PyJSG 0.12.2

Python JSON Schema Grammar interpreter

This repository was originally developed by Harold Solbrig and was kindly contributed to the LinkML organization because of his retirement. All credit for the original development of this repository goes to him.

PyJSG -- JSON Schema Grammar Bindings for Python

Translate JSON Schema Grammar into Python objects.

This tool generates Python 3 objects that represent the JSON objects defined in a JSG schema. It uses the Python Typing library to add type hints to Python IDE's and includes a library to validate the python objects against the library definitions.

Examples

JSON Grammar	Python Objects
doc { status:"ready" }	class _Anon1(jsg.JSGString): pattern = jsg.JSGPattern(r'ready') class doc(jsg.JSGObject): def __init__(self, status: _Anon1 = None, **_kwargs: Dict[str, object]): self.status = status super().__init__(self._context, **_kwargs)
doc { street:@string no:@int }	class doc(jsg.JSGObject): def __init__(self, street: str = None, no: int = None, **_kwargs: Dict[str, object]): self.street = jsg.String(street) self.no = jsg.Integer(no) super().__init__(self._context, **_kwargs)
doc { street:(NAME|"*"|TEMPLATE) } @terminals NAME : [A-Za-z].*; TEMPLATE : '{' .* '}';	class _Anon1(jsg.JSGString): pattern = jsg.JSGPattern(r'\*') class NAME(jsg.JSGString): pattern = jsg.JSGPattern(r'[A-Za-z].*') class TEMPLATE(jsg.JSGString): pattern = jsg.JSGPattern(r'\{.*\}') class doc(jsg.JSGObject): def __init__(self, street: Union[_Anon1, NAME, TEMPLATE] = None, **_kwargs: Dict[str, object]): self.street = street super().__init__(self._context, **_kwargs)
doc { street:nameOrTemplate } nameOrTemplate = (NAME | TEMPLATE) ; @terminals NAME : .*; TEMPLATE : '{' .* '}';	class NAME(jsg.JSGString): pattern = jsg.JSGPattern(r'.*') class TEMPLATE(jsg.JSGString): pattern = jsg.JSGPattern(r'\{.*\}') nameOrTemplate = Union[NAME, TEMPLATE] class doc(jsg.JSGObject): def __init__(self, street: nameOrTemplate = None, **_kwargs: Dict[str, object]): self.street = street super().__init__(self._context, **_kwargs)
doc { street:[(NAME | "*" | TEMPLATE){2,}] } @terminals NAME : .*; TEMPLATE : '{' .* '}';	class _Anon1(jsg.JSGString): pattern = jsg.JSGPattern(r'\*') class NAME(jsg.JSGString): pattern = jsg.JSGPattern(r'.*') class TEMPLATE(jsg.JSGString): pattern = jsg.JSGPattern(r'\{.*\}') class doc(jsg.JSGObject): def __init__(self, street: List[Union[_Anon1, NAME, TEMPLATE]] = None, **_kwargs: Dict[str, object]): self.street = street super().__init__(self._context, **_kwargs)

Usage

• Requires Python 3.x -- has been tested through Python 3.6.1. (This module depends on some of the internal features of the Python typing library, which is still under active development -- be careful upgrading to newer versions without first running the unit tests.)

> pip install pyjsg
> generate_parser -h
usage: generate_parser [-h] [-o OUTFILE] [-e] infile

positional arguments:
  infile                Input JSG specification

optional arguments:
  -h, --help            show this help message and exit
  -o OUTFILE, --outfile OUTFILE
                        Output python file (Default: {infile}.jsg)
  -e, --evaluate        Evaluate resulting python file as a test

Setup

> curl https://raw.githubusercontent.com/hsolbrig/shexTest/master/doc/ShExJ.jsg -o ShExJ.jsg
> generate_parser ShExJ.jsg
Output written to ShExJ.py

Python

from tests.py import ShExJ
    from pyjsg.jsglib.jsg import loads
    from io import StringIO

    # Load an exsting schema
    shexj = """{
      "@context": "http://www.w3.org/ns/shex.jsonld",
      "type": "Schema",
      "shapes": [
        {
          "id": "http://a.example/S1",
          "type": "Shape",
          "expression": {
            "type": "TripleConstraint",
            "predicate": "http://a.example/p1",
            "valueExpr": {
              "type": "NodeConstraint",
              "datatype": "http://a.example/dt1"
            }
          }
        }
      ]
    }
    """
    s: ShExJ.Schema = loads(shexj, ShExJ)
    print(f"type(Schema) = {s.type}")
    print(f"PREDICATE: {s.shapes[0].expression.predicate}")

    # Add a new element
    s.shapes[0].closed = Boolean("true")

    # Emit modified JSON
    print(s._as_json_dumps())

    # Validate the JSON
    print(f"Valid: {s._is_valid()")

    # Add an invalid element that isn't caught
    s.shapes[0].expression.valueExpr = "Just text"
    log = StringIO()
    if not s._is_valid(log):
        print(log.getvalue())

    # Attempt to add in invalid string
    try:
        s.shapes[0].closed = Boolean("0", True)
    except ValueError:
        print("String mismatch")

    # Attempt to add in invalid property
    try:
        s.shapes[0].closd = Boolean("true")
    except ValueError:
        print("No attribute named 'closd'")

Output

type(Shema): Schema
PREDICATE: http://a.example/p1
{
  "type": "Schema",
  "@context": "http://www.w3.org/ns/shex.jsonld",
  "shapes": [
     {
        "type": "Shape",
        "id": "http://a.example/S1",
        "closed": "true",
        "expression": {
           "type": "TripleConstraint",
           "predicate": "http://a.example/p1",
           "valueExpr": {
              "type": "NodeConstraint",
              "datatype": "http://a.example/dt1"
           }
        }
     }
  ]
}
Valid: True
String mismatch
No attribute named 'closd'