[pacman-dev] [PATCH] updpkgsums: drop in-place rewrite hack, use a tempfile

[Dave Reisner]

This apparently exposes (what I think is) a subtle bug in cygwin's
handling of subst'd drives. Let's just drop the hackery and use a
tempfile, which should always work.

Also, introduce a proper die() function which replaces previous
hand-rolled error+exit pattern, but which wrote to stdout.
---
 contrib/updpkgsums.sh.in | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/contrib/updpkgsums.sh.in b/contrib/updpkgsums.sh.in
index e0524bd..a40845b 100644
--- a/contrib/updpkgsums.sh.in
+++ b/contrib/updpkgsums.sh.in
@@ -40,6 +40,11 @@ version() {
        echo 'Copyright (C) 2012-2013 Dave Reisner <dreis...@archlinux.org>'
 }
 
+die() {
+       printf "==> ERROR: $1\n" "${@:2}" >&2
+       exit 1
+}
+
 case $1 in
        -h|--help) usage; exit ;;
        -V|--version) version; exit ;;
@@ -47,8 +52,7 @@ esac
 
 buildfile=${1:-PKGBUILD}
 if [[ ! -f $buildfile ]]; then
-       printf "==> ERROR: %s not found or is not a file\n" "$buildfile"
-       exit 1
+       die "%s not found or is not a file" "$buildfile"
 fi
 
 # Resolve any symlinks to avoid replacing the symlink with a file. But, we
@@ -71,18 +75,19 @@ fi
 
 # Check $PWD/ for permission to unlink the $buildfile and write a new one
 if [[ ! -w . ]]; then
-       printf "==> ERROR: No write permission in '%s'\n" "$PWD"
-       exit 1
+       die "No write permission in '%s'" "$PWD"
 fi
 
-{
-       # Generate the new sums and try to unlink the file before writing stdin 
back
-       # into it. This final precaution shouldn't fail based on the previous 
checks,
-       # but it's better to be extra careful before unlinking files.
-       export BUILDDIR=$(mktemp -d --tmpdir updpkgsums.XXXXXX)
-       trap "rm -rf '$BUILDDIR'" EXIT
-       newsums=$(makepkg -g -p "$buildfile") && rm -f "$buildfile" &&
-       awk -v newsums="$newsums" '
+# Generate the new sums
+export BUILDDIR=$(mktemp -d --tmpdir updpkgsums.XXXXXX)
+newbuildfile=$(mktemp --tmpdir updpkgsums.XXXXXX)
+
+# In case the eventual replacement fails, we don't want to leave behind
+# $newbuildfile as garbage in $TMPDIR. This fails silently if the replacement
+# succeeds.
+trap "rm -rf '$BUILDDIR' '$newbuildfile'" EXIT
+newsums=$(makepkg -g -p "$buildfile") &&
+awk -v newsums="$newsums" '
        
/^[[:blank:]]*(md|sha)[[:digit:]]+sums(_[^=]+)?=/,/\)[[:blank:]]*(#.*)?$/ {
                if (!w) {
                        print newsums
@@ -93,7 +98,11 @@ fi
 
        1
        END { if (!w) print newsums }
-       ' > "$buildfile"
-} < "$buildfile"
+' "$buildfile" > "$newbuildfile"
+
+# Replace the original buildfile.
+if ! mv -- "$newbuildfile" "$buildfile"; then
+       die "Failed to update %s. The file has not been modified." "$buildfile"
+fi
 
 # vim: set noet:
-- 
2.1.3