Overwriting a file with Data.write(to:) causes an error

[kkebo]

Description

The Wasm binary built with SwiftWasm can use Foundation's Data.write(to:). However, when the file already exists, the write itself succeeds but an error occurs.

That's because it tries to set permissions even though it does not have permission concept.

Steps to reproduce

$ tree .
.
├── Package.swift
└── Sources
    └── main.swift

2 directories, 2 files
$ cat Package.swift
// swift-tools-version: 6.0

import PackageDescription

let package = Package(
    name: "write_test",
    targets: [
        .executableTarget(name: "write_test")
    ]
)
$ cat Sources/main.swift
import Foundation
try! "test".data(using: .utf8)!.write(to: URL(fileURLWithPath: "./test.txt"))
$ swift build --swift-sdk wasm32-unknown-wasi
Building for debugging...
[1/1] Write swift-version-31C605C61487384.txt
Build complete! (0.13s)
$ wasmtime run --dir . .build/debug/write_test.wasm
$ cat test.txt
test
$ wasmtime run --dir . .build/debug/write_test.wasm
write_test/main.swift:3: Fatal error: 'try!' expression unexpectedly raised an error: Error Domain=NSCocoaErrorDomain Code=512 "(null)"
Error: failed to run main module `.build/debug/write_test.wasm`

Caused by:
    0: failed to invoke command default
    1: error while executing at wasm backtrace:
           0: 0x3a612 - <unknown>!$ss17_assertionFailure__4file4line5flagss5NeverOs12StaticStringV_SSAHSus6UInt32VtF
           1: 0xe04c8 - <unknown>!swift_unexpectedError
           2: 0x24192 - <unknown>!main
           3: 0xbd138c - <unknown>!__main_void
           4: 0x23b2b - <unknown>!_start
       note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable may show more debugging information
    2: wasm trap: wasm `unreachable` instruction executed

Environment

$ uname -a
Linux Brown-rhinoceros-beetle 6.8.10-400.asahi.fc40.aarch64+16k #1 SMP PREEMPT_DYNAMIC Mon May 27 16:05:41 UTC 2024 aarch64 GNU/Linux
$ which swift
/home/kebo/.local/bin/swift
$ swiftly list
Installed release toolchains
----------------------------

Installed snapshot toolchains
-----------------------------
6.0-snapshot-2024-06-07
main-snapshot-2024-06-07
main-snapshot-2024-06-06 (in use)
$ swift --version
Swift version 6.0-dev (LLVM 70f5988c1c84591, Swift 4f8181dde6a5a62)
Target: aarch64-unknown-linux-gnu
$ swift sdk list
DEVELOPMENT-SNAPSHOT-2024-06-07-a-wasm32-unknown-wasi
$ wasmtime -V
wasmtime-cli 19.0.0