1 files changed, 173 insertions, 0 deletions

diff --git a/crates/project_model/src/sysroot.rs b/crates/project_model/src/sysroot.rs
new file mode 100644
index 000000000..8239797b6
--- /dev/null
+++ b/crates/project_model/src/sysroot.rs
@@ -0,0 +1,173 @@
+//! FIXME: write short doc here
+
+use std::{convert::TryFrom, env, ops, path::Path, process::Command};
+
+use anyhow::{bail, format_err, Result};
+use arena::{Arena, Idx};
+use paths::{AbsPath, AbsPathBuf};
+
+use crate::utf8_stdout;
+
+#[derive(Default, Debug, Clone, Eq, PartialEq)]
+pub struct Sysroot {
+    crates: Arena<SysrootCrateData>,
+}
+
+pub type SysrootCrate = Idx<SysrootCrateData>;
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct SysrootCrateData {
+    pub name: String,
+    pub root: AbsPathBuf,
+    pub deps: Vec<SysrootCrate>,
+}
+
+impl ops::Index<SysrootCrate> for Sysroot {
+    type Output = SysrootCrateData;
+    fn index(&self, index: SysrootCrate) -> &SysrootCrateData {
+        &self.crates[index]
+    }
+}
+
+impl Sysroot {
+    pub fn core(&self) -> Option<SysrootCrate> {
+        self.by_name("core")
+    }
+
+    pub fn alloc(&self) -> Option<SysrootCrate> {
+        self.by_name("alloc")
+    }
+
+    pub fn std(&self) -> Option<SysrootCrate> {
+        self.by_name("std")
+    }
+
+    pub fn proc_macro(&self) -> Option<SysrootCrate> {
+        self.by_name("proc_macro")
+    }
+
+    pub fn crates<'a>(&'a self) -> impl Iterator<Item = SysrootCrate> + ExactSizeIterator + 'a {
+        self.crates.iter().map(|(id, _data)| id)
+    }
+
+    pub fn discover(cargo_toml: &AbsPath) -> Result<Sysroot> {
+        let src = get_or_install_rust_src(cargo_toml)?;
+        let mut sysroot = Sysroot { crates: Arena::default() };
+        for name in SYSROOT_CRATES.trim().lines() {
+            // FIXME: remove this path when 1.47 comes out
+            // https://github.com/rust-lang/rust/pull/73265
+            let root = src.join(format!("lib{}", name)).join("lib.rs");
+            if root.exists() {
+                sysroot.crates.alloc(SysrootCrateData {
+                    name: name.into(),
+                    root,
+                    deps: Vec::new(),
+                });
+            } else {
+                let root = src.join(name).join("src/lib.rs");
+                if root.exists() {
+                    sysroot.crates.alloc(SysrootCrateData {
+                        name: name.into(),
+                        root,
+                        deps: Vec::new(),
+                    });
+                }
+            }
+        }
+        if let Some(std) = sysroot.std() {
+            for dep in STD_DEPS.trim().lines() {
+                if let Some(dep) = sysroot.by_name(dep) {
+                    sysroot.crates[std].deps.push(dep)
+                }
+            }
+        }
+        if let Some(alloc) = sysroot.alloc() {
+            if let Some(core) = sysroot.core() {
+                sysroot.crates[alloc].deps.push(core);
+            }
+        }
+        Ok(sysroot)
+    }
+
+    fn by_name(&self, name: &str) -> Option<SysrootCrate> {
+        self.crates.iter().find(|(_id, data)| data.name == name).map(|(id, _data)| id)
+    }
+}
+
+fn get_or_install_rust_src(cargo_toml: &AbsPath) -> Result<AbsPathBuf> {
+    if let Ok(path) = env::var("RUST_SRC_PATH") {
+        let path = AbsPathBuf::try_from(path.as_str())
+            .map_err(|path| format_err!("RUST_SRC_PATH must be absolute: {}", path.display()))?;
+        return Ok(path);
+    }
+    let current_dir = cargo_toml.parent().unwrap();
+    let mut rustc = Command::new(toolchain::rustc());
+    rustc.current_dir(current_dir).args(&["--print", "sysroot"]);
+    let stdout = utf8_stdout(rustc)?;
+    let sysroot_path = AbsPath::assert(Path::new(stdout.trim()));
+    let mut src = get_rust_src(sysroot_path);
+    if src.is_none() {
+        let mut rustup = Command::new(toolchain::rustup());
+        rustup.current_dir(current_dir).args(&["component", "add", "rust-src"]);
+        utf8_stdout(rustup)?;
+        src = get_rust_src(sysroot_path);
+    }
+    match src {
+        Some(r) => Ok(r),
+        None => bail!(
+            "can't load standard library from sysroot\n\
+            {}\n\
+            (discovered via `rustc --print sysroot`)\n\
+            try running `rustup component add rust-src` or set `RUST_SRC_PATH`",
+            sysroot_path.display(),
+        ),
+    }
+}
+
+fn get_rust_src(sysroot_path: &AbsPath) -> Option<AbsPathBuf> {
+    // try the new path first since the old one still exists
+    let mut src_path = sysroot_path.join("lib/rustlib/src/rust/library");
+    if !src_path.exists() {
+        // FIXME: remove this path when 1.47 comes out
+        // https://github.com/rust-lang/rust/pull/73265
+        src_path = sysroot_path.join("lib/rustlib/src/rust/src");
+    }
+    if src_path.exists() {
+        Some(src_path)
+    } else {
+        None
+    }
+}
+
+impl SysrootCrateData {
+    pub fn root_dir(&self) -> &AbsPath {
+        self.root.parent().unwrap()
+    }
+}
+
+const SYSROOT_CRATES: &str = "
+alloc
+core
+panic_abort
+panic_unwind
+proc_macro
+profiler_builtins
+rtstartup
+std
+stdarch
+term
+test
+unwind";
+
+const STD_DEPS: &str = "
+alloc
+core
+panic_abort
+panic_unwind
+profiler_builtins
+rtstartup
+proc_macro
+stdarch
+term
+test
+unwind";