[wpiutil] Add std::expected shim (#6310)

Its tests use Catch2 instead of GoogleTest, so we can't import them.

upstream_utils/update_expected.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+
+import os
+import re
+import shutil
+
+from upstream_utils import (
+    get_repo_root,
+    clone_repo,
+    comment_out_invalid_includes,
+    walk_cwd_and_copy_if,
+    git_am,
+)
+
+
+def main():
+    upstream_root = clone_repo(
+        "https://github.com/TartanLlama/expected",
+        # master on 2024-01-25
+        "3f0ca7b19253129700a073abfa6d8638d9f7c80c",
+        shallow=False,
+    )
+    wpilib_root = get_repo_root()
+    wpiutil = os.path.join(wpilib_root, "wpiutil")
+
+    # Copy expected header into allwpilib
+    dest_filename = os.path.join(
+        wpiutil, "src/main/native/thirdparty/expected/include/wpi/expected"
+    )
+    shutil.copyfile(
+        os.path.join(upstream_root, "include/tl/expected.hpp"), dest_filename
+    )
+
+    # Rename namespace from tl to wpi
+    with open(dest_filename) as f:
+        content = f.read()
+    content = content.replace("namespace tl", "namespace wpi")
+    content = content.replace("tl::", "wpi::")
+    content = content.replace("TL_", "WPI_")
+    with open(dest_filename, "w") as f:
+        f.write(content)
+
+
+if __name__ == "__main__":
+    main()

wpiutil/.styleguide

@@ -3,6 +3,7 @@ cppHeaderFileInclude {
   \.hpp$
   \.inc$
   \.inl$
+  expected$
   math$
   numbers$
   scope$

wpiutil/CMakeLists.txt

@@ -197,6 +197,17 @@ else()
     endif()
 endif()
 
+install(
+    DIRECTORY src/main/native/thirdparty/expected/include/
+    DESTINATION "${include_dest}/wpiutil"
+)
+target_include_directories(
+    wpiutil
+    PUBLIC
+        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src/main/native/include>
+        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src/main/native/thirdparty/expected/include>
+        $<INSTALL_INTERFACE:${include_dest}/wpiutil>
+)
 install(DIRECTORY src/main/native/thirdparty/memory/include/ DESTINATION "${include_dest}/wpiutil")
 target_include_directories(
     wpiutil

wpiutil/build.gradle

@@ -180,6 +180,9 @@ nativeUtils.exportsConfigs {
 }
 
 cppHeadersZip {
+    from('src/main/native/thirdparty/expected/include') {
+        into '/'
+    }
     from('src/main/native/thirdparty/fmtlib/include') {
         into '/'
     }
@@ -232,7 +235,7 @@ model {
         all {
             it.sources.each {
                 it.exportedHeaders {
-                    srcDirs 'src/main/native/include', 'src/main/native/thirdparty/fmtlib/include', 'src/main/native/thirdparty/llvm/include', 'src/main/native/thirdparty/sigslot/include', 'src/main/native/thirdparty/json/include', 'src/main/native/thirdparty/memory/include', 'src/main/native/thirdparty/mpack/include', 'src/main/native/thirdparty/protobuf/include'
+                    srcDirs 'src/main/native/include', 'src/main/native/thirdparty/expected/include', 'src/main/native/thirdparty/fmtlib/include', 'src/main/native/thirdparty/llvm/include', 'src/main/native/thirdparty/sigslot/include', 'src/main/native/thirdparty/json/include', 'src/main/native/thirdparty/memory/include', 'src/main/native/thirdparty/mpack/include', 'src/main/native/thirdparty/protobuf/include'
                 }
             }
         }

wpiutil/src/test/native/cpp/expected/ExpectedTest.cpp

@@ -0,0 +1,58 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <initializer_list>
+#include <tuple>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+#include "wpi/expected"
+
+namespace {
+struct TakesInitAndVariadic {
+  std::vector<int> v;
+  std::tuple<int, int> t;
+
+  template <class... Args>
+  TakesInitAndVariadic(std::initializer_list<int> l,  // NOLINT
+                       Args&&... args)
+      : v(l), t(std::forward<Args>(args)...) {}
+};
+}  // namespace
+
+TEST(ExpectedTest, Emplace) {
+  {
+    wpi::expected<std::unique_ptr<int>, int> e;
+    e.emplace(new int{42});
+    EXPECT_TRUE(e);
+    EXPECT_EQ(**e, 42);
+  }
+
+  {
+    wpi::expected<std::vector<int>, int> e;
+    e.emplace({0, 1});
+    EXPECT_TRUE(e);
+    EXPECT_EQ((*e)[0], 0);
+    EXPECT_EQ((*e)[1], 1);
+  }
+
+  {
+    wpi::expected<std::tuple<int, int>, int> e;
+    e.emplace(2, 3);
+    EXPECT_TRUE(e);
+    EXPECT_EQ(std::get<0>(*e), 2);
+    EXPECT_EQ(std::get<1>(*e), 3);
+  }
+
+  {
+    wpi::expected<TakesInitAndVariadic, int> e = wpi::make_unexpected(0);
+    e.emplace({0, 1}, 2, 3);
+    EXPECT_TRUE(e);
+    EXPECT_EQ(e->v[0], 0);
+    EXPECT_EQ(e->v[1], 1);
+    EXPECT_EQ(std::get<0>(e->t), 2);
+    EXPECT_EQ(std::get<1>(e->t), 3);
+  }
+}