internal/lsp/cache: avoid returning errors when building source.Errors

We don't want to return an error for the whole package when we are just
building out error positions.

Change-Id: I56b5b88ff2b4b44da8a372ade81cd9b1534235c4
Reviewed-on: https://go-review.googlesource.com/c/tools/+/206597
Reviewed-by: Heschi Kreinick <[email protected]>
Run-TryBot: Heschi Kreinick <[email protected]>
(cherry picked from commit 52adfe5)
Reviewed-on: https://go-review.googlesource.com/c/tools/+/206877

Author: stamblerre

internal/lsp/cache/check.go

@@ -310,7 +310,8 @@ func typeCheck(ctx context.Context, fset *token.FileSet, m *metadata, mode sourc
 		for _, e := range rawErrors {
 			srcErr, err := sourceError(ctx, fset, pkg, e)
 			if err != nil {
-				return nil, err
+				log.Error(ctx, "unable to compute error positions", err, telemetry.Package.Of(pkg.ID()))
+				continue
 			}
 			pkg.errors = append(pkg.errors, srcErr)
 		}

internal/lsp/cache/errors.go

@@ -12,7 +12,9 @@ import (
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/lsp/source"
+	"golang.org/x/tools/internal/lsp/telemetry"
 	"golang.org/x/tools/internal/span"
+	"golang.org/x/tools/internal/telemetry/log"
 	errors "golang.org/x/xerrors"
 )
 
@@ -40,7 +42,8 @@ func sourceError(ctx context.Context, fset *token.FileSet, pkg *pkg, e interface
 		kind = source.ParseError
 		spn, err = scannerErrorRange(ctx, fset, pkg, e.Pos)
 		if err != nil {
-			return nil, err
+			log.Error(ctx, "no span for scanner.Error pos", err, telemetry.Package.Of(pkg.ID()))
+			spn = span.Parse(e.Pos.String())
 		}
 
 	case scanner.ErrorList:
@@ -52,9 +55,9 @@ func sourceError(ctx context.Context, fset *token.FileSet, pkg *pkg, e interface
 		kind = source.ParseError
 		spn, err = scannerErrorRange(ctx, fset, pkg, e[0].Pos)
 		if err != nil {
-			return nil, err
+			log.Error(ctx, "no span for scanner.Error pos", err, telemetry.Package.Of(pkg.ID()))
+			spn = span.Parse(e[0].Pos.String())
 		}
-
 	case types.Error:
 		msg = e.Msg
 		kind = source.TypeError