cli: add acquire_cli (#179837)

* cli: add acquire_cli

As given in my draft document, pipes a CLI of the given platform to the
specified process, for example:

```js
const cmd = await rpc.call('acquire_cli', {
	command: 'node',
	args: [
		'-e',
		'process.stdin.pipe(fs.createWriteStream("c:/users/conno/downloads/hello-cli"))',
	],
	platform: Platform.LinuxX64,
	quality: 'insider',
});
```

It genericizes caching so that the CLI is also cached on the host, just
like servers.

* fix bug

cli/src/util/errors.rs

@@ -477,9 +477,11 @@ pub enum CodeError {
 	UnsupportedPlatform(String),
 	#[error("This machine not meet {name}'s prerequisites, expected either...: {bullets}")]
 	PrerequisitesFailed { name: &'static str, bullets: String },
-
 	#[error("failed to spawn process: {0:?}")]
-	ProcessSpawnFailed(std::io::Error)
+	ProcessSpawnFailed(std::io::Error),
+
+	#[error("download appears corrupted, please retry ({0})")]
+	CorruptDownload(&'static str),
 }
 
 makeAnyError!(

cli/src/util/http.rs

@@ -59,14 +59,23 @@ pub struct SimpleResponse {
 	pub status_code: StatusCode,
 	pub headers: HeaderMap,
 	pub read: Pin<Box<dyn Send + AsyncRead + 'static>>,
-	pub url: String,
+	pub url: Option<url::Url>,
 }
 
 impl SimpleResponse {
-	pub fn generic_error(url: String) -> Self {
+	pub fn url_path_basename(&self) -> Option<String> {
+		self.url.as_ref().and_then(|u| {
+			u.path_segments()
+				.and_then(|s| s.last().map(|s| s.to_owned()))
+		})
+	}
+}
+
+impl SimpleResponse {
+	pub fn generic_error(url: &str) -> Self {
 		let (_, rx) = mpsc::unbounded_channel();
 		SimpleResponse {
-			url,
+			url: url::Url::parse(url).ok(),
 			status_code: StatusCode::INTERNAL_SERVER_ERROR,
 			headers: HeaderMap::new(),
 			read: Box::pin(DelegatedReader::new(rx)),
@@ -79,7 +88,10 @@ impl SimpleResponse {
 		self.read.read_to_string(&mut body).await.ok();
 
 		StatusError {
-			url: self.url,
+			url: self
+				.url
+				.map(|u| u.to_string())
+				.unwrap_or_else(|| "<invalid url>".to_owned()),
 			status_code: self.status_code.as_u16(),
 			body,
 		}
@@ -97,7 +109,7 @@ impl SimpleResponse {
 			.map_err(|e| wrap(e, "error reading response"))?;
 
 		let t = serde_json::from_slice(&buf)
-			.map_err(|e| wrap(e, format!("error decoding json from {}", self.url)))?;
+			.map_err(|e| wrap(e, format!("error decoding json from {:?}", self.url)))?;
 
 		Ok(t)
 	}
@@ -161,7 +173,7 @@ impl SimpleHttp for ReqwestSimpleHttp {
 		Ok(SimpleResponse {
 			status_code: res.status(),
 			headers: res.headers().clone(),
-			url,
+			url: Some(res.url().clone()),
 			read: Box::pin(
 				res.bytes_stream()
 					.map_err(|e| futures::io::Error::new(futures::io::ErrorKind::Other, e))
@@ -250,7 +262,7 @@ impl SimpleHttp for DelegatedSimpleHttp {
 			.await;
 
 		if sent.is_err() {
-			return Ok(SimpleResponse::generic_error(url)); // sender shut down
+			return Ok(SimpleResponse::generic_error(&url)); // sender shut down
 		}
 
 		match rx.recv().await {
@@ -275,16 +287,16 @@ impl SimpleHttp for DelegatedSimpleHttp {
 				}
 
 				Ok(SimpleResponse {
-					url,
+					url: url::Url::parse(&url).ok(),
 					status_code: StatusCode::from_u16(status_code)
 						.unwrap_or(StatusCode::INTERNAL_SERVER_ERROR),
 					headers: headers_map,
 					read: Box::pin(DelegatedReader::new(rx)),
 				})
 			}
-			Some(DelegatedHttpEvent::End) => Ok(SimpleResponse::generic_error(url)),
+			Some(DelegatedHttpEvent::End) => Ok(SimpleResponse::generic_error(&url)),
 			Some(_) => panic!("expected initresponse as first message from delegated http"),
-			None => Ok(SimpleResponse::generic_error(url)), // sender shut down
+			None => Ok(SimpleResponse::generic_error(&url)), // sender shut down
 		}
 	}
 }