Give a better error message if Cargo.toml is not present

CHANGELOG.md

@@ -4,8 +4,10 @@
 #### Fixes
 
 * Take `CARGO_TARGET_DIR` into account when looking for the target directory. [PR#66]
+* Give a better error message if Cargo.toml is not present. [PR#67]
 
 [PR#66]: https://github.com/deadlinks/cargo-deadlinks/pull/66
+[PR#67]: https://github.com/deadlinks/cargo-deadlinks/pull/67
 
 #### Changes
 

src/main.rs

@@ -97,10 +97,23 @@ pub fn metadata_run(additional_args: Option<String>) -> Result<Metadata, ()> {
         cmd.arg(&additional_args);
     }
 
-    let output = cmd.output().unwrap();
-    let stdout = std::str::from_utf8(&output.stdout).unwrap();
-    let meta = serde_json::from_str(stdout).unwrap();
-    Ok(meta)
+    let fail_msg = "failed to run `cargo metadata` - do you have cargo installed?";
+    let output = cmd
+        .stdout(process::Stdio::piped())
+        .spawn()
+        .expect(fail_msg)
+        .wait_with_output()
+        .expect(fail_msg);
+
+    if !output.status.success() {
+        // don't need more info because we didn't capture stderr;
+        // hopefully `cargo metadata` gave a useful error, but if not we can't do
+        // anything
+        return Err(());
+    }
+
+    let stdout = std::str::from_utf8(&output.stdout).expect("invalid UTF8");
+    Ok(serde_json::from_str(stdout).expect("invalid JSON"))
 }
 
 /// Initalizes the logger according to the provided config flags.
@@ -143,7 +156,7 @@ fn determine_dir() -> PathBuf {
             manifest.target_directory.join("doc").join(package_name)
         }
         Err(_) => {
-            error!("Could not find a Cargo.toml.");
+            error!("help: if this is not a cargo directory, use `--dir`");
             ::std::process::exit(1);
         }
     }

tests/simple_project.rs

@@ -2,7 +2,9 @@ extern crate assert_cmd;
 extern crate predicates;
 
 use assert_cmd::prelude::*;
+use predicate::str::contains;
 use predicates::prelude::*;
+use std::env;
 use std::process::Command;
 
 mod simple_project {
@@ -38,10 +40,22 @@ mod simple_project {
     }
 
     #[test]
-    fn it_checks_okay_project_correctly() {
-        use predicate::str::contains;
+    fn it_gives_help_if_cargo_toml_missing() {
+        Command::cargo_bin("cargo-deadlinks")
+            .unwrap()
+            .arg("deadlinks")
+            .current_dir(env::temp_dir())
+            .assert()
+            .failure()
+            .stderr(
+                contains("help: if this is not a cargo directory, use `--dir`")
+                    .and(contains("error: could not find `Cargo.toml`")),
+            );
+    }
 
-        std::env::remove_var("CARGO_TARGET_DIR");
+    #[test]
+    fn it_checks_okay_project_correctly() {
+        env::remove_var("CARGO_TARGET_DIR");
 
         // cargo-deadlinks fails when docs have not been generated before
         remove_all("./tests/simple_project/target");
@@ -63,12 +77,12 @@ mod simple_project {
         assert_doc().success();
 
         // NOTE: can't be parallel because of use of `set_var`
-        std::env::set_var("CARGO_TARGET_DIR", "target2");
+        env::set_var("CARGO_TARGET_DIR", "target2");
         remove_all("./tests/simple_project/target2");
         assert_doc().success();
 
-        std::env::remove_var("CARGO_TARGET_DIR");
-        std::env::set_var("CARGO_BUILD_TARGET", "x86_64-unknown-linux-gnu");
+        env::remove_var("CARGO_TARGET_DIR");
+        env::set_var("CARGO_BUILD_TARGET", "x86_64-unknown-linux-gnu");
         remove_all("./tests/simple_project/target");
         // This currently breaks due to a cargo bug: https://github.com/rust-lang/cargo/issues/8791
         assert_doc().failure();