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Querying configuration

Creating a tool

A Morepath-based application may over time grow big, have multiple authors and spread over many modules. In this case it is helpful to have a tool that helps you explore Morepath configuration and quickly find what directives are defined where. The Dectate library :ref:`details how to create such a tool <dectate:query_tool>`, but we repeat it here for Morepath:

import dectate
from mybigapp import App

def query_tool():
    dectate.query_tool(App.commit())

You save it in a module called query.py in the mybigapp package. Then you hook it up in setup.py so that a query script gets generated:

entry_points={
    'console_scripts': [
        'morepathq = mybigapp.query:query_tool',
    ]
},

Now when you re-install your project, you get a command-line query tool called morepathq that lets you issue queries.

What just happened?

  • In order to be able to query an app's configuration you need to commit it first. App.commit() also commits any other application you may have mounted into it. You get an iterable of apps that got committed.
  • You pass this iterable into the query_tool function. This lets the query tool search through the configuration of the apps you committed only.
  • You hook it up so that a command-line script gets generated using
    setuptool's console_scripts mechanism.

Usage

So now that you have a morepathq query tool, let's use it:

$ morepathq view
App: <class 'mybigapp.App'>
  File ".../somemodule.py", line 4
  @App.html(model=Foo)

  File ".../anothermodule.py", line 8
  @App.json(model=Bar)

Here we query for the view directive; since the view directive is grouped with json and html we get those back too. We get the module and line number where the directive was used.

You can also filter:

$ morepathq view model=mybigapp.model.Foo
App: <class 'mybigapp.App'>
  File ".../somemodule.py", line 4
  @App.html(model=Foo)

Here we query all views that have the model value set to Foo or one of its subclasses. Note that in able to refer to Foo in the query we use the dotted name to that class in the module it was defined.

You can query any Morepath directive this way:

$ morepathq path model=mybigapp.model.Foo
App: <class 'mybigapp.App'>
  File ".../path.py", line 8
  @App.path(model=Foo, path="/foo")