[clang] [clang-format] Add BreakBeforeTemplateClose option (PR #118046)

[Owen Pan via cfe-commits]

================
@@ -11220,6 +11220,333 @@ TEST_F(FormatTest, WrapsTemplateDeclarationsWithComments) {
       Style);
 }
 
+TEST_F(FormatTest, BreakBeforeTemplateCloser) {
+  FormatStyle Style = getGoogleStyle(FormatStyle::LK_Cpp);
+  // Begin with tests covering the case where there is no constraint on the
+  // column limit.
+  Style.ColumnLimit = 0;
+  // When BreakBeforeTemplateCloser is turned off, the line break that it adds
+  // shall be removed:
+  verifyFormat("template <\n"
+               "    typename Foo,\n"
+               "    typename Bar>\n"
+               "void foo() {}",
+               "template <\n"
+               "    typename Foo,\n"
+               "    typename Bar\n"
+               ">\n"
+               "void foo() {}",
+               Style);
+
+  Style.BreakBeforeTemplateCloser = FormatStyle::BBTCS_BlockIndent;
+  // BreakBeforeTemplateCloser should NOT force template declarations onto
+  // multiple lines.
+  verifyFormat("template <typename Foo>\n"
+               "void foo() {}",
+               Style);
+  verifyFormat("template <typename Foo, typename Bar>\n"
+               "void foo() {}",
+               Style);
+  // It should allow a line break, even when the typename is short.
+  // verifyNoChange is needed because the default behavior is one line.
+  verifyNoChange("template <\n"
+                 "    typename Foo\n"
+                 ">\n"
+                 "void foo() {}",
+                 Style);
+  verifyNoChange("template <\n"
+                 "    typename Foo,\n"
+                 "    typename Bar\n"
+                 ">\n"
+                 "void foo() {}",
+                 Style);
+  verifyNoChange("template <typename Foo,\n"
+                 "          typename Bar>\n"
+                 "void foo() {}",
+                 Style);
+  // It should add a line break before > if not already present:
+  verifyFormat("template <\n"
+               "    typename Foo\n"
+               ">\n"
+               "void foo() {}",
+               "template <\n"
+               "    typename Foo>\n"
+               "void foo() {}",
+               Style);
+  verifyFormat("template <\n"
+               "    typename Foo,\n"
+               "    typename Bar\n"
+               ">\n"
+               "void foo() {}",
+               "template <\n"
+               "    typename Foo,\n"
+               "    typename Bar>\n"
+               "void foo() {}",
+               Style);
+  // When within an indent scope, the > should be placed accordingly:
+  verifyFormat("struct Baz {\n"
+               "  template <\n"
+               "      typename Foo,\n"
+               "      typename Bar\n"
+               "  >\n"
+               "  void foo() {}\n"
+               "};",
+               "struct Baz {\n"
+               "  template <\n"
+               "      typename Foo,\n"
+               "      typename Bar>\n"
+               "  void foo() {}\n"
+               "};",
+               Style);
+
+  // Test from issue #80049:
+  verifyFormat(
+      "void foo() {\n"
+      "  using type = std::remove_cv_t<\n"
+      "      add_common_cv_reference<\n"
+      "          std::common_type_t<std::decay_t<T0>, std::decay_t<T1>>,\n"
+      "          T0,\n"
+      "          T1\n"
+      "      >\n"
+      "  >;\n"
+      "}",
+      "void foo() {\n"
+      "  using type = std::remove_cv_t<\n"
+      "      add_common_cv_reference<\n"
+      "          std::common_type_t<std::decay_t<T0>, std::decay_t<T1>>,\n"
+      "          T0,\n"
+      "          T1>>;\n"
+      "}",
----------------
owenca wrote:

```suggestion
  // Test from https://github.com/llvm/llvm-project/issues/80049:
  verifyFormat(
      "using type = std::remove_cv_t<\n"
      "    add_common_cv_reference<\n"
      "        std::common_type_t<std::decay_t<T0>, std::decay_t<T1>>,\n"
      "        T0,\n"
      "        T1\n"
      "    >\n"
      ">;",
      "using type = std::remove_cv_t<\n"
      "    add_common_cv_reference<\n"
      "        std::common_type_t<std::decay_t<T0>, std::decay_t<T1>>,\n"
      "        T0,\n"
      "        T1>>;",
```

https://github.com/llvm/llvm-project/pull/118046