fix(capi.lua): make Lua dependency identity exact

mcpp.toml

@@ -18,6 +18,7 @@ members = [
     "tests/examples/catch2-main",
     "tests/examples/catch2-v2",
     "tests/examples/catch2-v2-main",
+    "tests/examples/capi-lua",
     "tests/examples/cjson",
     "tests/examples/cmdline",
     "tests/examples/cli11",

pkgs/m/mcpplibs.capi.lua.lua

@@ -1,6 +1,8 @@
--- Form A descriptor: the upstream repo ships its own mcpp.toml from
--- 0.0.3 onwards, so we omit the `mcpp` field — mcpp default-look-up
--- finds <verdir>/lua-<tag>/mcpp.toml inside the GitHub tarball wrap.
+-- Form B descriptor for the immutable 0.0.3 payload.  Its upstream
+-- mcpp.toml predates exact package selectors and declares bare `lua`, which
+-- now means `(mcpplibs, lua)` and cannot identify the real C library at
+-- `(compat, lua)`.  Keep the release bytes unchanged and carry the canonical
+-- dependency here until a newer upstream release can return to Form A.
 package = {
     spec        = "1",
     namespace = "mcpplibs.capi",
@@ -39,4 +41,18 @@ package = {
             },
         },
     },
+
+    mcpp = {
+        schema       = "0.1",
+        language     = "c++23",
+        import_std   = false,
+        modules      = { "mcpplibs.capi.lua" },
+        include_dirs = { "*/src/capi" },
+        sources      = {
+            "*/src/capi/lua.cppm",
+            "*/src/capi/lua.cpp",
+        },
+        targets = { ["capi-lua"] = { kind = "lib" } },
+        deps    = { ["compat.lua"] = "5.4.7" },
+    },
 }

tests/examples/capi-lua/mcpp.toml

@@ -0,0 +1,9 @@
+[indices]
+"mcpplibs.capi" = { path = "../../.." }
+
+[package]
+name = "capi-lua-tests"
+version = "0.1.0"
+
+[dependencies.mcpplibs]
+capi.lua = "0.0.3"

tests/examples/capi-lua/tests/main.cpp

@@ -0,0 +1,13 @@
+import mcpplibs.capi.lua;
+
+namespace lua = mcpplibs::capi::lua;
+
+int main() {
+    auto* state = lua::L_newstate();
+    if (state == nullptr) return 1;
+
+    const int status = lua::L_dostring(state, "return 6 * 7");
+    const auto answer = lua::tointeger(state, -1);
+    lua::close(state);
+    return status == lua::OK && answer == 42 ? 0 : 1;
+}