[M5+] wire resolver::discover into cargoxx add

CHANGELOG.md

@@ -78,6 +78,21 @@ All notable changes to cargoxx will be documented in this file.
   and `[build]` honoring `warnings_as_errors` and `sanitizers`. Source
   paths emitted relative to `build/` (i.e. prefixed with `../`).
   Output is deterministic. `tests/codegen_cmake.cpp` covers 11 cases.
+- `cargoxx add <pkg>` now auto-resolves packages outside the curated
+  linkdb. On `LinkdbUnknownPackage`, `cmd_add` invokes
+  `resolver::discover` which: probes `nixpkgs#<pkg>` to confirm the
+  attribute exists and capture its store path; tries Conan, vcpkg, and
+  the nix-store CMake scan in order; for each candidate runs a real
+  `cargoxx build` against an empty `int main() {}` project via
+  `verify_link`; on first success persists a confirmed overlay row.
+  Subsequent `cargoxx add <pkg>` for the same package is an
+  overlay-cache hit (~ms). End-to-end live: a fresh `cargoxx add
+  simdjson` (not in our curated db) takes ~11 s including the verifying
+  nix+cmake build, then 0.002 s on the second invocation.
+  `linkdb::default_overlay_path()` is now exported as a public helper
+  so the resolver and CLI agree on the overlay file when no path is
+  explicitly passed. Tests opt out of the slow chain via
+  `CARGOXX_NO_AUTORESOLVE=1`.
 - `cargoxx.linkdb::Database::insert_provisional`,
   `confirm_provisional`, and `abort_provisional` — three-step lifecycle
   for non-`manual` overlay rows: insert with `verified_at = 0`, run a

CMakeLists.txt

@@ -57,6 +57,7 @@ target_sources(cargoxx
         src/resolver/conan_probe.cpp
         src/resolver/vcpkg_probe.cpp
         src/resolver/verify_link.cpp
+        src/resolver/discover.cpp
         src/cli/cmd_new.cpp
         src/cli/cmd_build.cpp
         src/cli/cmd_run.cpp

docs/auto-resolution.md

@@ -196,8 +196,8 @@ auto verify_link(const Recipe& candidate,
 | 2. nix_cmake_scan | ✅ | `e63ac69` |
 | 3. conan_probe + parse_conanfile | ✅ | `e5c173b` |
 | 4. vcpkg_probe + parse_vcpkg_usage | ✅ | `941d5b3` |
-| 5. verify_link (tmp project + cmd_build) | ✅ | (this commit) |
-| 6. Database::discover + cmd_add wire-up + failure caching | pending | — |
+| 5. verify_link (tmp project + cmd_build) | ✅ | `816ec99` |
+| 6. resolver::discover + cmd_add wire-up | ✅ | (this commit) |
 
 ## Testing strategy
 

src/cli/cmd_add.cpp

@@ -4,11 +4,63 @@ import std;
 import cargoxx.util;
 import cargoxx.manifest;
 import cargoxx.linkdb;
+import cargoxx.resolver;
 
 namespace cargoxx::cli {
 
 namespace fs = std::filesystem;
 
+namespace {
+
+// Returns true when the linkdb already has a recipe for this package (so
+// no discovery is needed), false when the lookup yielded
+// LinkdbUnknownPackage and we should fall through to auto-resolution.
+// Other errors (e.g. ComponentNotSupported) propagate unchanged.
+auto recipe_already_known(const std::string& name, const std::string& version,
+                          const std::vector<std::string>& components,
+                          const fs::path& overlay_path) -> util::Result<bool> {
+    auto db = linkdb::Database::open(overlay_path);
+    if (!db) {
+        return std::unexpected(db.error());
+    }
+    auto check = db->resolve(name, version, components);
+    if (check) {
+        return true;
+    }
+    if (check.error().code != util::ErrorCode::LinkdbUnknownPackage) {
+        return std::unexpected(check.error());
+    }
+    return false;
+}
+
+// Drives the resolver chain (Conan → vcpkg → nix-cmake-scan), running a
+// real `cmd_build` against each candidate via verify_link. On success the
+// overlay carries a confirmed row for the package.
+auto run_auto_resolution(const std::string& name, const std::string& version,
+                         const std::vector<std::string>& components,
+                         const fs::path& overlay_path) -> util::Result<void> {
+    auto build_fn = [&](const fs::path& root) {
+        return cmd_build(root, /*no_build=*/false, /*release=*/false,
+                         /*target=*/std::nullopt, overlay_path);
+    };
+    const auto scratch_root =
+        std::filesystem::temp_directory_path() /
+        std::format("cargoxx-discover-{}", std::random_device{}());
+
+    auto disc = resolver::discover(name, version, components, overlay_path,
+                                   scratch_root, build_fn);
+
+    std::error_code ec;
+    std::filesystem::remove_all(scratch_root, ec);
+
+    if (!disc) {
+        return std::unexpected(disc.error());
+    }
+    return {};
+}
+
+} // namespace
+
 auto cmd_add(const fs::path& project_root, const std::string& name,
              const std::string& version_spec, std::vector<std::string> components,
              std::optional<fs::path> overlay_path) -> util::Result<void> {
@@ -41,12 +93,30 @@ auto cmd_add(const fs::path& project_root, const std::string& name,
         }
     }
 
-    auto db = linkdb::Database::open(std::move(overlay_path));
-    if (!db) {
-        return std::unexpected(db.error());
+    const auto effective_overlay = overlay_path.value_or(linkdb::default_overlay_path());
+
+    auto known = recipe_already_known(name, effective_version, components,
+                                      effective_overlay);
+    if (!known) {
+        return std::unexpected(known.error());
     }
-    if (auto check = db->resolve(name, effective_version, components); !check) {
-        return std::unexpected(check.error());
+    if (!*known) {
+        // Tests opt out of the slow probe + verify-build chain by exporting
+        // CARGOXX_NO_AUTORESOLVE; in that mode we surface the same
+        // LinkdbUnknownPackage error the linkdb returned.
+        if (auto* env = std::getenv("CARGOXX_NO_AUTORESOLVE"); env && *env) {
+            return std::unexpected(util::Error{
+                util::ErrorCode::LinkdbUnknownPackage,
+                std::format("package '{}' has no known CMake link recipe", name),
+                "auto-resolution is disabled (CARGOXX_NO_AUTORESOLVE)",
+                std::nullopt, std::nullopt,
+            });
+        }
+        if (auto r = run_auto_resolution(name, effective_version, components,
+                                         effective_overlay);
+            !r) {
+            return std::unexpected(r.error());
+        }
     }
 
     m->dependencies.push_back(manifest::Dependency{

src/linkdb/curated.cpp

@@ -71,16 +71,6 @@ auto load_curated(const std::filesystem::path& path)
     return out;
 }
 
-auto default_overlay_path() -> std::filesystem::path {
-    namespace fs = std::filesystem;
-    if (auto* xdg = std::getenv("XDG_CACHE_HOME"); xdg && *xdg) {
-        return fs::path{xdg} / "cargoxx" / "linkdb.sqlite";
-    }
-    if (auto* home = std::getenv("HOME"); home && *home) {
-        return fs::path{home} / ".cache" / "cargoxx" / "linkdb.sqlite";
-    }
-    return fs::current_path() / ".cargoxx-linkdb.sqlite";
-}
 
 auto resolve_curated(const std::map<std::string, std::vector<detail::CuratedRecipe>>& curated,
                      const std::string& package, const std::string& version,
@@ -136,6 +126,17 @@ auto resolve_curated(const std::map<std::string, std::vector<detail::CuratedReci
 
 } // namespace
 
+auto default_overlay_path() -> std::filesystem::path {
+    namespace fs = std::filesystem;
+    if (auto* xdg = std::getenv("XDG_CACHE_HOME"); xdg && *xdg) {
+        return fs::path{xdg} / "cargoxx" / "linkdb.sqlite";
+    }
+    if (auto* home = std::getenv("HOME"); home && *home) {
+        return fs::path{home} / ".cache" / "cargoxx" / "linkdb.sqlite";
+    }
+    return fs::current_path() / ".cargoxx-linkdb.sqlite";
+}
+
 auto Database::open(std::optional<std::filesystem::path> overlay_path) -> util::Result<Database> {
     Database db;
 

src/linkdb/linkdb.cppm

@@ -131,6 +131,12 @@ class Database {
     std::unique_ptr<detail::OverlayState> overlay_;
 };
 
+// Returns the default overlay-database path:
+//   $XDG_CACHE_HOME/cargoxx/linkdb.sqlite   (if XDG_CACHE_HOME is set)
+//   $HOME/.cache/cargoxx/linkdb.sqlite       (else if HOME is set)
+//   <cwd>/.cargoxx-linkdb.sqlite             (final fallback)
+auto default_overlay_path() -> std::filesystem::path;
+
 // Pure helpers exported for unit testing.
 auto substitute_components(std::string find_package, const std::vector<std::string>& components)
     -> std::string;

src/linkdb/overlay.cpp

@@ -267,6 +267,14 @@ auto overlay_is_fresh(const OverlayRow& row, std::int64_t now) -> bool {
     if (row.source == "manual" || row.source == "curated") {
         return true;
     }
+    // verified_at == 0 marks a provisional row — written by
+    // resolver::verify_link before its build runs and either confirmed
+    // (verified_at = now) or deleted afterwards. The verifying build
+    // itself must see this row to surface the candidate recipe to its
+    // codegen step.
+    if (row.verified_at == 0) {
+        return true;
+    }
     return (now - row.verified_at) < THIRTY_DAYS_SECONDS;
 }
 

src/resolver/discover.cpp

@@ -0,0 +1,124 @@
+module cargoxx.resolver;
+
+import std;
+import cargoxx.util;
+import cargoxx.linkdb;
+
+namespace cargoxx::resolver {
+
+namespace fs = std::filesystem;
+
+namespace {
+
+auto error(util::ErrorCode code, std::string msg) -> util::Error {
+    return util::Error{code, std::move(msg), "", std::nullopt, std::nullopt};
+}
+
+// Build a linkdb::Recipe out of one of the probe outputs. The
+// nixpkgs_attr is always the package name (the attr we used to query
+// nixpkgs in step 1); find_package + targets come from the probe.
+auto recipe_from_conan(const ConanRecipe& c, const std::string& nixpkgs_attr,
+                       const std::string& source) -> linkdb::Recipe {
+    return linkdb::Recipe{
+        .nixpkgs_attr = nixpkgs_attr,
+        .find_package = c.find_package,
+        .targets = c.targets,
+        .source = source,
+    };
+}
+
+auto recipe_from_vcpkg(const VcpkgRecipe& v, const std::string& nixpkgs_attr,
+                       const std::string& source) -> linkdb::Recipe {
+    return linkdb::Recipe{
+        .nixpkgs_attr = nixpkgs_attr,
+        .find_package = v.find_package,
+        .targets = v.targets,
+        .source = source,
+    };
+}
+
+auto recipe_from_nix_scan(const NixCmakeCandidate& n,
+                          const std::string& nixpkgs_attr,
+                          const std::string& source) -> linkdb::Recipe {
+    return linkdb::Recipe{
+        .nixpkgs_attr = nixpkgs_attr,
+        .find_package = n.find_package,
+        .targets = n.targets,
+        .source = source,
+    };
+}
+
+struct Candidate {
+    std::string source;
+    linkdb::Recipe recipe;
+};
+
+auto try_verify(const Candidate& cand, const std::string& name,
+                const std::string& version_spec,
+                const std::vector<std::string>& components,
+                const fs::path& overlay_path, const fs::path& scratch_root,
+                const BuildFn& build_fn) -> util::Result<void> {
+    VerifyLinkRequest req{
+        .candidate = cand.recipe,
+        .source = cand.source,
+        .package_name = name,
+        .version_spec = version_spec,
+        .components = components,
+        .overlay_path = overlay_path,
+        .scratch_root = scratch_root,
+    };
+    return verify_link(req, build_fn);
+}
+
+} // namespace
+
+auto discover(const std::string& name, const std::string& version_spec,
+              const std::vector<std::string>& components,
+              const fs::path& overlay_path, const fs::path& scratch_root,
+              const BuildFn& build_fn) -> util::Result<Discovered> {
+    auto info = nixpkgs_probe(name);
+    if (!info) {
+        return std::unexpected(info.error());
+    }
+
+    std::vector<Candidate> candidates;
+
+    if (auto c = conan_probe(name); c) {
+        candidates.push_back({"conan", recipe_from_conan(*c, name, "conan")});
+    }
+    if (auto v = vcpkg_probe(name); v) {
+        candidates.push_back({"vcpkg", recipe_from_vcpkg(*v, name, "vcpkg")});
+    }
+    if (auto n = nix_cmake_scan(info->out_path, name); n) {
+        candidates.push_back(
+            {"nix-probe", recipe_from_nix_scan(*n, name, "nix-probe")});
+    }
+
+    if (candidates.empty()) {
+        return std::unexpected(error(
+            util::ErrorCode::ResolutionUnsatisfiable,
+            std::format("no recipe candidates for '{}' (Conan/vcpkg/nix-scan all empty)",
+                        name)));
+    }
+
+    util::Error last_error{
+        util::ErrorCode::ResolutionUnsatisfiable,
+        std::format("no candidate for '{}' verified", name), "",
+        std::nullopt, std::nullopt,
+    };
+    for (auto& cand : candidates) {
+        auto verified = try_verify(cand, name, version_spec, components, overlay_path,
+                                   scratch_root, build_fn);
+        if (verified) {
+            return Discovered{
+                .recipe = std::move(cand.recipe),
+                .source = std::move(cand.source),
+            };
+        }
+        last_error = verified.error();
+    }
+
+    return std::unexpected(last_error);
+}
+
+} // namespace cargoxx::resolver

src/resolver/resolver.cppm

@@ -115,4 +115,25 @@ struct VerifyLinkRequest {
 auto verify_link(const VerifyLinkRequest& req, const BuildFn& build_fn)
     -> util::Result<void>;
 
+// What discover() returns: the verified Recipe and a tag identifying
+// which probe yielded it ("conan", "vcpkg", or "nix-probe").
+struct Discovered {
+    linkdb::Recipe recipe;
+    std::string source;
+};
+
+// Walks the full auto-resolution chain for a package not present in the
+// curated linkdb or the user's overlay:
+//   1. nixpkgs_probe(name) — confirms the attribute exists, captures
+//      version + out_path
+//   2. for each of conan_probe, vcpkg_probe, nix_cmake_scan(out_path,…):
+//      build a candidate linkdb::Recipe, run verify_link on it, return
+//      on first success
+//   3. all candidates failed → ResolutionUnsatisfiable
+auto discover(const std::string& name, const std::string& version_spec,
+              const std::vector<std::string>& components,
+              const std::filesystem::path& overlay_path,
+              const std::filesystem::path& scratch_root, const BuildFn& build_fn)
+    -> util::Result<Discovered>;
+
 } // namespace cargoxx::resolver

tests/cmd_add.cpp

@@ -80,7 +80,9 @@ TEST_CASE("cmd_add with wildcard version still rejects unknown packages",
     auto parent = fresh_dir();
     auto root = scaffold(parent);
 
+    setenv("CARGOXX_NO_AUTORESOLVE", "1", /*overwrite=*/1);
     auto r = cmd_add(root, "obscurelib", "", {}, overlay_path(parent));
+    unsetenv("CARGOXX_NO_AUTORESOLVE");
     REQUIRE_FALSE(r.has_value());
     REQUIRE(r.error().code == ErrorCode::LinkdbUnknownPackage);
 }
@@ -89,7 +91,11 @@ TEST_CASE("cmd_add rejects an unknown package", "[cli][add]") {
     auto parent = fresh_dir();
     auto root = scaffold(parent);
 
+    // Disable the auto-resolution chain — keeps the unit test fast and
+    // independent of nixpkgs / Conan / vcpkg availability.
+    setenv("CARGOXX_NO_AUTORESOLVE", "1", /*overwrite=*/1);
     auto r = cmd_add(root, "obscurelib", "0.0.1", {}, overlay_path(parent));
+    unsetenv("CARGOXX_NO_AUTORESOLVE");
     REQUIRE_FALSE(r.has_value());
     REQUIRE(r.error().code == ErrorCode::LinkdbUnknownPackage);
 }