[clang] [clang-format] Add BreakBeforeTemplateClose option (PR #118046)
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Mon Jan 27 20:58:30 PST 2025
================
@@ -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"
+ "}",
+ 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"
+ ">\n"
+ "void foo() {}",
+ Style);
+ // But not when the name is looong. Note that these names are exactly 1
+ // character too long for the ColumnLimit.
+ verifyFormat("template <\n"
+ " typename Foo,\n"
+ " typename Barrrrrrrrrrrrrrrrrrrr\n"
+ ">\n"
+ "void foo() {}",
+ Style);
----------------
leijurv wrote:
I apologize for the off-by-one. You're correct that you've found unexpected behavior - when the column limit is 1 less than `template <typename Barr` then it splits properly, when the column limit is 1 more, then it allows it all on one line, but when the column limit is exactly equal to the length, it chooses to split before the `<` when we'd rather it split after the `<`.
I'm not certain whether to call this behavior "wrong", but sure it is unexpected. I would like to point out that I had already encountered this behavior with the lambdas, and I had written it into the unit test:
https://github.com/llvm/llvm-project/blob/fa15aca5c58a16760479fa3e53fa1286fc6adffa/clang/unittests/Format/FormatTest.cpp#L11455-L11468 I was okay with that behavior however it contradicts your suggestion here so I have trimmed down and modified the tests because I don't want to lock in behavior that is unexpected. I tried to make the lambda behavior make sense alongside this change, but, between the two, it is clear that lambda templates are not the common case.
See commit: https://github.com/llvm/llvm-project/pull/118046/commits/c0090c8ae6bea4091bc061601902f99903c1a89f
https://github.com/llvm/llvm-project/pull/118046
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