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verbose.go
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verbose.go
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// Copyright 2020-2023 Buf Technologies, Inc.
//
// 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 verbose
import (
"fmt"
"io"
"strings"
)
var (
// NopPrinter is a no-op printer.
//
// This generally aligns with the --verbose flag not being set.
NopPrinter = nopPrinter{}
)
// Printer prints verbose messages.
type Printer interface {
// Printf prints a new verbose message.
//
// Leading and trailing newlines are not respected.
//
// Callers should not rely on the print calls being reliable, i.e. errors to
// a backing Writer will be ignored.
Printf(format string, args ...interface{})
}
// NewWritePrinter returns a new Printer using the given Writer.
//
// The trimmed prefix is printed with a : before each line.
//
// This generally aligns with the --verbose flag being set and writer being stderr.
func NewWritePrinter(writer io.Writer, prefix string) Printer {
return newWritePrinter(writer, prefix)
}
type nopPrinter struct{}
func (nopPrinter) Printf(string, ...interface{}) {}
type writePrinter struct {
writer io.Writer
prefix string
}
func newWritePrinter(writer io.Writer, prefix string) *writePrinter {
prefix = strings.TrimSpace(prefix)
if prefix != "" {
prefix = prefix + ": "
}
return &writePrinter{
writer: writer,
prefix: prefix,
}
}
func (w *writePrinter) Printf(format string, args ...interface{}) {
if value := strings.TrimSpace(fmt.Sprintf(format, args...)); value != "" {
// Errors are ignored per the interface spec.
_, _ = w.writer.Write([]byte(w.prefix + value + "\n"))
}
}