internal/lsp, go/packages: don't log context cancellation errors

Instead of checking the context, check the error. This may expose some
errors that are not wrapped correctly. Replaced all uses of errors
with golang.org/x/xerrors.

Change-Id: Ia40160f8ea352e02618765f2a9415a4ece0dcd94
Reviewed-on: https://go-review.googlesource.com/c/tools/+/227036
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

go/packages/golist.go

@@ -25,6 +25,7 @@ import (
 	"golang.org/x/tools/go/internal/packagesdriver"
 	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/packagesinternal"
+	"golang.org/x/xerrors"
 )
 
 // debug controls verbose logging.
@@ -736,7 +737,7 @@ func (state *golistState) invokeGo(verb string, args ...string) (*bytes.Buffer,
 		if !ok {
 			// Catastrophic error:
 			// - context cancellation
-			return nil, fmt.Errorf("couldn't run 'go': %v", err)
+			return nil, xerrors.Errorf("couldn't run 'go': %w", err)
 		}
 
 		// Old go version?

go/packages/loadmode_string.go

@@ -38,7 +38,7 @@ var modeStrings = []string{
 func (mod LoadMode) String() string {
 	m := mod
 	if m == 0 {
-		return fmt.Sprintf("LoadMode(0)")
+		return "LoadMode(0)"
 	}
 	var out []string
 	for i, x := range allModes {

internal/lsp/debug/serve.go

@@ -34,6 +34,7 @@ import (
 	"golang.org/x/tools/internal/telemetry/export/metric"
 	"golang.org/x/tools/internal/telemetry/export/ocagent"
 	"golang.org/x/tools/internal/telemetry/export/prometheus"
+	"golang.org/x/xerrors"
 )
 
 type instanceKeyType int
@@ -543,9 +544,17 @@ func (i *Instance) writeMemoryDebug(threshold uint64) error {
 func makeGlobalExporter(stderr io.Writer) event.Exporter {
 	return func(ctx context.Context, ev event.Event, tags event.TagMap) context.Context {
 		i := GetInstance(ctx)
-		if ev.IsLog() && (event.Err.Get(ev.Map()) != nil || i == nil) {
+
+		if ev.IsLog() {
+			// Don't log context cancellation errors.
+			if err := event.Err.Get(ev.Map()); xerrors.Is(err, context.Canceled) {
+				return ctx
+			}
+			// Make sure any log messages without an instance go to stderr.
+			if i == nil {
 				fmt.Fprintf(stderr, "%v\n", ev)
 			}
+		}
 		ctx = protocol.LogEvent(ctx, ev, tags)
 		if i == nil {
 			return ctx

internal/lsp/generate.go

@@ -7,7 +7,6 @@ package lsp
 import (
 	"context"
 	"io"
-	"log"
 	"math/rand"
 	"strconv"
 
@@ -15,7 +14,7 @@ import (
 	"golang.org/x/tools/internal/lsp/debug/tag"
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/telemetry/event"
-	errors "golang.org/x/xerrors"
+	"golang.org/x/xerrors"
 )
 
 func (s *Server) runGenerate(ctx context.Context, dir string, recursive bool) {
@@ -43,13 +42,15 @@ func (s *Server) runGenerate(ctx context.Context, dir string, recursive bool) {
 	}
 	stderr := io.MultiWriter(er, wc)
 	err := inv.RunPiped(ctx, er, stderr)
-	if err != nil && !errors.Is(ctx.Err(), context.Canceled) {
-		log.Printf("generate: command error: %v", err)
+	if err != nil {
+		event.Error(ctx, "generate: command error: %v", err, tag.Directory.Of(dir))
+		if !xerrors.Is(err, context.Canceled) {
 			s.client.ShowMessage(ctx, &protocol.ShowMessageParams{
 				Type:    protocol.Error,
 				Message: "go generate exited with an error, check gopls logs",
 			})
 		}
+	}
 }
 
 // eventWriter writes every incoming []byte to

internal/lsp/protocol/context.go

@@ -19,9 +19,6 @@ func WithClient(ctx context.Context, client Client) context.Context {
 }
 
 func LogEvent(ctx context.Context, ev event.Event, tags event.TagMap) context.Context {
-	if ctx.Err() != nil {
-		return ctx
-	}
 	if !ev.IsLog() {
 		return ctx
 	}

internal/lsp/source/references.go

@@ -6,13 +6,13 @@ package source
 
 import (
 	"context"
-	"errors"
 	"go/ast"
 	"go/token"
 	"go/types"
 
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/telemetry/event"
+	"golang.org/x/xerrors"
 )
 
 // ReferenceInfo holds information about reference to an identifier in Go source.
@@ -33,7 +33,7 @@ func References(ctx context.Context, s Snapshot, f FileHandle, pp protocol.Posit
 
 	qualifiedObjs, err := qualifiedObjsAtProtocolPos(ctx, s, f, pp)
 	// Don't return references for builtin types.
-	if errors.Is(err, errBuiltin) {
+	if xerrors.Is(err, errBuiltin) {
 		return nil, nil
 	}
 	if err != nil {