internal/lsp: only load by view when there are no go.mod files

In debugging the metadata CLs, I noticed that when a view's only go.mod
file became unparseable, we would fall back into reloading the entire
view. In such cases, we should just not reinitialize.

Change-Id: I1b552158da8855bf80e9ded8b29c346c67564239
Reviewed-on: https://go-review.googlesource.com/c/tools/+/300674
Trust: Rebecca Stambler <[email protected]>
Run-TryBot: Rebecca Stambler <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: stamblerre

gopls/internal/regtest/diagnostics/diagnostics_test.go

@@ -1862,3 +1862,26 @@ package main
 		)
 	})
 }
+
+func TestInitialization(t *testing.T) {
+	const files = `
+-- go.mod --
+module mod.com
+
+go 1.16
+-- main.go --
+package main
+`
+	Run(t, files, func(t *testing.T, env *Env) {
+		env.OpenFile("go.mod")
+		env.Await(env.DoneWithOpen())
+		env.RegexpReplace("go.mod", "module", "modul")
+		env.SaveBufferWithoutActions("go.mod")
+		env.Await(
+			OnceMet(
+				env.DoneWithSave(),
+				NoLogMatching(protocol.Error, "initial workspace load failed"),
+			),
+		)
+	})
+}

internal/lsp/cache/view.go

@@ -546,28 +546,32 @@ func (s *snapshot) initialize(ctx context.Context, firstAttempt bool) {
 				Message:  err.Error(),
 			})
 		}
-		for modURI := range s.workspace.getActiveModFiles() {
-			fh, err := s.GetFile(ctx, modURI)
-			if err != nil {
-				addError(modURI, err)
-				continue
-			}
-			parsed, err := s.ParseMod(ctx, fh)
-			if err != nil {
-				addError(modURI, err)
-				continue
-			}
-			if parsed.File == nil || parsed.File.Module == nil {
-				addError(modURI, fmt.Errorf("no module path for %s", modURI))
-				continue
+		if len(s.workspace.getActiveModFiles()) > 0 {
+			for modURI := range s.workspace.getActiveModFiles() {
+				fh, err := s.GetFile(ctx, modURI)
+				if err != nil {
+					addError(modURI, err)
+					continue
+				}
+				parsed, err := s.ParseMod(ctx, fh)
+				if err != nil {
+					addError(modURI, err)
+					continue
+				}
+				if parsed.File == nil || parsed.File.Module == nil {
+					addError(modURI, fmt.Errorf("no module path for %s", modURI))
+					continue
+				}
+				path := parsed.File.Module.Mod.Path
+				scopes = append(scopes, moduleLoadScope(path))
 			}
-			path := parsed.File.Module.Mod.Path
-			scopes = append(scopes, moduleLoadScope(path))
-		}
-		if len(scopes) == 0 {
+		} else {
 			scopes = append(scopes, viewLoadScope("LOAD_VIEW"))
 		}
-		err := s.load(ctx, firstAttempt, append(scopes, packagePath("builtin"))...)
+		var err error
+		if len(scopes) > 0 {
+			err = s.load(ctx, firstAttempt, append(scopes, packagePath("builtin"))...)
+		}
 		if ctx.Err() != nil {
 			return
 		}
@@ -578,7 +582,12 @@ func (s *snapshot) initialize(ctx context.Context, firstAttempt bool) {
 				MainError: err,
 				DiagList:  append(modDiagnostics, extractedDiags...),
 			}
-		} else if len(modDiagnostics) != 0 {
+		} else if len(modDiagnostics) == 1 {
+			s.initializedErr = &source.CriticalError{
+				MainError: fmt.Errorf(modDiagnostics[0].Message),
+				DiagList:  modDiagnostics,
+			}
+		} else if len(modDiagnostics) > 1 {
 			s.initializedErr = &source.CriticalError{
 				MainError: fmt.Errorf("error loading module names"),
 				DiagList:  modDiagnostics,