issue_comments

Looks like I'm late to the party here, but wanted to join the convo if there's still time before this interface is solidified in v1.0. My plugin use case is for education / social science data, which is meta-data heavy in the documentation of measurement scales, instruments, collection procedures, etc. that I want to connect to columns, tables, and dbs (and render in static pages, but looks like I can do that with the jinja plugin hook). I'm still digging in and I think @brandonrobertz 's approach will work for me at least for now, but I want to bump this thread in the meantime -- are there still plans for an async metadata hook at some point in the future? (or are you considering other directions?)

Made a start on this here: https://datasette.io/tutorials

A lot of the code complexity here is caused by DataView (here), which has the logic for CSV streaming and plugin formats such that it can be shared between tables and custom queries.

It would be good to get rid of that subclassed shared code, figure out how to do it via a utility function instead.

Hah, found a TODO about this: https://github.com/simonw/datasette/blob/c5791156d92615f25696ba93dae5bb2dcc192c98/datasette/app.py#L997-L999

It would be neat if the plugin could spot old-style hyphen hash URLs (maybe on 404) and redirect those too.

I'm now convinced this is feasible enough that it's worth doing in time for Datasette 1.0.

This seems to do the job: python @hookimpl def startup(datasette): for name, database in datasette.databases.items(): if database.hash: new_name = "{}_{}".format(name, database.hash[:7]) del datasette.databases[name] datasette.databases[new_name] = database Would have to teach the rest of the plugin to split on _ and to only redirect if the user seems to be hitting the URL for an old hash after which Datasette has been restarted with an updated database.

Maybe the plugin should interfere with datasette.databases on startup and change the registered name for each one?

Built a prototype of that plugin: ```python from datasette import hookimpl from functools import wraps

@hookimpl def asgi_wrapper(datasette): def wrap_with_hashed_urls(app): @wraps(app) async def hashed_urls(scope, receive, send): # Only triggers on pages with a path not starting in /-/ # and where the first page component matches a database name if scope.get("type") != "http": await app(scope, receive, send) return path = scope["path"].lstrip("/") if not path or path.startswith("-/"): await app(scope, receive, send) return potential_database = path.split("/")[0] # It may or may not be already dbname~hash if "~" in potential_database: db_name, hash = potential_database.split("~", 1) else: db_name = potential_database hash = "" # Is db_name a database we have a hash for? try: db = datasette.get_database(db_name) except KeyError: await app(scope, receive, send) return

        if db.hash is not None:
            # TODO: make sure db.hash is documented
            if db.hash[:7] != hash:
                # Send a redirect
                path_bits = path.split("/")
                new_path = "/" + "/".join(["{}-{}".format(db_name, db.hash[:7])] + path_bits[1:])
                if scope.get("query_string"):
                    new_path += "?" + scope["query_string"].decode("latin-1")

                await send({
                    "type": "http.response.start",
                    "status": 302,
                    "headers": [
                        [b"location", new_path.encode("latin1")]
                    ],
                })
                await send({"type": "http.response.body", "body": b""})
                return
            else:
                # Add a far-future cache header
                async def wrapped_send(event):
                    if event["type"] == "http.response.start":
                        original_headers = event.get("headers") or []
                        event = {
                            "type": event["type"],
                            "status": event["status"],
                            "headers": original_headers + [
                                [b"Cache-Control", b"max-age=31536000"]
                            ],
                        }
                    await send(event)

                await app(scope, receive, wrapped_send)
                return

        await app(scope, receive, send)
    return hashed_urls
return wrap_with_hashed_urls

``` One catch: it doesn't affect the way URLs are generated - so every internal link within Datasette links to the non-hash version and then triggers a 302 redirect to the hashed version.