errors: formatting interfaces
Change-Id: I4623144e43a789cc71e372e4579f2cb1fbaadc8b
Reviewed-on: https://go-review.googlesource.com/c/139499
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/errors/format.go b/errors/format.go
new file mode 100644
index 0000000..aed5de3
--- /dev/null
+++ b/errors/format.go
@@ -0,0 +1,32 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package errors
+
+// A Formatter formats error messages.
+type Formatter interface {
+ // Format prints the receiver's first error and returns the next error in
+ // the error chain, if any.
+ Format(p Printer) (next error)
+}
+
+// A Printer formats error messages.
+//
+// The most common implementation of Printer is the one provided by package fmt
+// during Printf. Localization packages such as golang.org/x/text/message
+// typically provide their own implementations.
+type Printer interface {
+ // Print appends args to the message output.
+ Print(args ...interface{})
+
+ // Printf writes a formatted string.
+ Printf(format string, args ...interface{})
+
+ // Detail reports whether error detail is requested.
+ // After the first call to Detail, all text written to the Printer
+ // is formatted as additional detail, or ignored when
+ // detail has not been requested.
+ // If Detail returns false, the caller can avoid printing the detail at all.
+ Detail() bool
+}
