Only treat missing crate lists as empty

The motivation is that errors other than "file not found" could lead to
the file being overwritten by an empty config, e.g. if the `open` call
is interrupted and returns `EINTR`, then this code would read an empty
config and write it back later on. This can probably happen for other
errors as well (`ENFILE`, ...).

diff --git a/src/cargo/ops/cargo_install.rs b/src/cargo/ops/cargo_install.rs
index dc02233809e63b2e7176c6f968a2a9236019864d..dfe9ea3614134c2b911ab18b71e0fa1bb71e7639 100644 (file)
--- a/src/cargo/ops/cargo_install.rs
+++ b/src/cargo/ops/cargo_install.rs
@@ -4,6 +4,7 @@ use std::env;
 use std::ffi::OsString;
 use std::fs::{self, File};
 use std::io::prelude::*;
+use std::io;
 use std::path::{Path, PathBuf};
 
 use toml;
@@ -222,7 +223,15 @@ fn read_crate_list(path: &Path) -> CargoResult<CrateListingV1> {
     let metadata = path.join(".crates.toml");
     let mut f = match File::open(&metadata) {
         Ok(f) => f,
-        Err(..) => return Ok(CrateListingV1 { v1: BTreeMap::new() }),
+        Err(e) => {
+            if e.kind() == io::ErrorKind::NotFound {
+                return Ok(CrateListingV1 { v1: BTreeMap::new() });
+            }
+            return Err(e).chain_error(|| {
+                human(format!("failed to open crate metadata at `{}`",
+                              metadata.display()))
+            });
+        }
     };
     (|| -> CargoResult<_> {
         let mut contents = String::new();