[GROOVY-7465] ResourceGroovyMethods/NioGroovyMethods BOM behavior is inconsistent

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.5.0-alpha-1
• Component/s: groovy-jdk
• Labels: breaking_change
• Assignee: Keegan Witt
• Reporter: Keegan Witt
• Created: 11/Jun/15 13:18
• Updated: 02/May/17 02:03
• Resolved: 09/Dec/15 22:45

Description

Most users would expect withPrintWriter to be a convenience method that behaves the same as if they had called new PrintWriter themselves, but this is not the current behavior:

File file = new File("tmp.txt")
try {
    String text = " "
    String charset = "UTF-16LE"

    file.withPrintWriter(charset) { it << text }
    println "withPrintWriter"
    file.getBytes().each { System.out.format("%02x ", it) }

    PrintWriter w = new PrintWriter(file, charset)
    w.print(text)
    w.close()
    println "\n\nnew PrintWriter"
    file.getBytes().each { System.out.format("%02x ", it) }
} finally {
    file.delete()
}

Outputs

withPrintWriter
ff fe 20 00 

new PrintWriter
20 00

Additionally most users would expect that there's no difference in behavior between NIO and traditional methods, but this is also not the case

import java.nio.file.Files
import java.nio.file.FileSystems
import java.nio.file.Path

File file = new File("tmp1.txt")
Path path = FileSystems.getDefault().getPath("tmp2.txt")
try {
    String text = " "
    String charset = "UTF-16LE"

    file.withPrintWriter(charset) { it << text }
    println "withPrintWriter"
    file.getBytes().each { System.out.format("%02x ", it) }

    path.withPrintWriter(charset) { it << text }
    println "\n\nnio withPrintWriter"
    path.getBytes().each { System.out.format("%02x ", it) }
} finally {
    file.delete()
    Files.delete(path)
}

outputs

withPrintWriter
ff fe 20 00

nio withPrintWriter
20 00

This is because ResourceGroovyMethods have a writeUTF16BomIfRequired method that NioGroovyMethods don't.

Most likely we'd want to change ResourceGroovyMethods to not add the BOM by default, or at least allow the user to opt out of that behavior by doing something like adding a boolean argument to the existing methods that would control that behavior. The other option would be to make the NIO methods consistent by having them also use writeUTF16BomIfRequired.

This began as a discussion on the user mailing list.

Issue Links

• relates to: GROOVY-7661 Option to consume BOM if present