feat(okf): strict reject-by-default frontmatter parser (T2, TDD, +12)

tests/test_okf.py

@@ -0,0 +1,101 @@
+"""Tests for the OKF adapter (v0.2 stream 1).
+
+The adapter sits *on top of* the format-agnostic core: the core stays
+`text -> findings`; the adapter knows OKF structure and feeds scannable text
+regions into the existing machinery. No YAML/format awareness leaks into core.
+
+T2 — frontmatter parse-safety gate. A *strict, reject-by-default* loader for the
+minimal OKF frontmatter subset (flat `key: value` scalars + block `- item`
+lists). Every construct the "block anchor/alias DoS + dangerous type coercion"
+requirement names is a hard reject, by construction — you cannot suffer a
+billion-laughs expansion if anchors are refused before parsing.
+
+OKF spec facts used here (verified against okf/SPEC.md, 2026-07-06):
+- `type` is the only REQUIRED frontmatter key; `title`/`description`/`resource`/
+  `tags`/`timestamp` are recommended; producers MAY add arbitrary keys.
+- frontmatter is minimal by design — a flat block of scalars plus a `tags` list.
+"""
+import pytest
+
+from llm_ingestion_guard.okf import parse_frontmatter, OKFFrontmatterError
+
+
+# --- happy path: split + parse the minimal flat subset -----------------------
+
+def test_splits_frontmatter_from_body():
+    doc = "---\ntype: table\ntitle: Users\n---\nThe users table body.\n"
+    frontmatter, body = parse_frontmatter(doc)
+    assert frontmatter == {"type": "table", "title": "Users"}
+    assert body == "The users table body.\n"
+
+
+def test_no_frontmatter_returns_empty_and_full_body():
+    doc = "Just a body with no frontmatter fence.\n"
+    frontmatter, body = parse_frontmatter(doc)
+    assert frontmatter == {}
+    assert body == doc
+
+
+def test_parses_block_tags_list():
+    doc = "---\ntype: table\ntags:\n  - pii\n  - customers\n---\nbody\n"
+    frontmatter, body = parse_frontmatter(doc)
+    assert frontmatter == {"type": "table", "tags": ["pii", "customers"]}
+
+
+def test_blank_and_comment_lines_are_ignored():
+    doc = "---\ntype: table\n# a comment\n\ntitle: Users\n---\nbody\n"
+    frontmatter, _ = parse_frontmatter(doc)
+    assert frontmatter == {"type": "table", "title": "Users"}
+
+
+# --- reject-by-default: the dangerous YAML constructs ------------------------
+
+def test_rejects_anchor():
+    doc = "---\ntype: &a table\n---\nbody\n"
+    with pytest.raises(OKFFrontmatterError):
+        parse_frontmatter(doc)
+
+
+def test_rejects_alias():
+    doc = "---\ntype: table\ntitle: *a\n---\nbody\n"
+    with pytest.raises(OKFFrontmatterError):
+        parse_frontmatter(doc)
+
+
+def test_rejects_explicit_tag_type_coercion():
+    # the classic PyYAML RCE shape
+    doc = "---\ntype: !!python/object/apply:os.system ['id']\n---\nbody\n"
+    with pytest.raises(OKFFrontmatterError):
+        parse_frontmatter(doc)
+
+
+def test_rejects_merge_key():
+    doc = "---\ntype: table\n<<: *base\n---\nbody\n"
+    with pytest.raises(OKFFrontmatterError):
+        parse_frontmatter(doc)
+
+
+def test_rejects_block_scalar():
+    doc = "---\ntype: table\ndescription: |\n  multi\n  line\n---\nbody\n"
+    with pytest.raises(OKFFrontmatterError):
+        parse_frontmatter(doc)
+
+
+def test_rejects_nested_mapping():
+    doc = "---\ntype: table\nmeta:\n  nested: value\n---\nbody\n"
+    with pytest.raises(OKFFrontmatterError):
+        parse_frontmatter(doc)
+
+
+def test_rejects_unterminated_frontmatter():
+    doc = "---\ntype: table\ntitle: Users\n"  # no closing fence
+    with pytest.raises(OKFFrontmatterError):
+        parse_frontmatter(doc)
+
+
+def test_rejects_flow_collection():
+    # inline flow collections are outside the supported subset -> reject, don't
+    # silently mis-parse the bracket string as a scalar.
+    doc = "---\ntype: table\ntags: [pii, customers]\n---\nbody\n"
+    with pytest.raises(OKFFrontmatterError):
+        parse_frontmatter(doc)