Auto merge of #3869 - matklad:test-isolation, r=alexcrichton

Don't read ~/.cargo/config in tests

Closes #3863

r? @alexcrichton

src/cargo/core/workspace.rs

@@ -266,8 +266,7 @@ impl<'cfg> Workspace<'cfg> {
             }
         }
 
-        let mut cur = manifest_path.parent().and_then(|p| p.parent());
-        while let Some(path) = cur {
+        for path in paths::ancestors(manifest_path).skip(2) {
             let manifest = path.join("Cargo.toml");
             debug!("find_root - trying {}", manifest.display());
             if manifest.exists() {
@@ -286,7 +285,6 @@ impl<'cfg> Workspace<'cfg> {
                     WorkspaceConfig::Member { .. } => {}
                 }
             }
-            cur = path.parent();
         }
 
         Ok(None)

src/cargo/util/config.rs

@@ -17,6 +17,7 @@ use core::shell::{Verbosity, ColorConfig};
 use core::MultiShell;
 use util::{CargoResult, CargoError, ChainError, Rustc, internal, human};
 use util::{Filesystem, LazyCell};
+use util::paths;
 
 use util::toml as cargo_toml;
 
@@ -698,10 +699,9 @@ pub fn homedir(cwd: &Path) -> Option<PathBuf> {
 fn walk_tree<F>(pwd: &Path, mut walk: F) -> CargoResult<()>
     where F: FnMut(File, &Path) -> CargoResult<()>
 {
-    let mut current = pwd;
     let mut stash: HashSet<PathBuf> = HashSet::new();
 
-    loop {
+    for current in paths::ancestors(pwd) {
         let possible = current.join(".cargo").join("config");
         if fs::metadata(&possible).is_ok() {
             let file = File::open(&possible)?;
@@ -710,11 +710,6 @@ fn walk_tree<F>(pwd: &Path, mut walk: F) -> CargoResult<()>
 
             stash.insert(possible);
         }
-
-        match current.parent() {
-            Some(p) => current = p,
-            None => break,
-        }
     }
 
     // Once we're done, also be sure to walk the home directory even if it's not

src/cargo/util/paths.rs

@@ -142,3 +142,42 @@ pub fn bytes2path(bytes: &[u8]) -> CargoResult<PathBuf> {
         Err(..) => Err(human("invalid non-unicode path")),
     }
 }
+
+pub fn ancestors(path: &Path) -> PathAncestors {
+    PathAncestors::new(path)
+}
+
+pub struct PathAncestors<'a> {
+    current: Option<&'a Path>,
+    stop_at: Option<PathBuf>
+}
+
+impl<'a> PathAncestors<'a> {
+    fn new(path: &Path) -> PathAncestors {
+        PathAncestors {
+            current: Some(path),
+            //HACK: avoid reading `~/.cargo/config` when testing Cargo itself.
+            stop_at: env::var("__CARGO_TEST_ROOT").ok().map(PathBuf::from),
+        }
+    }
+}
+
+impl<'a> Iterator for PathAncestors<'a> {
+    type Item = &'a Path;
+
+    fn next(&mut self) -> Option<&'a Path> {
+        if let Some(path) = self.current {
+            self.current = path.parent();
+
+            if let Some(ref stop_at) = self.stop_at {
+                if path == stop_at {
+                    self.current = None;
+                }
+            }
+
+            Some(path)
+        } else {
+            None
+        }
+    }
+}

tests/cargotest/lib.rs

@@ -50,6 +50,7 @@ fn _process(t: &OsStr) -> cargo::util::ProcessBuilder {
      .env_remove("CARGO_HOME")
      .env("HOME", support::paths::home())
      .env("CARGO_HOME", support::paths::home().join(".cargo"))
+     .env("__CARGO_TEST_ROOT", support::paths::root())
      .env_remove("RUSTC")
      .env_remove("RUSTFLAGS")
      .env_remove("CARGO_INCREMENTAL")