Add experimental flag for adaptive parameter bin-packing.

This is not activated for any style, might change or go away
completely.

For those that want to play around with it, set
ExperimentalAutoDetectBinPacking to true.

clang-format will then:
Look at whether function calls/declarations/definitions are currently
formatted with one parameter per line (on a case-by-case basis). If so,
clang-format will avoid bin-packing the parameters. If all parameters
are on one line (thus that line is "inconclusive"), clang-format will
make the choice dependent on whether there are other bin-packed
calls/declarations in the same file.

The reason for this change is that bin-packing in some situations can be
really bad and an author might opt to put one parameter on each line. If
the author does that, he might want clang-format not to mess with that.
If the author is unhappy with the one-per-line formatting, clang-format
can easily be convinced to bin-pack by putting any two parameters on the
same line.

llvm-svn: 186003

1 files changed, 24 insertions, 0 deletions

diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 0192a0718b3..b87393a9da2 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -2644,6 +2644,30 @@ TEST_F(FormatTest, FormatsOneParameterPerLineIfNecessary) {
       NoBinPacking);
 }
 
+TEST_F(FormatTest, AdaptiveOnePerLineFormatting) {
+  FormatStyle Style = getLLVMStyleWithColumns(15);
+  Style.ExperimentalAutoDetectBinPacking = true;
+  EXPECT_EQ("aaa(aaaa,\n"
+            "    aaaa,\n"
+            "    aaaa);\n"
+            "aaa(aaaa,\n"
+            "    aaaa,\n"
+            "    aaaa);",
+            format("aaa(aaaa,\n" // one-per-line
+                   "  aaaa,\n"
+                   "    aaaa  );\n"
+                   "aaa(aaaa,  aaaa,  aaaa);", // inconclusive
+                   Style));
+  EXPECT_EQ("aaa(aaaa, aaaa,\n"
+            "    aaaa);\n"
+            "aaa(aaaa, aaaa,\n"
+            "    aaaa);",
+            format("aaa(aaaa,  aaaa,\n" // bin-packed
+                   "    aaaa  );\n"
+                   "aaa(aaaa,  aaaa,  aaaa);", // inconclusive
+                   Style));
+}
+
 TEST_F(FormatTest, FormatsBuilderPattern) {
   verifyFormat(
       "return llvm::StringSwitch<Reference::Kind>(name)\n"