Add std::os::windows::process::CommandExt, with set_creation_flags and add_creation_flags methods. Fixes #37827

This adds a CommandExt trait for Windows along with an implementation of it
for std::process::Command with methods to set the process creation flags that
are passed to CreateProcess.

2 files changed, 39 insertions, 2 deletions

diff --git a/src/libstd/sys/windows/ext/process.rs b/src/libstd/sys/windows/ext/process.rs
index bce32959a23..f5bf3354637 100644
--- a/src/libstd/sys/windows/ext/process.rs
+++ b/src/libstd/sys/windows/ext/process.rs
@@ -15,7 +15,7 @@
 use os::windows::io::{FromRawHandle, RawHandle, AsRawHandle, IntoRawHandle};
 use process;
 use sys;
-use sys_common::{AsInner, FromInner, IntoInner};
+use sys_common::{AsInnerMut, AsInner, FromInner, IntoInner};
 
 #[stable(feature = "process_extensions", since = "1.2.0")]
 impl FromRawHandle for process::Stdio {
@@ -97,3 +97,32 @@ impl ExitStatusExt for process::ExitStatus {
         process::ExitStatus::from_inner(From::from(raw))
     }
 }
+
+/// Windows-specific extensions to the `std::process::Command` builder
+#[unstable(feature = "windows_process_extensions", issue = "37827")]
+pub trait CommandExt {
+    /// Sets the [process creation flags][1] to be passed to `CreateProcess`.
+    ///
+    /// These will always be ORed with `CREATE_UNICODE_ENVIRONMENT`.
+    /// [1]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms684863(v=vs.85).aspx
+    #[unstable(feature = "windows_process_extensions", issue = "37827")]
+    fn set_creation_flags(&mut self, flags: u32) -> &mut process::Command;
+    /// Add `flags` to the the [process creation flags][1] to be passed to `CreateProcess`.
+    ///
+    /// These will always be ORed with `CREATE_UNICODE_ENVIRONMENT`.
+    /// [1]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms684863(v=vs.85).aspx
+    #[unstable(feature = "windows_process_extensions", issue = "37827")]
+    fn add_creation_flags(&mut self, flags: u32) -> &mut process::Command;
+}
+
+#[unstable(feature = "windows_process_extensions", issue = "37827")]
+impl CommandExt for process::Command {
+    fn set_creation_flags(&mut self, flags: u32) -> &mut process::Command {
+        self.as_inner_mut().set_creation_flags(flags);
+        self
+    }
+    fn add_creation_flags(&mut self, flags: u32) -> &mut process::Command {
+        self.as_inner_mut().add_creation_flags(flags);
+        self
+    }
+}
diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
index d371714ff0e..a221c67efd9 100644
--- a/src/libstd/sys/windows/process.rs
+++ b/src/libstd/sys/windows/process.rs
@@ -54,6 +54,7 @@ pub struct Command {
     args: Vec<OsString>,
     env: Option<HashMap<OsString, OsString>>,
     cwd: Option<OsString>,
+    flags: u32,
     detach: bool, // not currently exposed in std::process
     stdin: Option<Stdio>,
     stdout: Option<Stdio>,
@@ -84,6 +85,7 @@ impl Command {
             args: Vec::new(),
             env: None,
             cwd: None,
+            flags: 0,
             detach: false,
             stdin: None,
             stdout: None,
@@ -124,6 +126,12 @@ impl Command {
     pub fn stderr(&mut self, stderr: Stdio) {
         self.stderr = Some(stderr);
     }
+    pub fn set_creation_flags(&mut self, flags: u32) {
+        self.flags = flags;
+    }
+    pub fn add_creation_flags(&mut self, flags: u32) {
+        self.flags = self.flags | flags;
+    }
 
     pub fn spawn(&mut self, default: Stdio, needs_stdin: bool)
                  -> io::Result<(Process, StdioPipes)> {
@@ -157,7 +165,7 @@ impl Command {
         cmd_str.push(0); // add null terminator
 
         // stolen from the libuv code.
-        let mut flags = c::CREATE_UNICODE_ENVIRONMENT;
+        let mut flags = self.flags | c::CREATE_UNICODE_ENVIRONMENT;
         if self.detach {
             flags |= c::DETACHED_PROCESS | c::CREATE_NEW_PROCESS_GROUP;
         }