gopls/internal/lsp/source: make "chatty" diagnostics the default

This CL changes the default behavior of gopls to always publish
diagnostics for new file versions. In practice, this avoids stale
diagnostics in multiple LSP clients (golang/go#54983 has more details).

After this change, TestDownloadDeps was failing because it asserted on
the non-existence of published diagnostics. Update the test to treat an
empty diagnostic set the same as an unreceived diagnostic set.

Fixes golang/go#54983

Change-Id: I41ed2f859b748e14585e7feb53702d3f38dcd599
Reviewed-on: https://go-review.googlesource.com/c/tools/+/429935
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

gopls/internal/lsp/source/options.go

@@ -164,6 +164,7 @@ func DefaultOptions() *Options {
 				CompleteUnimported:      true,
 				CompletionDocumentation: true,
 				DeepCompletion:          true,
+				ChattyDiagnostics:       true,
 			},
 			Hooks: Hooks{
 				ComputeEdits:         myers.ComputeEdits,
@@ -587,11 +588,6 @@ type InternalOptions struct {
 	// ChattyDiagnostics controls whether to report file diagnostics for each
 	// file change. If unset, gopls only reports diagnostics when they change, or
 	// when a file is opened or closed.
-	//
-	// TODO(rfindley): is seems that for many clients this should be true by
-	// default. For example, coc.nvim seems to get confused if diagnostics are
-	// not re-published. Switch the default to true after some period of internal
-	// testing.
 	ChattyDiagnostics bool
 }
 
@@ -824,7 +820,6 @@ func (o *Options) EnableAllExperiments() {
 	o.ExperimentalUseInvalidMetadata = true
 	o.ExperimentalWatchedFileDelay = 50 * time.Millisecond
 	o.NewDiff = "checked"
-	o.ChattyDiagnostics = true
 }
 
 func (o *Options) enableAllExperimentMaps() {

gopls/internal/regtest/modfile/modfile_test.go

@@ -1189,8 +1189,8 @@ func main() {
 		)
 		env.ApplyQuickFixes("main.go", d.Diagnostics)
 		env.Await(
-			EmptyDiagnostics("main.go"),
-			NoDiagnostics("go.mod"),
+			EmptyOrNoDiagnostics("main.go"),
+			EmptyOrNoDiagnostics("go.mod"),
 		)
 	})
 }