I'm a new rustecean, so I apologize if this question is silly. I'm trying to understand why chaining methods on a TempDir causes File::create calls on the same Path to fail.
My situation is this: I'm writing a small library to convert between JSON and YAML to learn the language. I'm trying to write a test which does the following:
- Create a file with some json-encoded text
- Deserialize it to ensure that it becomes a
serde_json::Value
To do that, I've written the following code.
let temp_dir_path = TempDir::new("directory").expect("couldn't create directory");
let path = temp_dir.path().join("test-file.json");
let mut temp_file = File::create(&path).expect("failed to create file");
writeln!(temp_file, "{{\"key\": 2}}").expect("write failed");
// some stuff about loading the file and asserting on it
That works, but then I thought "why don't I just collapse the first two lines into one?" So I tried that and wrote the following:
let path = TempDir::new("directory")
.expect("couldn't create directory")
.path()
.join("test-file.json");
let mut temp_file = File::create(&path).expect("failed to create file");
writeln!(temp_file, "{{\"key\": 2}}").expect("write failed");
This code will consistently fail with a message of "failed to create file". The thing I don't understand though is "why". My intuition is that both of these calls should be the same (after all, I basically just inlined a variable); however, that clearly isn't happening. Is there something I don't understand happening with expect here which causes it to not work in these situations?
