flutter/bin/dart
Greg Spencer 379e11b641
Update the flutter script's locking mechanism and follow_links (#57590)
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.
2020-05-27 15:30:46 -07:00

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#!/usr/bin/env bash
# Copyright 2014 The Flutter Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
# ---------------------------------- NOTE ---------------------------------- #
#
# Please keep the logic in this file consistent with the logic in the
# `dart.bat` script in the same directory to ensure that Flutter & Dart continue
# to work across all platforms!
#
# -------------------------------------------------------------------------- #
set -e
# Needed because if it is set, cd may print the path it changed to.
unset CDPATH
# 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
cd -P "$(dirname -- "$file")"
file="$(readlink -- "$file")"
cd -P "$(dirname -- "$file")"
file="$PWD/$(basename -- "$file")"
done
echo "$file"
)
PROG_NAME="$(follow_links "$BASH_SOURCE")"
BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
# To define `shared::execute()` function
source "$BIN_DIR/shared.sh"
shared::execute "$@"