view tests/test-convert-cvs-detectmerge.t @ 26457:7e81305092a0

demandimport: replace more references to _demandmod instances

_demandmod instances may be referenced by multiple importing modules.
Before this patch, the _demandmod instance only maintained a reference
to its first consumer when using the "from X import Y" syntax. This is
because we only created a single _demandmod instance (attached to the
parent X module). If multiple modules A and B performed
"from X import Y", we'd produce a single _demandmod instance
"demandmod" with the following references:

  X.Y = <demandmod>
  A.Y = <demandmod>
  B.Y = <demandmod>

The locals from the first consumer (A) would be stored in <demandmod1>.
When <demandmod1> was loaded, we'd look at the locals for the first
consumer and replace the symbol, if necessary. This resulted in state:

  X.Y = <module>
  A.Y = <module>
  B.Y = <demandmod>

B's reference to Y wasn't updated and was still using the proxy object
because we just didn't record that B had a reference to <demandmod> that
needed updating!

With this patch, we add support for tracking which modules in addition
to the initial importer have a reference to the _demandmod instance and
we replace those references at module load time.

In the case of posix.py, this fixes an issue where the "encoding" module
was being proxied, resulting in hundreds of thousands of
__getattribute__ lookups on the _demandmod instance during dirstate
operations on mozilla-central, speeding up execution by many
milliseconds. There are likely several other operation that benefit from
this change as well.

The new mechanism isn't perfect: references in locals (not globals) may
likely linger. So, if there is an import inside a function and a symbol
from that module is used in a hot loop, we could have unwanted overhead
from proxying through _demandmod. Non-global imports are discouraged
anyway. So hopefully this isn't a big deal in practice. We could
potentially deploy a code checker that bans use of attribute lookups of
function-level-imported modules inside loops.

This deficiency in theory could be avoided by storing the set of globals
and locals dicts to update in the _demandmod instance. However, I tried
this and it didn't work. One reason is that some globals are _demandmod
instances. We could work around this, but it's a bit more work. There
also might be other module import foo at play. The solution as
implemented is better than what we had and IMO is good enough for the
time being.

It's worth noting that this sub-optimal behavior was made worse by the
introduction of absolute_import and its recommended "from . import X"
syntax for importing modules from the "mercurial" package. If we ever
wrote performance tests, measuring the amount of module imports and
__getattribute__ proxy calls through _demandmod instances would be
something I'd have it check.

#require cvs

Test config convert.cvsps.mergefrom config setting.
(Should test similar mergeto feature, but I don't understand it yet.)
Requires builtin cvsps.

  $ CVSROOT=`pwd`/cvsrepo
  $ export CVSROOT

  $ cvscall()
  > {
  >     cvs -f "$@"
  > }

output of 'cvs ci' varies unpredictably, so just discard it
XXX copied from test-convert-cvs-synthetic

  $ cvsci()
  > {
  >     sleep 1
  >     cvs -f ci "$@" > /dev/null
  > }

XXX copied from test-convert-cvs-synthetic

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > convert =
  > [convert]
  > cvsps.cache = 0
  > cvsps.mergefrom = \[MERGE from (\S+)\]
  > EOF

create cvs repository with one project

  $ cvscall -q -d "$CVSROOT" init
  $ mkdir cvsrepo/proj

populate cvs repository

  $ cvscall -Q co proj
  $ cd proj
  $ touch file1
  $ cvscall -Q add file1
  $ cvsci -m"add file1 on trunk"
  cvs commit: Examining .

create two release branches

  $ cvscall -q tag -b v1_0
  T file1
  $ cvscall -q tag -b v1_1
  T file1

modify file1 on branch v1_0

  $ cvscall -Q update -rv1_0
  $ sleep 1
  $ echo "change" >> file1
  $ cvsci -m"add text"
  cvs commit: Examining .

make unrelated change on v1_1

  $ cvscall -Q update -rv1_1
  $ touch unrelated
  $ cvscall -Q add unrelated
  $ cvsci -m"unrelated change"
  cvs commit: Examining .

merge file1 to v1_1

  $ cvscall -Q update -jv1_0
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  retrieving revision 1.1
  retrieving revision 1.1.2.1
  Merging differences between 1.1 and 1.1.2.1 into file1
  $ cvsci -m"add text [MERGE from v1_0]"
  cvs commit: Examining .

merge change to trunk

  $ cvscall -Q update -A
  $ cvscall -Q update -jv1_1
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  retrieving revision 1.1
  retrieving revision 1.1.4.1
  Merging differences between 1.1 and 1.1.4.1 into file1
  $ cvsci -m"add text [MERGE from v1_1]"
  cvs commit: Examining .

non-merged change on trunk

  $ echo "foo" > file2
  $ cvscall -Q add file2
  $ cvsci -m"add file2 on trunk" file2

this will create rev 1.3
change on trunk to backport

  $ echo "backport me" >> file1
  $ cvsci -m"add other text" file1
  $ cvscall log file1
  
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  Working file: file1
  head: 1.3
  branch:
  locks: strict
  access list:
  symbolic names:
  	v1_1: 1.1.0.4
  	v1_0: 1.1.0.2
  keyword substitution: kv
  total revisions: 5;	selected revisions: 5
  description:
  ----------------------------
  revision 1.3
  date: * (glob)
  add other text
  ----------------------------
  revision 1.2
  date: * (glob)
  add text [MERGE from v1_1]
  ----------------------------
  revision 1.1
  date: * (glob)
  branches:  1.1.2;  1.1.4;
  add file1 on trunk
  ----------------------------
  revision 1.1.4.1
  date: * (glob)
  add text [MERGE from v1_0]
  ----------------------------
  revision 1.1.2.1
  date: * (glob)
  add text
  =============================================================================

XXX how many ways are there to spell "trunk" with CVS?
backport trunk change to v1_1

  $ cvscall -Q update -rv1_1
  $ cvscall -Q update -j1.2 -j1.3 file1
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  retrieving revision 1.2
  retrieving revision 1.3
  Merging differences between 1.2 and 1.3 into file1
  $ cvsci -m"add other text [MERGE from HEAD]" file1

fix bug on v1_1, merge to trunk with error

  $ cvscall -Q update -rv1_1
  $ echo "merge forward" >> file1
  $ cvscall -Q tag unmerged
  $ cvsci -m"fix file1"
  cvs commit: Examining .
  $ cvscall -Q update -A
  $ cvscall -Q update -junmerged -jv1_1
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  retrieving revision 1.1.4.2
  retrieving revision 1.1.4.3
  Merging differences between 1.1.4.2 and 1.1.4.3 into file1

note the typo in the commit log message

  $ cvsci -m"fix file1 [MERGE from v1-1]"
  cvs commit: Examining .
  $ cvs -Q tag -d unmerged

convert to hg

  $ cd ..
  $ hg convert proj proj.hg
  initializing destination proj.hg repository
  connecting to $TESTTMP/cvsrepo
  scanning source...
  collecting CVS rlog
  12 log entries
  creating changesets
  warning: CVS commit message references non-existent branch 'v1-1':
  fix file1 [MERGE from v1-1]
  10 changeset entries
  sorting...
  converting...
  9 add file1 on trunk
  8 unrelated change
  7 add text
  6 add text [MERGE from v1_0]
  5 add text [MERGE from v1_1]
  4 add file2 on trunk
  3 add other text
  2 add other text [MERGE from HEAD]
  1 fix file1
  0 fix file1 [MERGE from v1-1]

complete log

  $ template="{rev}: '{branches}' {desc}\n"
  $ hg -R proj.hg log --template="$template"
  9: '' fix file1 [MERGE from v1-1]
  8: 'v1_1' fix file1
  7: 'v1_1' add other text [MERGE from HEAD]
  6: '' add other text
  5: '' add file2 on trunk
  4: '' add text [MERGE from v1_1]
  3: 'v1_1' add text [MERGE from v1_0]
  2: 'v1_0' add text
  1: 'v1_1' unrelated change
  0: '' add file1 on trunk

graphical log

  $ hg -R proj.hg log -G --template="$template"
  o  9: '' fix file1 [MERGE from v1-1]
  |
  | o  8: 'v1_1' fix file1
  | |
  | o  7: 'v1_1' add other text [MERGE from HEAD]
  |/|
  o |  6: '' add other text
  | |
  o |  5: '' add file2 on trunk
  | |
  o |  4: '' add text [MERGE from v1_1]
  |\|
  | o    3: 'v1_1' add text [MERGE from v1_0]
  | |\
  +---o  2: 'v1_0' add text
  | |
  | o  1: 'v1_1' unrelated change
  |/
  o  0: '' add file1 on trunk