gopls/internal/lsp: use matcher score in ranking unimported candidates

In the refactoring of CL 472183, we inadvertently dropped the fuzzy
matching factor from the unimported completion item score.

Fixes golang/go#62560

Change-Id: I35294c55d4229a885b781d3cdd0c6433e82f280b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/531418
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Findley <rfindley@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>

Author: findleyr

gopls/internal/lsp/regtest/marker.go

@@ -232,8 +232,11 @@ var update = flag.Bool("update", false, "if set, update test data during marker
 //     request at the given location, and verifies that each expected
 //     completion item occurs in the results, in the expected order. Other
 //     unexpected completion items may occur in the results.
-//     TODO(rfindley): this should accept a slice of labels, rather than
-//     completion items.
+//     TODO(rfindley): this exists for compatibility with the old marker tests.
+//     Replace this with rankl, and rename.
+//
+//   - rankl(location, ...label): like rank, but only cares about completion
+//     item labels.
 //
 //   - refs(location, want ...location): executes a textDocument/references
 //     request at the first location and asserts that the result is the set of
@@ -712,6 +715,7 @@ var actionMarkerFuncs = map[string]func(marker){
 	"hover":            actionMarkerFunc(hoverMarker),
 	"implementation":   actionMarkerFunc(implementationMarker),
 	"rank":             actionMarkerFunc(rankMarker),
+	"rankl":            actionMarkerFunc(ranklMarker),
 	"refs":             actionMarkerFunc(refsMarker),
 	"rename":           actionMarkerFunc(renameMarker),
 	"renameerr":        actionMarkerFunc(renameErrMarker),
@@ -1450,6 +1454,23 @@ func rankMarker(mark marker, src protocol.Location, items ...completionItem) {
 	}
 }
 
+func ranklMarker(mark marker, src protocol.Location, labels ...string) {
+	list := mark.run.env.Completion(src)
+	var got []string
+	// Collect results that are present in items, preserving their order.
+	for _, g := range list.Items {
+		for _, label := range labels {
+			if g.Label == label {
+				got = append(got, g.Label)
+				break
+			}
+		}
+	}
+	if diff := cmp.Diff(labels, got); diff != "" {
+		mark.errorf("completion rankings do not match (-want +got):\n%s", diff)
+	}
+}
+
 func snippetMarker(mark marker, src protocol.Location, item completionItem, want string) {
 	list := mark.run.env.Completion(src)
 	var (

gopls/internal/lsp/source/completion/completion.go

@@ -1296,7 +1296,7 @@ func (c *completer) selector(ctx context.Context, sel *ast.SelectorExpr) error {
 				Label:      id.Name,
 				Detail:     fmt.Sprintf("%s (from %q)", strings.ToLower(tok.String()), m.PkgPath),
 				InsertText: id.Name,
-				Score:      unimportedScore(relevances[path]),
+				Score:      float64(score) * unimportedScore(relevances[path]),
 			}
 			switch tok {
 			case token.FUNC:
@@ -1397,6 +1397,7 @@ func (c *completer) selector(ctx context.Context, sel *ast.SelectorExpr) error {
 		if ignoreUnimportedCompletion(pkgExport.Fix) {
 			return
 		}
+
 		mu.Lock()
 		defer mu.Unlock()
 		// TODO(adonovan): what if the actual package has a vendor/ prefix?

gopls/internal/regtest/marker/testdata/completion/issue62560.txt

@@ -0,0 +1,19 @@
+This test verifies that completion of package members in unimported packages
+reflects their fuzzy score, even when those members are present in the
+transitive import graph of the main module. (For technical reasons, this was
+the nature of the regression in golang/go#62560.)
+
+-- go.mod --
+module mod.test
+
+-- foo/foo.go --
+package foo
+
+func _() {
+	json.U //@rankl(re"U()", "Unmarshal", "InvalidUTF8Error"), diag("json", re"(undefined|undeclared)")
+}
+
+-- bar/bar.go --
+package bar
+
+import _ "encoding/json"