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
$ echo "[extensions]" >> $HGRCPATH
$ echo "rebase=" >> $HGRCPATH
initialize repository
$ hg init
$ echo 'a' > a
$ hg ci -A -m "0"
adding a
$ echo 'b' > b
$ hg ci -A -m "1"
adding b
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo 'c' > c
$ hg ci -A -m "2"
adding c
created new head
$ echo 'd' > d
$ hg ci -A -m "3"
adding d
$ hg bookmark -r 1 one
$ hg bookmark -r 3 two
$ hg up -q two
bookmark list
$ hg bookmark
one 1:925d80f479bb
* two 3:2ae46b1d99a7
rebase
$ hg rebase -s two -d one
rebasing 3:2ae46b1d99a7 "3" (two tip)
saved backup bundle to $TESTTMP/.hg/strip-backup/2ae46b1d99a7-e6b057bc-rebase.hg
$ hg log
changeset: 3:42e5ed2cdcf4
bookmark: two
tag: tip
parent: 1:925d80f479bb
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 3
changeset: 2:db815d6d32e6
parent: 0:f7b1eb17ad24
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 2
changeset: 1:925d80f479bb
bookmark: one
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 1
changeset: 0:f7b1eb17ad24
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
aborted rebase should restore active bookmark.
$ hg up 1
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
(leaving bookmark two)
$ echo 'e' > d
$ hg ci -A -m "4"
adding d
created new head
$ hg bookmark three
$ hg rebase -s three -d two
rebasing 4:dd7c838e8362 "4" (three tip)
merging d
warning: conflicts while merging d! (edit, then use 'hg resolve --mark')
unresolved conflicts (see hg resolve, then hg rebase --continue)
[1]
$ hg rebase --abort
rebase aborted
$ hg bookmark
one 1:925d80f479bb
* three 4:dd7c838e8362
two 3:42e5ed2cdcf4
after aborted rebase, restoring a bookmark that has been removed should not fail
$ hg rebase -s three -d two
rebasing 4:dd7c838e8362 "4" (three tip)
merging d
warning: conflicts while merging d! (edit, then use 'hg resolve --mark')
unresolved conflicts (see hg resolve, then hg rebase --continue)
[1]
$ hg bookmark -d three
$ hg rebase --abort
rebase aborted
$ hg bookmark
one 1:925d80f479bb
two 3:42e5ed2cdcf4