view tests/test-eol-update.t @ 26375:3686fa2b8eee

windows: insert file positioning call between reads and writes

fopen() and fdopen() have a unique-to-Windows requirement that
transitions between read and write operations in files opened
in modes r+, w+, and a+ perform a file positioning call
(fsetpos, fseek, or rewind) in between. While the MSDN docs don't
say what will happen if this is not done, observations reveal
that Python raises an IOError with errno 0. Furthermore, I
/think/ this behavior isn't deterministic. But I can reproduce
it reliably with subsequent patches applied that open revlogs
in a+ mode and perform both reads and writes.

This patch introduces a proxy class for file handles opened
in r+, w+, and a+ mode on Windows. The class intercepts calls
and audits whether a file positioning function has been called
between read and write operations. If not, a dummy, no-op seek
to the current file position is performed. This appears to be
sufficient to "trick" Windows into allowing transitions between
read and writes without raising errors.

Test EOL update

  $ cat >> $HGRCPATH <<EOF
  > [diff]
  > git = 1
  > EOF

  $ seteol () {
  >     if [ $1 = "LF" ]; then
  >         EOL='\n'
  >     else
  >         EOL='\r\n'
  >     fi
  > }

  $ makerepo () {
  >     echo
  >     echo "# ==== setup repository ===="
  >     echo '% hg init'
  >     hg init repo
  >     cd repo
  > 
  >     cat > .hgeol <<EOF
  > [patterns]
  > **.txt = LF
  > EOF
  > 
  >     printf "first\nsecond\nthird\n" > a.txt
  >     hg commit --addremove -m 'LF commit'
  > 
  >     cat > .hgeol <<EOF
  > [patterns]
  > **.txt = CRLF
  > EOF
  > 
  >     printf "first\r\nsecond\r\nthird\r\n" > a.txt
  >     hg commit -m 'CRLF commit'
  > 
  >     cd ..
  > }

  $ dotest () {
  >     seteol $1
  > 
  >     echo
  >     echo "% hg clone repo repo-$1"
  >     hg clone --noupdate repo repo-$1
  >     cd repo-$1
  > 
  >     cat > .hg/hgrc <<EOF
  > [extensions]
  > eol =
  > EOF
  > 
  >     hg update
  > 
  >     echo '% a.txt (before)'
  >     cat a.txt
  > 
  >     printf "first${EOL}third${EOL}" > a.txt
  > 
  >     echo '% a.txt (after)'
  >     cat a.txt
  >     echo '% hg diff'
  >     hg diff
  > 
  >     echo '% hg update 0'
  >     hg update 0
  > 
  >     echo '% a.txt'
  >     cat a.txt
  >     echo '% hg diff'
  >     hg diff
  > 
  > 
  >     cd ..
  >     rm -r repo-$1
  > }

  $ makerepo
  
  # ==== setup repository ====
  % hg init
  adding .hgeol
  adding a.txt
  $ dotest LF
  
  % hg clone repo repo-LF
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  % a.txt (before)
  first\r (esc)
  second\r (esc)
  third\r (esc)
  % a.txt (after)
  first
  third
  % hg diff
  diff --git a/a.txt b/a.txt
  --- a/a.txt
  +++ b/a.txt
  @@ -1,3 +1,2 @@
   first\r (esc)
  -second\r (esc)
   third\r (esc)
  % hg update 0
  merging a.txt
  1 files updated, 1 files merged, 0 files removed, 0 files unresolved
  % a.txt
  first
  third
  % hg diff
  diff --git a/a.txt b/a.txt
  --- a/a.txt
  +++ b/a.txt
  @@ -1,3 +1,2 @@
   first
  -second
   third
  $ dotest CRLF
  
  % hg clone repo repo-CRLF
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  % a.txt (before)
  first\r (esc)
  second\r (esc)
  third\r (esc)
  % a.txt (after)
  first\r (esc)
  third\r (esc)
  % hg diff
  diff --git a/a.txt b/a.txt
  --- a/a.txt
  +++ b/a.txt
  @@ -1,3 +1,2 @@
   first\r (esc)
  -second\r (esc)
   third\r (esc)
  % hg update 0
  merging a.txt
  1 files updated, 1 files merged, 0 files removed, 0 files unresolved
  % a.txt
  first
  third
  % hg diff
  diff --git a/a.txt b/a.txt
  --- a/a.txt
  +++ b/a.txt
  @@ -1,3 +1,2 @@
   first
  -second
   third
  $ rm -r repo