Handle non-utf8 evaluation result

src/main.rs

@@ -257,12 +257,12 @@ fn run_nix_shell(inp: &NixShellInput) -> NixShellOutput {
         if !exec.status.success() {
             exit(1);
         }
-        let output = String::from_utf8(exec.stdout).expect("failed to decode");
+        // Path to .drv file is always in ASCII, so no information is lost.
+        let output = String::from_utf8_lossy(&exec.stdout);
         let output: serde_json::Value =
             serde_json::from_str(&output).expect("failed to parse json");
-
+        // The first key of the toplevel object contains the path to .drv file.
         let (drv, _) = output.as_object().unwrap().into_iter().next().unwrap();
-
         drv.clone()
     };
 

tests/t10-non-utf8.sh

@@ -66,3 +66,21 @@ run cached-nix-shell ./tmp/shellhook.nix --pure --keep VAR_IN \
 	--run 'printf "%s\n" "$VAR_OUT"'
 check_contains '^out:VAR_IN=aM-pb\^@$'
 unset VAR_IN
+
+
+# Non-utf8 evaluation result
+put ./tmp/evaluation.nix << EOF # unquoted
+with import <nixpkgs> { };
+mkShell {
+  "VAR1" = "A${F0}B";
+  "VAR${F1}2" = "CD";
+}
+EOF
+
+run cached-nix-shell ./tmp/evaluation.nix --pure \
+	--run 'env -0 | LANG=C grep -z "^VAR1=" | cat -v'
+check_contains '^VAR1=AM-pB\^@$'
+
+run cached-nix-shell ./tmp/evaluation.nix --pure \
+	--run 'env -0 | LANG=C grep -z "^VAR.2=" | cat -v'
+check_contains '^VARM-q2=CD\^@$'