Change lock file format to use an attribute representation of flake refs rather than URLs

src/libstore/fetchers/fetchers.cc

@@ -2,6 +2,8 @@
 #include "parse.hh"
 #include "store-api.hh"
 
+#include <nlohmann/json.hpp>
+
 namespace nix::fetchers {
 
 std::unique_ptr<std::vector<std::unique_ptr<InputScheme>>> inputSchemes = nullptr;
@@ -26,6 +28,54 @@ std::unique_ptr<Input> inputFromURL(const std::string & url)
     return inputFromURL(parseURL(url));
 }
 
+std::unique_ptr<Input> inputFromAttrs(const Input::Attrs & attrs)
+{
+    for (auto & inputScheme : *inputSchemes) {
+        auto res = inputScheme->inputFromAttrs(attrs);
+        if (res) return res;
+    }
+    throw Error("input '%s' is unsupported", attrsToJson(attrs));
+}
+
+nlohmann::json attrsToJson(const fetchers::Input::Attrs & attrs)
+{
+    nlohmann::json json;
+    for (auto & attr : attrs) {
+        if (auto v = std::get_if<int64_t>(&attr.second)) {
+            json[attr.first] = *v;
+        } else if (auto v = std::get_if<std::string>(&attr.second)) {
+            json[attr.first] = *v;
+        } else abort();
+    }
+    return json;
+}
+
+Input::Attrs Input::toAttrs() const
+{
+    auto attrs = toAttrsInternal();
+    if (narHash)
+        attrs.emplace("narHash", narHash->to_string(SRI));
+    attrs.emplace("type", type());
+    return attrs;
+}
+
+std::optional<std::string> maybeGetStrAttr(const Input::Attrs & attrs, const std::string & name)
+{
+    auto i = attrs.find(name);
+    if (i == attrs.end()) return {};
+    if (auto v = std::get_if<std::string>(&i->second))
+        return *v;
+    throw Error("input attribute '%s' is not a string", name);
+}
+
+std::string getStrAttr(const Input::Attrs & attrs, const std::string & name)
+{
+    auto s = maybeGetStrAttr(attrs, name);
+    if (!s)
+        throw Error("input attribute '%s' is missing", name);
+    return *s;
+}
+
 std::pair<Tree, std::shared_ptr<const Input>> Input::fetchTree(ref<Store> store) const
 {
     auto [tree, input] = fetchTreeInternal(store);

src/libstore/fetchers/fetchers.hh

@@ -5,6 +5,9 @@
 #include "path.hh"
 
 #include <memory>
+#include <variant>
+
+#include <nlohmann/json_fwd.hpp>
 
 namespace nix { class Store; }
 
@@ -24,9 +27,10 @@ struct Tree
 
 struct Input : std::enable_shared_from_this<Input>
 {
-    std::string type;
     std::optional<Hash> narHash; // FIXME: implement
 
+    virtual std::string type() const = 0;
+
     virtual ~Input() { }
 
     virtual bool operator ==(const Input & other) const { return false; }
@@ -43,6 +47,11 @@ struct Input : std::enable_shared_from_this<Input>
 
     virtual std::string to_string() const = 0;
 
+    typedef std::variant<std::string, int64_t> Attr;
+    typedef std::map<std::string, Attr> Attrs;
+
+    Attrs toAttrs() const;
+
     std::pair<Tree, std::shared_ptr<const Input>> fetchTree(ref<Store> store) const;
 
     virtual std::shared_ptr<const Input> applyOverrides(
@@ -59,6 +68,8 @@ struct Input : std::enable_shared_from_this<Input>
 private:
 
     virtual std::pair<Tree, std::shared_ptr<const Input>> fetchTreeInternal(ref<Store> store) const = 0;
+
+    virtual Attrs toAttrsInternal() const = 0;
 };
 
 struct ParsedURL;
@@ -68,12 +79,22 @@ struct InputScheme
     virtual ~InputScheme() { }
 
     virtual std::unique_ptr<Input> inputFromURL(const ParsedURL & url) = 0;
+
+    virtual std::unique_ptr<Input> inputFromAttrs(const Input::Attrs & attrs) = 0;
 };
 
 std::unique_ptr<Input> inputFromURL(const ParsedURL & url);
 
 std::unique_ptr<Input> inputFromURL(const std::string & url);
 
+std::unique_ptr<Input> inputFromAttrs(const Input::Attrs & attrs);
+
 void registerInputScheme(std::unique_ptr<InputScheme> && fetcher);
 
+nlohmann::json attrsToJson(const Input::Attrs & attrs);
+
+std::optional<std::string> maybeGetStrAttr(const Input::Attrs & attrs, const std::string & name);
+
+std::string getStrAttr(const Input::Attrs & attrs, const std::string & name);
+
 }

src/libstore/fetchers/git.cc

@@ -74,9 +74,9 @@ struct GitInput : Input
     std::optional<Hash> rev;
 
     GitInput(const ParsedURL & url) : url(url)
-    {
-        type = "git";
-    }
+    { }
+
+    std::string type() const override { return "git"; }
 
     bool operator ==(const Input & other) const override
     {
@@ -105,6 +105,17 @@ struct GitInput : Input
         return url2.to_string();
     }
 
+    Attrs toAttrsInternal() const override
+    {
+        Attrs attrs;
+        attrs.emplace("url", url.to_string());
+        if (ref)
+            attrs.emplace("ref", *ref);
+        if (rev)
+            attrs.emplace("rev", rev->gitRev());
+        return attrs;
+    }
+
     void clone(const Path & destDir) const override
     {
         auto [isLocal, actualUrl] = getActualUrl();
@@ -379,6 +390,16 @@ struct GitInputScheme : InputScheme
 
         return input;
     }
+
+    std::unique_ptr<Input> inputFromAttrs(const Input::Attrs & attrs) override
+    {
+        if (maybeGetStrAttr(attrs, "type") != "git") return {};
+        auto input = std::make_unique<GitInput>(parseURL(getStrAttr(attrs, "url")));
+        input->ref = maybeGetStrAttr(attrs, "ref");
+        if (auto rev = maybeGetStrAttr(attrs, "rev"))
+            input->rev = Hash(*rev, htSHA1);
+        return input;
+    }
 };
 
 static auto r1 = OnStartup([] { registerInputScheme(std::make_unique<GitInputScheme>()); });

src/libstore/fetchers/github.cc

@@ -19,6 +19,8 @@ struct GitHubInput : Input
     std::optional<std::string> ref;
     std::optional<Hash> rev;
 
+    std::string type() const override { return "github"; }
+
     bool operator ==(const Input & other) const override
     {
         auto other2 = dynamic_cast<const GitHubInput *>(&other);
@@ -48,6 +50,18 @@ struct GitHubInput : Input
         return s;
     }
 
+    Attrs toAttrsInternal() const override
+    {
+        Attrs attrs;
+        attrs.emplace("owner", owner);
+        attrs.emplace("repo", repo);
+        if (ref)
+            attrs.emplace("ref", *ref);
+        if (rev)
+            attrs.emplace("rev", rev->gitRev());
+        return attrs;
+    }
+
     void clone(const Path & destDir) const override
     {
         std::shared_ptr<const Input> input = inputFromURL(fmt("git+ssh://git@github.com/%s/%s.git", owner, repo));
@@ -138,7 +152,6 @@ struct GitHubInputScheme : InputScheme
 
         auto path = tokenizeString<std::vector<std::string>>(url.path, "/");
         auto input = std::make_unique<GitHubInput>();
-        input->type = "github";
 
         if (path.size() == 2) {
         } else if (path.size() == 3) {
@@ -176,6 +189,18 @@ struct GitHubInputScheme : InputScheme
 
         return input;
     }
+
+    std::unique_ptr<Input> inputFromAttrs(const Input::Attrs & attrs) override
+    {
+        if (maybeGetStrAttr(attrs, "type") != "github") return {};
+        auto input = std::make_unique<GitHubInput>();
+        input->owner = getStrAttr(attrs, "owner");
+        input->repo = getStrAttr(attrs, "repo");
+        input->ref = maybeGetStrAttr(attrs, "ref");
+        if (auto rev = maybeGetStrAttr(attrs, "rev"))
+            input->rev = Hash(*rev, htSHA1);
+        return input;
+    }
 };
 
 static auto r1 = OnStartup([] { registerInputScheme(std::make_unique<GitHubInputScheme>()); });

src/libstore/fetchers/indirect.cc

@@ -12,6 +12,8 @@ struct IndirectInput : Input
     std::optional<Hash> rev;
     std::optional<std::string> ref;
 
+    std::string type() const override { return "indirect"; }
+
     bool operator ==(const Input & other) const override
     {
         auto other2 = dynamic_cast<const IndirectInput *>(&other);
@@ -51,6 +53,17 @@ struct IndirectInput : Input
         return url.to_string();
     }
 
+    Attrs toAttrsInternal() const override
+    {
+        Attrs attrs;
+        attrs.emplace("id", id);
+        if (ref)
+            attrs.emplace("ref", *ref);
+        if (rev)
+            attrs.emplace("rev", rev->gitRev());
+        return attrs;
+    }
+
     std::shared_ptr<const Input> applyOverrides(
         std::optional<std::string> ref,
         std::optional<Hash> rev) const override
@@ -79,7 +92,6 @@ struct IndirectInputScheme : InputScheme
 
         auto path = tokenizeString<std::vector<std::string>>(url.path, "/");
         auto input = std::make_unique<IndirectInput>();
-        input->type = "indirect";
 
         if (path.size() == 1) {
         } else if (path.size() == 2) {
@@ -107,6 +119,17 @@ struct IndirectInputScheme : InputScheme
 
         return input;
     }
+
+    std::unique_ptr<Input> inputFromAttrs(const Input::Attrs & attrs) override
+    {
+        if (maybeGetStrAttr(attrs, "type") != "indirect") return {};
+        auto input = std::make_unique<IndirectInput>();
+        input->id = getStrAttr(attrs, "id");
+        input->ref = maybeGetStrAttr(attrs, "ref");
+        if (auto rev = maybeGetStrAttr(attrs, "rev"))
+            input->rev = Hash(*rev, htSHA1);
+        return input;
+    }
 };
 
 static auto r1 = OnStartup([] { registerInputScheme(std::make_unique<IndirectInputScheme>()); });

src/libstore/fetchers/mercurial.cc

@@ -20,9 +20,9 @@ struct MercurialInput : Input
     std::optional<Hash> rev;
 
     MercurialInput(const ParsedURL & url) : url(url)
-    {
-        type = "hg";
-    }
+    { }
+
+    std::string type() const override { return "hg"; }
 
     bool operator ==(const Input & other) const override
     {
@@ -51,6 +51,17 @@ struct MercurialInput : Input
         return url2.to_string();
     }
 
+    Attrs toAttrsInternal() const override
+    {
+        Attrs attrs;
+        attrs.emplace("url", url.to_string());
+        if (ref)
+            attrs.emplace("ref", *ref);
+        if (rev)
+            attrs.emplace("rev", rev->gitRev());
+        return attrs;
+    }
+
     std::shared_ptr<const Input> applyOverrides(
         std::optional<std::string> ref,
         std::optional<Hash> rev) const override
@@ -273,6 +284,16 @@ struct MercurialInputScheme : InputScheme
 
         return input;
     }
+
+    std::unique_ptr<Input> inputFromAttrs(const Input::Attrs & attrs) override
+    {
+        if (maybeGetStrAttr(attrs, "type") != "hg") return {};
+        auto input = std::make_unique<MercurialInput>(parseURL(getStrAttr(attrs, "url")));
+        input->ref = maybeGetStrAttr(attrs, "ref");
+        if (auto rev = maybeGetStrAttr(attrs, "rev"))
+            input->rev = Hash(*rev, htSHA1);
+        return input;
+    }
 };
 
 static auto r1 = OnStartup([] { registerInputScheme(std::make_unique<MercurialInputScheme>()); });

src/libstore/fetchers/tarball.cc

@@ -11,6 +11,11 @@ struct TarballInput : Input
     ParsedURL url;
     std::optional<Hash> hash;
 
+    TarballInput(const ParsedURL & url) : url(url)
+    { }
+
+    std::string type() const override { return "tarball"; }
+
     bool operator ==(const Input & other) const override
     {
         auto other2 = dynamic_cast<const TarballInput *>(&other);
@@ -22,17 +27,32 @@ struct TarballInput : Input
 
     bool isImmutable() const override
     {
-        return (bool) hash;
+        return hash || narHash;
     }
 
     std::string to_string() const override
     {
         auto url2(url);
+        // NAR hashes are preferred over file hashes since tar/zip files
+        // don't have a canonical representation.
         if (narHash)
             url2.query.insert_or_assign("narHash", narHash->to_string(SRI));
+        else if (hash)
+            url2.query.insert_or_assign("hash", hash->to_string(SRI));
         return url2.to_string();
     }
 
+    Attrs toAttrsInternal() const override
+    {
+        Attrs attrs;
+        attrs.emplace("url", url.to_string());
+        if (narHash)
+            attrs.emplace("narHash", hash->to_string(SRI));
+        else if (hash)
+            attrs.emplace("hash", hash->to_string(SRI));
+        return attrs;
+    }
+
     std::pair<Tree, std::shared_ptr<const Input>> fetchTreeInternal(nix::ref<Store> store) const override
     {
         CachedDownloadRequest request(url.to_string());
@@ -72,18 +92,33 @@ struct TarballInputScheme : InputScheme
             && !hasSuffix(url.path, ".tar.bz2"))
             return nullptr;
 
-        auto input = std::make_unique<TarballInput>();
-        input->type = "tarball";
-        input->url = url;
+        auto input = std::make_unique<TarballInput>(url);
+
+        auto hash = url.query.find("hash");
+        if (hash != url.query.end())
+            // FIXME: require SRI hash.
+            input->hash = Hash(hash->second);
 
         auto narHash = url.query.find("narHash");
-        if (narHash != url.query.end()) {
+        if (narHash != url.query.end())
             // FIXME: require SRI hash.
             input->narHash = Hash(narHash->second);
-        }
 
         return input;
     }
+
+    std::unique_ptr<Input> inputFromAttrs(const Input::Attrs & attrs) override
+    {
+        if (maybeGetStrAttr(attrs, "type") != "tarball") return {};
+        auto input = std::make_unique<TarballInput>(parseURL(getStrAttr(attrs, "url")));
+        if (auto hash = maybeGetStrAttr(attrs, "hash"))
+            // FIXME: require SRI hash.
+            input->hash = Hash(*hash);
+        if (auto narHash = maybeGetStrAttr(attrs, "narHash"))
+            // FIXME: require SRI hash.
+            input->narHash = Hash(*narHash);
+        return input;
+    }
 };
 
 static auto r1 = OnStartup([] { registerInputScheme(std::make_unique<TarballInputScheme>()); });