internal/lsp: allow for multiple ad-hoc packages in the workspace

Add the scope to the command-line-arguments package ID and path so that
multiple command-line-arguments packages can coexist in the workspace.

Fixes golang/go#47584

Change-Id: Icbfe90d67627f384c54f352e46270ab2bf4240bd
Reviewed-on: https://go-review.googlesource.com/c/tools/+/341611
Trust: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

gopls/internal/regtest/misc/multiple_adhoc_test.go

@@ -0,0 +1,44 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package misc
+
+import (
+	"testing"
+
+	. "golang.org/x/tools/internal/lsp/regtest"
+)
+
+func TestMultipleAdHocPackages(t *testing.T) {
+	Run(t, `
+-- a/a.go --
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("")
+}
+-- a/b.go --
+package main
+
+import "fmt"
+
+func main() () {
+	fmt.Println("")
+}
+`, func(t *testing.T, env *Env) {
+		env.OpenFile("a/a.go")
+		if list := env.Completion("a/a.go", env.RegexpSearch("a/a.go", "Println")); list == nil || len(list.Items) == 0 {
+			t.Fatal("expected completions, got none")
+		}
+		env.OpenFile("a/b.go")
+		if list := env.Completion("a/b.go", env.RegexpSearch("a/b.go", "Println")); list == nil || len(list.Items) == 0 {
+			t.Fatal("expected completions, got none")
+		}
+		if list := env.Completion("a/a.go", env.RegexpSearch("a/a.go", "Println")); list == nil || len(list.Items) == 0 {
+			t.Fatal("expected completions, got none")
+		}
+	})
+}

internal/lsp/cache/load.go

@@ -205,7 +205,7 @@ func (s *snapshot) load(ctx context.Context, allowNetwork bool, scopes ...interf
 		}
 		// Set the metadata for this package.
 		s.mu.Lock()
-		m, err := s.setMetadataLocked(ctx, packagePath(pkg.PkgPath), pkg, cfg, map[packageID]struct{}{})
+		m, err := s.setMetadataLocked(ctx, packagePath(pkg.PkgPath), pkg, cfg, query, map[packageID]struct{}{})
 		s.mu.Unlock()
 		if err != nil {
 			return err
@@ -403,8 +403,13 @@ func getWorkspaceDir(ctx context.Context, h *memoize.Handle, g *memoize.Generati
 // setMetadataLocked extracts metadata from pkg and records it in s. It
 // recurses through pkg.Imports to ensure that metadata exists for all
 // dependencies.
-func (s *snapshot) setMetadataLocked(ctx context.Context, pkgPath packagePath, pkg *packages.Package, cfg *packages.Config, seen map[packageID]struct{}) (*metadata, error) {
+func (s *snapshot) setMetadataLocked(ctx context.Context, pkgPath packagePath, pkg *packages.Package, cfg *packages.Config, query []string, seen map[packageID]struct{}) (*metadata, error) {
 	id := packageID(pkg.ID)
+	if source.IsCommandLineArguments(pkg.ID) {
+		suffix := ":" + strings.Join(query, ",")
+		id = packageID(string(id) + suffix)
+		pkgPath = packagePath(string(pkgPath) + suffix)
+	}
 	if _, ok := seen[id]; ok {
 		return nil, errors.Errorf("import cycle detected: %q", id)
 	}
@@ -465,7 +470,7 @@ func (s *snapshot) setMetadataLocked(ctx context.Context, pkgPath packagePath, p
 			continue
 		}
 		if s.noValidMetadataForIDLocked(importID) {
-			if _, err := s.setMetadataLocked(ctx, importPkgPath, importPkg, cfg, copied); err != nil {
+			if _, err := s.setMetadataLocked(ctx, importPkgPath, importPkg, cfg, query, copied); err != nil {
 				event.Error(ctx, "error in dependency", err)
 			}
 		}