networkdoctor: flesh out messaging a bit

Summary: Add better error formatting and add user visible "treatment" (i.e. tips/instructions on how to resolve the problem).

Reviewed By: DurhamG

Differential Revision: D34649752

fbshipit-source-id: 26a3ab77084ceeaac2eb6cf5ae31c01760645ad8

eden/scm/lib/doctor/network/Cargo.toml

@@ -7,4 +7,5 @@ edition = "2021"
 
 [dependencies]
 configmodel = { version = "0.1.0", path = "../../configmodel" }
+thiserror = "1.0.29"
 url = "2.2.2"

eden/scm/lib/doctor/network/src/lib.rs

@@ -14,23 +14,46 @@ use std::vec;
 
 use configmodel::Config;
 use configmodel::ConfigExt;
+use thiserror::Error;
 use url::Host;
 use url::Url;
 
-#[derive(Debug)]
+#[derive(Debug, Error)]
 pub enum HostError {
+    #[error("invalid host config: {0}")]
     Config(String),
+    #[error("DNS error: {0}")]
     DNS(io::Error),
+    #[error("TCP error: {0}")]
     TCP(io::Error),
 }
 
-#[derive(Debug)]
+#[derive(Debug, Error)]
 pub enum Diagnosis {
+    #[error("invalid config: {0}")]
     BadConfig(String),
+    #[error("no internet connectivity: {0}")]
     NoInternet(HostError),
+    #[error("no corp connectivity: {0}")]
     NoCorp(HostError),
 }
 
+impl Diagnosis {
+    pub fn treatment(&self) -> String {
+        match self {
+            Self::NoCorp(_) => {
+                "Please check your VPN connection (internet okay, but can't reach corp)."
+                    .to_string()
+            }
+            Self::NoInternet(_) => {
+                "Please check your internet connection (failed external connectivity test)."
+                    .to_string()
+            }
+            Self::BadConfig(msg) => format!("Invalid config: {}", msg),
+        }
+    }
+}
+
 pub struct Doctor {
     // Allow tests to stub DNS responses.
     dns_lookup: Box<dyn Fn(&str) -> io::Result<vec::IntoIter<SocketAddr>>>,