Mirrors/fish-shell
2
0
Fork 0
mirror of https://github.com/fish-shell/fish-shell synced 2024-12-26 12:53:13 +00:00
Code Issues Projects Releases Packages Wiki Activity

Fix: eval should preserve previous $status if the evaluated block does not change it

Browse source 
Empty functions may return 1 when eval is used due to the $status not being correctly preserved inside the function definition.
This commit is contained in:
Jorge Bucaran 2015-01-15 02:58:07 +09:00 committed by Konrad Borowski
parent 3c0902b7e4
commit 2018b9b217
1 changed files with 22 additions and 21 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

43
share/functions/eval.fish
View file

@ -1,4 +1,12 @@
function eval -S -d "Evaluate parameters as a command"
# keep a copy of the previous $status and use restore_status
# to preserve the status in case the block that is evaluated
# does not modify the status itself.
set -l status_copy $status
function -S restore_status
return $status_copy
end
if not set -q argv[2]
# like most builtins, we only check for -h/--help
# if we only have a single argument
@ -28,28 +36,21 @@ function eval -S -d "Evaluate parameters as a command"
status --job-control full
end
# rfish: 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’
# 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.
echo "begin; $argv "\n" ;end <&3 3<&-" | source 3<&0
restore_status
echo "begin; $argv "\n" ;end eval2_inner <&3 3<&-" | source 3<&0
set -l res $status
status --job-control $mode