1. docker
  2. Commit b422d8da8f1d1e51da6cfff4890e6a08252da7c5
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engine.Tail() to ignore trailing whitespaces.

In its current form, if an error message has two trailing "\n" instead
of one, an empty line is resulted (see engine/job.go for an example of
such usages).

Skipping all trailing whitespaces will give a better error message.

Signed-off-by: Nghia Tran <nghia@google.com>

Nghia Tran authored on 2015/02/21 12:18:30
Showing 2 changed files
engine/streams.go
History View file @ b422d8d
... ... 
@@ -5,7 +5,9 @@ import (
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 	"fmt"
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 	"io"
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 	"io/ioutil"
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+	"strings"
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 	"sync"
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+	"unicode"
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 )
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 type Output struct {
... ... 
@@ -16,25 +18,25 @@ type Output struct {
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 }
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 // Tail returns the n last lines of a buffer
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-// stripped out of the last \n, if any
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+// stripped out of trailing white spaces, if any.
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+//
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 // if n <= 0, returns an empty string
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 func Tail(buffer *bytes.Buffer, n int) string {
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 	if n <= 0 {
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 		return ""
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 	}
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-	bytes := buffer.Bytes()
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-	if len(bytes) > 0 && bytes[len(bytes)-1] == '\n' {
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-		bytes = bytes[:len(bytes)-1]
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-	}
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-	for i := buffer.Len() - 2; i >= 0; i-- {
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-		if bytes[i] == '\n' {
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+	s := strings.TrimRightFunc(buffer.String(), unicode.IsSpace)
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+	i := len(s) - 1
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+	for ; i >= 0 && n > 0; i-- {
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+		if s[i] == '\n' {
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 			n--
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 			if n == 0 {
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-				return string(bytes[i+1:])
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+				break
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 			}
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 		}
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 	}
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-	return string(bytes)
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+	// when i == -1, return the whole string which is s[0:]
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+	return s[i+1:]
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 }
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 // NewOutput returns a new Output object with no destinations attached.
engine/streams_test.go
History View file @ b422d8d
... ... 
@@ -111,6 +111,11 @@ func TestTail(t *testing.T) {
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 		"Two\nThree",
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 		"One\nTwo\nThree",
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 	}
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+	tests["One\nTwo\n\n\n"] = []string{
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+		"",
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+		"Two",
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+		"One\nTwo",
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+	}
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 	for input, outputs := range tests {
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 		for n, expectedOutput := range outputs {
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 			output := Tail(bytes.NewBufferString(input), n)