jinja2 3.1.4: Verify that Environment(trim_blocks=True, lstrip_blocks=True) completely removes the whitespace surrounding block tags.

# Jinja2 Environment Whitespace Control

When rendering templates, blocks like `{% for %}` or `{% if %}` naturally inject whitespace into the final output based on their indentation and trailing newlines. This sample verifies the exact behaviour of the `Environment` parameters `trim_blocks` and `lstrip_blocks` in Jinja2 version 3.1.4.

A search for known solutions for `Environment` whitespace control in Jinja2 returned `NO_SAFE_MATCH`, so this behaviour is being proven fresh.

By setting both `trim_blocks=True` and `lstrip_blocks=True`, the whitespace surrounding the block tags is completely removed. This means the leading spaces (or tabs) before a block tag and the first newline immediately after a block tag are stripped. The result is that you can indent template logic to make the source readable without introducing unwanted blank lines or indentation in the rendered output.

The contract pins Jinja2 3.1.4 and proves this by rendering a simple `<ul>` loop where the logic is indented inside the HTML tags, showing that the resulting HTML is perfectly formatted without any extraneous whitespace from the `{% for %}` and `{% endfor %}` lines.

{"case":{"caseId":"case:sha256:087d2325662ee4b24fd9f927a46e321a82a75f702b3fe87342159edcc8e45467","contract":["Environment(trim_blocks=True, lstrip_blocks=True) completely removes the whitespace surrounding block tags, allowing loops to render without injecting blank lines or indentation.","assert env.from_string(template).render(items=[1, 2]) == expected"],"goal":"Verify that Environment(trim_blocks=True, lstrip_blocks=True) completely removes the whitespace surrounding block tags.","kind":"HOW","packages":["pkg:pypi/jinja2@3.1.4"],"schemaVersion":1,"symbols":["Environment"]},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","ecosystem":"pypi","executionContext":"python","language":"python","os":"linux","packageManager":"pip","runtime":"python","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/jinja2@3.1.4","pkg:pypi/markupsafe@3.0.3"],"schemaVersion":1,"symbols":["Environment"],"verifierAdapter":"python@1"}

Jinja2==3.1.4
MarkupSafe==3.0.3

from jinja2 import Environment

def test_trim_and_lstrip():
    env = Environment(trim_blocks=True, lstrip_blocks=True)
    template = """<ul>
  {% for item in items %}
  <li>{{ item }}</li>
  {% endfor %}
</ul>"""
    
    expected = """<ul>
  <li>1</li>
  <li>2</li>
</ul>"""
    
    actual = env.from_string(template).render(items=[1, 2])
    assert actual == expected, f"Expected:\\n{expected}\\nActual:\\n{actual}"

if __name__ == "__main__":
    test_trim_and_lstrip()
    print("Contract passed!")