[clang] [clang-format] Don't apply severe penalty if no possible column formats (PR #76675)

[James Grant via cfe-commits]

https://github.com/jamesg-nz created https://github.com/llvm/llvm-project/pull/76675

If there are possible column formats, but they weren't selected because they don't fit within remaining characters for the current path then applying severe penalty to induce column layout by selection of a different path seems fair.

But if due to style configuration or what the input code is, there are no possible column formats, different paths aren't going to have column layouts. Seems wrong to apply the severe penalty to induce column layouts if there are none available.

It just causes selection of sub-optimal paths, e.g. get bad formatting when brace initializers are used inside lambda bodies.

Fixes #56350

>From 68f7dee10e20b4ceeaba67f1ebe6b1153647e6ff Mon Sep 17 00:00:00 2001
From: James Grant <42079499+jamesg-nz at users.noreply.github.com>
Date: Mon, 1 Jan 2024 21:35:11 +1300
Subject: [PATCH] [clang-format] Don't apply severe penalty if no possible
 column formats

If there are possible column formats, but they weren't selected because
they don't fit within remaining characters for the current path then
applying severe penalty to induce column layout by selection of a
different path seems fair.

But if due to style configuration or what the input code is, there are
no possible column formats, different paths aren't going to have column
layouts. Seems wrong to apply the severe penalty to induce column
layouts if there are none available.

It just causes selection of sub-optimal paths, e.g. get bad formatting
when brace initializers are used inside lambda bodies.

Fixes #56350
---
 clang/lib/Format/FormatToken.cpp      |  4 ++--
 clang/unittests/Format/FormatTest.cpp | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Format/FormatToken.cpp b/clang/lib/Format/FormatToken.cpp
index 7a2df8c53952f9..b791c5a26bbe3a 100644
--- a/clang/lib/Format/FormatToken.cpp
+++ b/clang/lib/Format/FormatToken.cpp
@@ -113,8 +113,8 @@ unsigned CommaSeparatedList::formatAfterToken(LineState &State,
   if (!State.NextToken || !State.NextToken->Previous)
     return 0;
 
-  if (Formats.size() == 1)
-    return 0; // Handled by formatFromToken
+  if (Formats.size() <= 1)
+    return 0; // Handled by formatFromToken (1) or avoid severe penalty (0).
 
   // Ensure that we start on the opening brace.
   const FormatToken *LBrace =
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 881993ede17c3d..b7350b2fe66d9b 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -13875,6 +13875,21 @@ TEST_F(FormatTest, FormatsBracedListsInColumnLayout) {
                getLLVMStyleWithColumns(35));
   verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(aaaaaaaaaaaaaaaaaaa, {},\n"
                "                               aaaaaaaaaaaaaaaaaaaaaaa);");
+
+  // No possible column formats, don't want the optimal paths penalized.
+  verifyFormat(
+      "waarudo::unit desk = {\n"
+      "    .s = \"desk\", .p = p, .b = [] { return w::r{3, 10} * w::m; }};");
+  verifyFormat("SomeType something1([](const Input &i) -> Output { return "
+               "Output{1, 2}; },\n"
+               "                    [](const Input &i) -> Output { return "
+               "Output{1, 2}; });");
+  FormatStyle NoBinPacking = getLLVMStyle();
+  NoBinPacking.BinPackParameters = false;
+  verifyFormat("waarudo::unit desk = {\n"
+               "    .s = \"desk\", .p = p, .b = [] { return w::r{3, 10, 1, 1, "
+               "1, 1} * w::m; }};",
+               NoBinPacking);
 }
 
 TEST_F(FormatTest, PullTrivialFunctionDefinitionsIntoSingleLine) {