Format a line if a range in its leading whitespace was selected.

With [] marking the selected range, clang-format invoked on

    [  ]   int a;

Would so far not reformat anything. With this patch, it formats a
line if its leading whitespace is touched.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176435 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Format/Format.cpp

@@ -995,6 +995,9 @@ public:
     // Consume and record whitespace until we find a significant token.
     while (FormatTok.Tok.is(tok::unknown)) {
       unsigned Newlines = Text.count('\n');
+      if (Newlines > 0)
+        FormatTok.LastNewlineOffset =
+            FormatTok.WhiteSpaceLength + Text.rfind('\n') + 1;
       unsigned EscapedNewlines = Text.count("\\\n");
       FormatTok.NewlinesBefore += Newlines;
       FormatTok.HasUnescapedNewline |= EscapedNewlines != Newlines;
@@ -1371,7 +1374,8 @@ private:
     const FormatToken *First = &TheLine.First.FormatTok;
     const FormatToken *Last = &TheLine.Last->FormatTok;
     CharSourceRange LineRange = CharSourceRange::getTokenRange(
-        First->Tok.getLocation(), Last->Tok.getLocation());
+        First->WhiteSpaceStart.getLocWithOffset(First->LastNewlineOffset),
+        Last->Tok.getLocation());
     for (unsigned i = 0, e = Ranges.size(); i != e; ++i) {
       if (!SourceMgr.isBeforeInTranslationUnit(LineRange.getEnd(),
                                                Ranges[i].getBegin()) &&

lib/Format/UnwrappedLineParser.h

@@ -33,8 +33,8 @@ namespace format {
 struct FormatToken {
   FormatToken()
       : NewlinesBefore(0), HasUnescapedNewline(false), WhiteSpaceLength(0),
-        TokenLength(0), IsFirst(false), MustBreakBefore(false) {
-  }
+        LastNewlineOffset(0), TokenLength(0), IsFirst(false),
+        MustBreakBefore(false) {}
 
   /// \brief The \c Token.
   Token Tok;
@@ -59,6 +59,10 @@ struct FormatToken {
   /// the \c Token.
   unsigned WhiteSpaceLength;
 
+  /// \brief The offset just past the last '\n' in this token's leading
+  /// whitespace (relative to \c WhiteSpaceStart). 0 if there is no '\n'.
+  unsigned LastNewlineOffset;
+
   /// \brief The length of the non-whitespace parts of the token. This is
   /// necessary because we need to handle escaped newlines that are stored
   /// with the token.

unittests/Format/FormatTest.cpp

@@ -172,6 +172,28 @@ TEST_F(FormatTest, RemovesTrailingWhitespaceOfFormattedLine) {
             format("int a;  \nint b;    ", 0, 0, getLLVMStyle()));
 }
 
+TEST_F(FormatTest, FormatsCorrectRegionForLeadingWhitespace) {
+  EXPECT_EQ("int b;\nint a;",
+            format("int b;\n   int a;", 7, 0, getLLVMStyle()));
+  EXPECT_EQ("int b;\n   int a;",
+            format("int b;\n   int a;", 6, 0, getLLVMStyle()));
+
+  EXPECT_EQ("#define A  \\\n"
+            "  int a;   \\\n"
+            "  int b;",
+            format("#define A  \\\n"
+                   "  int a;   \\\n"
+                   "    int b;",
+                   26, 0, getLLVMStyleWithColumns(12)));
+  EXPECT_EQ("#define A  \\\n"
+            "  int a;   \\\n"
+            "    int b;",
+            format("#define A  \\\n"
+                   "  int a;   \\\n"
+                   "    int b;",
+                   25, 0, getLLVMStyleWithColumns(12)));
+}
+
 TEST_F(FormatTest, ReformatsMovedLines) {
   EXPECT_EQ(
       "template <typename T> T *getFETokenInfo() const {\n"