Improvements to raw-string parsing and expanding tests

As suggested in the review, use Lexer::getEscapedNewLineSize() instead
of implementing our own logic for it.

Author: tru

clang/lib/Lex/DependencyDirectivesScanner.cpp

@@ -210,13 +210,17 @@ static void skipOverSpaces(const char *&First, const char *const End) {
 static char previousChar(const char *First, const char *&Current) {
   assert(Current > First);
   --Current;
-  while (Current > First + 1 && isVerticalWhitespace(*Current)) {
-    const char PrevChar = *(Current - 1);
-    if (PrevChar == '\\') {
-      Current -= 2; // backslash + (\n or \r)
-    } else if (Current > First + 2 && isVerticalWhitespace(PrevChar) &&
-               PrevChar != *Current && *(Current - 2) == '\\') {
-      Current -= 3; // backslash + (\n\r or \r\n)
+  while (Current > First && isVerticalWhitespace(*Current)) {
+    // Check if the previous character is a backslash
+    if (Current > First && *(Current - 1) == '\\') {
+      // Use Lexer's getEscapedNewLineSize to get the size of the escaped newline
+      unsigned EscapeSize = Lexer::getEscapedNewLineSize(Current);
+      if (EscapeSize > 0) {
+        // Skip back over the entire escaped newline sequence (backslash + newline)
+        Current -= (1 + EscapeSize);
+      } else {
+        break;
+      }
     } else {
       break;
     }

clang/test/ClangScanDeps/raw-strings.cpp

@@ -12,6 +12,16 @@
 //--- include/header2.h
 //--- include/header3.h
 //--- include/header4.h
+//--- include/header5.h
+//--- include/header6.h
+//--- include/header7.h
+//--- include/header8.h
+//--- include/header9.h
+//--- include/header10.h
+//--- include/header11.h
+//--- include/header12.h
+//--- include/header13.h
+//--- include/header14.h
 //--- tu.c
 #if 0
 R"x()x"
@@ -47,9 +57,92 @@ R"z()y";
 //")z"
 #endif
 
+// Test u8 prefix with escaped newline
+#if 0
+u8R\
+"prefix(test)prefix"
+#endif
+#include "header5.h"
+
+// Test u prefix with multiple escaped newlines
+#if 0
+uR\
+\
+"multi(test)multi"
+#endif
+#include "header6.h"
+
+// Test U prefix with escaped newline
+#if 0
+UR\
+"upper(test)upper"
+#endif
+#include "header7.h"
+
+// Test L prefix with escaped newline
+#if 0
+LR\
+"wide(test)wide"
+#endif
+#include "header8.h"
+
+// Test escaped newline with \r\n style
+#if 0
+R\
+"crlf(test)crlf"
+#endif
+#include "header9.h"
+
+// Test multiple escaped newlines in different positions
+#if 0
+u\
+8\
+R\
+"complex(test)complex"
+#endif
+#include "header10.h"
+
+// Test raw string that should NOT be treated as raw (no R prefix due to identifier continuation)
+#if 0
+identifierR"notraw(test)notraw"
+#endif
+#include "header11.h"
+
+// Test raw string with whitespace before escaped newline
+#if 0
+R \
+"whitespace(test)whitespace"
+#endif
+#include "header12.h"
+
+// Test nested raw strings in disabled code
+#if 0
+R"outer(
+    R"inner(content)inner"
+)outer"
+#endif
+#include "header13.h"
+
+// Test raw string with empty delimiter
+#if 0
+R\
+"(empty delimiter)";
+#endif
+#include "header14.h"
+
 // RUN: clang-scan-deps -compilation-database %t/cdb.json -mode preprocess | FileCheck %s
 // RUN: clang-scan-deps -compilation-database %t/cdb.json -mode preprocess-dependency-directives | FileCheck %s
 // CHECK: tu.c
 // CHECK-NEXT: header.h
 // CHECK-NEXT: header3.h
 // CHECK-NEXT: header4.h
+// CHECK-NEXT: header5.h
+// CHECK-NEXT: header6.h
+// CHECK-NEXT: header7.h
+// CHECK-NEXT: header8.h
+// CHECK-NEXT: header9.h
+// CHECK-NEXT: header10.h
+// CHECK-NEXT: header11.h
+// CHECK-NEXT: header12.h
+// CHECK-NEXT: header13.h
+// CHECK-NEXT: header14.h