Permit @ in JS modules

Closes #3179

Author: lpil

CHANGELOG.md

@@ -301,6 +301,9 @@
 
     ([Giacomo Cavalieri](https://github.com/giacomocavalieri))
 
+- JavaScript external module names may now include the character `@`.
+  ([Louis Pilfold](https://github.com/lpil))
+
 ### Formatter
 
 - Redundant alias names for imported modules are now removed.

compiler-core/src/analyse.rs

@@ -578,7 +578,7 @@ impl<'a, A> ModuleAnalyzer<'a, A> {
             Some(external) => external,
         };
         if !MODULE
-            .get_or_init(|| Regex::new("^[a-zA-Z0-9\\./:_-]+$").expect("regex"))
+            .get_or_init(|| Regex::new("^[@a-zA-Z0-9\\./:_-]+$").expect("regex"))
             .is_match(module)
         {
             self.errors.push(Error::InvalidExternalJavascriptModule {

compiler-core/src/javascript/tests/externals.rs

@@ -14,6 +14,15 @@ fn show(x: anything) -> Nil"#,
     );
 }
 
+#[test]
+fn at_namespace_module() {
+    assert_js!(
+        r#"
+@external(javascript, "@namespace/package", "inspect")
+fn show(x: anything) -> Nil"#,
+    );
+}
+
 #[test]
 fn pub_module_fn() {
     assert_js!(

compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__externals__at_namespace_module.snap

@@ -0,0 +1,6 @@
+---
+source: compiler-core/src/javascript/tests/externals.rs
+assertion_line: 19
+expression: "\n@external(javascript, \"@namespace/package\", \"inspect\")\nfn show(x: anything) -> Nil"
+---
+import { inspect as show } from "@namespace/package";