Address review comments.

src/client.rs

@@ -11,18 +11,37 @@ use crate::server::RequestExt;
 
 const REDDIT_URL_BASE: &str = "https://www.reddit.com";
 
-/// Gets the canonical path for a resource on Reddit. On success, a
-/// `Some(Option<String>)` will be returned. If Reddit responds with
-/// anything other than an HTTP 3xx, a `None` will be returned. Any
-/// other error results in an `Err(String)`.
+/// Gets the canonical path for a resource on Reddit. This is accomplished by
+/// making a `HEAD` request to Reddit at the path given in `path`.
+///
+/// This function returns `Ok(Some(path))`, where `path`'s value is identical
+/// to that of the value of the argument `path`, if Reddit responds to our
+/// `HEAD` request with a 2xx-family HTTP code. It will also return an
+/// `Ok(Some(String))` if Reddit responds to our `HEAD` request with a
+/// `Location` header in the response, and the HTTP code is in the 3xx-family;
+/// the `String` will contain the path as reported in `Location`. The return
+/// value is `Ok(None)` if Reddit responded with a 3xx, but did not provide a
+/// `Location` header. An `Err(String)` is returned if Reddit responds with a
+/// 429, or if we were unable to decode the value in the `Location` header.
 #[cached(size = 1024, time = 600, result = true)]
 pub async fn canonical_path(path: String) -> Result<Option<String>, String> {
-	let res = reddit_head(path, true).await?;
+	let res = reddit_head(path.clone(), true).await?;
 
 	if res.status() == 429 {
 		return Err("Too many requests.".to_string());
 	};
 
+	// If Reddit responds with a 2xx, then the path is already canonical.
+	if res.status().to_string().starts_with('2') {
+		return Ok(Some(path));
+	}
+
+	// If Reddit responds with anything other than 3xx (except for the 2xx as
+	// above), return a None.
+	if !res.status().to_string().starts_with('3') {
+		return Ok(None);
+	}
+
 	match res.headers().get(header::LOCATION) {
 		None => Ok(None),
 		Some(hdr) => match hdr.to_str() {
@@ -111,8 +130,8 @@ fn request(method: &'static Method, path: String, redirect: bool, quarantine: bo
 	// Construct the hyper client from the HTTPS connector.
 	let client: client::Client<_, hyper::Body> = client::Client::builder().build(https);
 
-	// Build request to Reddit. When making a GET, request gzip compression
-	// (Reddit doesn't do brotli yet)
+	// Build request to Reddit. When making a GET, request gzip compression.
+	// (Reddit doesn't do brotli yet.)
 	let builder = Request::builder()
 		.method(method)
 		.uri(&url)
@@ -187,9 +206,8 @@ fn request(method: &'static Method, path: String, redirect: bool, quarantine: bo
 								};
 
 								decompressed = Vec::<u8>::new();
-								match io::copy(&mut decoder, &mut decompressed) {
-									Ok(_) => {}
-									Err(e) => return Err(e.to_string()),
+								if let Err(e) = io::copy(&mut decoder, &mut decompressed) {
+									return Err(e.to_string());
 								};
 							}