/test_neo4j_exporter.py

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+import json
+import pytest
+from unittest.mock import MagicMock, patch, mock_open
+from elementary_neo4j.neo4j_exporter import Neo4jLineageExporter
+from elementary_neo4j.neo4j_config import Neo4jConfig
+
+
+@pytest.fixture
+def config():
+    return Neo4jConfig(
+        uri="bolt://localhost:7687",
+        username="neo4j",
+        password="test",
+        database="neo4j"
+    )
+
+
+@pytest.fixture
+def exporter(config):
+    with patch("elementary_neo4j.neo4j_exporter.GraphDatabase.driver"):
+        return Neo4jLineageExporter(config)
+
+
+@pytest.fixture
+def sample_manifest():
+    return {
+        "nodes": {
+            "model.my_project.dim_customers": {
+                "name": "dim_customers",
+                "resource_type": "model",
+                "schema": "analytics",
+                "database": "snowflake_db",
+                "package_name": "my_project",
+                "description": "Customer dimension table",
+                "depends_on": {
+                    "nodes": ["source.my_project.raw_customers"]
+                }
+            },
+            "model.my_project.fct_orders": {
+                "name": "fct_orders",
+                "resource_type": "model",
+                "schema": "analytics",
+                "database": "snowflake_db",
+                "package_name": "my_project",
+                "description": "Orders fact table",
+                "depends_on": {
+                    "nodes": ["model.my_project.dim_customers"]
+                }
+            }
+        },
+        "sources": {
+            "source.my_project.raw_customers": {
+                "name": "raw_customers",
+                "resource_type": "source",
+                "schema": "raw",
+                "database": "snowflake_db",
+                "package_name": "my_project",
+                "description": "Raw customers source"
+            }
+        }
+    }
+
+
+def test_extract_nodes_returns_models_and_sources(exporter, sample_manifest):
+    nodes = exporter.extract_nodes(sample_manifest)
+    assert len(nodes) == 3
+    resource_types = [n["resource_type"] for n in nodes]
+    assert "model" in resource_types
+    assert "source" in resource_types
+
+
+def test_extract_nodes_contains_correct_fields(exporter, sample_manifest):
+    nodes = exporter.extract_nodes(sample_manifest)
+    model_node = next(n for n in nodes if n["name"] == "dim_customers")
+    assert model_node["schema"] == "analytics"
+    assert model_node["database"] == "snowflake_db"
+    assert model_node["description"] == "Customer dimension table"
+
+
+def test_extract_dependencies_correct_count(exporter, sample_manifest):
+    dependencies = exporter.extract_dependencies(sample_manifest)
+    assert len(dependencies) == 2
+
+
+def test_extract_dependencies_correct_direction(exporter, sample_manifest):
+    dependencies = exporter.extract_dependencies(sample_manifest)
+    dep = next(
+        d for d in dependencies
+        if d["to_id"] == "model.my_project.dim_customers"
+    )
+    assert dep["from_id"] == "source.my_project.raw_customers"
+
+
+def test_load_manifest_file_not_found(exporter):
+    with pytest.raises(FileNotFoundError):
+        exporter.load_manifest("nonexistent/path/manifest.json")
+
+
+def test_load_manifest_reads_correctly(exporter, sample_manifest):
+    mock_data = json.dumps(sample_manifest)
+    with patch("builtins.open", mock_open(read_data=mock_data)):
+        with patch("pathlib.Path.exists", return_value=True):
+            result = exporter.load_manifest("fake/manifest.json")
+    assert "nodes" in result
+    assert "sources" in result
+
+
+def test_export_nodes_calls_session(exporter, sample_manifest):
+    nodes = exporter.extract_nodes(sample_manifest)
+    mock_session = MagicMock()
+    exporter.driver.session.return_value.__enter__ = MagicMock(
+        return_value=mock_session
+    )
+    exporter.driver.session.return_value.__exit__ = MagicMock(
+        return_value=False
+    )
+    exporter.export_nodes(nodes)
+    assert mock_session.run.call_count == len(nodes)
+
+
+def test_export_returns_correct_counts(exporter, sample_manifest):
+    with patch.object(exporter, "load_manifest", return_value=sample_manifest):
+        with patch.object(exporter, "export_nodes"):
+            with patch.object(exporter, "export_dependencies"):
+                result = exporter.export("fake/manifest.json")
+    assert result["nodes_exported"] == 3
+    assert result["dependencies_exported"] == 2