[clang] [clang-format] revert to string << string handling to previous default (PR #88490)

[Björn Schäpers via cfe-commits]

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@@ -5598,11 +5598,45 @@ bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
   // FIXME: Breaking after newlines seems useful in general. Turn this into an
   // option and recognize more cases like endl etc, and break independent of
   // what comes after operator lessless.
-  if (Right.is(tok::lessless) && Right.Next &&
-      Right.Next->is(tok::string_literal) && Left.is(tok::string_literal) &&
-      Left.TokenText.ends_with("\\n\"")) {
-    return true;
+  switch (Style.BreakStreamOperator) {
+  case FormatStyle::BCOS_BetweenStrings: {
+    if (Right.is(tok::lessless) && Right.Next && Left.is(tok::string_literal) &&
+        Right.Next->is(tok::string_literal)) {
+      return true;
+    }
+    break;
+  }
+  case FormatStyle::BCOS_BetweenNewlineStrings: {
+    if (Right.is(tok::lessless) && Right.Next &&
+        Right.Next->is(tok::string_literal) && Left.is(tok::string_literal) &&
+        Left.TokenText.ends_with("\\n\"")) {
+      return true;
+    }
+    break;
+  }
+  case FormatStyle::BCOS_Always: {
+    // Don't break after the very first << or >>
+    // but the Left token can be os or std::os so
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HazardyKnusperkeks wrote:

Still don't understand the part of `os` or `std::os`.

https://github.com/llvm/llvm-project/pull/88490