procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
" Vim syntax file
" Language: Mercurial unified tests
" Author: Steve Losh (steve@stevelosh.com)
"
" Place this file in ~/.vim/syntax/ and add the following line to your
" ~/.vimrc to enable:
" au BufNewFile,BufRead *.t set filetype=hgtest
"
" If you want folding you'll need the following line as well:
" let hgtest_fold=1
"
" You might also want to set the starting foldlevel for hgtest files:
" autocmd Syntax hgtest setlocal foldlevel=1
if exists("b:current_syntax")
finish
endif
syn include @Shell syntax/sh.vim
syn match hgtestComment /^[^ ].*$/
syn region hgtestOutput start=/^ [^$>]/ start=/^ $/ end=/\v.(\n\n*[^ ])\@=/me=s end=/^ [$>]/me=e-3 end=/^$/ fold containedin=hgtestBlock
syn match hgtestCommandStart /^ \$ / containedin=hgtestCommand
syn region hgtestCommand start=/^ \$ /hs=s+4,rs=s+4 end=/^ [^>]/me=e-3 end=/^ $/me=e-2 containedin=hgtestBlock contains=@Shell keepend
syn region hgtestBlock start=/^ /ms=e-2 end=/\v.(\n\n*[^ ])\@=/me=s end=/^$/me=e-1 fold keepend
hi link hgtestCommandStart Keyword
hi link hgtestComment Normal
hi link hgtestOutput Comment
if exists("hgtest_fold")
setlocal foldmethod=syntax
endif
syn sync match hgtestSync grouphere NONE "^$"
syn sync maxlines=200
" It's okay to set tab settings here, because an indent of two spaces is specified
" by the file format.
setlocal tabstop=2 softtabstop=2 shiftwidth=2 expandtab
let b:current_syntax = "hgtest"