Preserve escaped backslash-newline text in UsePortableNewlines

[martinfrancois]

Suggested review order: 9 of 52 (Score: 8)
Review first: #988

What's changed?

Updates UsePortableNewlines to distinguish a Java newline escape from an escaped backslash followed by n. The recipe keeps J.Literal.value and J.Literal.valueSource aligned for ordinary strings and text blocks, including Unicode escapes, octal line feeds, CRLF input, and text-block continuations.

What's your motivation?

Recipe: org.openrewrite.staticanalysis.UsePortableNewlines.

I found this by running org.openrewrite.staticanalysis.UsePortableNewlines from org.openrewrite.recipe:rewrite-static-analysis:2.39.0 on CodexModelDefaultsResolverTest.java in Symphony-Trello at a8013f27. I reproduced the same result with the latest released recipe artifact, org.openrewrite.recipe:rewrite-static-analysis:2.41.0. ./mvnw -DskipTests test-compile then fails with illegal escape character in this file and three other affected test files.

Before

printf '%%s\\n' '{"jsonrpc":"2.0","id":1,"result":{}}'

Actual after the recipe

printf '%%s\%n' '{"jsonrpc":"2.0","id":1,"result":{}}'

Expected after the recipe

(unchanged)

The source contains data for a generated shell script: two Java backslashes encode one runtime backslash. Replacing the n creates the invalid Java escape \%, so the transformed checkout no longer compiles.

Confirmed real-world execution

• Project: Symphony-Trello.
• Location: CodexModelDefaultsResolverTest.java at a8013f27.
• Discovery checkout: martinfrancois/symphony-trello@a8013f27.

Anything in particular you'd like reviewers to focus on?

Please review the source-to-runtime newline mapping. A formatter newline such as "line=%s\\n" remains eligible, while escaped backslash-newline data remains unchanged.

Have you considered any alternatives or workarounds?

Counting only consecutive raw backslashes does not account for Unicode escapes or text-block continuations and leaves the literal's semantic value inconsistent with its printed source in those cases.

Any additional context

Pre-existing tests changed: None.

• Target commit: martinfrancois/symphony-trello@a8013f27
• Discovery release: org.openrewrite.recipe:rewrite-static-analysis:2.39.0
• Latest verification release: org.openrewrite.recipe:rewrite-static-analysis:2.41.0
• Focused test: UsePortableNewlinesTest.doesNotCorruptEscapedBackslashNewlineInFormattedTextBlock
• Upstream reproduction commit: openrewrite/rewrite-static-analysis@43b51de2

This change was prepared with AI assistance. I reviewed the target execution evidence, implementation, tests, and contribution text.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've run ./gradlew build locally, and committed any resulting changes to recipes.csv
• I've formatted the lines I changed, without reformatting code I didn't touch