feat: add fmt 12.2.0 as C++23 module package (import fmt;)

.github/workflows/validate.yml

@@ -206,3 +206,37 @@ jobs:
         run: |
           "$MCPP" --version
           timeout 1800 bash tests/smoke_imgui_module.sh
+
+  # ── Exception: the public `fmt` C++23-module package (namespace "") ──
+  # Same story as imgui-module above: empty namespace maps to the builtin default
+  # index, which a workspace member can't point at a local path, so it keeps a
+  # thin driver that reseeds the default index and consumes `import fmt;`.
+  fmt-module:
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@v4
+      - name: Restore mcpp registry cache
+        uses: actions/cache@v4
+        with:
+          path: ~/.mcpp/registry
+          key: mcpp-registry-${{ runner.os }}-${{ env.MCPP_VERSION }}-${{ hashFiles('pkgs/**/*.lua', 'tests/**', '.github/workflows/validate.yml') }}
+          restore-keys: |
+            mcpp-registry-${{ runner.os }}-${{ env.MCPP_VERSION }}-
+      - name: Download mcpp
+        run: |
+          curl -L -fsS -o mcpp.tar.gz \
+            "https://github.com/mcpp-community/mcpp/releases/download/v${MCPP_VERSION}/mcpp-${MCPP_VERSION}-linux-x86_64.tar.gz"
+          tar -xzf mcpp.tar.gz
+          root="$PWD/mcpp-${MCPP_VERSION}-linux-x86_64"
+          mkdir -p "$HOME/.mcpp/registry"
+          cp -a "$root/registry/." "$HOME/.mcpp/registry/"
+          echo "MCPP=$root/bin/mcpp" >> "$GITHUB_ENV"
+          echo "MCPP_VENDORED_XLINGS=$root/registry/bin/xlings" >> "$GITHUB_ENV"
+          echo "$root/bin" >> "$GITHUB_PATH"
+      - name: fmt module package smoke
+        env:
+          MCPP_INDEX_MIRROR: GLOBAL
+        run: |
+          "$MCPP" --version
+          timeout 1800 bash tests/smoke_fmt_module.sh

pkgs/f/fmt.lua

@@ -0,0 +1,67 @@
+-- Form B inline descriptor for {fmt} exposed as the C++23 module `fmt`, so
+-- users can write `import fmt;` out of the box (no `#include` needed). This is
+-- the module sibling of the header-based `compat.fmt` package. Empty namespace
+-- (like the public `imgui` module package) so the dependency key and the module
+-- name are both simply `fmt`.
+--
+-- fmt's release DOES ship an official C++20 module interface unit at
+-- `src/fmt.cc` (`export module fmt;`), but it cannot be fed to mcpp verbatim:
+-- mcpp's M1 module scanner rejects ANY `import` that appears inside a
+-- conditional preprocessor block (even a dead one), and fmt.cc carries
+-- `#ifdef FMT_IMPORT_STD / import std; / #endif`. So we reproduce fmt.cc via
+-- `generated_files` with exactly those three lines removed — everything else is
+-- upstream fmt.cc verbatim: the global-module-fragment `#include`s, the
+-- `export module fmt;` line, the FMT_EXPORT macro plumbing (fmt's headers
+-- self-`export` under FMT_MODULE), and the tail `#include "format.cc"` /
+-- `"os.cc"` that pulls the implementation INTO the module (so its definitions
+-- attach to module `fmt`; compiling them as standalone TUs would leave them on
+-- the global module and break module linkage).
+--
+-- include_dirs exposes BOTH `*/include` (so the module unit's `#include
+-- <fmt/*.h>` resolves) and `*/src` (so the tail `#include "format.cc"` /
+-- `"os.cc"` resolve). The wrapper path under mcpp_generated/ is verdir-relative
+-- (no glob), like nlohmann.json / compat.eigen.
+package = {
+    spec        = "1",
+    namespace   = "",
+    name        = "fmt",
+    description = "A modern formatting library for C++, exposed as C++23 module fmt",
+    licenses    = {"MIT"},
+    repo        = "https://github.com/fmtlib/fmt",
+    type        = "package",
+
+    xpm = {
+        linux = {
+            ["12.2.0"] = {
+                url    = "https://github.com/fmtlib/fmt/archive/refs/tags/12.2.0.tar.gz",
+                sha256 = "8b852bb5aa6e7d8564f9e81394055395dd1d1936d38dfd3a17792a02bebd7af0",
+            },
+        },
+        macosx = {
+            ["12.2.0"] = {
+                url    = "https://github.com/fmtlib/fmt/archive/refs/tags/12.2.0.tar.gz",
+                sha256 = "8b852bb5aa6e7d8564f9e81394055395dd1d1936d38dfd3a17792a02bebd7af0",
+            },
+        },
+        windows = {
+            ["12.2.0"] = {
+                url    = "https://github.com/fmtlib/fmt/archive/refs/tags/12.2.0.tar.gz",
+                sha256 = "8b852bb5aa6e7d8564f9e81394055395dd1d1936d38dfd3a17792a02bebd7af0",
+            },
+        },
+    },
+
+    mcpp = {
+        schema       = "0.1",
+        language     = "c++23",
+        import_std   = false,
+        modules      = { "fmt" },
+        include_dirs = { "*/include", "*/src" },
+        generated_files = {
+            ["mcpp_generated/fmt_module.cc"] = "// Formatting library for C++ - C++20 module\n//\n// Copyright (c) 2012 - present, Victor Zverovich and {fmt} contributors\n// All rights reserved.\n//\n// For the license information refer to format.h.\n\nmodule;\n\n#define FMT_MODULE\n\n#ifdef _MSVC_LANG\n#  define FMT_CPLUSPLUS _MSVC_LANG\n#else\n#  define FMT_CPLUSPLUS __cplusplus\n#endif\n\n// Put all implementation-provided headers into the global module fragment\n// to prevent attachment to this module.\n#ifndef FMT_IMPORT_STD\n#  include <algorithm>\n#  include <bitset>\n#  include <chrono>\n#  include <cmath>\n#  include <complex>\n#  include <cstddef>\n#  include <cstdint>\n#  include <cstdio>\n#  include <cstdlib>\n#  include <cstring>\n#  include <ctime>\n#  include <exception>\n#  if FMT_CPLUSPLUS > 202002L\n#    include <expected>\n#  endif\n#  include <filesystem>\n#  include <fstream>\n#  include <functional>\n#  include <iterator>\n#  include <limits>\n#  include <locale>\n#  include <memory>\n#  include <optional>\n#  include <ostream>\n#  include <source_location>\n#  include <stdexcept>\n#  include <string>\n#  include <string_view>\n#  include <system_error>\n#  include <thread>\n#  include <type_traits>\n#  include <typeinfo>\n#  include <utility>\n#  include <variant>\n#  include <vector>\n#else\n#  include <limits.h>\n#  include <stdint.h>\n#  include <stdio.h>\n#  include <stdlib.h>\n#  include <string.h>\n#  include <time.h>\n#endif\n#include <cerrno>\n#include <climits>\n#include <version>\n\n#if __has_include(<cxxabi.h>)\n#  include <cxxabi.h>\n#endif\n#if defined(_MSC_VER) || defined(__MINGW32__)\n#  include <intrin.h>\n#endif\n#if defined __APPLE__ || defined(__FreeBSD__)\n#  include <xlocale.h>\n#endif\n#if __has_include(<winapifamily.h>)\n#  include <winapifamily.h>\n#endif\n#if (__has_include(<fcntl.h>) || defined(__APPLE__) || \\\n     defined(__linux__)) &&                            \\\n    (!defined(WINAPI_FAMILY) || (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))\n#  include <fcntl.h>\n#  include <sys/stat.h>\n#  include <sys/types.h>\n#  ifndef _WIN32\n#    include <unistd.h>\n#  else\n#    include <io.h>\n#  endif\n#endif\n#ifdef _WIN32\n#  if defined(__GLIBCXX__)\n#    include <ext/stdio_filebuf.h>\n#    include <ext/stdio_sync_filebuf.h>\n#  endif\n#  define WIN32_LEAN_AND_MEAN\n#  include <windows.h>\n#endif\n\nexport module fmt;\n\n\n#define FMT_EXPORT export\n#define FMT_BEGIN_EXPORT export {\n#define FMT_END_EXPORT }\n\n// If you define FMT_ATTACH_TO_GLOBAL_MODULE\n//  - all declarations are detached from module 'fmt'\n//  - the module behaves like a traditional static library, too\n//  - all library symbols are mangled traditionally\n//  - you can mix TUs with either importing or #including the {fmt} API\n#ifdef FMT_ATTACH_TO_GLOBAL_MODULE\nextern \"C++\" {\n#endif\n\n#ifndef FMT_OS\n#  define FMT_OS 1\n#endif\n\n// All library-provided declarations and definitions must be in the module\n// purview to be exported.\n#include \"fmt/args.h\"\n#include \"fmt/chrono.h\"\n#include \"fmt/color.h\"\n#include \"fmt/compile.h\"\n#include \"fmt/format.h\"\n#if FMT_OS\n#  include \"fmt/os.h\"\n#endif\n#include \"fmt/ostream.h\"\n#include \"fmt/printf.h\"\n#include \"fmt/ranges.h\"\n#include \"fmt/std.h\"\n#include \"fmt/xchar.h\"\n\n#ifdef FMT_ATTACH_TO_GLOBAL_MODULE\n}\n#endif\n\n#ifdef FMT_ATTACH_TO_GLOBAL_MODULE\nextern \"C++\" {\n#endif\n\n#if FMT_HAS_INCLUDE(\"format.cc\")\n#  include \"format.cc\"\n#endif\n#if FMT_OS && FMT_HAS_INCLUDE(\"os.cc\")\n#  include \"os.cc\"\n#endif\n\n#ifdef FMT_ATTACH_TO_GLOBAL_MODULE\n}\n#endif\n",
+        },
+        sources      = { "mcpp_generated/fmt_module.cc" },
+        targets      = { ["fmt"] = { kind = "lib" } },
+        deps         = { },
+    },
+}

tests/smoke_fmt_module.sh

@@ -0,0 +1,101 @@
+#!/usr/bin/env bash
+# Smoke-test the public `fmt` module package through this checkout as a local
+# mcpp path index. Validates user-facing import-only consumption (`import fmt;`).
+# Mirrors tests/smoke_imgui_module.sh — the empty-namespace `fmt` package maps to
+# the builtin default index (mcpplibs), which a workspace member cannot point at
+# a local path, so it needs this thin driver that reseeds the default index.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+MCPP_BIN="${MCPP:-}"
+if [[ -z "$MCPP_BIN" ]]; then
+    MCPP_BIN="$(command -v mcpp || true)"
+fi
+if [[ -z "$MCPP_BIN" || ! -x "$MCPP_BIN" ]]; then
+    echo "FATAL: set MCPP=/path/to/mcpp or put mcpp on PATH" >&2
+    exit 1
+fi
+
+TMP="$(mktemp -d)"
+if [[ "${MCPP_INDEX_KEEP_SMOKE_TMP:-0}" == "1" ]]; then
+    echo "KEEP: $TMP"
+else
+    trap 'rm -rf "$TMP"' EXIT
+fi
+
+if [[ -n "${MCPP_INDEX_SMOKE_MCPP_HOME:-}" ]]; then
+    export MCPP_HOME="$MCPP_INDEX_SMOKE_MCPP_HOME"
+else
+    export MCPP_HOME="$TMP/mcpp-home"
+fi
+mkdir -p "$MCPP_HOME/registry/data/xpkgs"
+
+USER_MCPP="${HOME}/.mcpp"
+link_xpkgs() {
+    local src="$1"
+    [[ -d "$src" ]] || return 0
+    find "$src" -mindepth 1 -maxdepth 1 -type d | while read -r pkg; do
+        ln -s "$pkg" "$MCPP_HOME/registry/data/xpkgs/$(basename "$pkg")" 2>/dev/null || true
+    done
+}
+link_xpkgs "${MCPP_INDEX_SMOKE_XPKGS_DIR:-}"
+link_xpkgs "$USER_MCPP/registry/data/xpkgs"
+if [[ -d "$USER_MCPP/registry/data/xim-pkgindex" ]]; then
+    mkdir -p "$MCPP_HOME/registry/data/xim-pkgindex"
+    cp -a "$USER_MCPP/registry/data/xim-pkgindex/." "$MCPP_HOME/registry/data/xim-pkgindex/" 2>/dev/null || true
+    rm -f "$MCPP_HOME/registry/data/xim-pkgindex/.xlings-index-cache.json"
+fi
+if [[ -d "$USER_MCPP/registry/bin" ]]; then
+    mkdir -p "$MCPP_HOME/registry"
+    ln -s "$USER_MCPP/registry/bin" "$MCPP_HOME/registry/bin" 2>/dev/null || true
+fi
+if [[ -f "$USER_MCPP/config.toml" ]]; then
+    cp -f "$USER_MCPP/config.toml" "$MCPP_HOME/config.toml" 2>/dev/null || true
+fi
+
+default_index="$MCPP_HOME/registry/data/mcpplibs"
+# Reseed cleanly (see smoke_imgui_module.sh for why .git is skipped).
+rm -rf "$default_index"
+mkdir -p "$default_index"
+( cd "$ROOT" && find . -mindepth 1 -maxdepth 1 ! -name .git -exec cp -a {} "$default_index/" \; )
+rm -f "$default_index/.xlings-index-cache.json"
+printf 'ok\n' > "$default_index/.mcpp-index-updated"
+
+"$MCPP_BIN" self config --mirror "${MCPP_INDEX_MIRROR:-GLOBAL}" >/dev/null
+
+mkdir -p "$TMP/fmt-module-smoke/src"
+cd "$TMP/fmt-module-smoke"
+cat > mcpp.toml <<EOF
+[package]
+name = "fmt-module-smoke"
+version = "0.1.0"
+
+[toolchain]
+default = "${MCPP_INDEX_FMT_MODULE_TOOLCHAIN:-gcc@16.1.0}"
+
+[dependencies]
+fmt = "12.2.0"
+
+[targets.fmt-module-smoke]
+kind = "bin"
+main = "src/main.cpp"
+EOF
+
+cat > src/main.cpp <<'EOF'
+import std;
+import fmt;
+
+int main() {
+    std::string a = fmt::format("{} + {} = {}", 2, 3, 2 + 3);
+    std::string b = fmt::format("{:08.3f}", 3.14159);
+    std::string c = fmt::format("{0}-{1}-{0}", "x", "y");
+    std::string d = fmt::format("{:#x}", 255);
+
+    bool ok = a == "2 + 3 = 5" && b == "0003.142" && c == "x-y-x" && d == "0xff";
+    std::println("fmt module package ok: {}", a);
+    return ok ? 0 : 1;
+}
+EOF
+
+"$MCPP_BIN" build
+"$MCPP_BIN" run