Implement Serialize/Deserialize for OsStr/OsString

This commit implements the two serde traits for the libstd `OsStr` and
`OsString` types. This came up as a use case during implementing sccache where
we're basically just doing IPC to communicate paths around. Additionally the
`Path` and `PathBuf` implementations have been updated to delegate to the os
string ones.

These types are platform-specific, however, so the serialization/deserialization
isn't trivial. Currently this "fakes" a newtype variant for Unix/Windows to
prevent cross-platform serialization/deserialization. This means if you're doing
IPC within the same OS (e.g. Windows to Windows) then serialization should be
infallible. If you're doing IPC across platforms (e.g.  Unix to Windows) then
using `OsString` is guaranteed to fail as bytes from one OS won't deserialize on
the other (even if they're unicode).

appveyor.yml

@@ -0,0 +1,17 @@
+environment:
+  matrix:
+    - APPVEYOR_RUST_CHANNEL: stable
+    - APPVEYOR_RUST_CHANNEL: nightly
+
+install:
+  # Install rust, x86_64-pc-windows-msvc host
+  - appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe
+  - rustup-init.exe -y --default-host x86_64-pc-windows-msvc --default-toolchain %APPVEYOR_RUST_CHANNEL%
+  - set PATH=C:\msys64\usr\bin;%PATH%;C:\Users\appveyor\.cargo\bin
+  - rustc -vV
+  - cargo -vV
+
+build: false
+
+test_script:
+  - sh -c 'PATH=`rustc --print sysroot`/bin:$PATH ./travis.sh'

serde/src/de/impls.rs

@@ -26,7 +26,7 @@ use std::net;
 use std::path;
 use core::str;
 #[cfg(feature = "std")]
-use std::ffi::CString;
+use std::ffi::{CString, OsString};
 #[cfg(all(feature = "std", feature="unstable"))]
 use std::ffi::CStr;
 
@@ -910,6 +910,7 @@ impl Visitor for PathBufVisitor {
     }
 }
 
+
 #[cfg(feature = "std")]
 impl Deserialize for path::PathBuf {
     fn deserialize<D>(deserializer: D) -> Result<path::PathBuf, D::Error>
@@ -921,6 +922,110 @@ impl Deserialize for path::PathBuf {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+#[cfg(all(feature = "std", any(unix, windows)))]
+enum OsStringKind {
+    Unix,
+    Windows,
+}
+
+#[cfg(all(feature = "std", any(unix, windows)))]
+static OSSTR_VARIANTS: &'static [&'static str] = &["Unix", "Windows"];
+
+#[cfg(all(feature = "std", any(unix, windows)))]
+impl Deserialize for OsStringKind {
+    fn deserialize<D>(deserializer: D) -> Result<OsStringKind, D::Error>
+        where D: Deserializer
+    {
+        struct KindVisitor;
+
+        impl Visitor for KindVisitor {
+            type Value = OsStringKind;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("`Unix` or `Windows`")
+            }
+
+            fn visit_u32<E>(self, value: u32) -> Result<OsStringKind, E>
+                where E: Error,
+            {
+                match value {
+                    0 => Ok(OsStringKind::Unix),
+                    1 => Ok(OsStringKind::Windows),
+                    _ => Err(Error::invalid_value(Unexpected::Unsigned(value as u64), &self))
+                }
+            }
+
+            fn visit_str<E>(self, value: &str) -> Result<OsStringKind, E>
+                where E: Error,
+            {
+                match value {
+                    "Unix" => Ok(OsStringKind::Unix),
+                    "Windows" => Ok(OsStringKind::Windows),
+                    _ => Err(Error::unknown_variant(value, OSSTR_VARIANTS)),
+                }
+            }
+
+            fn visit_bytes<E>(self, value: &[u8]) -> Result<OsStringKind, E>
+                where E: Error,
+            {
+                match value {
+                    b"Unix" => Ok(OsStringKind::Unix),
+                    b"Windows" => Ok(OsStringKind::Windows),
+                    _ => {
+                        match str::from_utf8(value) {
+                            Ok(value) => Err(Error::unknown_variant(value, OSSTR_VARIANTS)),
+                            Err(_) => {
+                                Err(Error::invalid_value(Unexpected::Bytes(value), &self))
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        deserializer.deserialize(KindVisitor)
+    }
+}
+
+#[cfg(all(feature = "std", any(unix, windows)))]
+struct OsStringVisitor;
+
+#[cfg(all(feature = "std", any(unix, windows)))]
+impl Visitor for OsStringVisitor {
+    type Value = OsString;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("os string")
+    }
+
+    #[cfg(unix)]
+    fn visit_enum<V>(self, visitor: V) -> Result<OsString, V::Error>
+        where V: EnumVisitor,
+    {
+        use std::os::unix::ffi::OsStringExt;
+
+        match try!(visitor.visit_variant()) {
+            (OsStringKind::Unix, variant) => {
+                variant.visit_newtype().map(OsString::from_vec)
+            }
+            (OsStringKind::Windows, _) => {
+                Err(Error::custom("cannot deserialize windows os string on unix"))
+            }
+        }
+    }
+}
+
+#[cfg(all(feature = "std", any(unix, windows)))]
+impl Deserialize for OsString {
+    fn deserialize<D>(deserializer: D) -> Result<OsString, D::Error>
+        where D: Deserializer
+    {
+        deserializer.deserialize_enum("OsString", OSSTR_VARIANTS, OsStringVisitor)
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<T: Deserialize> Deserialize for Box<T> {
     fn deserialize<D>(deserializer: D) -> Result<Box<T>, D::Error>

serde/src/ser/impls.rs

@@ -20,7 +20,7 @@ use core::ops;
 #[cfg(feature = "std")]
 use std::path;
 #[cfg(feature = "std")]
-use std::ffi::{CString, CStr};
+use std::ffi::{CString, CStr, OsString, OsStr};
 #[cfg(feature = "std")]
 use std::rc::Rc;
 #[cfg(all(feature = "alloc", not(feature = "std")))]
@@ -714,6 +714,41 @@ impl Serialize for path::PathBuf {
     }
 }
 
+#[cfg(all(feature = "std", any(unix, windows)))]
+impl Serialize for OsStr {
+    #[cfg(unix)]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        use std::os::unix::ffi::OsStrExt;
+        serializer.serialize_newtype_variant("OsString",
+                                             0,
+                                             "Unix",
+                                             self.as_bytes())
+    }
+    #[cfg(windows)]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        use std::os::windows::ffi::OsStrExt;
+        let val = self.encode_wide().collect::<Vec<_>>();
+        serializer.serialize_newtype_variant("OsString",
+                                             1,
+                                             "Windows",
+                                             &val)
+    }
+}
+
+#[cfg(all(feature = "std", any(unix, windows)))]
+#[cfg(feature = "std")]
+impl Serialize for OsString {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        self.as_os_str().serialize(serializer)
+    }
+}
+
 #[cfg(feature = "unstable")]
 impl<T> Serialize for NonZero<T>
     where T: Serialize + Zeroable

test_suite/no_std/src/main.rs

@@ -1,7 +1,8 @@
-#![feature(lang_items, start, libc)]
+#![feature(lang_items, start, libc, compiler_builtins_lib)]
 #![no_std]
 
 extern crate libc;
+extern crate compiler_builtins;
 
 #[start]
 fn start(_argc: isize, _argv: *const *const u8) -> isize {

test_suite/tests/test_de.rs

@@ -8,7 +8,7 @@ use std::net;
 use std::path::PathBuf;
 use std::time::Duration;
 use std::default::Default;
-use std::ffi::CString;
+use std::ffi::{CString, OsString};
 
 #[cfg(feature = "unstable")]
 use std::ffi::CStr;
@@ -913,6 +913,56 @@ declare_tests! {
     }
 }
 
+#[cfg(unix)]
+#[test]
+fn test_osstring() {
+    use std::os::unix::ffi::OsStringExt;
+
+    let value = OsString::from_vec(vec![1, 2, 3]);
+    let tokens = [
+        Token::EnumStart("OsString"),
+        Token::Str("Unix"),
+        Token::SeqStart(Some(2)),
+            Token::SeqSep,
+            Token::U8(1),
+
+            Token::SeqSep,
+            Token::U8(2),
+
+            Token::SeqSep,
+            Token::U8(3),
+        Token::SeqEnd,
+    ];
+
+    assert_de_tokens(&value, &tokens);
+    assert_de_tokens_ignore(&tokens);
+}
+
+#[cfg(windows)]
+#[test]
+fn test_osstring() {
+    use std::os::windows::ffi::OsStringExt;
+
+    let value = OsString::from_wide(&[1, 2, 3]);
+    let tokens = [
+        Token::EnumStart("OsString"),
+        Token::Str("Windows"),
+        Token::SeqStart(Some(2)),
+            Token::SeqSep,
+            Token::U16(1),
+
+            Token::SeqSep,
+            Token::U16(2),
+
+            Token::SeqSep,
+            Token::U16(3),
+        Token::SeqEnd,
+    ];
+
+    assert_de_tokens(&value, &tokens);
+    assert_de_tokens_ignore(&tokens);
+}
+
 #[cfg(feature = "unstable")]
 #[test]
 fn test_cstr() {

test_suite/tests/test_ser.rs

@@ -422,6 +422,7 @@ fn test_net_ipaddr() {
 }
 
 #[test]
+#[cfg(unix)]
 fn test_cannot_serialize_paths() {
     let path = unsafe {
         str::from_utf8_unchecked(b"Hello \xF0\x90\x80World")

travis.sh

@@ -10,6 +10,11 @@ channel() {
             pwd
             (set -x; cargo "$@")
         fi
+    elif [ -n "${APPVEYOR}" ]; then
+        if [ "${APPVEYOR_RUST_CHANNEL}" = "${CHANNEL}" ]; then
+            pwd
+            (set -x; cargo "$@")
+        fi
     else
         pwd
         (set -x; cargo "+${CHANNEL}" "$@")