tests/test_template_syntax.py

from pathlib import Path
import re


PROJECT_DIR = Path(__file__).resolve().parents[1]

TEMPLATE_EXPR = re.compile(r"{{\s*([^}]*)\s*}}")


def _exprs_in(path: Path):
    text = path.read_text(encoding='utf-8')
    return TEMPLATE_EXPR.findall(text)


def test_no_arithmetic_in_templates_public_goods_instructions():
    """oTree's template engine does not support arithmetic in expressions.
    This catches cases like `{{ C.PLAYERS_PER_GROUP - 1 }}` or `{{ 60*C.MULTIPLIER }}`.
    """
    tpl = PROJECT_DIR / 'public_goods_simple' / 'instructions.html'
    assert tpl.exists(), 'Expected public_goods_simple/instructions.html to exist'
    for expr in _exprs_in(tpl):
        assert not any(op in expr for op in ('-', '*', '/', '+')), (
            f"Unsupported arithmetic found in template expression: {expr}"
        )