boolia 0.1.1

Tiny, safe boolean-expression language with dotted paths, functions, and rule books.

boolia

A tiny, safe boolean expression engine: like Jinja for logic.

• Grammar: and, or, not, parentheses, comparisons (== != > >= <= <), in
• Values: numbers, strings, booleans, null/None, identifiers, dotted paths (user.age, house.light.on)
• Tags: bare identifiers evaluate True if present in a tags: set[str]
• Functions: user-registered, safe callables (starts_with, matches, ...)
• RuleBook: name your rules and evaluate them later
• RuleGroup: compose rules with all/any semantics and nested groups
• Missing policy: choose to raise or substitute None/False/custom default

from boolia import evaluate, RuleBook, DEFAULT_FUNCTIONS

expr = "(car and elephant) or house.light.on"
print(evaluate(expr, context={"house": {"light": {"on": True}}}, tags={"car"}))  # True

Install (local)

pip install -e .[dev]
pytest -q
ruff check .
mypy .

Tooling

The project ships with Ruff for linting and MyPy for type checking. After installing the development extras you can run the primary checks with:

ruff check .
mypy .

Quick start

from boolia import evaluate, DEFAULT_FUNCTIONS

ctx  = {"user": {"age": 21, "roles": ["admin", "ops"]}}
tags = {"beta"}
expr = "user.age >= 18 and 'admin' in user.roles"
print(evaluate(expr, context=ctx, tags=tags))  # True

Functions

from boolia import evaluate, DEFAULT_FUNCTIONS

DEFAULT_FUNCTIONS.register("starts_with", lambda s, p: str(s).startswith(str(p)))

expr = "starts_with(user.name, 'Sn')"
print(evaluate(expr, context={"user": {"name": "Snoopy"}}))  # True

RuleBook

from boolia import RuleBook, RuleGroup

rules = RuleBook()
rules.add("adult", "user.age >= 18")
rules.add("brazilian", "starts_with(user.country, 'Br')")
rules.add("vip", "contains(user.roles, 'vip')")
rules.add_group(
    "eligible",
    mode="all",
    members=[
        "adult",
        RuleGroup(mode="any", members=["brazilian", "vip"]),
    ],
)

ok = rules.evaluate(
    "eligible",
    context={"user": {"age": 22, "country": "Brazil", "roles": ["member"]}},
)
print(ok)  # True

print(rules.evaluate("eligible", context={"user": {"age": 22, "country": "Chile", "roles": ["vip"]}}))  # True
print(rules.evaluate("eligible", context={"user": {"age": 17, "country": "Chile", "roles": ["member"]}}))  # False

RuleGroup members can be rule names, already compiled Rule objects, or other RuleGroup instances. Nested groups short-circuit according to their mode (all/any), empty groups are vacuously True/False, and cycles raise a helpful error. Add groups with RuleBook.add_group or register existing ones with RuleBook.register.

Missing policy

from boolia import evaluate, MissingVariableError

try:
    evaluate("user.age >= 18 and house.light.on", context={"user": {"age": 20}}, on_missing="raise")
except MissingVariableError as e:
    print(e)  # Missing variable/path: house.light.on

print(evaluate("score >= 10", context={}, on_missing="default", default_value=0))  # False
print(evaluate("flag and beta", context={}, tags={"beta"}, on_missing="none"))     # False (flag is None)

Notes

• Use on_missing="none" if you want tags to override missing bare identifiers.
• For stricter semantics on dotted paths, keep on_missing="raise" and allow tags only for bare names.