[clang-format] Discourage breaks in submessage entries, hard rule

Summary:
Currently clang-format allows this for text protos:
```
submessage:
    { key: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' }
```
when it is under the column limit and when putting it all on one line exceeds the column limit.

This is not a very intuitive formatting, so I'd prefer having
```
submessage: {
  key: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
}
```
instead, even if it takes one line more.

This patch prevents clang-format from inserting a break between `: {` and similar cases.

Reviewers: djasper, sammccall

Reviewed By: sammccall

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D48063

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@334517 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 29 insertions, 0 deletions

diff --git a/unittests/Format/FormatTestProto.cpp b/unittests/Format/FormatTestProto.cpp
index a15ba62ffc..d25aeb846a 100644
--- a/unittests/Format/FormatTestProto.cpp
+++ b/unittests/Format/FormatTestProto.cpp
@@ -624,5 +624,34 @@ TEST_F(FormatTestProto, BreaksEntriesOfSubmessagesContainingSubmessages) {
                "}");
 }
 
+TEST_F(FormatTestProto, PreventBreaksBetweenKeyAndSubmessages) {
+  verifyFormat("option (MyProto.options) = {\n"
+               "  submessage: {\n"
+               "    key: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'\n"
+               "  }\n"
+               "}");
+  verifyFormat("option (MyProto.options) = {\n"
+               "  submessage {\n"
+               "    key: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'\n"
+               "  }\n"
+               "}");
+  verifyFormat("option (MyProto.options) = {\n"
+               "  submessage: <\n"
+               "    key: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'\n"
+               "  >\n"
+               "}");
+  verifyFormat("option (MyProto.options) = {\n"
+               "  submessage <\n"
+               "    key: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'\n"
+               "  >\n"
+               "}");
+  verifyFormat("option (MyProto.options) = {\n"
+               "  repeatedd: [\n"
+               "    'eyaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'\n"
+               "  ]\n"
+               "}");
+}
+
+
 } // end namespace tooling
 } // end namespace clang