fix(pm): resolve namespaced local path index entries

Author: Sunrisepeak

.agents/docs/2026-05-30-package-owned-build-flags-plan.md

@@ -25,6 +25,7 @@ xlings 现在可以用 `mcpp 0.0.34` 构建，但工程文件里有大量 C 库
 - [x] 包级 include dirs 在编译该包源码时优先于全局 include dirs。
 - [x] build fingerprint / cache key 包含包级 flags，避免 flags 变化后误用缓存。
 - [x] Form B 描述支持 `generated_files`，让官方索引包可以生成少量包私有配置头。
+- [x] 本地 `path` 索引读取使用命名空间候选，支持 `pkgs/c/compat.foo.lua` 这类官方索引布局。
 - [x] 保持现有项目级 flags 兼容，不破坏已有 manifest。
 - [x] 用 xlings 当前项目验证 `mcpp build` 和 `mcpp build --target x86_64-linux-musl`。
 
@@ -65,6 +66,8 @@ cd /home/speak/workspace/github/openxlings/xlings
 - [x] package-owned generated support files implementation:
   - `tests/unit/test_manifest.cpp` 覆盖 Form B `generated_files` 解析。
   - `tests/e2e/51_package_generated_files.sh` 覆盖生成文件参与依赖包编译。
+- [x] local path index namespace lookup:
+  - `tests/e2e/52_local_path_namespaced_index.sh` 覆盖 `compat` 命名空间文件名候选。
 - [x] xlings local validation:
   - `mcpp build` -> `target/x86_64-linux-gnu/ff952c89919589bb/bin/xlings --version` = `xlings 0.4.45`.
   - `mcpp build --target x86_64-linux-musl` -> `target/x86_64-linux-musl/7e48a312cd4dbb49/bin/xlings` static ELF.

src/cli.cppm

@@ -1604,7 +1604,7 @@ prepare_build(bool print_fingerprint,
         if (idxSpec && idxSpec->is_local()) {
             auto indexPath = mcpp::config::resolve_project_index_path(*root, *idxSpec);
             auto luaCheck = mcpp::fetcher::Fetcher::read_xpkg_lua_from_path(
-                indexPath, shortName);
+                indexPath, ns, shortName);
             if (!luaCheck) return std::unexpected(std::format(
                 "dependency '{}': not found in local index at '{}'",
                 depName, indexPath.string()));
@@ -1687,7 +1687,7 @@ prepare_build(bool print_fingerprint,
         if (idxSpec && idxSpec->is_local()) {
             auto indexPath = mcpp::config::resolve_project_index_path(*root, *idxSpec);
             luaContent = mcpp::fetcher::Fetcher::read_xpkg_lua_from_path(
-                indexPath, shortName);
+                indexPath, ns, shortName);
         } else if (idxSpec && !idxSpec->is_builtin()) {
             luaContent = mcpp::fetcher::Fetcher::read_xpkg_lua_from_project_data(
                 *root, ns, shortName);

src/pm/package_fetcher.cppm

@@ -113,6 +113,7 @@ public:
     // Used for [indices] entries with `path = "/some/dir"`.
     static std::optional<std::string>
         read_xpkg_lua_from_path(const std::filesystem::path& indexPath,
+                                std::string_view ns,
                                 std::string_view shortName);
 
     // Read xpkg .lua from a project-level xlings data directory.
@@ -451,21 +452,27 @@ Fetcher::read_xpkg_lua(std::string_view ns, std::string_view shortName) const
 
 std::optional<std::string>
 Fetcher::read_xpkg_lua_from_path(const std::filesystem::path& indexPath,
+                                  std::string_view ns,
                                   std::string_view shortName)
 {
     if (shortName.empty()) return std::nullopt;
 
     auto pkgsDir = indexPath / "pkgs";
     if (!std::filesystem::exists(pkgsDir)) return std::nullopt;
 
-    char first = static_cast<char>(std::tolower(
-        static_cast<unsigned char>(shortName.front())));
-    auto candidate = pkgsDir / std::string(1, first) / (std::string(shortName) + ".lua");
-    if (!std::filesystem::exists(candidate)) return std::nullopt;
-
-    std::ifstream is(candidate);
-    std::stringstream ss; ss << is.rdbuf();
-    return ss.str();
+    auto filenames = mcpp::pm::compat::xpkg_lua_candidates(ns, shortName);
+    for (auto& fname : filenames) {
+        if (fname.empty()) continue;
+        char first = static_cast<char>(std::tolower(
+            static_cast<unsigned char>(fname.front())));
+        auto candidate = pkgsDir / std::string(1, first) / fname;
+        if (!std::filesystem::exists(candidate)) continue;
+
+        std::ifstream is(candidate);
+        std::stringstream ss; ss << is.rdbuf();
+        return ss.str();
+    }
+    return std::nullopt;
 }
 
 // ─── read_xpkg_lua from project-level data dir ─────────────────────

tests/e2e/52_local_path_namespaced_index.sh

@@ -0,0 +1,84 @@
+#!/usr/bin/env bash
+# requires: gcc fresh-sandbox
+# Local path indices must use the same namespace-aware filename candidates
+# as cloned/builtin indices, e.g. pkgs/c/compat.foo.lua.
+set -e
+
+TMP=$(mktemp -d)
+trap "rm -rf $TMP" EXIT
+
+export MCPP_HOME="$TMP/mcpp-home"
+source "$(dirname "$0")/_inherit_toolchain.sh"
+
+INDEX_DIR="$TMP/local-index"
+mkdir -p "$INDEX_DIR/pkgs/c"
+cat > "$INDEX_DIR/pkgs/c/compat.cfg.lua" <<'EOF'
+package = {
+    spec = "1",
+    namespace = "compat",
+    name = "compat.cfg",
+    description = "Namespaced local path index package",
+    licenses = {"MIT"},
+    type = "package",
+    xpm = {
+        linux = {
+            ["1.0.0"] = {
+                url = "https://example.invalid/cfg-1.0.0.tar.gz",
+                sha256 = "0000000000000000000000000000000000000000000000000000000000000000",
+            },
+        },
+    },
+    mcpp = {
+        language = "c++23",
+        import_std = false,
+        sources = { "src/*.c" },
+        targets = { ["cfg"] = { kind = "lib" } },
+        deps = {},
+    },
+}
+EOF
+
+mkdir -p "$TMP/project/app/src" \
+         "$TMP/project/app/.mcpp/.xlings/data/xpkgs/compat.cfg/1.0.0/src"
+cd "$TMP/project/app"
+
+cat > .mcpp/.xlings/data/xpkgs/compat.cfg/1.0.0/src/cfg.c <<'EOF'
+int cfg_value(void) {
+    return 42;
+}
+EOF
+
+cat > src/main.cpp <<'EOF'
+extern "C" int cfg_value(void);
+int main() {
+    return cfg_value() == 42 ? 0 : 1;
+}
+EOF
+
+cat > mcpp.toml <<EOF
+[package]
+name = "app"
+version = "0.1.0"
+
+[indices]
+compat = { path = "$INDEX_DIR" }
+
+[dependencies.compat]
+cfg = "1.0.0"
+
+[targets.app]
+kind = "bin"
+main = "src/main.cpp"
+EOF
+
+"$MCPP" build > build.log 2>&1 || {
+    cat build.log
+    exit 1
+}
+
+"$MCPP" run > run.log 2>&1 || {
+    cat run.log
+    exit 1
+}
+
+echo "OK"