74 lines
1.8 KiB
Rust
74 lines
1.8 KiB
Rust
// errors1.rs
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// This function refuses to generate text to be printed on a nametag if
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// you pass it an empty string. It'd be nicer if it explained what the problem
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// was, instead of just sometimes returning `None`. The 2nd test currently
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// does not compile or pass, but it illustrates the behavior we would like
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// this function to have.
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// Scroll down for hints!!!
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pub fn generate_nametag_text(name: String) -> Option<String> {
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if name.len() > 0 {
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Some(format!("Hi! My name is {}", name))
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} else {
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// Empty names aren't allowed.
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None
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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// This test passes initially if you comment out the 2nd test.
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// You'll need to update what this test expects when you change
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// the function under test!
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#[test]
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fn generates_nametag_text_for_a_nonempty_name() {
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assert_eq!(
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generate_nametag_text("Beyoncé".into()),
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Some("Hi! My name is Beyoncé".into())
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);
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}
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#[test]
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fn explains_why_generating_nametag_text_fails() {
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assert_eq!(
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generate_nametag_text("".into()),
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Err("`name` was empty; it must be nonempty.".into())
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);
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}
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}
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// `Err` is one of the variants of `Result`, so what the 2nd test is saying
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// is that `generate_nametag_text` should return a `Result` instead of an
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// `Option`.
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// To make this change, you'll need to:
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// - update the return type in the function signature to be a Result that
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// could be the variants `Ok(String)` and `Err(String)`
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// - change the body of the function to return `Ok(stuff)` where it currently
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// returns `Some(stuff)`
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// - change the body of the function to return `Err(error message)` where it
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// currently returns `None`
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// - change the first test to expect `Ok(stuff)` where it currently expects
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// `Some(stuff)`.
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