id,page,ref,title,content,breadcrumbs,references
plugin_hooks:plugin-hook-extra-template-vars,plugin_hooks,plugin-hook-extra-template-vars,"extra_template_vars(template, database, table, columns, view_name, request, datasette)","Extra template variables that should be made available in the rendered template context. 
                 
                     
                         template  - string 
                         
                             The template that is being rendered, e.g.  database.html 
                         
                     
                     
                         database  - string or None 
                         
                             The name of the database, or  None  if the page does not correspond to a database (e.g. the root page) 
                         
                     
                     
                         table  - string or None 
                         
                             The name of the table, or  None  if the page does not correct to a table 
                         
                     
                     
                         columns  - list of strings or None 
                         
                             The names of the database columns that will be displayed on this page.  None  if the page does not contain a table. 
                         
                     
                     
                         view_name  - string 
                         
                             The name of the view being displayed. ( index ,  database ,  table , and  row  are the most important ones.) 
                         
                     
                     
                         request  -  Request object  or None 
                         
                             The current HTTP request. This can be  None  if the request object is not available. 
                         
                     
                     
                         datasette  -  Datasette class 
                         
                             You can use this to access plugin configuration options via  datasette.plugin_config(your_plugin_name) 
                         
                     
                 
                 This hook can return one of three different types: 
                 
                     
                         Dictionary 
                         
                             If you return a dictionary its keys and values will be merged into the template context. 
                         
                     
                     
                         Function that returns a dictionary 
                         
                             If you return a function it will be executed. If it returns a dictionary those values will will be merged into the template context. 
                         
                     
                     
                         Function that returns an awaitable function that returns a dictionary 
                         
                             You can also return a function which returns an awaitable function which returns a dictionary. 
                         
                     
                 
                 Datasette runs Jinja2 in  async mode , which means you can add awaitable functions to the template scope and they will be automatically awaited when they are rendered by the template. 
                 Here's an example plugin that adds a  ""user_agent""  variable to the template context containing the current request's User-Agent header: 
                 @hookimpl
def extra_template_vars(request):
    return {""user_agent"": request.headers.get(""user-agent"")} 
                 This example returns an awaitable function which adds a list of  hidden_table_names  to the context: 
                 @hookimpl
def extra_template_vars(datasette, database):
    async def hidden_table_names():
        if database:
            db = datasette.databases[database]
            return {
                ""hidden_table_names"": await db.hidden_table_names()
            }
        else:
            return {}

    return hidden_table_names 
                 And here's an example which adds a  sql_first(sql_query)  function which executes a SQL statement and returns the first column of the first row of results: 
                 @hookimpl
def extra_template_vars(datasette, database):
    async def sql_first(sql, dbname=None):
        dbname = (
            dbname
            or database
            or next(iter(datasette.databases.keys()))
        )
        result = await datasette.execute(dbname, sql)
        return result.rows[0][0]

    return {""sql_first"": sql_first} 
                 You can then use the new function in a template like so: 
                 SQLite version: {{ sql_first(""select sqlite_version()"") }} 
                 Examples:  datasette-search-all ,  datasette-template-sql","[""Plugin hooks"", ""Page extras""]","[{""href"": ""https://jinja.palletsprojects.com/en/2.10.x/api/#async-support"", ""label"": ""async mode""}, {""href"": ""https://datasette.io/plugins/datasette-search-all"", ""label"": ""datasette-search-all""}, {""href"": ""https://datasette.io/plugins/datasette-template-sql"", ""label"": ""datasette-template-sql""}]"