id,page,ref,title,content,breadcrumbs,references
writing_plugins:writing-plugins-extra-hooks,writing_plugins,writing-plugins-extra-hooks,Plugins that define new plugin hooks,"Plugins can define new plugin hooks that other plugins can use to further extend their functionality. 
             datasette-graphql  is one example of a plugin that does this. It defines a new hook called  graphql_extra_fields ,  described here , which other plugins can use to define additional fields that should be included in the GraphQL schema. 
             To define additional hooks, add a file to the plugin called  datasette_your_plugin/hookspecs.py  with content that looks like this: 
             from pluggy import HookspecMarker

hookspec = HookspecMarker(""datasette"")


@hookspec
def name_of_your_hook_goes_here(datasette):
    ""Description of your hook."" 
             You should define your own hook name and arguments here, following the documentation for  Pluggy specifications . Make sure to pick a name that is unlikely to clash with hooks provided by any other plugins. 
             Then, to register your plugin hooks, add the following code to your  datasette_your_plugin/__init__.py  file: 
             from datasette.plugins import pm
from . import hookspecs

pm.add_hookspecs(hookspecs) 
             This will register your plugin hooks as part of the  datasette  plugin hook namespace. 
             Within your plugin code you can trigger the hook using this pattern: 
             from datasette.plugins import pm

for (
    plugin_return_value
) in pm.hook.name_of_your_hook_goes_here(
    datasette=datasette
):
    # Do something with plugin_return_value
    pass 
             Other plugins will then be able to register their own implementations of your hook using this syntax: 
             from datasette import hookimpl


@hookimpl
def name_of_your_hook_goes_here(datasette):
    return ""Response from this plugin hook"" 
             These plugin implementations can accept 0 or more of the named arguments that you defined in your hook specification.","[""Writing plugins""]","[{""href"": ""https://github.com/simonw/datasette-graphql"", ""label"": ""datasette-graphql""}, {""href"": ""https://github.com/simonw/datasette-graphql/blob/main/README.md#adding-custom-fields-with-plugins"", ""label"": ""described here""}, {""href"": ""https://pluggy.readthedocs.io/en/stable/#specs"", ""label"": ""Pluggy specifications""}]"