From 290cefb46d4093a74e2646e5a783f9e6f8c4edd8 Mon Sep 17 00:00:00 2001
From: Tyler Veness <calcmogul@gmail.com>
Date: Mon, 1 Apr 2024 14:24:12 -0700
Subject: [PATCH] [wpimath] Support formatting Eigen array types

---
 wpimath/src/main/native/include/frc/fmt/Eigen.h | 4 ++--
 wpimath/src/test/native/cpp/FormatterTest.cpp   | 9 ++++++---
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/wpimath/src/main/native/include/frc/fmt/Eigen.h b/wpimath/src/main/native/include/frc/fmt/Eigen.h
index 2438b9f1de6..3adfaec5695 100644
--- a/wpimath/src/main/native/include/frc/fmt/Eigen.h
+++ b/wpimath/src/main/native/include/frc/fmt/Eigen.h
@@ -11,11 +11,11 @@
 #include <fmt/format.h>
 
 /**
- * Formatter for classes derived from Eigen::MatrixBase<Derived> or
+ * Formatter for classes derived from Eigen::DenseBase<Derived> or
  * Eigen::SparseCompressedBase<Derived>.
  */
 template <typename Derived, typename CharT>
-  requires std::derived_from<Derived, Eigen::MatrixBase<Derived>> ||
+  requires std::derived_from<Derived, Eigen::DenseBase<Derived>> ||
            std::derived_from<Derived, Eigen::SparseCompressedBase<Derived>>
 struct fmt::formatter<Derived, CharT> {
   constexpr auto parse(fmt::format_parse_context& ctx) {
diff --git a/wpimath/src/test/native/cpp/FormatterTest.cpp b/wpimath/src/test/native/cpp/FormatterTest.cpp
index 0b6d5904988..f1d2d46594b 100644
--- a/wpimath/src/test/native/cpp/FormatterTest.cpp
+++ b/wpimath/src/test/native/cpp/FormatterTest.cpp
@@ -25,19 +25,22 @@ TEST(FormatterTest, Eigen) {
       "  4.000000  5.000000",
       fmt::format("{:f}", B));
 
-  Eigen::SparseMatrix<double> C{3, 2};
+  Eigen::Array2d C{0.0, 1.0};
+  EXPECT_EQ("  0.000000\n  1.000000", fmt::format("{:f}", C));
+
+  Eigen::SparseMatrix<double> D{3, 2};
   std::vector<Eigen::Triplet<double>> triplets;
   triplets.emplace_back(0, 1, 1.0);
   triplets.emplace_back(1, 0, 2.0);
   triplets.emplace_back(1, 1, 3.0);
   triplets.emplace_back(2, 0, 4.0);
   triplets.emplace_back(2, 1, 5.0);
-  C.setFromTriplets(triplets.begin(), triplets.end());
+  D.setFromTriplets(triplets.begin(), triplets.end());
   EXPECT_EQ(
       "  0.000000  1.000000\n"
       "  2.000000  3.000000\n"
       "  4.000000  5.000000",
-      fmt::format("{:f}", C));
+      fmt::format("{:f}", D));
 }
 
 TEST(FormatterTest, Units) {