feat(evidence): define source and corpus contracts

This commit is contained in:
2026-07-12 03:02:10 +02:00
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# Evidence / Preprocessing Task 1 Report
## Outcome
Implemented the additive Evidence source port and canonical corpus records. Existing evidence,
search, vector, and session runtime code is unchanged.
## Contract
- `EvidenceSource` is a runtime-checkable protocol with `discover` and `acquire` operations.
- `SourceObject` and `AcquiredDocument` are frozen, reject extra fields, use independent metadata
defaults, and restrict metadata to Pydantic `JsonValue` values.
- `CanonicalDocument`, `CanonicalChunk`, and `CorpusManifest` are frozen and reject extra fields.
- Provenance includes stable source IDs, canonical URIs, fingerprints, modification time, and
content hashes.
- Pipeline versions are recorded on documents, chunks, and manifests. Manifests also carry schema
version, optional publish ID/vector generation, and paired embedding model/dimension fields.
- Credential-like metadata keys are rejected recursively. Credentials are not model fields and
therefore cannot enter serialized canonical artifacts through extras.
## TDD evidence
The initial focused run failed during collection because `tht.ports.evidence` and `tht.corpus`
did not exist. After implementation, the focused suite passed.
## Verification
- Focused models/protocol tests: 13 passed.
- Harness excluding Docker-backed L0 and the network-dependent wheel packaging test: 444 passed,
5 deselected.
- Focused Ruff: passed.
- Full-repository Ruff remains blocked by 34 pre-existing findings outside the task files.
- An unrestricted `pytest -q` attempt reached 453 passed and 5 deselected, but reported 47 Docker
setup errors plus 4 Docker parity failures because the sandbox cannot access the Docker socket;
the wheel packaging test also failed because its isolated `uv build` needs unavailable network.
## Concerns / follow-up
- Pydantic's `frozen=True` prevents model field reassignment but does not recursively freeze list
and dict contents. `default_factory` prevents shared mutable defaults. Later pipeline stages should
treat these value objects as immutable and construct replacements rather than mutate collections.
- The adapter and normalization tasks should preserve the credential-free boundary by passing only
these records beyond acquisition.
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from datetime import UTC, datetime
import pytest
from pydantic import ValidationError
from tht.corpus.models import CanonicalChunk, CanonicalDocument, CorpusManifest
def document(source_uri: str = "https://host/a.md") -> CanonicalDocument:
return CanonicalDocument(
document_id="doc:abc",
source_id="source:a",
source_uri=source_uri,
source_fingerprint="etag:abc",
content_hash="sha256:def",
title="A",
content="# A",
media_type="text/markdown",
pipeline_version="normalize-v1",
)
def chunk() -> CanonicalChunk:
return CanonicalChunk(
chunk_id="chunk:abc:0",
document_id="doc:abc",
ordinal=0,
content="# A",
content_hash="sha256:def",
source_uri="https://host/a.md",
pipeline_version="chunk-v1",
)
def test_manifest_contains_provenance_without_credentials():
manifest = CorpusManifest(
manifest_id="manifest:abc",
created_at=datetime(2026, 7, 12, tzinfo=UTC),
pipeline_version="evidence-v1",
embedding_model="nomic-embed-text",
embedding_dimensions=768,
documents=[document()],
chunks=[chunk()],
)
payload = manifest.model_dump_json()
assert "https://host/a.md" in payload
assert "etag:abc" in payload
assert "evidence-v1" in payload
assert "nomic-embed-text" in payload
assert "api_key" not in payload
def test_manifest_can_be_assembled_before_publish_identifiers_are_assigned():
manifest = CorpusManifest(documents=[document()])
assert manifest.documents[0].source_uri == "https://host/a.md"
assert manifest.manifest_id is None
@pytest.mark.parametrize("model", [document(), chunk()])
def test_canonical_records_are_frozen(model):
with pytest.raises(ValidationError):
model.pipeline_version = "changed" # type: ignore[misc]
def test_manifest_collections_have_independent_defaults():
first = CorpusManifest(
manifest_id="one", created_at=datetime.now(UTC), pipeline_version="v1"
)
second = CorpusManifest(
manifest_id="two", created_at=datetime.now(UTC), pipeline_version="v1"
)
first.documents.append(document())
assert second.documents == []
def test_manifest_validates_embedding_compatibility_fields():
with pytest.raises(ValidationError):
CorpusManifest(
manifest_id="bad",
created_at=datetime.now(UTC),
pipeline_version="v1",
embedding_dimensions=0,
)
def test_canonical_metadata_rejects_secrets_and_non_json_values():
with pytest.raises(ValidationError, match="credential-like"):
CanonicalDocument.model_validate(
{**document().model_dump(), "metadata": {"password": "secret"}}
)
with pytest.raises(ValidationError):
CanonicalChunk(
chunk_id="c",
document_id="d",
ordinal=0,
content="x",
content_hash="sha256:x",
source_uri="file:///x",
pipeline_version="v1",
metadata={"bad": object()},
)
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from datetime import UTC, datetime
import pytest
from pydantic import ValidationError
from tht.ports.evidence import AcquiredDocument, EvidenceSource, SourceObject
class StubSource:
def discover(self):
return iter(
[
SourceObject(
source_id="handbook",
uri="https://host/handbook.md",
fingerprint="sha256:abc",
)
]
)
def acquire(self, item: SourceObject) -> AcquiredDocument:
return AcquiredDocument(
source=item,
content=b"# Handbook",
acquired_at=datetime(2026, 7, 12, tzinfo=UTC),
media_type="text/markdown",
)
def test_runtime_checkable_source_protocol():
source = StubSource()
assert isinstance(source, EvidenceSource)
assert source.acquire(next(source.discover())).content == b"# Handbook"
def test_source_objects_are_frozen_and_metadata_defaults_are_independent():
first = SourceObject(source_id="a", uri="file:///a", fingerprint="sha256:a")
second = SourceObject(source_id="b", uri="file:///b", fingerprint="sha256:b")
with pytest.raises(ValidationError):
first.uri = "file:///changed" # type: ignore[misc]
first.metadata["owner"] = "team-a"
assert second.metadata == {}
@pytest.mark.parametrize("metadata", [{"api_key": "secret"}, {"auth": {"token": "secret"}}])
def test_source_metadata_rejects_credentials(metadata):
with pytest.raises(ValidationError, match="credential-like"):
SourceObject(
source_id="a", uri="https://host/a", fingerprint="etag:abc", metadata=metadata
)
def test_source_metadata_must_be_json_safe():
with pytest.raises(ValidationError):
SourceObject(
source_id="a",
uri="file:///a",
fingerprint="sha256:a",
metadata={"path": object()},
)
def test_acquired_document_does_not_accept_credentials_as_extra_fields():
item = SourceObject(source_id="a", uri="https://host/a", fingerprint="etag:abc")
with pytest.raises(ValidationError):
AcquiredDocument(source=item, content=b"a", api_key="secret")
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"""Canonical, transport-independent Evidence corpus."""
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"""Immutable records emitted by the Evidence preprocessing pipeline."""
from datetime import UTC, datetime
from pydantic import BaseModel, ConfigDict, Field, JsonValue, field_validator, model_validator
from tht.ports.evidence import _reject_credentials
class _CanonicalValue(BaseModel):
model_config = ConfigDict(frozen=True, extra="forbid")
class _WithMetadata(_CanonicalValue):
metadata: dict[str, JsonValue] = Field(default_factory=dict)
@field_validator("metadata")
@classmethod
def metadata_has_no_credentials(cls, value: dict[str, JsonValue]) -> dict[str, JsonValue]:
_reject_credentials(value)
return value
class CanonicalDocument(_WithMetadata):
document_id: str = Field(min_length=1)
source_id: str = Field(min_length=1)
source_uri: str = Field(min_length=1)
source_fingerprint: str = Field(min_length=1)
content_hash: str = Field(min_length=1)
title: str = ""
content: str
media_type: str = "text/plain"
modified_at: datetime | None = None
pipeline_version: str = Field(min_length=1)
class CanonicalChunk(_WithMetadata):
chunk_id: str = Field(min_length=1)
document_id: str = Field(min_length=1)
ordinal: int = Field(ge=0)
content: str
content_hash: str = Field(min_length=1)
source_uri: str = Field(min_length=1)
pipeline_version: str = Field(min_length=1)
class CorpusManifest(_WithMetadata):
"""Description of one publishable canonical/vector generation."""
schema_version: int = Field(default=1, ge=1)
manifest_id: str | None = None
created_at: datetime = Field(default_factory=lambda: datetime.now(UTC))
pipeline_version: str = Field(default="1", min_length=1)
embedding_model: str | None = None
embedding_dimensions: int | None = Field(default=None, gt=0)
vector_generation: str | None = None
documents: list[CanonicalDocument] = Field(default_factory=list)
chunks: list[CanonicalChunk] = Field(default_factory=list)
@model_validator(mode="after")
def embedding_fields_are_complete(self) -> "CorpusManifest":
if (self.embedding_model is None) != (self.embedding_dimensions is None):
raise ValueError("embedding_model and embedding_dimensions must be set together")
return self
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"""Port for discovering and acquiring Evidence source objects.
Source adapters own transport details and credentials. The values crossing this
boundary are deliberately credential-free so they can safely become provenance.
"""
from datetime import datetime
from typing import Iterable, Protocol, runtime_checkable
from pydantic import BaseModel, ConfigDict, Field, JsonValue, field_validator
_SECRET_KEYS = {
"api_key",
"apikey",
"authorization",
"credential",
"credentials",
"password",
"secret",
"token",
}
def _reject_credentials(value: JsonValue, path: str = "metadata") -> JsonValue:
if isinstance(value, dict):
for key, child in value.items():
normalized = key.lower().replace("-", "_")
if normalized in _SECRET_KEYS or normalized.endswith(("_password", "_secret", "_token")):
raise ValueError(f"credential-like metadata key is not allowed: {path}.{key}")
_reject_credentials(child, f"{path}.{key}")
elif isinstance(value, list):
for index, child in enumerate(value):
_reject_credentials(child, f"{path}[{index}]")
return value
class _EvidenceValue(BaseModel):
model_config = ConfigDict(frozen=True, extra="forbid")
class SourceObject(_EvidenceValue):
source_id: str = Field(min_length=1)
uri: str = Field(min_length=1)
fingerprint: str = Field(min_length=1)
modified_at: datetime | None = None
metadata: dict[str, JsonValue] = Field(default_factory=dict)
@field_validator("metadata")
@classmethod
def metadata_has_no_credentials(cls, value: dict[str, JsonValue]) -> dict[str, JsonValue]:
_reject_credentials(value)
return value
class AcquiredDocument(_EvidenceValue):
source: SourceObject
content: bytes
media_type: str | None = None
acquired_at: datetime | None = None
metadata: dict[str, JsonValue] = Field(default_factory=dict)
@field_validator("metadata")
@classmethod
def metadata_has_no_credentials(cls, value: dict[str, JsonValue]) -> dict[str, JsonValue]:
_reject_credentials(value)
return value
@runtime_checkable
class EvidenceSource(Protocol):
def discover(self) -> Iterable[SourceObject]: ...
def acquire(self, item: SourceObject) -> AcquiredDocument: ...