ed543ae2f6
Fix wasi::fs::OpenOptions to imply write when append is on This PR fixes a bug in `OpenOptions` of `wasi` platform that it currently doesn't imply write mode when only `append` is enabled. As explained in the [doc of OpenOptions#append](https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.append), calling `.append(true)` should imply `.write(true)` as well. ## Reproduce Given below simple Rust program: ```rust use std::fs::OpenOptions; use std::io::Write; fn main() { let mut file = OpenOptions::new() .write(true) .create(true) .open("foo.txt") .unwrap(); writeln!(file, "abc").unwrap(); } ``` it can successfully compiled into wasm and execute by `wasmtime` runtime: ```sh $ rustc --target wasm32-wasi write.rs $ ~/wasmtime/target/debug/wasmtime run --dir=. write.wasm $ cat foo.txt abc ``` However when I change `.write(true)` to `.append(true)`, it fails to execute by the error "Capabilities insufficient": ```sh $ ~/wasmtime/target/debug/wasmtime run --dir=. append.wasm thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 76, kind: Other, message: "Capabilities insufficient" }', append.rs:10:5 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace Error: failed to run main module `append.wasm` ... ``` This is because of lacking "rights" on the opened file: ```sh $ RUST_LOG=trace ~/wasmtime/target/debug/wasmtime run --dir=. append.wasm 2>&1 | grep validate_rights TRACE wasi_common::entry > | validate_rights failed: required rights = HandleRights { base: fd_write (0x40), inheriting: empty (0x0) }; actual rights = HandleRights { base: fd_seek|fd_fdstat_set_flags|fd_sync|fd_tell|fd_advise|fd_filestat_set_times|poll_fd_readwrite (0x88000bc), inheriting: empty (0x0) } ``` |
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