internal/lsp: disable nilness analyzer, unless staticcheck enabled

Users with staticcheck enabled will be more tolerant of increased RAM
usage. We might be able to disable this check entirely once the next
version of staticcheck is released with a similar analysis (https://staticcheck.io/docs/checks#SA5011).

Change-Id: I1a844cc226e34e0f62222f12912797a6cc9d06e2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/219018
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
(cherry picked from commit 6822f1a)
Reviewed-on: https://go-review.googlesource.com/c/tools/+/219198
Reviewed-by: Robert Findley <rfindley@google.com>

Author: stamblerre

gopls/internal/hooks/analysis.go

@@ -5,6 +5,7 @@
 package hooks
 
 import (
+	"golang.org/x/tools/go/analysis/passes/nilness"
 	"golang.org/x/tools/internal/lsp/source"
 	"honnef.co/go/tools/simple"
 	"honnef.co/go/tools/staticcheck"
@@ -26,5 +27,10 @@ func updateAnalyzers(options *source.Options) {
 		for _, a := range stylecheck.Analyzers {
 			options.Analyzers[a.Name] = a
 		}
+		// Add the nilness analyzer only for users who have enabled staticcheck.
+		// The assumption here is that a user who has enabled staticcheck will
+		// be fine with gopls using significantly more memory. nilness requires
+		// SSA, which makes it expensive.
+		options.Analyzers[nilness.Analyzer.Name] = nilness.Analyzer
 	}
 }

internal/lsp/source/options.go

@@ -26,7 +26,6 @@ import (
 	"golang.org/x/tools/go/analysis/passes/loopclosure"
 	"golang.org/x/tools/go/analysis/passes/lostcancel"
 	"golang.org/x/tools/go/analysis/passes/nilfunc"
-	"golang.org/x/tools/go/analysis/passes/nilness"
 	"golang.org/x/tools/go/analysis/passes/printf"
 	"golang.org/x/tools/go/analysis/passes/shift"
 	"golang.org/x/tools/go/analysis/passes/sortslice"
@@ -493,7 +492,6 @@ var defaultAnalyzers = map[string]*analysis.Analyzer{
 
 	// Non-vet analyzers
 	deepequalerrors.Analyzer.Name:  deepequalerrors.Analyzer,
-	nilness.Analyzer.Name:          nilness.Analyzer,
 	sortslice.Analyzer.Name:        sortslice.Analyzer,
 	testinggoroutine.Analyzer.Name: testinggoroutine.Analyzer,
 }