[WIP] Partial bot skeleton, non-functional though

vendor/github.com/cockroachdb/errors/barriers/barriers.go

@@ -0,0 +1,151 @@
+// Copyright 2019 The Cockroach Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+// implied. See the License for the specific language governing
+// permissions and limitations under the License.
+
+package barriers
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/cockroachdb/errors/errbase"
+	"github.com/cockroachdb/redact"
+	"github.com/gogo/protobuf/proto"
+)
+
+// Handled swallows the provided error and hides it from the
+// Cause()/Unwrap() interface, and thus the Is() facility that
+// identifies causes. However, it retains it for the purpose of
+// printing the error out (e.g. for troubleshooting). The error
+// message is preserved in full.
+//
+// Detail is shown:
+// - via `errors.GetSafeDetails()`, shows details from hidden error.
+// - when formatting with `%+v`.
+// - in Sentry reports.
+func Handled(err error) error {
+	if err == nil {
+		return nil
+	}
+	return HandledWithSafeMessage(err, redact.Sprint(err))
+}
+
+// HandledWithMessage is like Handled except the message is overridden.
+// This can be used e.g. to hide message details or to prevent
+// downstream code to make assertions on the message's contents.
+func HandledWithMessage(err error, msg string) error {
+	if err == nil {
+		return nil
+	}
+	return HandledWithSafeMessage(err, redact.Sprint(msg))
+}
+
+// HandledWithSafeMessage is like Handled except the message is overridden.
+// This can be used e.g. to hide message details or to prevent
+// downstream code to make assertions on the message's contents.
+func HandledWithSafeMessage(err error, msg redact.RedactableString) error {
+	return &barrierErr{maskedErr: err, smsg: msg}
+}
+
+// HandledWithMessagef is like HandledWithMessagef except the message
+// is formatted.
+func HandledWithMessagef(err error, format string, args ...interface{}) error {
+	if err == nil {
+		return nil
+	}
+	return &barrierErr{maskedErr: err, smsg: redact.Sprintf(format, args...)}
+}
+
+// barrierErr is a leaf error type. It encapsulates a chain of
+// original causes, but these causes are hidden so that they inhibit
+// matching via Is() and the Cause()/Unwrap() recursions.
+type barrierErr struct {
+	// Message for the barrier itself.
+	// In the common case, the message from the masked error
+	// is used as-is (see Handled() above) however it is
+	// useful to cache it here since the masked error may
+	// have a long chain of wrappers and its Error() call
+	// may be expensive.
+	smsg redact.RedactableString
+	// Masked error chain.
+	maskedErr error
+}
+
+var _ error = (*barrierErr)(nil)
+var _ errbase.SafeDetailer = (*barrierErr)(nil)
+var _ errbase.SafeFormatter = (*barrierErr)(nil)
+var _ fmt.Formatter = (*barrierErr)(nil)
+
+// barrierErr is an error.
+func (e *barrierErr) Error() string { return e.smsg.StripMarkers() }
+
+// SafeDetails reports the PII-free details from the masked error.
+func (e *barrierErr) SafeDetails() []string {
+	var details []string
+	for err := e.maskedErr; err != nil; err = errbase.UnwrapOnce(err) {
+		sd := errbase.GetSafeDetails(err)
+		details = sd.Fill(details)
+	}
+	details = append(details, redact.Sprintf("masked error: %+v", e.maskedErr).Redact().StripMarkers())
+	return details
+}
+
+// Printing a barrier reveals the details.
+func (e *barrierErr) Format(s fmt.State, verb rune) { errbase.FormatError(e, s, verb) }
+
+func (e *barrierErr) SafeFormatError(p errbase.Printer) (next error) {
+	p.Print(e.smsg)
+	if p.Detail() {
+		p.Printf("-- cause hidden behind barrier\n%+v", e.maskedErr)
+	}
+	return nil
+}
+
+// A barrier error is encoded exactly.
+func encodeBarrier(
+	ctx context.Context, err error,
+) (msg string, details []string, payload proto.Message) {
+	e := err.(*barrierErr)
+	enc := errbase.EncodeError(ctx, e.maskedErr)
+	return string(e.smsg), e.SafeDetails(), &enc
+}
+
+// A barrier error is decoded exactly.
+func decodeBarrier(ctx context.Context, msg string, _ []string, payload proto.Message) error {
+	enc := payload.(*errbase.EncodedError)
+	return &barrierErr{smsg: redact.RedactableString(msg), maskedErr: errbase.DecodeError(ctx, *enc)}
+}
+
+// Previous versions of barrier errors.
+func decodeBarrierPrev(ctx context.Context, msg string, _ []string, payload proto.Message) error {
+	enc := payload.(*errbase.EncodedError)
+	return &barrierErr{smsg: redact.Sprint(msg), maskedErr: errbase.DecodeError(ctx, *enc)}
+}
+
+// barrierError is the "old" type name of barrierErr. We use a new
+// name now to ensure a different decode function is used when
+// importing barriers from the previous structure, where the
+// message is not redactable.
+type barrierError struct {
+	msg       string
+	maskedErr error
+}
+
+func (b *barrierError) Error() string { return "" }
+
+func init() {
+	errbase.RegisterLeafDecoder(errbase.GetTypeKey((*barrierError)(nil)), decodeBarrierPrev)
+	tn := errbase.GetTypeKey((*barrierErr)(nil))
+	errbase.RegisterLeafDecoder(tn, decodeBarrier)
+	errbase.RegisterLeafEncoder(tn, encodeBarrier)
+}