[clang-format] put non-empty catch block on one line with AllowShortBlocksOnASingleLine: Empty

[MyDeveloperDay]

Summary

https://github.com/llvm/llvm-project/issues/52715

Fixes #52715

AllowShortBlocksOnASingleLine seems to never be checked for "Empty" as such if its used it will be considered "Always" as we only ever check AllowShortBlocksOnASingleLine != Never

This impacts C++ as well as C# hence the slightly duplicated test.

[curdeius]

LGTM.

clang/lib/Format/UnwrappedLineFormatter.cpp

if (Line.First->is(tok::kw_default)) {
         return 0;
     }
     if (Line.First->isOneOf(tok::kw_if, tok::kw_else, tok::kw_while, tok::kw_do,
                             tok::kw_try, tok::kw___try, tok::kw_catch,
                             tok::kw___finally, tok::kw_for, tok::r_brace,
                             Keywords.kw___except)) {
       if (Style.AllowShortBlocksOnASingleLine == FormatStyle::SBS_Never)
         return 0;
+      if (Style.AllowShortBlocksOnASingleLine == FormatStyle::SBS_Empty &&
+          !I[1]->First->is(tok::r_brace))
+        return 0;
       // Don't merge when we can't except the case when
       // the control statement block is empty
       if (!Style.AllowShortIfStatementsOnASingleLine &&
           Line.First->isOneOf(tok::kw_if, tok::kw_else) &&
           !Style.BraceWrapping.AfterControlStatement &&
           !I[1]->First->is(tok::r_brace))
         return 0;
       if (!Style.AllowShortIfStatementsOnASingleLine &&

clang/unittests/Format/FormatTest.cpp

TEST_F(FormatTest, CoroutineCoReturn) {
   verifyFormat("co_return (42);");
   verifyFormat("co_return;");
   verifyFormat("co_return {};");
   verifyFormat("co_return x;");
   verifyFormat("co_return co_await foo();");
   verifyFormat("co_return co_yield foo();");
 }
 
+TEST_F(FormatTest, EmptyShortBlock) {
+  auto Style = getLLVMStyle();
+  Style.AllowShortBlocksOnASingleLine = FormatStyle::SBS_Empty;
+
+  verifyFormat("try {\n"
+               "  doA();\n"
+               "} catch (Exception &e) {\n"
+               "  e.printStackTrace();\n"
+               "}\n",
+               Style);
+
+  verifyFormat("try {\n"
+               "  doA();\n"
+               "} catch (Exception &e) {}\n",
+               Style);
+}
+
 } // namespace
 } // namespace format
 } // namespace clang

clang/unittests/Format/FormatTestCSharp.cpp

TEST_F(FormatTestCSharp, SwitchExpression) {
   verifyFormat("int x = a switch {\n"
                "    1 => (0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0),\n"
                "    2 => 1,\n"
                "    _ => 2\n"
                "};\n",
                Style);
 }
 
+TEST_F(FormatTestCSharp, EmptyShortBlock) {
+  auto Style = getLLVMStyle();
+  Style.AllowShortBlocksOnASingleLine = FormatStyle::SBS_Empty;
+
+  verifyFormat("try {\n"
+               "  doA();\n"
+               "} catch (Exception e) {\n"
+               "  e.printStackTrace();\n"
+               "}\n",
+               Style);
+
+  verifyFormat("try {\n"
+               "  doA();\n"
+               "} catch (Exception e) {}\n",
+               Style);
+}
+
 } // namespace format
 } // end namespace clang