maint: Harden ScopedContextChange

libmamba/tests/include/mambatests.hpp

@@ -9,11 +9,13 @@
 
 #include <array>
 #include <functional>
+#include <ranges>
 #include <string_view>
 #include <unordered_set>
 #include <vector>
 
 #include "mamba/core/context.hpp"
+#include "mamba/core/invoke.hpp"
 #include "mamba/core/output.hpp"
 #include "mamba/fs/filesystem.hpp"
 #include "mamba/util/environment.hpp"
@@ -91,8 +93,10 @@ namespace mambatests
     };
 
     // RAII helper for C++ tests that temporarily override fields on the shared Context
-    // singleton (see context()). Tests often need to point at a temp prefix, tweak channels,
-    // or flip feature flags; without restoration, later tests inherit stale state.
+    // singleton (see context()). A future improvement would be to give each test its own
+    // Context instance instead of mutating the singleton (see singletons() FIXME). Until then,
+    // tests often need to point at a temp prefix, tweak channels, or flip feature flags;
+    // without restoration, later tests inherit stale state.
     //
     // Save the value of each touched field on first use and restore it when the guard is
     // destroyed. Repeated calls to the same setter only change the live value — the original
@@ -107,7 +111,7 @@ namespace mambatests
     //   mambatests::ScopedContextChange context_change{ ctx };
     //   context_change.set_channels({ "conda-forge" }).set_offline(false);
     //
-    //   context_change.preserve(&mamba::Context::use_sharded_repodata);
+    //   context_change.preserve(ctx.use_sharded_repodata);
     //   ctx.use_sharded_repodata = false;  // restored to the pre-preserve value at scope end
     class ScopedContextChange
     {
@@ -120,73 +124,69 @@ namespace mambatests
 
         ~ScopedContextChange()
         {
-            for (auto it = m_restorers.rbegin(); it != m_restorers.rend(); ++it)
+            for (auto& restorer : std::ranges::reverse_view(m_restorers))
             {
-                (*it)();
+                [[maybe_unused]] auto result = mamba::safe_invoke(restorer);
             }
         }
 
         ScopedContextChange& set_target_prefix(const mamba::fs::u8path& prefix)
         {
-            touch(
-                &mamba::Context::prefix_params,
-                [&](auto& params) { params.target_prefix = prefix; }
-            );
+            touch(m_ctx.prefix_params, [&](auto& params) { params.target_prefix = prefix; });
             return *this;
         }
 
         ScopedContextChange& set_root_prefix(const mamba::fs::u8path& prefix)
         {
-            touch(&mamba::Context::prefix_params, [&](auto& params) { params.root_prefix = prefix; });
+            touch(m_ctx.prefix_params, [&](auto& params) { params.root_prefix = prefix; });
             return *this;
         }
 
         ScopedContextChange& set_envs_dirs(std::vector<mamba::fs::u8path> dirs)
         {
-            touch(&mamba::Context::envs_dirs, [&](auto& field) { field = std::move(dirs); });
+            touch(m_ctx.envs_dirs, [&](auto& field) { field = std::move(dirs); });
             return *this;
         }
 
         ScopedContextChange& set_pkgs_dirs(std::vector<mamba::fs::u8path> dirs)
         {
-            touch(&mamba::Context::pkgs_dirs, [&](auto& field) { field = std::move(dirs); });
+            touch(m_ctx.pkgs_dirs, [&](auto& field) { field = std::move(dirs); });
             return *this;
         }
 
         ScopedContextChange& set_prefix_data_interoperability(bool value)
         {
-            touch(&mamba::Context::prefix_data_interoperability, [&](auto& field) { field = value; });
+            touch(m_ctx.prefix_data_interoperability, [&](auto& field) { field = value; });
             return *this;
         }
 
         ScopedContextChange& set_channels(std::vector<std::string> channels)
         {
-            touch(&mamba::Context::channels, [&](auto& field) { field = std::move(channels); });
+            touch(m_ctx.channels, [&](auto& field) { field = std::move(channels); });
             return *this;
         }
 
         ScopedContextChange& set_use_sharded_repodata(bool value)
         {
-            touch(&mamba::Context::use_sharded_repodata, [&](auto& field) { field = value; });
+            touch(m_ctx.use_sharded_repodata, [&](auto& field) { field = value; });
             return *this;
         }
 
         ScopedContextChange& set_offline(bool value)
         {
-            touch(&mamba::Context::offline, [&](auto& field) { field = value; });
+            touch(m_ctx.offline, [&](auto& field) { field = value; });
             return *this;
         }
 
         ScopedContextChange& set_platform(std::string platform)
         {
-            touch(&mamba::Context::platform, [&](auto& field) { field = std::move(platform); });
+            touch(m_ctx.platform, [&](auto& field) { field = std::move(platform); });
             return *this;
         }
 
-        // Snapshot member for restoration without assigning a new value. The member pointer
-        // syntax (e.g. &mamba::Context::platform) selects which Context field to guard.
+        // Snapshot member for restoration without assigning a new value.
         template <typename T>
-        ScopedContextChange& preserve(T mamba::Context::* member)
+        ScopedContextChange& preserve(T& member)
         {
             touch(member, [](auto&) {});
             return *this;
@@ -200,15 +200,14 @@ namespace mambatests
     private:
 
         template <typename T, typename F>
-        void touch(T mamba::Context::* member, F&& mutator)
+        void touch(T& member, F&& mutator)
         {
-            auto& field = m_ctx.*member;
-            if (m_saved_fields.insert(static_cast<const void*>(&field)).second)
+            if (m_saved_fields.insert(static_cast<const void*>(&member)).second)
             {
-                m_restorers.push_back([&field, initial = field]() mutable
-                                      { field = std::move(initial); });
+                m_restorers.push_back([&member, initial = member]() mutable
+                                      { member = std::move(initial); });
             }
-            mutator(field);
+            std::invoke(std::forward<F>(mutator), member);
         }
 
         mamba::Context& m_ctx;

libmamba/tests/src/core/test_channel_loader.cpp

@@ -162,12 +162,12 @@ TEST_CASE("load_channels", "[mamba::api][channel_loader]")
     // Use test singletons so Console/progress bar are initialized (avoids SIGABRT)
     Context& ctx = mambatests::context();
     mambatests::ScopedContextChange context_change{ ctx };
-    context_change.preserve(&mamba::Context::channels)
-        .preserve(&mamba::Context::mirrored_channels)
-        .preserve(&mamba::Context::pkgs_dirs)
-        .preserve(&mamba::Context::offline)
-        .preserve(&mamba::Context::remote_fetch_params)
-        .preserve(&mamba::Context::channel_alias);
+    context_change.preserve(ctx.channels)
+        .preserve(ctx.mirrored_channels)
+        .preserve(ctx.pkgs_dirs)
+        .preserve(ctx.offline)
+        .preserve(ctx.remote_fetch_params)
+        .preserve(ctx.channel_alias);
 
     ctx.channels = {};
     ctx.mirrored_channels = {};

libmamba/tests/src/core/test_channels_hook.cpp

@@ -43,7 +43,7 @@ namespace mamba::testing
 
         ChannelsHookFixture()
         {
-            m_context_change.preserve(&mamba::Context::channel_alias).preserve(&mamba::Context::channels);
+            m_context_change.preserve(ctx.channel_alias).preserve(ctx.channels);
         }
 
         ~ChannelsHookFixture()

libmamba/tests/src/core/test_configuration.cpp

@@ -39,8 +39,7 @@ namespace mamba
 
             Configuration()
             {
-                m_context_change.preserve(&mamba::Context::channel_alias)
-                    .preserve(&mamba::Context::remote_fetch_params);
+                m_context_change.preserve(ctx.channel_alias).preserve(ctx.remote_fetch_params);
             }
 
             ~Configuration()
@@ -865,7 +864,7 @@ namespace mamba
             TEST_CASE_METHOD(Configuration, "platform")
             {
                 mambatests::ScopedContextChange context_change{ ctx };
-                context_change.preserve(&mamba::Context::platform);
+                context_change.preserve(ctx.platform);
 
                 REQUIRE(ctx.platform == ctx.host_platform);
 

libmamba/tests/src/core/test_output.cpp

@@ -19,7 +19,7 @@ namespace mamba
         {
             auto& ctx = mambatests::context();
             mambatests::ScopedContextChange context_change{ ctx };
-            context_change.preserve(&mamba::Context::graphics_params);
+            context_change.preserve(ctx.graphics_params);
 
             ctx.graphics_params.no_progress_bars = true;
             auto proxy = Console::instance().add_progress_bar("conda-forge");

libmamba/tests/src/core/test_sharded_repodata_integration.cpp

@@ -1290,8 +1290,7 @@ TEST_CASE("Sharded repodata - update scenarios", "[mamba::core][sharded][.integr
 
     // For update, we need to create prefix data and use Update request
     mambatests::ScopedContextChange update_context_change{ ctx };
-    update_context_change.preserve(&mamba::Context::use_sharded_repodata)
-        .preserve(&mamba::Context::validation_params);
+    update_context_change.preserve(ctx.use_sharded_repodata).preserve(ctx.validation_params);
 
     // Test traditional update
     ctx.use_sharded_repodata = false;
@@ -1615,8 +1614,7 @@ TEST_CASE("Sharded repodata - remove scenarios", "[mamba::core][sharded][.integr
 
     // For remove, we need to create prefix data and use Remove request
     mambatests::ScopedContextChange remove_context_change{ ctx };
-    remove_context_change.preserve(&mamba::Context::use_sharded_repodata)
-        .preserve(&mamba::Context::validation_params);
+    remove_context_change.preserve(ctx.use_sharded_repodata).preserve(ctx.validation_params);
 
     // Test traditional remove
     ctx.use_sharded_repodata = false;

libmamba/tests/src/core/test_virtual_packages.cpp

@@ -42,7 +42,7 @@ namespace mamba
 
                 auto& ctx = mambatests::context();
                 mambatests::ScopedContextChange context_change{ ctx };
-                context_change.preserve(&mamba::Context::platform);
+                context_change.preserve(ctx.platform);
 
                 auto pkgs = detail::dist_packages(ctx.platform);