tests/test-http-api.t

wireproto: implement basic frame reading and processing

We just implemented support for writing frames. Now let's implement
support for reading them.

The bulk of the new code is for a class that maintains the state of
a server. Essentially, you construct an instance, feed frames to it,
and it tells you what you should do next. The design is inspired by
the "sans I/O" movement and the reactor pattern. We don't want to
perform I/O or any major blocking event during frame ingestion because
this arbitrarily limits ways that server pieces can be implemented.
For example, it makes it much harder to swap in an alternate
implementation based on asyncio or do crazy things like have requests
dispatch to other processes.

We do still implement readframe() which does I/O. But it is decoupled
from the server reactor. And important parsing of frame headers is
a standalone function. So I/O is only needed to obtain frame data.

Because testing server-side ingest is useful and difficult on running
servers, we create a new "debugreflect" endpoint that will echo back
to the client what was received and how it was interpreted. This could
be useful for a server admin, someone implementing a client. But
immediately, it is useful for testing: we're able to demonstrate that
frames are parsed correctly and turned into requests to run commands
without having to implement command dispatch on the server!

In addition, we implement Python level unit tests for the reactor.
This is vastly more efficient than sending requests to the
"debugreflect" endpoint and vastly more powerful for advanced
testing.

Differential Revision: https://phab.mercurial-scm.org/D2852

  $ send() {
  >   hg --verbose debugwireproto --peer raw http://$LOCALIP:$HGPORT/
  > }

  $ hg init server
  $ hg -R server serve -p $HGPORT -d --pid-file hg.pid
  $ cat hg.pid > $DAEMON_PIDS

Request to /api fails unless web.apiserver is enabled

  $ send << EOF
  > httprequest GET api
  >     user-agent: test
  > EOF
  using raw connection to peer
  s>     GET /api HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     user-agent: test\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     \r\n
  s> makefile('rb', None)
  s>     HTTP/1.1 404 Not Found\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: text/plain\r\n
  s>     Content-Length: 44\r\n
  s>     \r\n
  s>     Experimental API server endpoint not enabled

  $ send << EOF
  > httprequest GET api/
  >     user-agent: test
  > EOF
  using raw connection to peer
  s>     GET /api/ HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     user-agent: test\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     \r\n
  s> makefile('rb', None)
  s>     HTTP/1.1 404 Not Found\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: text/plain\r\n
  s>     Content-Length: 44\r\n
  s>     \r\n
  s>     Experimental API server endpoint not enabled

Restart server with support for API server

  $ killdaemons.py
  $ cat > server/.hg/hgrc << EOF
  > [experimental]
  > web.apiserver = true
  > EOF

  $ hg -R server serve -p $HGPORT -d --pid-file hg.pid
  $ cat hg.pid > $DAEMON_PIDS

/api lists available APIs (empty since none are available by default)

  $ send << EOF
  > httprequest GET api
  >     user-agent: test
  > EOF
  using raw connection to peer
  s>     GET /api HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     user-agent: test\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     \r\n
  s> makefile('rb', None)
  s>     HTTP/1.1 200 OK\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: text/plain\r\n
  s>     Content-Length: 100\r\n
  s>     \r\n
  s>     APIs can be accessed at /api/<name>, where <name> can be one of the following:\n
  s>     \n
  s>     (no available APIs)\n

  $ send << EOF
  > httprequest GET api/
  >     user-agent: test
  > EOF
  using raw connection to peer
  s>     GET /api/ HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     user-agent: test\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     \r\n
  s> makefile('rb', None)
  s>     HTTP/1.1 200 OK\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: text/plain\r\n
  s>     Content-Length: 100\r\n
  s>     \r\n
  s>     APIs can be accessed at /api/<name>, where <name> can be one of the following:\n
  s>     \n
  s>     (no available APIs)\n

Accessing an unknown API yields a 404

  $ send << EOF
  > httprequest GET api/unknown
  >     user-agent: test
  > EOF
  using raw connection to peer
  s>     GET /api/unknown HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     user-agent: test\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     \r\n
  s> makefile('rb', None)
  s>     HTTP/1.1 404 Not Found\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: text/plain\r\n
  s>     Content-Length: 33\r\n
  s>     \r\n
  s>     Unknown API: unknown\n
  s>     Known APIs: 

Accessing a known but not enabled API yields a different error

  $ send << EOF
  > httprequest GET api/exp-http-v2-0001
  >     user-agent: test
  > EOF
  using raw connection to peer
  s>     GET /api/exp-http-v2-0001 HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     user-agent: test\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     \r\n
  s> makefile('rb', None)
  s>     HTTP/1.1 404 Not Found\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: text/plain\r\n
  s>     Content-Length: 33\r\n
  s>     \r\n
  s>     API exp-http-v2-0001 not enabled\n

Restart server with support for HTTP v2 API

  $ killdaemons.py
  $ cat > server/.hg/hgrc << EOF
  > [experimental]
  > web.apiserver = true
  > web.api.http-v2 = true
  > EOF

  $ hg -R server serve -p $HGPORT -d --pid-file hg.pid
  $ cat hg.pid > $DAEMON_PIDS

/api lists the HTTP v2 protocol as available

  $ send << EOF
  > httprequest GET api
  >     user-agent: test
  > EOF
  using raw connection to peer
  s>     GET /api HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     user-agent: test\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     \r\n
  s> makefile('rb', None)
  s>     HTTP/1.1 200 OK\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: text/plain\r\n
  s>     Content-Length: 96\r\n
  s>     \r\n
  s>     APIs can be accessed at /api/<name>, where <name> can be one of the following:\n
  s>     \n
  s>     exp-http-v2-0001

  $ send << EOF
  > httprequest GET api/
  >     user-agent: test
  > EOF
  using raw connection to peer
  s>     GET /api/ HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     user-agent: test\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     \r\n
  s> makefile('rb', None)
  s>     HTTP/1.1 200 OK\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: text/plain\r\n
  s>     Content-Length: 96\r\n
  s>     \r\n
  s>     APIs can be accessed at /api/<name>, where <name> can be one of the following:\n
  s>     \n
  s>     exp-http-v2-0001