diff --git a/internal/lsp/cmd/check.go b/internal/lsp/cmd/check.go
index 384a3239b5..33310535f1 100644
--- a/internal/lsp/cmd/check.go
+++ b/internal/lsp/cmd/check.go
@@ -59,6 +59,9 @@ func (c *check) Run(ctx context.Context, args ...string) error {
 	if err := conn.diagnoseFiles(ctx, uris); err != nil {
 		return err
 	}
+	conn.Client.filesMu.Lock()
+	defer conn.Client.filesMu.Unlock()
+
 	for _, file := range checking {
 		for _, d := range file.diagnostics {
 			spn, err := file.mapper.RangeSpan(d.Range)
diff --git a/internal/lsp/diagnostics.go b/internal/lsp/diagnostics.go
index c3ce41cb30..2bcf640b09 100644
--- a/internal/lsp/diagnostics.go
+++ b/internal/lsp/diagnostics.go
@@ -32,7 +32,7 @@ func (s *Server) diagnoseSnapshot(ctx context.Context, snapshot source.Snapshot)
 				log.Error(ctx, "diagnoseSnapshot: no diagnostics", err, telemetry.Package.Of(ph.ID()))
 				return
 			}
-			s.publishReports(ctx, snapshot, reports, false, false)
+			s.publishReports(ctx, snapshot, reports, false)
 		}(ph)
 	}
 	// Run diagnostics on the go.mod file.
@@ -60,8 +60,7 @@ func (s *Server) diagnoseFile(snapshot source.Snapshot, fh source.FileHandle) {
 		}
 		return
 	}
-	// Publish empty diagnostics for files.
-	s.publishReports(ctx, snapshot, reports, true, true)
+	s.publishReports(ctx, snapshot, reports, true)
 }
 
 func (s *Server) diagnoseModfile(snapshot source.Snapshot) {
@@ -76,11 +75,10 @@ func (s *Server) diagnoseModfile(snapshot source.Snapshot) {
 		}
 		return
 	}
-	// Publish empty diagnostics for files.
-	s.publishReports(ctx, snapshot, reports, true, true)
+	s.publishReports(ctx, snapshot, reports, false)
 }
 
-func (s *Server) publishReports(ctx context.Context, snapshot source.Snapshot, reports map[source.FileIdentity][]source.Diagnostic, publishEmpty, withAnalysis bool) {
+func (s *Server) publishReports(ctx context.Context, snapshot source.Snapshot, reports map[source.FileIdentity][]source.Diagnostic, withAnalysis bool) {
 	// Check for context cancellation before publishing diagnostics.
 	if ctx.Err() != nil {
 		return
@@ -104,34 +102,22 @@ func (s *Server) publishReports(ctx context.Context, snapshot source.Snapshot, r
 			withAnalysis: withAnalysis,
 			snapshotID:   snapshot.ID(),
 		}
-		delivered, ok := s.delivered[fileID.URI]
+		// We use the zero values if this is an unknown file.
+		delivered := s.delivered[fileID.URI]
 
-		// If diagnostics are empty and not previously delivered,
-		// only send them if we are publishing empty diagnostics.
-		if !ok && len(diagnostics) == 0 && !publishEmpty {
-			// Update the delivered map to cache the diagnostics.
+		// Reuse cached diagnostics and update the delivered map.
+		if fileID.Version >= delivered.version && equalDiagnostics(delivered.sorted, diagnostics) {
 			s.delivered[fileID.URI] = toSend
 			continue
 		}
-		// Reuse equivalent cached diagnostics for subsequent file versions (if known),
-		// or identical files (if versions are not known).
-		if ok {
-			geqVersion := fileID.Version >= delivered.version && delivered.version > 0
-			noVersions := (fileID.Version == 0 && delivered.version == 0) && delivered.identifier == fileID.Identifier
-			if (geqVersion || noVersions) && equalDiagnostics(delivered.sorted, toSend.sorted) {
-				// Update the delivered map even if we reuse cached diagnostics.
-				s.delivered[fileID.URI] = toSend
-				continue
-			}
-			// If we've already delivered diagnostics with analyses for this file, for this snapshot,
-			// at this version, do not send diagnostics without analyses.
-			if delivered.snapshotID == toSend.snapshotID && delivered.version == toSend.version &&
-				delivered.withAnalysis && !toSend.withAnalysis {
-				continue
-			}
+		// If we've already delivered diagnostics with analyses for this file, for this snapshot,
+		// at this version, do not send diagnostics without analyses.
+		if delivered.snapshotID == toSend.snapshotID && delivered.version == toSend.version &&
+			delivered.withAnalysis && !toSend.withAnalysis {
+			continue
 		}
 		if err := s.client.PublishDiagnostics(ctx, &protocol.PublishDiagnosticsParams{
-			Diagnostics: toProtocolDiagnostics(ctx, diagnostics),
+			Diagnostics: toProtocolDiagnostics(diagnostics),
 			URI:         protocol.NewURI(fileID.URI),
 			Version:     fileID.Version,
 		}); err != nil {
@@ -157,7 +143,7 @@ func equalDiagnostics(a, b []source.Diagnostic) bool {
 	return true
 }
 
-func toProtocolDiagnostics(ctx context.Context, diagnostics []source.Diagnostic) []protocol.Diagnostic {
+func toProtocolDiagnostics(diagnostics []source.Diagnostic) []protocol.Diagnostic {
 	reports := []protocol.Diagnostic{}
 	for _, diag := range diagnostics {
 		related := make([]protocol.DiagnosticRelatedInformation, 0, len(diag.Related))
diff --git a/internal/lsp/lsp_test.go b/internal/lsp/lsp_test.go
index f2b5008a94..060cf584c1 100644
--- a/internal/lsp/lsp_test.go
+++ b/internal/lsp/lsp_test.go
@@ -357,7 +357,7 @@ func (r *runner) SuggestedFix(t *testing.T, spn span.Span) {
 		},
 		Context: protocol.CodeActionContext{
 			Only:        []protocol.CodeActionKind{protocol.QuickFix},
-			Diagnostics: toProtocolDiagnostics(r.ctx, diagnostics[fileID]),
+			Diagnostics: toProtocolDiagnostics(diagnostics[fileID]),
 		},
 	})
 	if err != nil {
@@ -979,7 +979,7 @@ func TestModfileSuggestedFixes(t *testing.T) {
 					},
 					Context: protocol.CodeActionContext{
 						Only:        []protocol.CodeActionKind{protocol.SourceOrganizeImports},
-						Diagnostics: toProtocolDiagnostics(ctx, diags),
+						Diagnostics: toProtocolDiagnostics(diags),
 					},
 				})
 				if err != nil {
diff --git a/internal/lsp/server.go b/internal/lsp/server.go
index 417efe7ce8..d279012b7a 100644
--- a/internal/lsp/server.go
+++ b/internal/lsp/server.go
@@ -15,6 +15,7 @@ import (
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/lsp/source"
 	"golang.org/x/tools/internal/span"
+	errors "golang.org/x/xerrors"
 )
 
 // NewClientServer
@@ -299,7 +300,27 @@ func (s *Server) NonstandardRequest(ctx context.Context, method string, params i
 			if err != nil {
 				return nil, err
 			}
-			s.diagnoseFile(view.Snapshot(), view.Session().GetFile(span.URI(uri)))
+			snapshot := view.Snapshot()
+			fh, err := snapshot.GetFile(uri)
+			if err != nil {
+				return nil, err
+			}
+			reports, _, err := source.FileDiagnostics(ctx, view.Snapshot(), fh, true, nil)
+			if err != nil {
+				return nil, err
+			}
+			fileID := fh.Identity()
+			diagnostics, ok := reports[fileID]
+			if !ok {
+				return nil, errors.Errorf("no diagnostics for %s", uri)
+			}
+			if err := s.client.PublishDiagnostics(ctx, &protocol.PublishDiagnosticsParams{
+				URI:         protocol.NewURI(uri),
+				Diagnostics: toProtocolDiagnostics(diagnostics),
+				Version:     fileID.Version,
+			}); err != nil {
+				return nil, err
+			}
 		}
 		if err := s.client.PublishDiagnostics(ctx, &protocol.PublishDiagnosticsParams{
 			URI: "gopls://diagnostics-done",