fix(loader): preserve non-env {{...}} placeholders in ConfigLoader (#81)

[owen-pengtao]

Summary

Fixes #81 — ConfigLoader.load_config blanks non-env {{...}} placeholders in the plugin config.

load_config renders the entire config.yaml through one jinja pass with the default (empty) Undefined:

jinja_env = SandboxedEnvironment(loader=jinja2.BaseLoader(), autoescape=True)
rendered_template = jinja_env.from_string(template).render(env=os.environ)

Because the render only defines env, any {{...}} that is not an env reference is silently rendered to "" at load time — including placeholders a plugin legitimately stores in its config to render itself later, at runtime. The reported symptom: WebhookNotification's default_template

{ "event": "{{event}}", "timestamp": "{{timestamp}}", "violation": {{violation}}, "metadata": {{metadata}} }

is blanked to { "event": "", "timestamp": "", "violation": , ... } at load, so the plugin posts an all-empty, invalid-JSON body.

Fix

Render with jinja2.DebugUndefined (issue #81's suggested option 1) so undefined names — everything except the env.* values passed to render() — survive verbatim as {{ name }} instead of being blanked, while env.* references are still substituted.

jinja_env = SandboxedEnvironment(loader=jinja2.BaseLoader(), autoescape=True, undefined=jinja2.DebugUndefined)

Behavior note

A bare {{ env.MISSING }} for an unset env var now renders literally as {{ env.MISSING }} instead of "". Configs that want an empty fallback should use the default filter ({{ env.X | default('') }}), which continues to work. This is the documented trade-off of the DebugUndefined approach.

Tests

Adds tests/unit/cpex/framework/loader/test_config_loader.py:

• env.* reference is still substituted;
• a non-env {{...}} runtime template placeholder is preserved (the [BUG]: ConfigLoader.load_config Jinja pass blanks non-env {{...}} placeholders in plugin config #81 regression);
• use_jinja=False leaves everything literal.

Verified against the real 0.1.x ConfigLoader: current behavior blanks the placeholders; with this change the three tests pass and the WebhookNotification-style default_template survives load.

Signed-off-by: Owen Peng tao.peng@tibco.com