Missing ANSI Italic Style and Rendering Error in Underline Style

[raphaelNguyen]

Description

After upgrading to version >= 2.25.0, when rendering ansi, italic styling on log message no longer works (triggers a warning that the style italic is invalid) while underline styling on log message produces italic effect on rendered text. The warning message includes a stack trace that points to AnsiEscape.createSequence failing to create sequence for style name italic at the line below in JAnsiTextRenderer.

logging-log4j2/log4j-core/src/main/java/org/apache/logging/log4j/core/pattern/JAnsiTextRenderer.java

Line 251 in 76c8bef

merge(AnsiEscape.createSequence(styleName), output, first);

This seems to boil down to #3070, which rewrites JAnsiTextRenderer to use AnsiEscape instead of depending on external Jansi library to generate ansi escape sequences. However, the enum AnsiEscape differs from the enums in the old external Jansi library in that:

• AnsiEscape does not have the ITALIC entry.
• AnsiEscape.UNDERLINE has the code value of 3 which correspond to ITALIC.
• Code value 4 which corresponds to underline style seems to not be assigned to any enum value in AnsiEscape.

(Style code referenced from https://en.wikipedia.org/wiki/ANSI_escape_code#Select_Graphic_Rendition_parameters)

I'm wondering if this was a bug that existed in AnsiEscape from a long time ago that was just never noticed. The enum values from this file seems to have been unchanged for a long time. Thank you for your assistant with this issue.

Configuration

Version: >= 2.25.0

Operating system: Windows 11

JDK: 17.0.16

Logs

// to be supplied
[Stacktraces, errors, etc. relevant applications logs.]

Reproduction

Will supplement this at a later time.
[An isolated test reproducing the test.
JUnit tests similar to the ones in the code base are extremely appreciated.]

[vy]

• AnsiEscape does not have the ITALIC entry.
• AnsiEscape.UNDERLINE has the code value of 3 which correspond to ITALIC.
• Code value 4 which corresponds to underline style seems to not be assigned to any enum value in AnsiEscape.

@raphaelNguyen, thanks so much for the report and the through analysis. @ppkarwasz was the main figure behind the #3070 improvement, but AFAICS:

Removed JAnsiTextRenderer::toCode was using org.fusesource.jansi.AnsiRenderer.Code:

https://github.com/apache/logging-log4j2/pull/3070/changes#diff-17d0910e25d63f1dbdae9e77b69133454db40f1db1922485863bfbe43c937697L341-L343

Code enum gets the codes from org.fusesource.jansi.Ansi.Attribute:

https://github.com/fusesource/jansi/blob/c10d43f48cfdd80ba14dc78b194bc5449f23236d/src/main/java/org/fusesource/jansi/AnsiRenderer.java#L207

And there ITALIC and UNDERLINE exist:

https://github.com/fusesource/jansi/blob/c10d43f48cfdd80ba14dc78b194bc5449f23236d/src/main/java/org/fusesource/jansi/Ansi.java#L89

I suspect AnsiEscape needs to updated to include ITALIC, get the code for UNDERLINE fixed, and checked for other differences.

@raphaelNguyen, would you be interested in contributing this fix?

[raphaelNguyen]

I suspect AnsiEscape needs to updated to include ITALIC, get the code for UNDERLINE fixed, and checked for other differences.

Hi @vy, your suspicion is also what I thought the fix would be. I'll be happy to contribute a fix.

[vy]

@raphaelNguyen, thanks! I'm ramping down for the 2.26.0. If you can submit a PR (with a changelog entry!) in a day or two, it'll be great. If not, that is also fine, but then it will need to wait for the next release.

[vy]

@raphaelNguyen, you might consider adapting JAnsiTextRendererTest.

[raphaelNguyen]

Hi @vy. Thanks you for the release headsup and your suggestion on the test. I might take a week or so to contribute this due to some other commitments if that's okay. I'm okay with missing the upcoming release.