Keep XML comments trailing an element on the same line

[timtebeek]

Fixes https://github.com/moderneinc/customer-requests/issues/2926

What

XML auto-format moved a comment that trailed an element on the same line onto its own following line:

-  <exclude>com.example.profit.ProfitFactory.processProfit.1</exclude> <!--tmp logic, tested elsewhere-->
-  <exclude>com.example.profit.io.ProfitUtils</exclude><!--tmp logic, tested elsewhere-->
+  <exclude>com.example.profit.ProfitFactory.processProfit.1</exclude>
+  <!--tmp logic, tested elsewhere-->
+  <exclude>com.example.profit.io.ProfitUtils</exclude>
+  <!--tmp logic, tested elsewhere-->

Besides being pure review noise on a migration PR, this silently changes what each comment documents: by XML convention the reflowed comment now reads as annotating the next <exclude>, and the last one dangles with nothing after it.

Why

The XML LST has no notion of a trailing comment — the whitespace separating it from the preceding sibling lives in the comment's own prefix, so that prefix is the only carrier of the author's intent. LineBreaksVisitor.visitComment called minimumLines(..., 1) unconditionally, which prepends "\n" to any newline-free prefix; TabsAndIndentsVisitor then indented the now-multiline prefix. Latent since XML auto-format was written (0b1efb7706, 2022), and untested — grepping rewrite-xml/rewrite-maven/rewrite-gradle for </tag> <!-- returned zero fixtures.

How

Skip the line break when the comment is on the same line as a preceding sibling — i.e. its prefix contains no newline and it is not the first content of its parent tag. Existing behavior is preserved for:

• a comment that is the first content of a tag (<dependencies><!--comment-->), which the existing LineBreaksTest#comments case asserts should reflow;
• a comment already on its own line, which still gets re-indented;
• prolog/misc comments, which are untouched.

Tests

• LineBreaksTest#trailingCommentsStayOnSameLine
• AutoFormatTest#trailingCommentStaysOnSameLine (the reproducer from the issue)
• AutoFormatTest#trailingCommentAfterTagContentStaysOnSameLine
• AutoFormatTest#misindentedTrailingCommentIsStillIndented (guards the contrast case)

All three new same-line tests fail on main and pass with the fix. :rewrite-xml:test, :rewrite-maven:test and :rewrite-gradle:test are green.

Not covered here

The issue also asks which recipe auto-formatted a scope far wider than it changed (OrderPomElements, AddAnnotationProcessor over the whole <plugins> block are the likely candidates). This fix stops the comment reflow regardless of the caller; the over-wide auto-format scope is a separate question.