{"id": "plugin_hooks:plugin-hook-extra-template-vars", "page": "plugin_hooks", "ref": "plugin-hook-extra-template-vars", "title": "extra_template_vars(template, database, table, columns, view_name, request, datasette)", "content": "Extra template variables that should be made available in the rendered template context. \n                 \n                     \n                         template  - string \n                         \n                             The template that is being rendered, e.g.  database.html \n                         \n                     \n                     \n                         database  - string or None \n                         \n                             The name of the database, or  None  if the page does not correspond to a database (e.g. the root page) \n                         \n                     \n                     \n                         table  - string or None \n                         \n                             The name of the table, or  None  if the page does not correct to a table \n                         \n                     \n                     \n                         columns  - list of strings or None \n                         \n                             The names of the database columns that will be displayed on this page.  None  if the page does not contain a table. \n                         \n                     \n                     \n                         view_name  - string \n                         \n                             The name of the view being displayed. ( index ,  database ,  table , and  row  are the most important ones.) \n                         \n                     \n                     \n                         request  -  Request object  or None \n                         \n                             The current HTTP request. This can be  None  if the request object is not available. \n                         \n                     \n                     \n                         datasette  -  Datasette class \n                         \n                             You can use this to access plugin configuration options via  datasette.plugin_config(your_plugin_name) \n                         \n                     \n                 \n                 This hook can return one of three different types: \n                 \n                     \n                         Dictionary \n                         \n                             If you return a dictionary its keys and values will be merged into the template context. \n                         \n                     \n                     \n                         Function that returns a dictionary \n                         \n                             If you return a function it will be executed. If it returns a dictionary those values will will be merged into the template context. \n                         \n                     \n                     \n                         Function that returns an awaitable function that returns a dictionary \n                         \n                             You can also return a function which returns an awaitable function which returns a dictionary. \n                         \n                     \n                 \n                 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. \n                 Here's an example plugin that adds a  \"user_agent\"  variable to the template context containing the current request's User-Agent header: \n                 @hookimpl\ndef extra_template_vars(request):\n    return {\"user_agent\": request.headers.get(\"user-agent\")} \n                 This example returns an awaitable function which adds a list of  hidden_table_names  to the context: \n                 @hookimpl\ndef extra_template_vars(datasette, database):\n    async def hidden_table_names():\n        if database:\n            db = datasette.databases[database]\n            return {\n                \"hidden_table_names\": await db.hidden_table_names()\n            }\n        else:\n            return {}\n\n    return hidden_table_names \n                 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: \n                 @hookimpl\ndef extra_template_vars(datasette, database):\n    async def sql_first(sql, dbname=None):\n        dbname = (\n            dbname\n            or database\n            or next(iter(datasette.databases.keys()))\n        )\n        result = await datasette.execute(dbname, sql)\n        return result.rows[0][0]\n\n    return {\"sql_first\": sql_first} \n                 You can then use the new function in a template like so: \n                 SQLite version: {{ sql_first(\"select sqlite_version()\") }} \n                 Examples:  datasette-search-all ,  datasette-template-sql", "breadcrumbs": "[\"Plugin hooks\", \"Page extras\"]", "references": "[{\"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\"}]"}