preload-module.py - mozsearch

Enable keyboard shortcuts

import json

import time

# Serves a JavaScript module for modulepreload tests, letting the test control

# when each module is served.

# Query parameters:

#   uuid=<uuid>     Names the request so that the test can block and release it.

#                   Required by all of the below.

#   block=1         Block the response until a release=1 request with the same

#                   uuid arrives (used to keep a module outstanding while the

#                   test observes something else).

#   release=1       Release the blocked request with the same uuid.

#   import=<url>    Emit `import "<url>";` so the module has a dependency.

#   syntaxerror=1   Emit a module with a parse error.

#   (otherwise)     Emit an empty module.

# Only release=1 ever writes to the stash and only a blocked request ever reads

# from it, so there is no read-modify-write to race over.

def main(request, response):

    params = request.GET

    uuid = params.first(b"uuid").decode()

    if b"release" in params:

        try:

            request.server.stash.put(uuid, True)

        except Exception:

            # Already released and not yet taken; nothing to do.

            pass

        return (200, [(b"Content-Type", b"text/javascript"),

                      (b"Cache-Control", b"no-store")], b"")

    if b"block" in params:

        remaining = 300  # ~30s safety timeout

        while remaining > 0 and not request.server.stash.take(uuid):

            time.sleep(0.1)

            remaining -= 1

    headers = [(b"Content-Type", b"text/javascript"),

               (b"Cache-Control", b"no-store")]

    if b"syntaxerror" in params:

        return (200, headers, b"if (")

    if b"import" in params:

        dep = params.first(b"import").decode()

        return (200, headers, ("import " + json.dumps(dep) + ";\n").encode())

    return (200, headers, b"export default 1;\n")