Allow multiple keywords in crate search

This commit allows multiple `keyword=` parameters in the querystring to
enable searching for all crates under the specified keywords

Towards #1461

Author: Paul Woolcock

src/controllers/krate/search.rs

@@ -95,7 +95,18 @@ pub fn search(req: &mut dyn Request) -> CargoResult<Response> {
         );
     }
 
-    if let Some(kw) = params.get("keyword") {
+    if let Some(kws) = params.get("all_keywords") {
+        let names: Vec<_> = kws.split_whitespace().map(|name| name.to_lowercase()).collect();
+
+        query = query.filter(
+            crates::id.eq_any(
+                crates_keywords::table
+                    .select(crates_keywords::crate_id)
+                    .inner_join(keywords::table)
+                    .filter(crate::lower(keywords::keyword).eq(any(names))),
+            ),
+        );
+    } else if let Some(kw) = params.get("keyword") {
         query = query.filter(
             crates::id.eq_any(
                 crates_keywords::table

src/tests/krate.rs

@@ -139,6 +139,7 @@ fn index_queries() {
     assert_eq!(anon.search("keyword=kw1").crates.len(), 2);
     assert_eq!(anon.search("keyword=KW1").crates.len(), 2);
     assert_eq!(anon.search("keyword=kw2").crates.len(), 0);
+    assert_eq!(anon.search("keyword=kw1&keyword=kw3").crates.len(), 3);
 
     assert_eq!(anon.search("q=foo&keyword=kw1").crates.len(), 1);
     assert_eq!(anon.search("q=foo2&keyword=kw1").crates.len(), 0);