Turn flake inputs into an attrset

Instead of a list, inputs are now an attrset like

  inputs = {
    nixpkgs.uri = github:NixOS/nixpkgs;
  };

If 'uri' is omitted, than the flake is a lookup in the flake registry, e.g.

  inputs = {
    nixpkgs = {};
  };

but in that case, you can also just omit the input altogether and
specify it as an argument to the 'outputs' function, as in

  outputs = { self, nixpkgs }: ...

This also gets rid of 'nonFlakeInputs', which are now just a special
kind of input that have a 'flake = false' attribute, e.g.

  inputs = {
    someRepo = {
      uri = github:example/repo;
      flake = false;
    };
  };

src/libexpr/flake/flake.cc

@@ -248,22 +248,28 @@ Flake getFlake(EvalState & state, const FlakeRef & flakeRef)
         flake.description = state.forceStringNoCtx(*(**description).value, *(**description).pos);
 
     auto sInputs = state.symbols.create("inputs");
+    auto sUri = state.symbols.create("uri");
+    auto sFlake = state.symbols.create("flake");
 
-    if (auto inputs = vInfo.attrs->get(sInputs)) {
+    if (std::optional<Attr *> inputs = vInfo.attrs->get(sInputs)) {
-        state.forceList(*(**inputs).value, *(**inputs).pos);
+        state.forceAttrs(*(**inputs).value, *(**inputs).pos);
-        for (unsigned int n = 0; n < (**inputs).value->listSize(); ++n)
+
-            flake.inputs.push_back(FlakeRef(state.forceStringNoCtx(
+        for (Attr inputAttr : *(*(**inputs).value).attrs) {
-                *(**inputs).value->listElems()[n], *(**inputs).pos)));
+            state.forceAttrs(*inputAttr.value, *inputAttr.pos);
+
+            FlakeInput input(FlakeRef(inputAttr.name));
+
+            for (Attr attr : *(inputAttr.value->attrs)) {
+                if (attr.name == sUri) {
+                    input.ref = state.forceStringNoCtx(*attr.value, *attr.pos);
+                } else if (attr.name == sFlake) {
+                    input.isFlake = state.forceBool(*attr.value, *attr.pos);
+                } else
+                    throw Error("flake input '%s' has an unsupported attribute '%s', at %s",
+                        inputAttr.name, attr.name, *attr.pos);
             }
 
-    auto sNonFlakeInputs = state.symbols.create("nonFlakeInputs");
+            flake.inputs.emplace(inputAttr.name, input);
-
-    if (std::optional<Attr *> nonFlakeInputs = vInfo.attrs->get(sNonFlakeInputs)) {
-        state.forceAttrs(*(**nonFlakeInputs).value, *(**nonFlakeInputs).pos);
-        for (Attr attr : *(*(**nonFlakeInputs).value).attrs) {
-            std::string myNonFlakeUri = state.forceStringNoCtx(*attr.value, *attr.pos);
-            FlakeRef nonFlakeRef = FlakeRef(myNonFlakeUri);
-            flake.nonFlakeInputs.insert_or_assign(attr.name, nonFlakeRef);
         }
     }
 
@@ -275,9 +281,8 @@ Flake getFlake(EvalState & state, const FlakeRef & flakeRef)
 
         if (flake.vOutputs->lambda.fun->matchAttrs) {
             for (auto & formal : flake.vOutputs->lambda.fun->formals->formals) {
-                if (formal.name != state.sSelf) {
+                if (formal.name != state.sSelf)
-                    flake.inputs.push_back(FlakeRef(formal.name));
+                    flake.inputs.emplace(formal.name, FlakeInput(FlakeRef(formal.name)));
-                }
             }
         }
 
@@ -290,7 +295,6 @@ Flake getFlake(EvalState & state, const FlakeRef & flakeRef)
             attr.name != state.sName &&
             attr.name != state.sDescription &&
             attr.name != sInputs &&
-            attr.name != sNonFlakeInputs &&
             attr.name != sOutputs)
             throw Error("flake '%s' has an unsupported attribute '%s', at %s",
                 flakeRef, attr.name, *attr.pos);
@@ -299,21 +303,19 @@ Flake getFlake(EvalState & state, const FlakeRef & flakeRef)
     return flake;
 }
 
-NonFlake getNonFlake(EvalState & state, const FlakeRef & flakeRef)
+static SourceInfo getNonFlake(EvalState & state, const FlakeRef & flakeRef)
 {
     auto sourceInfo = fetchFlake(state, flakeRef);
     debug("got non-flake source '%s' with flakeref %s", sourceInfo.storePath, sourceInfo.resolvedRef.to_string());
 
     FlakeRef resolvedRef = sourceInfo.resolvedRef;
 
-    NonFlake nonFlake(flakeRef, sourceInfo);
+    state.store->assertStorePath(sourceInfo.storePath);
-
-    state.store->assertStorePath(nonFlake.sourceInfo.storePath);
 
     if (state.allowedPaths)
-        state.allowedPaths->insert(nonFlake.sourceInfo.storePath);
+        state.allowedPaths->insert(sourceInfo.storePath);
 
-    return nonFlake;
+    return sourceInfo;
 }
 
 bool allowedToWrite(HandleLockFile handle)
@@ -346,46 +348,33 @@ bool allowedToUseRegistries(HandleLockFile handle, bool isTopRef)
 
    Note that this is lazy: we only recursively fetch inputs that are
    not in the lockfile yet. */
-static std::pair<Flake, FlakeInput> updateLocks(
+static std::pair<Flake, LockedInput> updateLocks(
     EvalState & state,
     const Flake & flake,
     HandleLockFile handleLockFile,
-    const FlakeInputs & oldEntry,
+    const LockedInputs & oldEntry,
     bool topRef)
 {
-    FlakeInput newEntry(
+    LockedInput newEntry(
-        flake.id,
         flake.sourceInfo.resolvedRef,
         flake.sourceInfo.narHash);
 
-    for (auto & input : flake.nonFlakeInputs) {
+    for (auto & [id, input] : flake.inputs) {
-        auto & id = input.first;
+        auto i = oldEntry.inputs.find(id);
-        auto & ref = input.second;
+        if (i != oldEntry.inputs.end()) {
-        auto i = oldEntry.nonFlakeInputs.find(id);
+            newEntry.inputs.insert_or_assign(id, i->second);
-        if (i != oldEntry.nonFlakeInputs.end()) {
-            newEntry.nonFlakeInputs.insert_or_assign(i->first, i->second);
         } else {
             if (handleLockFile == AllPure || handleLockFile == TopRefUsesRegistries)
-                throw Error("cannot update non-flake dependency '%s' in pure mode", id);
+                throw Error("cannot update flake input '%s' in pure mode", id);
-            auto nonFlake = getNonFlake(state, maybeLookupFlake(state, ref, allowedToUseRegistries(handleLockFile, false)));
+            if (input.isFlake)
-            newEntry.nonFlakeInputs.insert_or_assign(id,
+                newEntry.inputs.insert_or_assign(id,
-                NonFlakeInput(
-                    nonFlake.sourceInfo.resolvedRef,
-                    nonFlake.sourceInfo.narHash));
-        }
-    }
-
-    for (auto & inputRef : flake.inputs) {
-        auto i = oldEntry.flakeInputs.find(inputRef);
-        if (i != oldEntry.flakeInputs.end()) {
-            newEntry.flakeInputs.insert_or_assign(inputRef, i->second);
-        } else {
-            if (handleLockFile == AllPure || handleLockFile == TopRefUsesRegistries)
-                throw Error("cannot update flake dependency '%s' in pure mode", inputRef);
-            newEntry.flakeInputs.insert_or_assign(inputRef,
                     updateLocks(state,
-                    getFlake(state, maybeLookupFlake(state, inputRef, allowedToUseRegistries(handleLockFile, false))),
+                        getFlake(state, maybeLookupFlake(state, input.ref, allowedToUseRegistries(handleLockFile, false))),
                         handleLockFile, {}, false).second);
+            else {
+                auto sourceInfo = getNonFlake(state, maybeLookupFlake(state, input.ref, allowedToUseRegistries(handleLockFile, false)));
+                newEntry.inputs.insert_or_assign(id, LockedInput(sourceInfo.resolvedRef, sourceInfo.narHash));
+            }
         }
     }
 
@@ -462,81 +451,69 @@ static void emitSourceInfoAttrs(EvalState & state, const SourceInfo & sourceInfo
                 std::put_time(std::gmtime(&*sourceInfo.lastModified), "%Y%m%d%H%M%S")));
 }
 
+struct LazyInput
+{
+    bool isFlake;
+    LockedInput lockedInput;
+};
+
 /* Helper primop to make callFlake (below) fetch/call its inputs
    lazily. Note that this primop cannot be called by user code since
    it doesn't appear in 'builtins'. */
 static void prim_callFlake(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    auto lazyFlake = (FlakeInput *) args[0]->attrs;
+    auto lazyInput = (LazyInput *) args[0]->attrs;
 
-    assert(lazyFlake->ref.isImmutable());
+    assert(lazyInput->lockedInput.ref.isImmutable());
 
-    auto flake = getFlake(state, lazyFlake->ref);
+    if (lazyInput->isFlake) {
+        auto flake = getFlake(state, lazyInput->lockedInput.ref);
 
-    if (flake.sourceInfo.narHash != lazyFlake->narHash)
+        if (flake.sourceInfo.narHash != lazyInput->lockedInput.narHash)
             throw Error("the content hash of flake '%s' doesn't match the hash recorded in the referring lockfile", flake.sourceInfo.resolvedRef);
 
-    callFlake(state, flake, *lazyFlake, v);
+        callFlake(state, flake, lazyInput->lockedInput, v);
-}
+    } else {
+        auto sourceInfo = getNonFlake(state, lazyInput->lockedInput.ref);
 
-static void prim_callNonFlake(EvalState & state, const Pos & pos, Value * * args, Value & v)
+        if (sourceInfo.narHash != lazyInput->lockedInput.narHash)
-{
+            throw Error("the content hash of repository '%s' doesn't match the hash recorded in the referring lockfile", sourceInfo.resolvedRef);
-    auto lazyNonFlake = (NonFlakeInput *) args[0]->attrs;
-
-    assert(lazyNonFlake->ref.isImmutable());
-
-    auto nonFlake = getNonFlake(state, lazyNonFlake->ref);
-
-    if (nonFlake.sourceInfo.narHash != lazyNonFlake->narHash)
-        throw Error("the content hash of repository '%s' doesn't match the hash recorded in the referring lockfile", nonFlake.sourceInfo.resolvedRef);
 
         state.mkAttrs(v, 8);
 
-    assert(state.store->isValidPath(nonFlake.sourceInfo.storePath));
+        assert(state.store->isValidPath(sourceInfo.storePath));
 
         mkString(*state.allocAttr(v, state.sOutPath),
-        nonFlake.sourceInfo.storePath, {nonFlake.sourceInfo.storePath});
+            sourceInfo.storePath, {sourceInfo.storePath});
 
-    emitSourceInfoAttrs(state, nonFlake.sourceInfo, v);
+        emitSourceInfoAttrs(state, sourceInfo, v);
+    }
 }
 
 void callFlake(EvalState & state,
     const Flake & flake,
-    const FlakeInputs & inputs,
+    const LockedInputs & lockedInputs,
     Value & vRes)
 {
     auto & vInputs = *state.allocValue();
 
-    state.mkAttrs(vInputs,
+    state.mkAttrs(vInputs, flake.inputs.size() + 1);
-        inputs.flakeInputs.size() +
-        inputs.nonFlakeInputs.size() + 1);
 
-    for (auto & dep : inputs.flakeInputs) {
+    for (auto & [inputId, input] : flake.inputs) {
-        auto vFlake = state.allocAttr(vInputs, dep.second.id);
+        auto vFlake = state.allocAttr(vInputs, inputId);
         auto vPrimOp = state.allocValue();
         static auto primOp = new PrimOp(prim_callFlake, 1, state.symbols.create("callFlake"));
         vPrimOp->type = tPrimOp;
         vPrimOp->primOp = primOp;
         auto vArg = state.allocValue();
         vArg->type = tNull;
+        auto lockedInput = lockedInputs.inputs.find(inputId);
+        assert(lockedInput != lockedInputs.inputs.end());
         // FIXME: leak
-        vArg->attrs = (Bindings *) new FlakeInput(dep.second); // evil! also inefficient
+        vArg->attrs = (Bindings *) new LazyInput{input.isFlake, lockedInput->second};
         mkApp(*vFlake, *vPrimOp, *vArg);
     }
 
-    for (auto & dep : inputs.nonFlakeInputs) {
-        auto vNonFlake = state.allocAttr(vInputs, dep.first);
-        auto vPrimOp = state.allocValue();
-        static auto primOp = new PrimOp(prim_callNonFlake, 1, state.symbols.create("callNonFlake"));
-        vPrimOp->type = tPrimOp;
-        vPrimOp->primOp = primOp;
-        auto vArg = state.allocValue();
-        vArg->type = tNull;
-        // FIXME: leak
-        vArg->attrs = (Bindings *) new NonFlakeInput(dep.second); // evil! also inefficient
-        mkApp(*vNonFlake, *vPrimOp, *vArg);
-    }
-
     auto & vSourceInfo = *state.allocValue();
     state.mkAttrs(vSourceInfo, 8);
     emitSourceInfoAttrs(state, flake.sourceInfo, vSourceInfo);

src/libexpr/flake/flake.hh

@@ -58,14 +58,20 @@ struct SourceInfo
     SourceInfo(const FlakeRef & resolvRef) : resolvedRef(resolvRef) {};
 };
 
+struct FlakeInput
+{
+    FlakeRef ref;
+    bool isFlake = true;
+    FlakeInput(const FlakeRef & ref) : ref(ref) {};
+};
+
 struct Flake
 {
     FlakeId id;
     FlakeRef originalRef;
     std::string description;
     SourceInfo sourceInfo;
-    std::vector<FlakeRef> inputs;
+    std::map<FlakeId, FlakeInput> inputs;
-    std::map<FlakeAlias, FlakeRef> nonFlakeInputs;
     Value * vOutputs; // FIXME: gc
     unsigned int edition;
 
@@ -73,14 +79,6 @@ struct Flake
         : originalRef(origRef), sourceInfo(sourceInfo) {};
 };
 
-struct NonFlake
-{
-    FlakeRef originalRef;
-    SourceInfo sourceInfo;
-    NonFlake(const FlakeRef & origRef, const SourceInfo & sourceInfo)
-        : originalRef(origRef), sourceInfo(sourceInfo) {};
-};
-
 Flake getFlake(EvalState &, const FlakeRef &);
 
 /* If 'allowLookup' is true, then resolve 'flakeRef' using the
@@ -108,7 +106,7 @@ ResolvedFlake resolveFlake(EvalState &, const FlakeRef &, HandleLockFile);
 
 void callFlake(EvalState & state,
     const Flake & flake,
-    const FlakeInputs & inputs,
+    const LockedInputs & inputs,
     Value & v);
 
 void callFlake(EvalState & state,

src/libexpr/flake/lockfile.cc

@@ -3,83 +3,57 @@
 
 namespace nix::flake {
 
-AbstractInput::AbstractInput(const nlohmann::json & json)
+LockedInput::LockedInput(const nlohmann::json & json)
-    : ref(json["uri"])
+    : LockedInputs(json)
+    , ref(json["uri"])
     , narHash(Hash((std::string) json["narHash"]))
 {
     if (!ref.isImmutable())
         throw Error("lockfile contains mutable flakeref '%s'", ref);
 }
 
-nlohmann::json AbstractInput::toJson() const
+nlohmann::json LockedInput::toJson() const
 {
-    nlohmann::json json;
+    auto json = LockedInputs::toJson();
     json["uri"] = ref.to_string();
     json["narHash"] = narHash.to_string(SRI);
     return json;
 }
 
-Path AbstractInput::computeStorePath(Store & store) const
+Path LockedInput::computeStorePath(Store & store) const
 {
     return store.makeFixedOutputPath(true, narHash, "source");
 }
 
-FlakeInput::FlakeInput(const nlohmann::json & json)
+LockedInputs::LockedInputs(const nlohmann::json & json)
-    : FlakeInputs(json)
-    , AbstractInput(json)
-    , id(json["id"])
 {
-}
-
-nlohmann::json FlakeInput::toJson() const
-{
-    auto json = FlakeInputs::toJson();
-    json.update(AbstractInput::toJson());
-    json["id"] = id;
-    return json;
-}
-
-FlakeInputs::FlakeInputs(const nlohmann::json & json)
-{
-    for (auto & i : json["nonFlakeInputs"].items())
-        nonFlakeInputs.insert_or_assign(i.key(), NonFlakeInput(i.value()));
-
     for (auto & i : json["inputs"].items())
-        flakeInputs.insert_or_assign(i.key(), FlakeInput(i.value()));
+        inputs.insert_or_assign(i.key(), LockedInput(i.value()));
 }
 
-nlohmann::json FlakeInputs::toJson() const
+nlohmann::json LockedInputs::toJson() const
 {
     nlohmann::json json;
     {
         auto j = nlohmann::json::object();
-        for (auto & i : nonFlakeInputs)
+        for (auto & i : inputs)
             j[i.first] = i.second.toJson();
-        json["nonFlakeInputs"] = std::move(j);
-    }
-    {
-        auto j = nlohmann::json::object();
-        for (auto & i : flakeInputs)
-            j[i.first.to_string()] = i.second.toJson();
         json["inputs"] = std::move(j);
     }
     return json;
 }
 
-bool FlakeInputs::isDirty() const
+bool LockedInputs::isDirty() const
 {
-    for (auto & i : flakeInputs)
+    for (auto & i : inputs)
         if (i.second.ref.isDirty() || i.second.isDirty()) return true;
 
-    for (auto & i : nonFlakeInputs)
-        if (i.second.ref.isDirty()) return true;
-
     return false;
 }
 
 nlohmann::json LockFile::toJson() const
 {
-    auto json = FlakeInputs::toJson();
+    auto json = LockedInputs::toJson();
     json["version"] = 2;
     return json;
 }

src/libexpr/flake/lockfile.hh

@@ -10,47 +10,15 @@ class Store;
 
 namespace nix::flake {
 
-/* Common lock file information about a flake input, namely the
+struct LockedInput;
-   immutable ref and the NAR hash. */
-struct AbstractInput
-{
-    FlakeRef ref;
-    Hash narHash;
-
-    AbstractInput(const FlakeRef & flakeRef, const Hash & narHash)
-        : ref(flakeRef), narHash(narHash)
-    {
-        assert(ref.isImmutable());
-    };
-
-    AbstractInput(const nlohmann::json & json);
-
-    nlohmann::json toJson() const;
-
-    Path computeStorePath(Store & store) const;
-};
-
-/* Lock file information about a non-flake input. */
-struct NonFlakeInput : AbstractInput
-{
-    using AbstractInput::AbstractInput;
-
-    bool operator ==(const NonFlakeInput & other) const
-    {
-        return ref == other.ref && narHash == other.narHash;
-    }
-};
-
-struct FlakeInput;
 
 /* Lock file information about the dependencies of a flake. */
-struct FlakeInputs
+struct LockedInputs
 {
-    std::map<FlakeRef, FlakeInput> flakeInputs;
+    std::map<FlakeId, LockedInput> inputs;
-    std::map<FlakeAlias, NonFlakeInput> nonFlakeInputs;
 
-    FlakeInputs() {};
+    LockedInputs() {};
-    FlakeInputs(const nlohmann::json & json);
+    LockedInputs(const nlohmann::json & json);
 
     nlohmann::json toJson() const;
 
@@ -60,47 +28,48 @@ struct FlakeInputs
 };
 
 /* Lock file information about a flake input. */
-struct FlakeInput : FlakeInputs, AbstractInput
+struct LockedInput : LockedInputs
 {
-    FlakeId id;
+    FlakeRef ref;
+    Hash narHash;
 
-    FlakeInput(const FlakeId & id, const FlakeRef & flakeRef, const Hash & narHash)
+    LockedInput(const FlakeRef & ref, const Hash & narHash)
-        : AbstractInput(flakeRef, narHash), id(id) {};
+        : ref(ref), narHash(narHash)
+    {
+        assert(ref.isImmutable());
+    };
 
-    FlakeInput(const nlohmann::json & json);
+    LockedInput(const nlohmann::json & json);
 
-    bool operator ==(const FlakeInput & other) const
+    bool operator ==(const LockedInput & other) const
     {
         return
-            id == other.id
+            ref == other.ref
-            && ref == other.ref
             && narHash == other.narHash
-            && flakeInputs == other.flakeInputs
+            && inputs == other.inputs;
-            && nonFlakeInputs == other.nonFlakeInputs;
     }
 
     nlohmann::json toJson() const;
+
+    Path computeStorePath(Store & store) const;
 };
 
 /* An entire lock file. Note that this cannot be a FlakeInput for the
    top-level flake, because then the lock file would need to contain
    the hash of the top-level flake, but committing the lock file
    would invalidate that hash. */
-struct LockFile : FlakeInputs
+struct LockFile : LockedInputs
 {
     bool operator ==(const LockFile & other) const
     {
-        return
+        return inputs == other.inputs;
-            flakeInputs == other.flakeInputs
-            && nonFlakeInputs == other.nonFlakeInputs;
     }
 
     LockFile() {}
-    LockFile(const nlohmann::json & json) : FlakeInputs(json) {}
+    LockFile(const nlohmann::json & json) : LockedInputs(json) {}
-    LockFile(FlakeInput && dep)
+    LockFile(LockedInput && dep)
     {
-        flakeInputs = std::move(dep.flakeInputs);
+        inputs = std::move(dep.inputs);
-        nonFlakeInputs = std::move(dep.nonFlakeInputs);
     }
 
     nlohmann::json toJson() const;

src/libexpr/primops/fetchGit.cc

@@ -31,7 +31,6 @@ GitInfo exportGit(ref<Store> store, std::string uri,
     // or revision is given, then allow the use of an unclean working
     // tree.
     if (!ref && !rev && isLocal) {
-
         bool clean = true;
 
         try {

src/nix/installables.cc

@@ -217,25 +217,20 @@ void makeFlakeClosureGCRoot(Store & store,
     assert(store.isValidPath(resFlake.flake.sourceInfo.storePath));
     closure.insert(resFlake.flake.sourceInfo.storePath);
 
-    std::queue<std::reference_wrapper<const flake::FlakeInputs>> queue;
+    std::queue<std::reference_wrapper<const flake::LockedInputs>> queue;
     queue.push(resFlake.lockFile);
 
     while (!queue.empty()) {
-        const flake::FlakeInputs & flake = queue.front();
+        const flake::LockedInputs & flake = queue.front();
         queue.pop();
         /* Note: due to lazy fetching, these paths might not exist
            yet. */
-        for (auto & dep : flake.flakeInputs) {
+        for (auto & dep : flake.inputs) {
             auto path = dep.second.computeStorePath(store);
             if (store.isValidPath(path))
                 closure.insert(path);
             queue.push(dep.second);
         }
-        for (auto & dep : flake.nonFlakeInputs) {
-            auto path = dep.second.computeStorePath(store);
-            if (store.isValidPath(path))
-                closure.insert(path);
-        }
     }
 
     if (closure.empty()) return;

tests/flakes.sh

@@ -240,10 +240,13 @@ cat > $flake3Dir/flake.nix <<EOF
 
   edition = 201909;
 
-  inputs = [ "flake1" "flake2" ];
+  inputs = {
-
+    flake1 = {};
-  nonFlakeInputs = {
+    flake2 = {};
-    nonFlake = "$nonFlakeDir";
+    nonFlake = {
+      uri = "$nonFlakeDir";
+      flake = false;
+    };
   };
 
   description = "Fnord";
@@ -306,23 +309,24 @@ cat > $flake3Dir/flake.nix <<EOF
 
   edition = 201909;
 
-  inputs = [ "flake1" "flake2" ];
+  inputs = {
-
+    nonFlake = {
-  nonFlakeInputs = {
+      uri = "$nonFlakeDir";
-    nonFlake = "$nonFlakeDir";
+      flake = false;
+    };
   };
 
   description = "Fnord";
 
-  outputs = inputs: rec {
+  outputs = { self, flake1, flake2, nonFlake }: rec {
-    packages.sth = inputs.flake1.packages.foo;
+    packages.sth = flake1.packages.foo;
     packages.fnord =
       with import ./config.nix;
       mkDerivation {
         inherit system;
         name = "fnord";
         buildCommand = ''
-          cat \${inputs.nonFlake}/README.md > \$out
+          cat \${nonFlake}/README.md > \$out
         '';
       };
   };