feat(tests): public module packages as workspace members (zero shell)

tinyhttps/imgui/ffmpeg/opencv consume their bare names from THIS checkout
via a member-level '[indices] default = { path = "../../.." }' (mcpp >=
0.0.97). Test sources are line-for-line ports of the smoke consumers
(assertions unchanged); ffmpeg/opencv/imgui members are cfg(linux)-gated
to the CI-validated surface with no-op mains elsewhere. The four reseeding
smoke shells are deleted.

Notes:
- exactly ONE [indices] entry per member: xlings fails silently with >1
  project-scoped index repo (mcpp#238); root-level centralization (#224)
  is deferred until that lands.
- the old smoke's llvm@20.1.7 pin for imgui is dropped: it predates gcc16
  module support; imgui-m upstream CI builds with gcc@16.1.0 (verified
  locally: member passes with the workspace default toolchain).

Author: Sunrisepeak

mcpp.toml

@@ -1,7 +1,7 @@
 # mcpp-index is simultaneously the package index (pkgs/) AND a mcpp workspace that
 # tests it: a virtual workspace whose members are per-library TEST projects under
-# tests/examples/ — each depends on this repo's own compat.<lib> via a local
-# [indices] path and asserts behavior in tests/*.cpp. The whole suite runs as a
+# tests/examples/ — each depends on this repo's own packages via a per-member
+# local [indices] redirect and asserts behavior in tests/*.cpp. The whole suite runs as a
 # single shell-free command, `mcpp test --workspace` (or `mcpp test -p <lib>`).
 # "Eat our own dog food." See
 # .agents/docs/2026-06-29-mcpp-native-workspace-ci-design.md and
@@ -15,15 +15,27 @@ members = [
     "tests/examples/core",
     "tests/examples/eigen",
     "tests/examples/ffmpeg",
+    "tests/examples/ffmpeg-module",
     "tests/examples/fmtlib.fmt",
     "tests/examples/gui-stack",
     "tests/examples/imgui",
+    "tests/examples/imgui-module",
     "tests/examples/imgui-window",
     "tests/examples/marzer.tomlplusplus",
     "tests/examples/nlohmann.json",
     "tests/examples/openblas",
     "tests/examples/opencv",
     "tests/examples/opencv5",
+    "tests/examples/opencv-module",
     "tests/examples/spdlog",
     "tests/examples/spdlog-compiled",
+    "tests/examples/tinyhttps",
 ]
+
+
+# NOTE: each member declares exactly ONE `[indices] <ns> = { path = "../../.." }`
+# entry for the namespace it consumes (module packages use `default`, the
+# builtin mcpplibs namespace — mcpp >= 0.0.97). Root-level centralization of
+# these redirects (mcpp #224) is deliberately NOT used yet: xlings fails
+# silently when a project has more than one project-scoped index repo
+# (mcpp-community/mcpp#238); revisit once fixed.

tests/examples/ffmpeg-module/mcpp.toml

@@ -0,0 +1,20 @@
+# Public `ffmpeg` C++23-module package test (bare-name consumption from the
+# builtin default namespace — resolved against THIS checkout via the
+# member-level `[indices] default` redirect, mcpp >= 0.0.97; kept per-member
+# and single-entry because xlings breaks with >1 project index repo, mcpp#238). Replaces the
+# former tests/smoke_ffmpeg_module.sh reseeding driver. The package is
+# linux-only (source build with 157 NASM .asm units); off-Linux the test
+# compiles to a no-op main().
+[package]
+name    = "ffmpeg-module-tests"
+version = "0.1.0"
+
+# The module package's own transitive dep (compat.ffmpeg) resolves from the
+# GLOBAL published compat index (the compat namespace is not redirected here
+# — see the mcpp#238 single-repo constraint); the compat descriptor itself is
+# pre-merge-validated by its dedicated member.
+[indices]
+default = { path = "../../.." }
+
+[target.'cfg(linux)'.dependencies]
+ffmpeg = "0.0.1"

tests/examples/ffmpeg-module/tests/ffmpeg_module.cpp

@@ -0,0 +1,31 @@
+// Public ffmpeg module package end-to-end assertion: import-only consumption
+// (`import ffmpeg.av;`), libavutil version of the FFmpeg 8.1.x train, core
+// decoders present, demuxer registry populated. Linux-only (see mcpp.toml).
+#ifdef __linux__
+import std;
+import ffmpeg.av;
+
+int main() {
+    unsigned v { avutil_version() };
+    std::println("libavutil {}.{} module package ok", v >> 16, (v >> 8) & 0xff);
+    if ((v >> 16) != 60u) {   // libavutil major of the FFmpeg 8.1.x train
+        return 1;
+    }
+
+    for (auto name : { "h264", "hevc", "av1", "aac" }) {
+        const AVCodec* dec { avcodec_find_decoder_by_name(name) };
+        if (dec == nullptr) {
+            std::println("decoder {} MISSING", name);
+            return 2;
+        }
+    }
+
+    void* it { nullptr };
+    long demuxers { 0 };
+    while (av_demuxer_iterate(&it)) ++demuxers;
+    std::println("{} demuxers registered", demuxers);
+    return demuxers > 300 ? 0 : 3;
+}
+#else
+int main() { return 0; }
+#endif

tests/examples/imgui-module/mcpp.toml

@@ -0,0 +1,19 @@
+# Public `imgui` C++23-module package test (bare-name consumption from the
+# builtin default namespace — resolved against THIS checkout via the
+# member-level `[indices] default` redirect, mcpp >= 0.0.97; kept per-member
+# and single-entry because xlings breaks with >1 project index repo, mcpp#238). Replaces the
+# former tests/smoke_imgui_module.sh reseeding driver. Linux-gated to the
+# validated surface: the package descriptor covers three platforms, but only
+# linux has ever been exercised by index CI; off-Linux the test compiles to a
+# no-op main(). Toolchain: workspace default (gcc@16.1.0) — the old smoke's
+# llvm@20.1.7 pin predates gcc16 module support; imgui-m upstream CI builds
+# the module layer with gcc@16.1.0.
+[package]
+name    = "imgui-module-tests"
+version = "0.1.0"
+
+[indices]
+default = { path = "../../.." }
+
+[target.'cfg(linux)'.dependencies]
+imgui = "0.0.1"

tests/examples/imgui-module/tests/imgui_module.cpp

@@ -0,0 +1,46 @@
+// Public imgui module package end-to-end assertion: import-only consumption
+// (imgui.core + glfw_opengl3 backend), context + font atlas + one frame,
+// software-only (no window). Linux-only (see mcpp.toml).
+#ifdef __linux__
+import std;
+import imgui.core;
+import imgui.backend.glfw_opengl3;
+
+int main() {
+    auto init = &ImGui::Backend::GlfwOpenGL3::Init;
+    auto shutdown = &ImGui::Backend::GlfwOpenGL3::Shutdown;
+    if (init == nullptr || shutdown == nullptr) {
+        return 1;
+    }
+
+    ImGuiContext* context = ImGui::CreateContext();
+    if (context == nullptr) {
+        return 2;
+    }
+    ImGui::SetCurrentContext(context);
+
+    ImGuiIO& io = ImGui::GetIO();
+    io.DisplaySize = ImVec2 { 320.0f, 240.0f };
+    unsigned char* pixels = nullptr;
+    int width = 0;
+    int height = 0;
+    io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
+    if (pixels == nullptr || width <= 0 || height <= 0) {
+        ImGui::DestroyContext(context);
+        return 3;
+    }
+
+    ImGui::NewFrame();
+    bool open = true;
+    ImGui::Begin("mcpp-index imgui smoke", &open);
+    ImGui::TextUnformatted("import imgui.core");
+    ImGui::End();
+    ImGui::Render();
+
+    std::println("Dear ImGui {} module package ok", ImGui::GetVersion());
+    ImGui::DestroyContext(context);
+    return 0;
+}
+#else
+int main() { return 0; }
+#endif

tests/examples/opencv-module/mcpp.toml

@@ -0,0 +1,20 @@
+# Public `opencv` C++23-module package test (bare-name consumption from the
+# builtin default namespace — resolved against THIS checkout via the
+# member-level `[indices] default` redirect, mcpp >= 0.0.97; kept per-member
+# and single-entry because xlings breaks with >1 project index repo, mcpp#238). Replaces the
+# former tests/smoke_opencv_module.sh reseeding driver. The package is
+# linux-only (it pulls the linux-only compat.opencv5 source build); off-Linux
+# the test compiles to a no-op main().
+[package]
+name    = "opencv-module-tests"
+version = "0.1.0"
+
+# The module package's own transitive dep (compat.opencv5) resolves from the
+# GLOBAL published compat index (the compat namespace is not redirected here
+# — see the mcpp#238 single-repo constraint); the compat descriptor itself is
+# pre-merge-validated by its dedicated member.
+[indices]
+default = { path = "../../.." }
+
+[target.'cfg(linux)'.dependencies]
+opencv = "0.0.2"

tests/examples/opencv-module/tests/opencv_module.cpp

@@ -0,0 +1,33 @@
+// Public opencv module package end-to-end assertion: import-only consumption
+// (`import opencv.cv;`), pinned version, Mat/imgproc ops (incl. the
+// replacement operator surface: Size comparison via != crosses the module
+// boundary — the v0.0.1 regression scenario), PNG+JPEG codec roundtrips,
+// videoio registry. Linux-only (see mcpp.toml).
+#ifdef __linux__
+import std;
+import opencv.cv;
+
+int main() {
+    if (cv::getVersionString() != "5.0.0") return 1;
+
+    cv::Mat img(64, 64, cv::CV_8UC3, cv::Scalar(30, 60, 90));
+    cv::circle(img, {32, 32}, 20, {255, 255, 255}, -1);
+    cv::Mat big, gray;
+    cv::resize(img, big, {128, 128}, 0, 0, cv::INTER_CUBIC);
+    cv::cvtColor(big, gray, cv::COLOR_BGR2GRAY);
+    if (gray.size() != cv::Size(128, 128)) return 2;
+
+    for (const char* ext : { ".png", ".jpg" }) {
+        std::vector<unsigned char> buf;
+        if (!cv::imencode(ext, big, buf)) return 3;
+        cv::Mat back = cv::imdecode(buf, cv::IMREAD_COLOR);
+        if (back.empty() || back.size() != big.size()) return 4;
+    }
+
+    if (cv::videoio_registry::getBackends().empty()) return 5;
+    std::println("OpenCV {} module package ok", cv::getVersionString());
+    return 0;
+}
+#else
+int main() { return 0; }
+#endif

tests/examples/tinyhttps/mcpp.toml

@@ -2,5 +2,8 @@
 name = "tinyhttps-tests"
 version = "0.1.0"
 
+[indices]
+default = { path = "../../.." }
+
 [dependencies]
 tinyhttps = "0.2.9"