Better conflict output

Author: Keats

src/main.rs

@@ -158,20 +158,14 @@ fn resolve_dependencies(context: &CliContext) -> Vec<ResolvedDependency> {
     );
     if !resolution.is_success() {
         eprintln!("Failed to resolve all dependencies");
+        let req_error_messages = resolution.req_error_messages();
 
         for d in resolution.failed {
             eprintln!("    {d}");
         }
 
-        for (name, requirements) in resolution.req_failures {
-            eprintln!(
-                "    {name}: {}",
-                requirements
-                    .iter()
-                    .map(|x| x.to_string())
-                    .collect::<Vec<_>>()
-                    .join(", ")
-            );
+        if !req_error_messages.is_empty() {
+            eprintln!("{}", req_error_messages.join("\n"));
         }
 
         ::std::process::exit(1)

src/resolver/result.rs

@@ -95,4 +95,34 @@ impl<'d> Resolution<'d> {
     pub fn is_success(&self) -> bool {
         self.failed.is_empty() && self.req_failures.is_empty()
     }
+
+    pub fn req_error_messages(&self) -> Vec<String> {
+        self.req_failures
+            .iter()
+            .map(|(name, reqs)| {
+                let versions_msg = self
+                    .found
+                    .iter()
+                    .filter(|f| f.name == name.as_ref())
+                    .map(|x| format!("        * {} (from {})", x.version.original, x.source))
+                    .collect::<Vec<_>>()
+                    .join("\n");
+
+                let reqs_msg = reqs
+                    .iter()
+                    .map(|x| x.to_string())
+                    .collect::<Vec<_>>()
+                    .join(", ");
+
+                if versions_msg.is_empty() {
+                    format!("{}:\n  - {} and no versions were found", name, reqs_msg)
+                } else {
+                    format!(
+                        "{}:\n  - {} and the following version(s) were found:\n{}",
+                        name, reqs_msg, versions_msg
+                    )
+                }
+            })
+            .collect()
+    }
 }