feat(add): check if given crate argument would be valid with inserted @ symbol, suggest fixed argument

Author: dawedawe

src/bin/cargo/commands/install.rs

@@ -148,7 +148,7 @@ pub fn exec(gctx: &mut GlobalContext, args: &ArgMatches) -> CliResult {
                 }
             }
         }
-        
+
         if let Some(toolchain) = crate_name.strip_prefix("+") {
             return Err(anyhow!(
                 "invalid character `+` in package name: `+{toolchain}`

src/cargo/ops/cargo_add/crate_spec.rs

@@ -28,7 +28,23 @@ impl CrateSpec {
             .map(|(n, v)| (n, Some(v)))
             .unwrap_or((pkg_id, None));
 
-        PackageName::new(name)?;
+        let package_name = PackageName::new(name);
+        if !pkg_id.contains("@") && package_name.is_err() {
+            for (idx, ch) in pkg_id.char_indices() {
+                if !(unicode_xid::UnicodeXID::is_xid_continue(ch) || ch == '-') {
+                    let mut suggested_pkg_id = pkg_id.to_string();
+                    suggested_pkg_id.insert_str(idx, "@");
+                    if let Ok(_) = CrateSpec::resolve(&suggested_pkg_id.as_str()) {
+                        return Err(anyhow::anyhow!(
+                            "possible missing `@` detected in package name `{pkg_id}`. Try `{suggested_pkg_id}` instead."
+                        ))
+                        .into();
+                    }
+                }
+            }
+        }
+
+        package_name?;
 
         if let Some(version) = version {
             semver::VersionReq::parse(version)