Mechanism for enabling pluggy tracing

[simonw]

Could be useful for debugging plugins: https://pluggy.readthedocs.io/en/latest/#call-tracing

I tried this out by adding these two lines in plugins.py:

pm = pluggy.PluginManager("datasette")
pm.add_hookspecs(hookspecs)
# Added these:
pm.trace.root.setwriter(print)
pm.enable_tracing()

Output looked something like this:

INFO:     127.0.0.1:52724 - "GET /-/-/static/app.css HTTP/1.1" 404 Not Found
  actor_from_request [hook]
      datasette: <datasette.app.Datasette object at 0x106277ad0>
      request: <datasette.utils.asgi.Request object at 0x106550a50>

  finish actor_from_request --> [] [hook]

  extra_body_script [hook]
      template: show_json.html
      database: None
      table: None
      view_name: json_data
      datasette: <datasette.app.Datasette object at 0x106277ad0>

  finish extra_body_script --> [] [hook]

  extra_template_vars [hook]
      template: show_json.html
      database: None
      table: None
      view_name: json_data
      request: <datasette.utils.asgi.Request object at 0x1065504d0>
      datasette: <datasette.app.Datasette object at 0x106277ad0>

  finish extra_template_vars --> [] [hook]

  extra_css_urls [hook]
      template: show_json.html
      database: None
      table: None
      datasette: <datasette.app.Datasette object at 0x106277ad0>

  finish extra_css_urls --> [] [hook]

  extra_js_urls [hook]
      template: show_json.html
      database: None
      table: None
      datasette: <datasette.app.Datasette object at 0x106277ad0>

  finish extra_js_urls --> [] [hook]

INFO:     127.0.0.1:52724 - "GET /-/actor HTTP/1.1" 200 OK
  actor_from_request [hook]
      datasette: <datasette.app.Datasette object at 0x106277ad0>
      request: <datasette.utils.asgi.Request object at 0x1065500d0>

  finish actor_from_request --> [] [hook]

[simonw]

Easiest way to do this would be with an environment variable.

[simonw]

Or I could get fancy and implement my own pm.trace.root.setwriter function which collects data that can be appended to the ?_trace=1 dump.