Associate each derivation with a single ExtraPathInfo

Do this as opposed to associating it with each `DerivedPath` produced by
the installable. (Installables can produce multiple). `getExtraPathInfo`
is a new method which gets instead.

Additionally, the new `getExtraPathInfo`, and `nixpkgsFlakeRef`, are moved
to `InstallableValue`.

To my pleasant surprise, the extra path infos associated with each
`DerivedPath` of a given installable were all the same, so this was an
easy refactor with no behavior change.

I did this because NixOS/rfcs#134 ; with these
things moved to `InstallableValue`, the base `Installable` no longer
depends on libexpr! This is a major step towards that.

src/libcmd/command.hh

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "installables.hh"
+#include "installable-value.hh"
 #include "args.hh"
 #include "common-eval-args.hh"
 #include "path.hh"

src/libcmd/installable-attr-path.cc

@@ -44,7 +44,7 @@ std::pair<Value *, PosIdx> InstallableAttrPath::toValue(EvalState & state)
     return {vRes, pos};
 }
 
-DerivedPathsWithInfo InstallableAttrPath::toDerivedPaths()
+DerivedPaths InstallableAttrPath::toDerivedPaths()
 {
     auto v = toValue(*state).first;
 
@@ -80,10 +80,10 @@ DerivedPathsWithInfo InstallableAttrPath::toDerivedPaths()
             iter->second = iter->second.union_(newOutputs);
     }
 
-    DerivedPathsWithInfo res;
+    DerivedPaths res;
     for (auto & [drvPath, outputs] : byDrvPath)
         res.push_back({
-            .path = DerivedPath::Built {
+            DerivedPath::Built {
                 .drvPath = drvPath,
                 .outputs = outputs,
             },
@@ -92,6 +92,11 @@ DerivedPathsWithInfo InstallableAttrPath::toDerivedPaths()
     return res;
 }
 
+ExtraPathInfo InstallableAttrPath::getExtraPathInfo()
+{
+    return {};
+}
+
 InstallableAttrPath InstallableAttrPath::parse(
     ref<EvalState> state,
     SourceExprCommand & cmd,

src/libcmd/installable-attr-path.hh

@@ -41,7 +41,9 @@ class InstallableAttrPath : public InstallableValue
 
     std::pair<Value *, PosIdx> toValue(EvalState & state) override;
 
-    DerivedPathsWithInfo toDerivedPaths() override;
+    DerivedPaths toDerivedPaths() override;
+
+    ExtraPathInfo getExtraPathInfo() override;
 
 public:
 

src/libcmd/installable-derived-path.cc

@@ -8,9 +8,9 @@ std::string InstallableDerivedPath::what() const
     return derivedPath.to_string(*store);
 }
 
-DerivedPathsWithInfo InstallableDerivedPath::toDerivedPaths()
+DerivedPaths InstallableDerivedPath::toDerivedPaths()
 {
-    return {{.path = derivedPath, .info = {} }};
+    return {derivedPath};
 }
 
 std::optional<StorePath> InstallableDerivedPath::getStorePath()

src/libcmd/installable-derived-path.hh

@@ -15,7 +15,7 @@ struct InstallableDerivedPath : Installable
 
     std::string what() const override;
 
-    DerivedPathsWithInfo toDerivedPaths() override;
+    DerivedPaths toDerivedPaths() override;
 
     std::optional<StorePath> getStorePath() override;
 

src/libcmd/installable-flake.cc

@@ -82,7 +82,7 @@ InstallableFlake::InstallableFlake(
         throw UsageError("'--arg' and '--argstr' are incompatible with flakes");
 }
 
-DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
+DerivedPaths InstallableFlake::toDerivedPaths()
 {
     Activity act(*logger, lvlTalkative, actUnknown, fmt("evaluating derivation '%s'", what()));
 
@@ -98,23 +98,23 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
         if (v.type() == nPath) {
             PathSet context;
             auto storePath = state->copyPathToStore(context, Path(v.path));
-            return {{
-                .path = DerivedPath::Opaque {
+            return {
+                DerivedPath::Opaque {
                     .path = std::move(storePath),
                 }
-            }};
+            };
         }
 
         else if (v.type() == nString) {
             PathSet context;
             auto s = state->forceString(v, context, noPos, fmt("while evaluating the flake output attribute '%s'", attrPath));
             auto storePath = state->store->maybeParseStorePath(s);
             if (storePath && context.count(std::string(s))) {
-                return {{
-                    .path = DerivedPath::Opaque {
+                return {
+                    DerivedPath::Opaque {
                         .path = std::move(*storePath),
                     }
-                }};
+                };
             } else
                 throw Error("flake output attribute '%s' evaluates to the string '%s' which is not a store path", attrPath, s);
         }
@@ -125,16 +125,12 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
 
     auto drvPath = attr->forceDerivation();
 
-    std::optional<NixInt> priority;
-
-    if (attr->maybeGetAttr(state->sOutputSpecified)) {
-    } else if (auto aMeta = attr->maybeGetAttr(state->sMeta)) {
-        if (auto aPriority = aMeta->maybeGetAttr("priority"))
-            priority = aPriority->getInt();
-    }
+    // Do this for side effects, like setting `applyNixConfig`.
+    // FIXME do this differently.
+    getLockedFlake();
 
-    return {{
-        .path = DerivedPath::Built {
+    return {
+        DerivedPath::Built {
             .drvPath = std::move(drvPath),
             .outputs = std::visit(overloaded {
                 [&](const ExtendedOutputsSpec::Default & d) -> OutputsSpec {
@@ -160,14 +156,30 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
                 },
             }, extendedOutputsSpec.raw()),
         },
-        .info = {
-            .priority = priority,
-            .originalRef = flakeRef,
-            .resolvedRef = getLockedFlake()->flake.lockedRef,
-            .attrPath = attrPath,
-            .extendedOutputsSpec = extendedOutputsSpec,
-        }
-    }};
+    };
+}
+
+ExtraPathInfo InstallableFlake::getExtraPathInfo()
+{
+    auto attr = getCursor(*state);
+
+    auto attrPath = attr->getAttrPathStr();
+
+    std::optional<NixInt> priority;
+
+    if (attr->maybeGetAttr(state->sOutputSpecified)) {
+    } else if (auto aMeta = attr->maybeGetAttr(state->sMeta)) {
+        if (auto aPriority = aMeta->maybeGetAttr("priority"))
+            priority = aPriority->getInt();
+    }
+
+    return {
+        .priority = priority,
+        .originalRef = flakeRef,
+        .resolvedRef = getLockedFlake()->flake.lockedRef,
+        .attrPath = attrPath,
+        .extendedOutputsSpec = extendedOutputsSpec,
+    };
 }
 
 std::pair<Value *, PosIdx> InstallableFlake::toValue(EvalState & state)
@@ -213,6 +225,7 @@ std::shared_ptr<flake::LockedFlake> InstallableFlake::getLockedFlake() const
 {
     if (!_lockedFlake) {
         flake::LockFlags lockFlagsApplyConfig = lockFlags;
+        // FIXME why this side effect?
         lockFlagsApplyConfig.applyNixConfig = true;
         _lockedFlake = std::make_shared<flake::LockedFlake>(lockFlake(*state, flakeRef, lockFlagsApplyConfig));
     }
@@ -230,7 +243,7 @@ FlakeRef InstallableFlake::nixpkgsFlakeRef() const
         }
     }
 
-    return Installable::nixpkgsFlakeRef();
+    return InstallableValue::nixpkgsFlakeRef();
 }
 
 }

src/libcmd/installable-flake.hh

@@ -29,7 +29,9 @@ struct InstallableFlake : InstallableValue
 
     Value * getFlakeOutputs(EvalState & state, const flake::LockedFlake & lockedFlake);
 
-    DerivedPathsWithInfo toDerivedPaths() override;
+    DerivedPaths toDerivedPaths() override;
+
+    ExtraPathInfo getExtraPathInfo() override;
 
     std::pair<Value *, PosIdx> toValue(EvalState & state) override;
 

src/libcmd/installable-value.hh

@@ -1,9 +1,15 @@
 #pragma once
 
 #include "installables.hh"
+#include "flake/flake.hh"
 
 namespace nix {
 
+struct DrvInfo;
+struct SourceExprCommand;
+
+namespace eval_cache { class EvalCache; class AttrCursor; }
+
 struct App
 {
     std::vector<DerivedPath> context;
@@ -17,12 +23,26 @@ struct UnresolvedApp
     App resolve(ref<Store> evalStore, ref<Store> store);
 };
 
+struct ExtraPathInfo
+{
+    std::optional<NixInt> priority;
+    std::optional<FlakeRef> originalRef;
+    std::optional<FlakeRef> resolvedRef;
+    std::optional<std::string> attrPath;
+    // FIXME: merge with DerivedPath's 'outputs' field?
+    std::optional<ExtendedOutputsSpec> extendedOutputsSpec;
+};
+
 struct InstallableValue : Installable
 {
     ref<EvalState> state;
 
     InstallableValue(ref<EvalState> state) : state(state) {}
 
+    virtual ~InstallableValue() { }
+
+    virtual ExtraPathInfo getExtraPathInfo() = 0;
+
     virtual std::pair<Value *, PosIdx> toValue(EvalState & state) = 0;
 
     /* Get a cursor to each value this Installable could refer to. However
@@ -37,6 +57,11 @@ struct InstallableValue : Installable
 
     UnresolvedApp toApp(EvalState & state);
 
+    virtual FlakeRef nixpkgsFlakeRef() const
+    {
+        return FlakeRef::fromAttrs({{"type","indirect"}, {"id", "nixpkgs"}});
+    }
+
     static InstallableValue & require(Installable & installable);
     static ref<InstallableValue> require(ref<Installable> installable);
 };

src/libcmd/installables.cc

@@ -356,7 +356,7 @@ void completeFlakeRef(ref<Store> store, std::string_view prefix)
     }
 }
 
-DerivedPathWithInfo Installable::toDerivedPath()
+DerivedPath Installable::toDerivedPath()
 {
     auto buildables = toDerivedPaths();
     if (buildables.size() != 1)
@@ -515,19 +515,13 @@ std::vector<std::pair<ref<Installable>, BuiltPathWithResult>> Installable::build
     if (mode == Realise::Nothing)
         settings.readOnlyMode = true;
 
-    struct Aux
-    {
-        ExtraPathInfo info;
-        ref<Installable> installable;
-    };
-
     std::vector<DerivedPath> pathsToBuild;
-    std::map<DerivedPath, std::vector<Aux>> backmap;
+    std::map<DerivedPath, std::vector<ref<Installable>>> backmap;
 
     for (auto & i : installables) {
         for (auto b : i->toDerivedPaths()) {
-            pathsToBuild.push_back(b.path);
-            backmap[b.path].push_back({.info = b.info, .installable = i});
+            pathsToBuild.push_back(b);
+            backmap[b].push_back(i);
         }
     }
 
@@ -540,18 +534,18 @@ std::vector<std::pair<ref<Installable>, BuiltPathWithResult>> Installable::build
         printMissing(store, pathsToBuild, lvlError);
 
         for (auto & path : pathsToBuild) {
-            for (auto & aux : backmap[path]) {
+            for (auto & installable : backmap[path]) {
                 std::visit(overloaded {
                     [&](const DerivedPath::Built & bfd) {
                         auto outputs = resolveDerivedPath(*store, bfd, &*evalStore);
-                        res.push_back({aux.installable, {
+                        res.push_back({installable, {
                             .path = BuiltPath::Built { bfd.drvPath, outputs },
-                            .info = aux.info}});
+                        }});
                     },
                     [&](const DerivedPath::Opaque & bo) {
-                        res.push_back({aux.installable, {
+                        res.push_back({installable, {
                             .path = BuiltPath::Opaque { bo.path },
-                            .info = aux.info}});
+                        }});
                     },
                 }, path.raw());
             }
@@ -567,21 +561,19 @@ std::vector<std::pair<ref<Installable>, BuiltPathWithResult>> Installable::build
             if (!buildResult.success())
                 buildResult.rethrow();
 
-            for (auto & aux : backmap[buildResult.path]) {
+            for (auto & installable : backmap[buildResult.path]) {
                 std::visit(overloaded {
                     [&](const DerivedPath::Built & bfd) {
                         std::map<std::string, StorePath> outputs;
                         for (auto & path : buildResult.builtOutputs)
                             outputs.emplace(path.first.outputName, path.second.outPath);
-                        res.push_back({aux.installable, {
+                        res.push_back({installable, {
                             .path = BuiltPath::Built { bfd.drvPath, outputs },
-                            .info = aux.info,
                             .result = buildResult}});
                     },
                     [&](const DerivedPath::Opaque & bo) {
-                        res.push_back({aux.installable, {
+                        res.push_back({installable, {
                             .path = BuiltPath::Opaque { bo.path },
-                            .info = aux.info,
                             .result = buildResult}});
                     },
                 }, buildResult.path.raw());
@@ -667,7 +659,7 @@ StorePathSet Installable::toDerivations(
                 [&](const DerivedPath::Built & bfd) {
                     drvPaths.insert(bfd.drvPath);
                 },
-            }, b.path.raw());
+            }, b.raw());
 
     return drvPaths;
 }