internal/lsp/cache: have NewView create view even if load all packages fails

Even if the packages.Load of the directory the NewView is being created for
fails, create and add the view. But also return the error from NewView, just
after the new view has been added.

Fixes golang/go#35468

Change-Id: I76c2d3cbe1a508ad0794a6fcd3bc67cd48c97e22
Reviewed-on: https://go-review.googlesource.com/c/tools/+/206497
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/cache/load.go

@@ -64,10 +64,12 @@ func (s *snapshot) load(ctx context.Context, scope source.Scope) ([]*metadata, e
 		return nil, errors.Errorf("no metadata for %s: %v", uri, err)
 	}
 	log.Print(ctx, "go/packages.Load", tag.Of("packages", len(pkgs)))
-	if _, ok := scope.(source.FileURI); len(pkgs) == 0 && ok {
+	if len(pkgs) == 0 {
 		if err == nil {
 			err = errNoPackagesFound
 		}
+	}
+	if err != nil {
 		return nil, err
 	}
 	m, prevMissingImports, err := s.updateMetadata(ctx, scope, pkgs, cfg)

internal/lsp/cache/session.go

@@ -6,6 +6,7 @@ package cache
 
 import (
 	"context"
+	"fmt"
 	"path/filepath"
 	"sort"
 	"strconv"
@@ -126,8 +127,9 @@ func (s *session) NewView(ctx context.Context, name string, folder span.URI, opt
 	v.snapshotMu.Lock()
 	defer v.snapshotMu.Unlock() // The code after the snapshot is used isn't expensive.
 	m, err := v.snapshot.load(ctx, source.DirectoryURI(folder))
+	var loadErr error
 	if err != nil && err != errNoPackagesFound {
-		return nil, err
+		loadErr = fmt.Errorf("Error loading packages: %v", err)
 	}
 
 	// Prepare CheckPackageHandles for every package that's been loaded.
@@ -144,7 +146,7 @@ func (s *session) NewView(ctx context.Context, name string, folder span.URI, opt
 	// we always need to drop the view map
 	s.viewMap = make(map[span.URI]source.View)
 	debug.AddView(debugView{v})
-	return v, nil
+	return v, loadErr
 }
 
 // View returns the view by name.