Visualize CR and LF symbols

CR and LF are invisible in Spotless output.

For instance:

      src/core/src/main/java/org/apache/jmeter/SplashScreen.java
          @@ -52,7 +52,7 @@
                   setLocationRelativeTo(null);\n
               }\n
           \n
          -    private int x=2;\r\n
          +    private int x=2;\n
           \n
               /**\n
                * Show screen\n

So far so good. Spotless shows that \n should not be there (which is true because I’m on macOS, and lines should end with LF).

However, if I add one more line with “trailing whitespace”, then the output becomes

      src/core/src/main/java/org/apache/jmeter/SplashScreen.java
          @@ -53,7 +53,7 @@
           ····}

           ·····private·int·x=2;
          -·····private·int·y=3;··
          +·····private·int·y=3;

           ····/**
           ·····*·Show·screen

Note: x=2 still has the wrong line ending, however, spotless does not print a warning on that.

spotlessApply corrects both issues (newline and the trailing whitespace).

Have you considered to use unicode characters like SYMBOL FOR CARRIAGE RETURN, ␍ SYMBOL FOR LINE FEED, ␊ ?

Then the output could be like

      src/core/src/main/java/org/apache/jmeter/SplashScreen.java
          @@ -53,7 +53,7 @@
           ····}

          -·····private·int·x=2;␍␊
          -·····private·int·y=3;··␊
          -·····private·int·x=2;␊
          +·····private·int·y=3;␊

           ····/**
           ·····*·Show·screen

[vlsi]

Running Spotless with file.encoding=ISO-8859-1 produces something like

17:01:43            �*���http://www.apache.org/licenses/LICENSE-2.0
17:01:43            �*
17:01:43            �*�Unless�required�by�applicable�law�or�agreed�to�in�writing,�software
17:01:43           -�*�distributed��under�the��License�is�distributed�on�an�"AS�IS"�BASIS,
17:01:43           -�*�WITHOUT��WARRANTIES�OR�CONDITIONS��OF�ANY�KIND,�either��express��or
17:01:43           -�*�implied.
17:01:43           -�*
17:01:43           +�*�distributed�under�the�License�is�distributed�on�an�"AS�IS"�BASIS,
17:01:43           +�*�WITHOUT�WARRANTIES�OR�CONDITIONS�OF�ANY�KIND,�either�express�or�implied.
17:01:43            �*�See�the�License�for�the�specific�language�governing�permissions�and
17:01:43            �*�limitations�under�the�License.
17:01:43           +�*

In other words, Spotless should probably refrain from using characters that are not encodable with file.encoding.

In other words, there should probably be two styles of “whitespace visualization”, and the default one should be selected based on the encoding capabilities.

[vlsi]

Migrated to https://github.com/autostyle/autostyle/issues/2