[clang-format] Propagate `LeadingEmptyLinesAffected` when joining lines (#146761)

Before this commit, when `LineJoiner` joins a line with affected leading
whitespace, it would drop the knowledge of this entirely. However, when
the `AffectedRangeManager` is computing the affected lines, the leading
empty whitespace lines are potentially considered for non-first tokens
in the `AnnotatedLine`. This causes a discrepancy in behavior when an
`AnnotatedLine` is put together from joining multiple lines versus when
it is not.

We change `LineJoiner::join` to follow `AffectedRangeManager`'s logic,
considering the leading whitespace when determining `Affected` for a
token.


https://github.com/llvm/llvm-project/blob/a63f57262898588b576d66e5fd79c0aa64b35f2d/clang/lib/Format/AffectedRangeManager.cpp#L111-L130

Fixes #138942.

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index f2ed027..ac8c0c8 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -986,8 +986,10 @@ private:
   void join(AnnotatedLine &A, const AnnotatedLine &B) {
     assert(!A.Last->Next);
     assert(!B.First->Previous);
-    if (B.Affected)
+    if (B.Affected || B.LeadingEmptyLinesAffected) {
+      assert(B.Affected || A.Last->Children.empty());
       A.Affected = true;
+    }
     A.Last->Next = B.First;
     B.First->Previous = A.Last;
     B.First->CanBreakBefore = true;