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Clean up recent fix for #1892

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Restore 906d235 and simplify how __fish_restore_status works
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ridiculousfish 2015-01-17 15:24:47 -08:00
parent 7164769d33
commit 75a76c596c
1 changed files with 24 additions and 17 deletions
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41
share/functions/eval.fish
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@ -3,8 +3,8 @@ function eval -S -d "Evaluate parameters as a command"
# to preserve the status in case the block that is evaluated
# does not modify the status itself.
set -l status_copy $status
function -S __fish_restore_status
return $status_copy
function __fish_restore_status
return $argv[1]
end
if not set -q argv[2]
@ -35,22 +35,29 @@ function eval -S -d "Evaluate parameters as a command"
if status --is-interactive
status --job-control full
end
__fish_restore_status $status_copy
# rfish: To eval 'foo', we construct a block "begin ; foo; end <&3 3<&-"
# The 'eval2_inner' is a param to 'begin' itself; I believe it does nothing.
# Note the redirections are also within the quotes.
#
# We then pipe this to 'source 3<&0' which dup2's 3 to stdin.
#
# You might expect that the dup2(3, stdin) should overwrite stdin,
# and therefore prevent 'source' from reading the piped-in block. This doesn't happen
# because when you pipe to a builtin, we don't overwrite stdin with the read end
# of the block; instead we set a separate fd in a variable 'builtin_stdin', which is
# what it reads from. So builtins are magic in that, in pipes, their stdin
# is not fd 0.
__fish_restore_status
echo "begin; $argv "\n" ;end eval2_inner <&3 3<&-" | source 3<&0
# To eval 'foo', we construct a block "begin ; foo; end <&3 3<&-"
# Note the redirections are also within the quotes.
#
# We then pipe this to 'source 3<&0’.
#
# You might expect that the dup2(3, stdin) should overwrite stdin,
# and therefore prevent 'source' from reading the piped-in block. This doesn't happen
# because when you pipe to a builtin, we don't overwrite stdin with the read end
# of the block; instead we set a separate fd in a variable 'builtin_stdin', which is
# what it reads from. So builtins are magic in that, in pipes, their stdin
# is not fd 0.
#
# ‘source’ does not apply the redirections to itself. Instead it saves them and passes
# them as block-level redirections to parser.eval(). Ultimately the eval’d code sees
# the following redirections (in the following order):
# dup2 0 -> 3
# dup2 pipe -> 0
# dup2 3 -> 0
# where the pipe is the pipe we get from piping ‘echo’ to ‘source’. Thus the redirection
# effectively makes stdin fd0, instead of the thing that was piped to ‘source’
echo "begin; $argv "\n" ;end <&3 3<&-" | source 3<&0
set -l res $status
status --job-control $mode