fix(template): support boolean argument in Jinja default filter

[hertznsk]

Summary

Fixes #288.

Conductor overrides Jinja2's built-in default filter with a custom implementation that previously only accepted two parameters. Valid Jinja templates using the standard third boolean argument raised TypeError: _default_filter() takes from 1 to 2 positional arguments but 3 were given.

This PR makes TemplateRenderer._default_filter signature-compatible with Jinja's built-in default(value, default_value="", boolean=False).

What changed

src/conductor/executor/template.py — _default_filter now accepts boolean: bool = False:

• boolean=False (default): preserves existing Conductor behavior — only None triggers the default; empty strings, 0, False, [], {} are returned as-is.
• boolean=True: standard Jinja falsey semantics — any falsey value (None, "", 0, False, [], {}) returns the default; truthy values pass through unchanged.

The parameter name default is kept (not renamed to default_value) to avoid breaking any existing keyword-argument callers.

Tests

tests/test_executor/test_template.py — 14 new tests under TestTemplateRendererDefaultFilter:

• boolean=True with each falsey value (None, "", 0, False, [], {}) → default
• boolean=True with a truthy value → value returned unchanged
• Two-arg form regression: None → default; "", 0, False, [], {} → returned as-is
• Explicit boolean=False regression for the same edge cases

Verification

• uv run pytest tests/test_executor/test_template.py -v → 60/60 passed
• make check (ruff check + ruff format + ty) → exit 0
• Manual: uv run python -c 'from conductor.executor.template import TemplateRenderer; r = TemplateRenderer(); print(r.render("{{ value | default(\\"x\\", true) }}", {"value": None}))' → prints x without TypeError

Out of scope

Per the issue's suggested direction, item 1 ("Return default_value for Jinja Undefined values") is intentionally not changed here: Conductor runs with StrictUndefined, so undefined variables raise TemplateError before reaching the filter — the existing fail-fast behavior is preserved.

[jrob5756]

Good change. Some small things, the new argument works for defined falsey values, but the missing-variable path still differs from Jinja and needs a regression test. I also left a small docstring clarification.

If you can wrap these up, we can merge! Thanks again.

[jrob5756]

This still breaks the missing-value case from #288. With StrictUndefined, not value calls StrictUndefined.__bool__ and raises, while Jinja's built-in default returns the fallback. Please check Undefined before testing truthiness and add coverage for a missing variable in both forms. This replacement also needs Undefined imported from jinja2.

Suggested change

	if boolean:
	if not value:
	return default
	else:
	if value is None:
	return default
	return value
	if isinstance(value, Undefined):
	return default
	if boolean and not value:
	return default
	if value is None:
	return default
	return value

[hertznsk]

Fixed in 0ab6c6c. Undefined is now imported from jinja2 and checked first, before any truthiness test, so StrictUndefined.__bool__ is never reached:

if isinstance(value, Undefined):
    return default
if boolean and not value:
    return default
if value is None:
    return default
return value

Both {{ v | default('x') }} and {{ v | default('x', true) }} now return the fallback for a missing variable, while unguarded {{ missing }} still raises under StrictUndefined (fail-fast preserved). Added regression tests for a missing top-level variable in both the two-arg and boolean=True forms (including the positional true shorthand), plus a missing nested dict key.

[jrob5756]

This reads as though every falsey value uses the fallback. Empty strings, zero, False, and empty collections are preserved unless boolean=True.

Suggested change

	default: Default value to return if value is None or falsey.
	default: Value returned for None, or for any falsey value when boolean=True.

[hertznsk]

Reworded in 0ab6c6c to make clear that empty strings, zero, False, and empty collections are preserved unless boolean=True:

default: Value returned for None, Undefined, or for any falsey value
    when boolean=True.

I used your suggested phrasing and added Undefined since the filter now also returns the fallback for undefined values.

[jrob5756]

lgtm. approved