Fix unexpected_cfgs warnings. (#358)

* Fix unexpected_cfgs warnings.

Fix warnings about cfgs that aren't declared, by declaring the cfgs we
do use in build.rs files. And fix a bug this turned up, around the usage
of unix_file_vectored_at.

* Fix an unexpected_cfg warning.

* Use `cargo:` instead of `cargo::` for broader compatibility.

* Fix `cfg(feature = "async_std")` in cap-fs-ext.

* Fix the test to be independent of the expected error message.

Author: sunfishcode

build.rs

@@ -17,6 +17,9 @@ fn main() {
                                                   // https://doc.rust-lang.org/unstable-book/library-features/windows-file-type-ext.html
     use_feature_or_nothing("windows_file_type_ext");
 
+    // Cfgs that users may set.
+    println!("cargo:rustc-check-cfg=cfg(racy_asserts)");
+
     // Don't rerun this on changes other than build.rs, as we only depend on
     // the rustc version.
     println!("cargo:rerun-if-changed=build.rs");
@@ -26,6 +29,7 @@ fn use_feature_or_nothing(feature: &str) {
     if has_feature(feature) {
         use_feature(feature);
     }
+    println!("cargo:rustc-check-cfg=cfg({})", feature);
 }
 
 fn use_feature(feature: &str) {

cap-fs-ext/Cargo.toml

@@ -28,6 +28,7 @@ default = ["std"]
 fs_utf8 = ["cap-std/fs_utf8", "camino"]
 arf_strings = ["cap-std/arf_strings", "fs_utf8", "arf-strings"]
 std = ["cap-std"]
+# Temporarily disable cap-async-std.
 #async_std = ["cap-async-std", "async-std", "io-lifetimes/async-std", "async-trait"]
 #async_std_fs_utf8 = ["cap-async-std/fs_utf8", "camino"]
 #async_std_arf_strings = ["cap-async-std/arf_strings", "async_std_fs_utf8", "arf-strings"]

cap-fs-ext/build.rs

@@ -13,6 +13,7 @@ fn use_feature_or_nothing(feature: &str) {
     if has_feature(feature) {
         use_feature(feature);
     }
+    println!("cargo:rustc-check-cfg=cfg({})", feature);
 }
 
 fn use_feature(feature: &str) {

cap-fs-ext/src/dir_ext.rs

@@ -1393,13 +1393,13 @@ impl AsyncDirExtUtf8 for cap_async_std::fs_utf8::Dir {
 
 #[cfg(all(any(feature = "std", feature = "async_std"), feature = "fs_utf8"))]
 #[cfg(not(feature = "arf_strings"))]
-fn from_utf8<'a>(path: &'a Utf8Path) -> std::io::Result<&'a std::path::Path> {
+fn from_utf8<'a>(path: &'a Utf8Path) -> io::Result<&'a std::path::Path> {
     Ok(path.as_std_path())
 }
 
 #[cfg(all(any(feature = "std", feature = "async_std"), feature = "fs_utf8"))]
 #[cfg(feature = "arf_strings")]
-fn from_utf8<'a>(path: &'a Utf8Path) -> std::io::Result<std::path::PathBuf> {
+fn from_utf8<'a>(path: &'a Utf8Path) -> io::Result<std::path::PathBuf> {
     #[cfg(not(windows))]
     let path = {
         #[cfg(unix)]

cap-fs-ext/src/lib.rs

@@ -9,6 +9,9 @@
 #![doc(
     html_favicon_url = "https://raw.githubusercontent.com/bytecodealliance/cap-std/main/media/cap-std.ico"
 )]
+// Allow cfg(feature = "async_std") even though it isn't a feature. async_std
+// support is temporarily disabled.
+#![allow(unexpected_cfgs)]
 
 mod dir_entry_ext;
 mod dir_ext;

cap-primitives/build.rs

@@ -9,6 +9,11 @@ fn main() {
     use_feature_or_nothing("io_error_more"); // https://github.com/rust-lang/rust/issues/86442
     use_feature_or_nothing("io_error_uncategorized");
 
+    // Cfgs that users may set.
+    println!("cargo:rustc-check-cfg=cfg(racy_asserts)");
+    println!("cargo:rustc-check-cfg=cfg(emulate_second_only_system)");
+    println!("cargo:rustc-check-cfg=cfg(io_lifetimes_use_std)");
+
     // Don't rerun this on changes other than build.rs, as we only depend on
     // the rustc version.
     println!("cargo:rerun-if-changed=build.rs");
@@ -18,6 +23,7 @@ fn use_feature_or_nothing(feature: &str) {
     if has_feature(feature) {
         use_feature(feature);
     }
+    println!("cargo:rustc-check-cfg=cfg({})", feature);
 }
 
 fn use_feature(feature: &str) {

cap-primitives/src/fs/file.rs

@@ -7,13 +7,9 @@ pub trait FileExt {
     fn read_at(&self, buf: &mut [u8], offset: u64) -> io::Result<usize>;
 
     /// Like `read_at`, except that it reads into a slice of buffers.
-    #[cfg(feature = "unix_file_vectored_at")]
-    fn read_vectored_at(
-        &self,
-        bufs: &mut [std::io::IoSliceMut<'_>],
-        offset: u64,
-    ) -> io::Result<usize> {
-        io::default_read_vectored(|b| self.read_at(b, offset), bufs)
+    #[cfg(unix_file_vectored_at)]
+    fn read_vectored_at(&self, bufs: &mut [io::IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
+        default_read_vectored(|b| self.read_at(b, offset), bufs)
     }
 
     /// Reads the exact number of bytes required to fill `buf` from the given offset.
@@ -44,9 +40,9 @@ pub trait FileExt {
     fn write_at(&self, buf: &[u8], offset: u64) -> io::Result<usize>;
 
     /// Like `write_at`, except that it writes from a slice of buffers.
-    #[cfg(feature = "unix_file_vectored_at")]
-    fn write_vectored_at(&self, bufs: &[std::io::IoSlice<'_>], offset: u64) -> io::Result<usize> {
-        io::default_write_vectored(|b| self.write_at(b, offset), bufs)
+    #[cfg(unix_file_vectored_at)]
+    fn write_vectored_at(&self, bufs: &[io::IoSlice<'_>], offset: u64) -> io::Result<usize> {
+        default_write_vectored(|b| self.write_at(b, offset), bufs)
     }
 
     /// Attempts to write an entire buffer starting from a given offset.
@@ -71,21 +67,41 @@ pub trait FileExt {
     }
 }
 
+#[cfg(unix_file_vectored_at)]
+fn default_read_vectored<F>(read: F, bufs: &mut [io::IoSliceMut<'_>]) -> io::Result<usize>
+where
+    F: FnOnce(&mut [u8]) -> io::Result<usize>,
+{
+    let buf = bufs
+        .iter_mut()
+        .find(|b| !b.is_empty())
+        .map_or(&mut [][..], |b| &mut **b);
+    read(buf)
+}
+
+#[cfg(unix_file_vectored_at)]
+fn default_write_vectored<F>(write: F, bufs: &[io::IoSlice<'_>]) -> io::Result<usize>
+where
+    F: FnOnce(&[u8]) -> io::Result<usize>,
+{
+    let buf = bufs
+        .iter()
+        .find(|b| !b.is_empty())
+        .map_or(&[][..], |b| &**b);
+    write(buf)
+}
+
 /// WASI-specific extensions to [`fs::File`].
 #[cfg(target_os = "wasi")]
 pub trait FileExt {
     /// Reads a number of bytes starting from a given offset.
     fn read_at(&self, buf: &mut [u8], offset: u64) -> io::Result<usize> {
-        let bufs = &mut [std::io::IoSliceMut::new(buf)];
+        let bufs = &mut [io::IoSliceMut::new(buf)];
         self.read_vectored_at(bufs, offset)
     }
 
     /// Reads a number of bytes starting from a given offset.
-    fn read_vectored_at(
-        &self,
-        bufs: &mut [std::io::IoSliceMut<'_>],
-        offset: u64,
-    ) -> io::Result<usize>;
+    fn read_vectored_at(&self, bufs: &mut [io::IoSliceMut<'_>], offset: u64) -> io::Result<usize>;
 
     /// Reads the exact number of byte required to fill `buf` from the given offset.
     fn read_exact_at(&self, mut buf: &mut [u8], mut offset: u64) -> io::Result<()> {
@@ -113,12 +129,12 @@ pub trait FileExt {
 
     /// Writes a number of bytes starting from a given offset.
     fn write_at(&self, buf: &[u8], offset: u64) -> io::Result<usize> {
-        let bufs = &[std::io::IoSlice::new(buf)];
+        let bufs = &[io::IoSlice::new(buf)];
         self.write_vectored_at(bufs, offset)
     }
 
     /// Writes a number of bytes starting from a given offset.
-    fn write_vectored_at(&self, bufs: &[std::io::IoSlice<'_>], offset: u64) -> io::Result<usize>;
+    fn write_vectored_at(&self, bufs: &[io::IoSlice<'_>], offset: u64) -> io::Result<usize>;
 
     /// Attempts to write an entire buffer starting from a given offset.
     fn write_all_at(&self, mut buf: &[u8], mut offset: u64) -> io::Result<()> {
@@ -145,19 +161,19 @@ pub trait FileExt {
     fn tell(&self) -> io::Result<u64>;
 
     /// Adjust the flags associated with this file.
-    fn fdstat_set_flags(&self, flags: u16) -> std::io::Result<()>;
+    fn fdstat_set_flags(&self, flags: u16) -> io::Result<()>;
 
     /// Adjust the rights associated with this file.
-    fn fdstat_set_rights(&self, rights: u64, inheriting: u64) -> std::io::Result<()>;
+    fn fdstat_set_rights(&self, rights: u64, inheriting: u64) -> io::Result<()>;
 
     /// Provide file advisory information on a file descriptor.
-    fn advise(&self, offset: u64, len: u64, advice: u8) -> std::io::Result<()>;
+    fn advise(&self, offset: u64, len: u64, advice: u8) -> io::Result<()>;
 
     /// Force the allocation of space in a file.
-    fn allocate(&self, offset: u64, len: u64) -> std::io::Result<()>;
+    fn allocate(&self, offset: u64, len: u64) -> io::Result<()>;
 
     /// Create a directory.
-    fn create_directory<P: AsRef<std::path::Path>>(&self, dir: P) -> std::io::Result<()>;
+    fn create_directory<P: AsRef<std::path::Path>>(&self, dir: P) -> io::Result<()>;
 
     /// Read the contents of a symbolic link.
     fn read_link<P: AsRef<std::path::Path>>(&self, path: P) -> io::Result<std::path::PathBuf>;

cap-std/Cargo.toml

@@ -14,7 +14,7 @@ edition = "2021"
 
 [package.metadata.docs.rs]
 all-features = true
-rustdoc-args = ["--cfg=doc_cfg"]
+rustdoc-args = ["--cfg=docsrs"]
 
 [dependencies]
 arf-strings = { version = "0.7.0", optional = true }

cap-std/build.rs

@@ -4,6 +4,10 @@ use std::io::Write;
 fn main() {
     use_feature_or_nothing("can_vector"); // https://github.com/rust-lang/rust/issues/69941
     use_feature_or_nothing("write_all_vectored"); // https://github.com/rust-lang/rust/issues/70436
+    use_feature_or_nothing("windows_file_type_ext");
+
+    // Cfgs that users may set.
+    println!("cargo:rustc-check-cfg=cfg(io_lifetimes_use_std)");
 
     // Don't rerun this on changes other than build.rs, as we only depend on
     // the rustc version.
@@ -14,6 +18,7 @@ fn use_feature_or_nothing(feature: &str) {
     if has_feature(feature) {
         use_feature(feature);
     }
+    println!("cargo:rustc-check-cfg=cfg({})", feature);
 }
 
 fn use_feature(feature: &str) {

cap-std/src/fs/file.rs

@@ -524,12 +524,12 @@ impl crate::fs::FileExt for File {
     }
 
     #[inline]
-    fn tell(&self) -> std::result::Result<u64, std::io::Error> {
+    fn tell(&self) -> std::result::Result<u64, io::Error> {
         std::os::wasi::fs::FileExt::tell(&self.std)
     }
 
     #[inline]
-    fn fdstat_set_flags(&self, flags: u16) -> std::result::Result<(), std::io::Error> {
+    fn fdstat_set_flags(&self, flags: u16) -> std::result::Result<(), io::Error> {
         std::os::wasi::fs::FileExt::fdstat_set_flags(&self.std, flags)
     }
 
@@ -538,30 +538,30 @@ impl crate::fs::FileExt for File {
         &self,
         rights: u64,
         inheriting: u64,
-    ) -> std::result::Result<(), std::io::Error> {
+    ) -> std::result::Result<(), io::Error> {
         std::os::wasi::fs::FileExt::fdstat_set_rights(&self.std, rights, inheriting)
     }
 
     #[inline]
-    fn advise(&self, offset: u64, len: u64, advice: u8) -> std::result::Result<(), std::io::Error> {
+    fn advise(&self, offset: u64, len: u64, advice: u8) -> std::result::Result<(), io::Error> {
         std::os::wasi::fs::FileExt::advise(&self.std, offset, len, advice)
     }
 
     #[inline]
-    fn allocate(&self, offset: u64, len: u64) -> std::result::Result<(), std::io::Error> {
+    fn allocate(&self, offset: u64, len: u64) -> std::result::Result<(), io::Error> {
         std::os::wasi::fs::FileExt::allocate(&self.std, offset, len)
     }
 
     #[inline]
-    fn create_directory<P: AsRef<Path>>(&self, dir: P) -> std::result::Result<(), std::io::Error> {
+    fn create_directory<P: AsRef<Path>>(&self, dir: P) -> std::result::Result<(), io::Error> {
         std::os::wasi::fs::FileExt::create_directory(&self.std, dir)
     }
 
     #[inline]
     fn read_link<P: AsRef<Path>>(
         &self,
         path: P,
-    ) -> std::result::Result<std::path::PathBuf, std::io::Error> {
+    ) -> std::result::Result<std::path::PathBuf, io::Error> {
         std::os::wasi::fs::FileExt::read_link(&self.std, path)
     }
 
@@ -570,17 +570,17 @@ impl crate::fs::FileExt for File {
         &self,
         lookup_flags: u32,
         path: P,
-    ) -> std::result::Result<std::fs::Metadata, std::io::Error> {
+    ) -> std::result::Result<std::fs::Metadata, io::Error> {
         std::os::wasi::fs::FileExt::metadata_at(&self.std, lookup_flags, path)
     }
 
     #[inline]
-    fn remove_file<P: AsRef<Path>>(&self, path: P) -> std::result::Result<(), std::io::Error> {
+    fn remove_file<P: AsRef<Path>>(&self, path: P) -> std::result::Result<(), io::Error> {
         std::os::wasi::fs::FileExt::remove_file(&self.std, path)
     }
 
     #[inline]
-    fn remove_directory<P: AsRef<Path>>(&self, path: P) -> std::result::Result<(), std::io::Error> {
+    fn remove_directory<P: AsRef<Path>>(&self, path: P) -> std::result::Result<(), io::Error> {
         std::os::wasi::fs::FileExt::remove_directory(&self.std, path)
     }
 }