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

[Owen Pan via cfe-commits]

================
@@ -11116,6 +11116,275 @@ TEST_F(FormatTest, WrapsTemplateDeclarationsWithComments) {
       Style);
 }
 
+TEST_F(FormatTest, BreakBeforeTemplateClose) {
+  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 BreakBeforeTemplateClose 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.BreakBeforeTemplateClose = true;
+  // BreakBeforeTemplateClose should NOT force template declarations onto multiple lines.
+  // Use verifyNoChange since ColumnLimit = 0.
+  verifyNoChange("template <typename Foo>\n"
+                 "void foo() {}",
+                 Style);
+  verifyNoChange("template <typename Foo, typename Bar>\n"
+                 "void foo() {}",
+                 Style);
+  // It should allow a line break, even when the typename is short:
+  verifyNoChange("template <\n"
+                 "    typename Foo\n"
+                 ">\n"
+                 "void foo() {}",
+                 Style);
+  verifyNoChange("template <\n"
+                 "    typename Foo,\n"
+                 "    typename Bar\n"
+                 ">\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"
+      "}",
+      Style);
+
+  // Test lambda goes to next line:
+  verifyFormat("void foo() {\n"
+               "  auto lambda = []<\n"
+               "                    typename T\n"
+               "                >(T t) {\n"
+               "  };\n"
+               "}",
+               "void foo() {\n"
+               "  auto lambda = []<\n"
+               "  typename T>(T t){\n"
+               "  };\n"
+               "}",
+               Style);
+  // With no column limit, two parameters can go on the same line:
+  verifyFormat("void foo() {\n"
+               "  auto lambda = []<\n"
+               "                    typename T, typename Foo\n"
+               "                >(T t) {\n"
+               "  };\n"
+               "}",
+               "void foo() {\n"
+               "  auto lambda = []<\n"
+               "  typename T, typename Foo>(T t){\n"
+               "  };\n"
+               "}",
+               Style);
+  // Or on different lines:
+  verifyFormat("void foo() {\n"
+               "  auto lambda = []<\n"
+               "                    typename T,\n"
+               "                    typename Foo\n"
+               "                >(T t) {\n"
+               "  };\n"
+               "}",
+               "void foo() {\n"
+               "  auto lambda = []<\n"
+               "  typename T,\n"
+               "  typename Foo>(T t){\n"
+               "  };\n"
+               "}",
+               Style);
+
+  // Note that this is the same line (no \n):
+  verifyFormat("void foo() {\n"
+               "  auto lambda = []<typename "
+               "Looooooooooooooooooooooooooooong>("
+               "Looooooooooooooooooooooooooooong t) {};\n"
+               "}",
+               Style);
+
+  // Test template usage goes to next line too:
+  verifyFormat("void foo() {\n"
+               "  myFunc<\n"
+               "      T\n"
+               "  >();\n"
+               "}",
+               "void foo() {\n"
+               "  myFunc<\n"
+               "  T>();\n"
+               "}",
+               Style);
+
+  // Now test that it handles the cases when the column limit forces wrapping.
+  Style.ColumnLimit = 40;
+  // When the column limit allows it, the template should be combined back into
+  // one line:
+  verifyFormat("template <typename Foo, typename Bar>\n"
+               "void foo() {}",
+               "template <\n"
+               "    typename Foo,\n"
+               "    typename Bar\n"
+               ">"
----------------
owenca wrote:

```suggestion
               ">\n"
```

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