File size: 3,332 Bytes
51943f5 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 | #!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""The gate used in README's 30-second example.
A small validator that understands the subset of JSON Schema that
schema.json uses, so the example needs nothing installed.
python gate.py <target-dir> # exit 0 = accept, exit 1 = reject
Replace it with your own gate: a linter, a CI step, a policy check, an LLM
guardrail — anything that exits non-zero to mean "reject".
"""
import json
import sys
from pathlib import Path
TYPES = {"string": str, "integer": int, "number": (int, float),
"boolean": bool, "array": list, "object": dict}
def check(schema, value, path="$"):
"""Return an error string, or None if the value satisfies the schema."""
if not isinstance(schema, dict):
return "%s: the schema for this value is not an object" % path
t = schema.get("type")
if t is not None:
py = TYPES.get(t)
if py is None:
return "%s: schema declares an unknown type %r" % (path, t)
if isinstance(value, bool) and t != "boolean":
return "%s: expected %s, got boolean" % (path, t)
if not isinstance(value, py):
return "%s: expected %s, got %s" % (path, t, type(value).__name__)
if "enum" in schema and value not in schema["enum"]:
return "%s: %r is not one of %s" % (path, value, schema["enum"])
if "minLength" in schema and isinstance(value, str) and len(value) < schema["minLength"]:
return "%s: shorter than minLength %d" % (path, schema["minLength"])
if isinstance(value, (int, float)) and not isinstance(value, bool):
if "minimum" in schema and value < schema["minimum"]:
return "%s: %r is below minimum %s" % (path, value, schema["minimum"])
if "maximum" in schema and value > schema["maximum"]:
return "%s: %r is above maximum %s" % (path, value, schema["maximum"])
if "minItems" in schema and isinstance(value, list) and len(value) < schema["minItems"]:
return "%s: fewer than minItems %d" % (path, schema["minItems"])
if isinstance(value, dict):
for key in schema.get("required", []):
if key not in value:
return "%s: missing required property %r" % (path, key)
for key, sub in schema.get("properties", {}).items():
if key in value:
err = check(sub, value[key], "%s.%s" % (path, key))
if err:
return err
if "items" in schema and isinstance(value, list):
for i, item in enumerate(value):
err = check(schema["items"], item, "%s[%d]" % (path, i))
if err:
return err
return None
def main() -> int:
target = Path(sys.argv[1]) if len(sys.argv) > 1 else Path(".")
try:
schema = json.loads((target / "schema.json").read_text(encoding="utf-8"))
data = json.loads((target / "data.json").read_text(encoding="utf-8"))
except Exception as exc: # an unreadable config counts as a rejection
print("REJECT: cannot read the config: %s: %s" % (type(exc).__name__, exc))
return 1
err = check(schema, data)
if err:
print("REJECT: %s" % err)
return 1
print("PASS: data.json satisfies schema.json")
return 0
if __name__ == "__main__":
sys.exit(main())
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