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Update the flutter script's locking mechanism and follow_links (#57590)

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Update the flutter and dart scripts' locking mechanism and follow_links function to be more robust and support more platforms.

This adds support for using mkdir as a fallback if the system doesn't have flock instead of using shlock, since shlock doesn't work on shared filesystems.

It also fixes a problem in the follow_links function where it failed when the link resolved to the root directory.
This commit is contained in:
Greg Spencer 2020-05-27 15:30:46 -07:00 committed by GitHub
parent 8ef2915453
commit 379e11b641
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 137 additions and 94 deletions
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43
bin/dart
View File

@ -13,28 +13,37 @@
set -e
# Needed because if it is set, cd may print the path it changed to.
unset CDPATH
function follow_links() {
cd -P "${1%/*}"
local file="$PWD/${1##*/}"
# On Mac OS, readlink -f doesn't work, so follow_links traverses the path one
# link at a time, and then cds into the link destination and find out where it
# ends up.
#
# The returned filesystem path must be a format usable by Dart's URI parser,
# since the Dart command line tool treats its argument as a file URI, not a
# filename. For instance, multiple consecutive slashes should be reduced to a
# single slash, since double-slashes indicate a URI "authority", and these are
# supposed to be filenames. There is an edge case where this will return
# multiple slashes: when the input resolves to the root directory. However, if
# that were the case, we wouldn't be running this shell, so we don't do anything
# about it.
#
# The function is enclosed in a subshell to avoid changing the working directory
# of the caller.
function follow_links() (
cd -P "$(dirname -- "$1")"
file="$PWD/$(basename -- "$1")"
while [[ -h "$file" ]]; do
# On Mac OS, readlink -f doesn't work.
cd -P "${file%/*}"
file="$(readlink "$file")"
cd -P "${file%/*}"
file="$PWD/${file##*/}"
cd -P "$(dirname -- "$file")"
file="$(readlink -- "$file")"
cd -P "$(dirname -- "$file")"
file="$PWD/$(basename -- "$file")"
done
echo "$PWD/${file##*/}"
}
echo "$file"
)
# Convert a filesystem path to a format usable by Dart's URI parser.
function path_uri() {
# Reduce multiple leading slashes to a single slash.
echo "$1" | sed -E -e "s,^/+,/,"
}
PROG_NAME="$(path_uri "$(follow_links "$BASH_SOURCE")")"
PROG_NAME="$(follow_links "$BASH_SOURCE")"
BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
# To define `shared::execute()` function

43
bin/flutter
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@ -13,28 +13,37 @@
set -e
# Needed because if it is set, cd may print the path it changed to.
unset CDPATH
function follow_links() {
cd -P "${1%/*}"
local file="$PWD/${1##*/}"
# On Mac OS, readlink -f doesn't work, so follow_links traverses the path one
# link at a time, and then cds into the link destination and find out where it
# ends up.
#
# The returned filesystem path must be a format usable by Dart's URI parser,
# since the Dart command line tool treats its argument as a file URI, not a
# filename. For instance, multiple consecutive slashes should be reduced to a
# single slash, since double-slashes indicate a URI "authority", and these are
# supposed to be filenames. There is an edge case where this will return
# multiple slashes: when the input resolves to the root directory. However, if
# that were the case, we wouldn't be running this shell, so we don't do anything
# about it.
#
# The function is enclosed in a subshell to avoid changing the working directory
# of the caller.
function follow_links() (
cd -P "$(dirname -- "$1")"
file="$PWD/$(basename -- "$1")"
while [[ -h "$file" ]]; do
# On Mac OS, readlink -f doesn't work.
cd -P "${file%/*}"
file="$(readlink "$file")"
cd -P "${file%/*}"
file="$PWD/${file##*/}"
cd -P "$(dirname -- "$file")"
file="$(readlink -- "$file")"
cd -P "$(dirname -- "$file")"
file="$PWD/$(basename -- "$file")"
done
echo "$PWD/${file##*/}"
}
echo "$file"
)
# Convert a filesystem path to a format usable by Dart's URI parser.
function path_uri() {
# Reduce multiple leading slashes to a single slash.
echo "$1" | sed -E -e "s,^/+,/,"
}
PROG_NAME="$(path_uri "$(follow_links "$BASH_SOURCE")")"
PROG_NAME="$(follow_links "$BASH_SOURCE")"
BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
# To define `shared::execute()` function

143
bin/shared.sh
View File

@ -14,12 +14,9 @@
set -e
# Needed because if it is set, cd may print the path it changed to.
unset CDPATH
function _rmlock () {
[ -n "$FLUTTER_UPGRADE_LOCK" ] && rm -f "$FLUTTER_UPGRADE_LOCK"
}
function retry_upgrade {
local total_tries="10"
local remaining_tries=$((total_tries - 1))
@ -37,50 +34,78 @@ function retry_upgrade {
return 0
}
function upgrade_flutter () {
# Trap function for removing any remaining lock file at exit.
function _rmlock () {
[ -n "$FLUTTER_UPGRADE_LOCK" ] && rm -rf "$FLUTTER_UPGRADE_LOCK"
}
# Determines which lock method to use, based on what is available on the system.
# Returns a non-zero value if the lock was not acquired, zero if acquired.
function _lock () {
if hash flock 2>/dev/null; then
flock --nonblock --exclusive 7 2>/dev/null
else
mkdir "$1" 2>/dev/null
fi
}
# Waits for an update lock to be acquired.
#
# To ensure that we don't simultaneously update Dart in multiple parallel
# instances, we try to obtain an exclusive lock on this file descriptor (and
# thus this script's source file) while we are updating Dart and compiling the
# script. To do this, we try to use the command line program "flock", which is
# available on many Unix-like platforms, in particular on most Linux
# distributions. You give it a file descriptor, and it locks the corresponding
# file, having inherited the file descriptor from the shell.
#
# Complicating matters, there are two major scenarios where this will not
# work.
#
# The first is if the platform doesn't have "flock", for example on macOS. There
# is not a direct equivalent, so on platforms that don't have flock, we fall
# back to using mkdir as an atomic operation to create a lock directory. If
# mkdir is able to create the directory, then the lock is acquired. To determine
# if we have "flock" available, we use the "hash" shell built-in.
#
# The second complication is NFS. On NFS, to obtain an exclusive lock you need a
# file descriptor that is open for writing. Thus, we ignore errors from flock by
# redirecting all output to /dev/null, since users will typically not care about
# errors from flock and are more likely to be confused by them than helped.
#
# The upgrade_flutter function calling _wait_for_lock is executed in a subshell
# with a redirect that pipes the source of this script into file descriptor 7.
# A flock lock is released when this subshell exits and file descriptor 7 is
# closed. The mkdir lock is released via an exit trap from the subshell that
# deletes the lock directory.
function _wait_for_lock () {
FLUTTER_UPGRADE_LOCK="$FLUTTER_ROOT/bin/cache/.upgrade_lock"
local waiting_message_displayed
while ! _lock "$FLUTTER_UPGRADE_LOCK"; do
if [[ -z $waiting_message_displayed ]]; then
# Print with a return so that if the Dart code also prints this message
# when it does its own lock, the message won't appear twice. Be sure that
# the clearing printf below has the same number of space characters.
printf "Waiting for another flutter command to release the startup lock...\r";
waiting_message_displayed="true"
fi
sleep .1;
done
# Clear the waiting message so it doesn't overlap any following text.
printf " \r";
unset waiting_message_displayed
# If the lock file is acquired, make sure that it is removed on exit.
trap _rmlock INT TERM EXIT
}
# This function is always run in a subshell. Running the function in a subshell
# is required to make sure any lock directory is cleaned up by the exit trap in
# _wait_for_lock.
function upgrade_flutter () (
mkdir -p "$FLUTTER_ROOT/bin/cache"
# This function is executed with a redirect that pipes the source of
# this script into file descriptor 3.
#
# To ensure that we don't simultaneously update Dart in multiple
# parallel instances, we try to obtain an exclusive lock on this
# file descriptor (and thus this script's source file) while we are
# updating Dart and compiling the script. To do this, we try to use
# the command line program "flock", which is available on many
# Unix-like platforms, in particular on most Linux distributions.
# You give it a file descriptor, and it locks the corresponding
# file, having inherited the file descriptor from the shell.
#
# Complicating matters, there are two major scenarios where this
# will not work.
#
# The first is if the platform doesn't have "flock", for example on Mac.
# There is not a direct equivalent, so on platforms that don't have flock,
# we fall back to using a lockfile and spinlock with "shlock". This
# doesn't work as well over NFS as it relies on PIDs. Any platform
# without either of these tools has no locking at all. To determine if we
# have "flock" or "shlock" available, we abuse the "hash" shell built-in.
#
# The second complication is NFS. On NFS, to obtain an exclusive
# lock you need a file descriptor that is open for writing, because
# NFS implements exclusive locks by writing, or some such. Thus, we
# ignore errors from flock. We do so by using the '|| true' trick,
# since we are running in a 'set -e' environment wherein all errors
# are fatal, and by redirecting all output to /dev/null, since
# users will typically not care about errors from flock and are
# more likely to be confused by them than helped.
#
# For "flock", the lock is released when the file descriptor goes out of
# scope, i.e. when this function returns. The lock is released via
# a trap when using "shlock".
if hash flock 2>/dev/null; then
flock 3 2>/dev/null || true
elif hash shlock 2>/dev/null; then
FLUTTER_UPGRADE_LOCK="$FLUTTER_ROOT/bin/cache/.upgrade_lock"
while ! shlock -f "$FLUTTER_UPGRADE_LOCK" -p $$ ; do sleep .1 ; done
trap _rmlock EXIT
fi
# Waits for the update lock to be acquired.
_wait_for_lock
local revision="$(cd "$FLUTTER_ROOT"; git rev-parse HEAD)"
@ -111,15 +136,15 @@ function upgrade_flutter () {
"$DART" --disable-dart-dev $FLUTTER_TOOL_ARGS --snapshot="$SNAPSHOT_PATH" --packages="$FLUTTER_TOOLS_DIR/.packages" --no-enable-mirrors "$SCRIPT_PATH"
echo "$revision" > "$STAMP_PATH"
fi
# The exit here is duplicitous since the function is run in a subshell,
# but this serves as documentation that running the function in a
# subshell is required to make sure any lockfile created by shlock
# is cleaned up.
# The exit here is extraneous since the function is run in a subshell, but
# this serves as documentation that running the function in a subshell is
# required to make sure any lock directory created by mkdir is cleaned up.
exit $?
}
)
# This function is intended to be executed by entrypoints (e.g. `//bin/flutter`
# and `//bin/dart`)
# and `//bin/dart`). PROG_NAME and BIN_DIR should already be set by those
# entrypoints.
function shared::execute() {
export FLUTTER_ROOT="$(cd "${BIN_DIR}/.." ; pwd -P)"
@ -132,8 +157,8 @@ function shared::execute() {
DART="$DART_SDK_PATH/bin/dart"
PUB="$DART_SDK_PATH/bin/pub"
# If running over git-bash, overrides the default UNIX
# executables with win32 executables
# If running over git-bash, overrides the default UNIX executables with win32
# executables
case "$(uname -s)" in
MINGW32*)
DART="$DART.exe"
@ -159,8 +184,8 @@ function shared::execute() {
if [[ ! -e "$FLUTTER_ROOT/.git" ]]; then
echo "Error: The Flutter directory is not a clone of the GitHub project."
echo " The flutter tool requires Git in order to operate properly;"
echo " to set up Flutter, run the following command:"
echo " git clone -b stable https://github.com/flutter/flutter.git"
echo " to install Flutter, see the instructions at:"
echo " https://flutter.dev/get-started"
exit 1
fi
@ -169,13 +194,13 @@ function shared::execute() {
# FLUTTER_TOOL_ARGS="--enable-asserts $FLUTTER_TOOL_ARGS"
# FLUTTER_TOOL_ARGS="$FLUTTER_TOOL_ARGS --observe=65432"
(upgrade_flutter) 3< "$PROG_NAME"
upgrade_flutter 7< "$PROG_NAME"
BIN_NAME="$(basename "$PROG_NAME")"
case "$BIN_NAME" in
flutter*)
# FLUTTER_TOOL_ARGS aren't quoted below, because it is meant to
# be considered as separate space-separated args.
# FLUTTER_TOOL_ARGS aren't quoted below, because it is meant to be
# considered as separate space-separated args.
"$DART" --disable-dart-dev --packages="$FLUTTER_TOOLS_DIR/.packages" $FLUTTER_TOOL_ARGS "$SNAPSHOT_PATH" "$@"
;;
dart*)

2
packages/flutter_tools/test/commands.shard/permeable/test_test.dart
View File

@ -218,7 +218,7 @@ Future<void> _testFile(
expect(exec.exitCode, exitCode);
final List<String> output = (exec.stdout as String).split('\n');
if (output.first == 'Waiting for another flutter command to release the startup lock...') {
if (output.first.startsWith('Waiting for another flutter command to release the startup lock...')) {
output.removeAt(0);
}
if (output.first.startsWith('Running "flutter pub get" in')) {