Add regression test for including extern crates in import filtering

Author: GuillaumeGomez

tests/rustdoc-js/import-filter.js

@@ -0,0 +1,20 @@
+// This test ensures that when filtering on `import`, `externcrate` items are also displayed.
+// It also ensures that the opposite is not true.
+
+const EXPECTED = [
+    {
+        'query': 'import:st',
+        'others': [
+            { 'path': 'foo', 'name': 'st', 'href': '../foo/index.html#reexport.st' },
+            // FIXME: `href` is wrong: <https://github.com/rust-lang/rust/issues/148300>
+            { 'path': 'foo', 'name': 'st2', 'href': '../st2/index.html' },
+        ],
+    },
+    {
+        'query': 'externcrate:st',
+        'others': [
+            // FIXME: `href` is wrong: <https://github.com/rust-lang/rust/issues/148300>
+            { 'path': 'foo', 'name': 'st2', 'href': '../st2/index.html' },
+        ],
+    },
+];

tests/rustdoc-js/import-filter.rs

@@ -0,0 +1,7 @@
+#![crate_name = "foo"]
+
+pub extern crate std as st2;
+
+pub use crate::Bar as st;
+
+pub struct Bar;