Add support for shell argfiles

compiler/rustc_driver_impl/src/args.rs

@@ -5,18 +5,92 @@ use std::io;
 
 use rustc_session::EarlyDiagCtxt;
 
-fn arg_expand(arg: String) -> Result<Vec<String>, Error> {
-    if let Some(path) = arg.strip_prefix('@') {
-        let file = match fs::read_to_string(path) {
-            Ok(file) => file,
-            Err(ref err) if err.kind() == io::ErrorKind::InvalidData => {
-                return Err(Error::Utf8Error(Some(path.to_string())));
+/// Expands argfiles in command line arguments.
+#[derive(Default)]
+struct Expander {
+    shell_argfiles: bool,
+    next_is_unstable_option: bool,
+    expanded: Vec<String>,
+}
+
+impl Expander {
+    /// Handles the next argument. If the argument is an argfile, it is expanded
+    /// inline.
+    fn arg(&mut self, arg: &str) -> Result<(), Error> {
+        if let Some(argfile) = arg.strip_prefix('@') {
+            match argfile.split_once(':') {
+                Some(("shell", path)) if self.shell_argfiles => {
+                    shlex::split(&Self::read_file(path)?)
+                        .ok_or_else(|| Error::ShellParseError(path.to_string()))?
+                        .into_iter()
+                        .for_each(|arg| self.push(arg));
+                }
+                _ => {
+                    let contents = Self::read_file(argfile)?;
+                    contents.lines().for_each(|arg| self.push(arg.to_string()));
+                }
             }
-            Err(err) => return Err(Error::IOError(path.to_string(), err)),
-        };
-        Ok(file.lines().map(ToString::to_string).collect())
-    } else {
-        Ok(vec![arg])
+        } else {
+            self.push(arg.to_string());
+        }
+
+        Ok(())
+    }
+
+    /// Adds a command line argument verbatim with no argfile expansion.
+    fn push(&mut self, arg: String) {
+        // Unfortunately, we have to do some eager argparsing to handle unstable
+        // options which change the behavior of argfile arguments.
+        //
+        // Normally, all of the argfile arguments (e.g. `@args.txt`) are
+        // expanded into our arguments list *and then* the whole list of
+        // arguments are passed on to be parsed. However, argfile parsing
+        // options like `-Zshell_argfiles` need to change the behavior of that
+        // argument expansion. So we have to do a little parsing on our own here
+        // instead of leaning on the existing logic.
+        //
+        // All we care about are unstable options, so we parse those out and
+        // look for any that affect how we expand argfiles. This argument
+        // inspection is very conservative; we only change behavior when we see
+        // exactly the options we're looking for and everything gets passed
+        // through.
+
+        if self.next_is_unstable_option {
+            self.inspect_unstable_option(&arg);
+            self.next_is_unstable_option = false;
+        } else if let Some(unstable_option) = arg.strip_prefix("-Z") {
+            if unstable_option.is_empty() {
+                self.next_is_unstable_option = true;
+            } else {
+                self.inspect_unstable_option(unstable_option);
+            }
+        }
+
+        self.expanded.push(arg);
+    }
+
+    /// Consumes the `Expander`, returning the expanded arguments.
+    fn finish(self) -> Vec<String> {
+        self.expanded
+    }
+
+    /// Parses any relevant unstable flags specified on the command line.
+    fn inspect_unstable_option(&mut self, option: &str) {
+        match option {
+            "shell-argfiles" => self.shell_argfiles = true,
+            _ => (),
+        }
+    }
+
+    /// Reads the contents of a file as UTF-8.
+    fn read_file(path: &str) -> Result<String, Error> {
+        fs::read_to_string(path).map_err(|e| {
+            if e.kind() == io::ErrorKind::InvalidData {
+                Error::Utf8Error(Some(path.to_string()))
+            } else {
+                Error::IOError(path.to_string(), e)
+            }
+        })
     }
 }
 
@@ -24,20 +98,20 @@ fn arg_expand(arg: String) -> Result<Vec<String>, Error> {
 /// If this function is intended to be used with command line arguments,
 /// `argv[0]` must be removed prior to calling it manually.
 pub fn arg_expand_all(early_dcx: &EarlyDiagCtxt, at_args: &[String]) -> Vec<String> {
-    let mut args = Vec::new();
+    let mut expander = Expander::default();
     for arg in at_args {
-        match arg_expand(arg.clone()) {
-            Ok(arg) => args.extend(arg),
-            Err(err) => early_dcx.early_fatal(format!("Failed to load argument file: {err}")),
+        if let Err(err) = expander.arg(arg) {
+            early_dcx.early_fatal(format!("Failed to load argument file: {err}"));
         }
     }
-    args
+    expander.finish()
 }
 
 #[derive(Debug)]
 pub enum Error {
     Utf8Error(Option<String>),
     IOError(String, io::Error),
+    ShellParseError(String),
 }
 
 impl fmt::Display for Error {
@@ -46,6 +120,7 @@ impl fmt::Display for Error {
             Error::Utf8Error(None) => write!(fmt, "Utf8 error"),
             Error::Utf8Error(Some(path)) => write!(fmt, "Utf8 error in {path}"),
             Error::IOError(path, err) => write!(fmt, "IO Error: {path}: {err}"),
+            Error::ShellParseError(path) => write!(fmt, "Invalid shell-style arguments in {path}"),
         }
     }
 }