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

Cargo.lock

@@ -376,6 +376,7 @@ dependencies = [
  "tracing-subscriber",
  "unicase",
  "unicode-width",
+ "unicode-xid",
  "url",
  "walkdir",
  "windows-sys 0.59.0",

Cargo.toml

@@ -216,6 +216,7 @@ tracing = { workspace = true, features = ["attributes"] }
 tracing-subscriber.workspace = true
 unicase.workspace = true
 unicode-width.workspace = true
+unicode-xid.workspace = true
 url.workspace = true
 walkdir.workspace = true
 

src/bin/cargo/commands/install.rs

@@ -8,6 +8,7 @@ use cargo::ops;
 use cargo::util::IntoUrl;
 use cargo::util::VersionExt;
 use cargo::CargoResult;
+use cargo_util_schemas::manifest::PackageName;
 use itertools::Itertools;
 use semver::VersionReq;
 
@@ -133,6 +134,22 @@ pub fn exec(gctx: &mut GlobalContext, args: &ArgMatches) -> CliResult {
         .collect::<crate::CargoResult<Vec<_>>>()?;
 
     for (crate_name, _) in krates.iter() {
+        let package_name = PackageName::new(crate_name);
+        if !crate_name.contains("@") && package_name.is_err() {
+            for (idx, ch) in crate_name.char_indices() {
+                if !(unicode_xid::UnicodeXID::is_xid_continue(ch) || ch == '-') {
+                    let mut suggested_crate_name = crate_name.to_string();
+                    suggested_crate_name.insert_str(idx, "@");
+                    if let Ok((_, Some(_))) = parse_crate(&suggested_crate_name.as_str()) {
+                        let err = package_name.unwrap_err();
+                        return Err(
+                            anyhow::format_err!("{err}\n\n\
+                                help: if this is meant to be a package name followed by a version, insert an `@` like `{suggested_crate_name}`").into());
+                    }
+                }
+            }
+        }
+
         if let Some(toolchain) = crate_name.strip_prefix("+") {
             return Err(anyhow!(
                 "invalid character `+` in package name: `+{toolchain}`

tests/testsuite/install.rs

@@ -402,8 +402,9 @@ fn missing_at_symbol_before_version() {
     cargo_process("install foo=0.2.0")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[UPDATING] `dummy-registry` index
-[ERROR] could not find `foo=0.2.0` in registry `crates-io` with version `*`
+[ERROR] invalid character `=` in package name: `foo=0.2.0`, characters must be Unicode XID characters (numbers, `-`, `_`, or most letters)
+
+[HELP] if this is meant to be a package name followed by a version, insert an `@` like `foo@=0.2.0`
 
 "#]])
         .run();