Stratify ExtraPathInfo along Installable hierarchy

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

@@ -87,6 +87,10 @@ DerivedPathsWithInfo InstallableAttrPath::toDerivedPaths()
                 .drvPath = drvPath,
                 .outputs = outputs,
             },
+            .info = make_ref<ExtraPathInfoValue>(ExtraPathInfoValue::Value {
+                /* FIXME: reconsider backwards compatibility above
+                   so we can fill in this info. */
+            }),
         });
 
     return res;

src/libcmd/installable-derived-path.cc

@@ -10,7 +10,10 @@ std::string InstallableDerivedPath::what() const
 
 DerivedPathsWithInfo InstallableDerivedPath::toDerivedPaths()
 {
-    return {{.path = derivedPath, .info = {} }};
+    return {{
+        .path = derivedPath,
+        .info = make_ref<ExtraPathInfo>(),
+    }};
 }
 
 std::optional<StorePath> InstallableDerivedPath::getStorePath()

src/libcmd/installable-flake.cc

@@ -101,7 +101,8 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
             return {{
                 .path = DerivedPath::Opaque {
                     .path = std::move(storePath),
-                }
+                },
+                .info = make_ref<ExtraPathInfo>(),
             }};
         }
 
@@ -113,7 +114,8 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
                 return {{
                     .path = DerivedPath::Opaque {
                         .path = std::move(*storePath),
-                    }
+                    },
+                    .info = make_ref<ExtraPathInfo>(),
                 }};
             } else
                 throw Error("flake output attribute '%s' evaluates to the string '%s' which is not a store path", attrPath, s);
@@ -160,13 +162,16 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
                 },
             }, extendedOutputsSpec.raw()),
         },
-        .info = {
-            .priority = priority,
-            .originalRef = flakeRef,
-            .resolvedRef = getLockedFlake()->flake.lockedRef,
-            .attrPath = attrPath,
-            .extendedOutputsSpec = extendedOutputsSpec,
-        }
+        .info = make_ref<ExtraPathInfoFlake>(
+            ExtraPathInfoValue::Value {
+                .priority = priority,
+                .attrPath = attrPath,
+                .extendedOutputsSpec = extendedOutputsSpec,
+            },
+            ExtraPathInfoFlake::Flake {
+                .originalRef = flakeRef,
+                .resolvedRef = getLockedFlake()->flake.lockedRef,
+            }),
     }};
 }
 
@@ -212,6 +217,7 @@ 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));
     }
@@ -229,7 +235,7 @@ FlakeRef InstallableFlake::nixpkgsFlakeRef() const
         }
     }
 
-    return Installable::nixpkgsFlakeRef();
+    return InstallableValue::nixpkgsFlakeRef();
 }
 
 }

src/libcmd/installable-flake.hh

@@ -4,6 +4,20 @@
 
 namespace nix {
 
+struct ExtraPathInfoFlake : ExtraPathInfoValue
+{
+    struct Flake {
+        FlakeRef originalRef;
+        FlakeRef resolvedRef;
+    };
+
+    Flake flake;
+
+    ExtraPathInfoFlake(Value && v, Flake && f)
+        : ExtraPathInfoValue(std::move(v)), flake(f)
+    { }
+};
+
 struct InstallableFlake : InstallableValue
 {
     FlakeRef flakeRef;

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 +23,32 @@ struct UnresolvedApp
     App resolve(ref<Store> evalStore, ref<Store> store);
 };
 
+struct ExtraPathInfoValue : ExtraPathInfo
+{
+    struct Value {
+        std::optional<NixInt> priority;
+        std::string attrPath;
+        // FIXME: merge with DerivedPath's 'outputs' field?
+        ExtendedOutputsSpec extendedOutputsSpec;
+    };
+
+    Value value;
+
+    ExtraPathInfoValue(Value && v)
+        : value(v)
+    { }
+
+    virtual ~ExtraPathInfoValue() = default;
+};
+
 struct InstallableValue : Installable
 {
     ref<EvalState> state;
 
     InstallableValue(ref<EvalState> state) : state(state) {}
 
+    virtual ~InstallableValue() { }
+
     virtual std::pair<Value *, PosIdx> toValue(EvalState & state) = 0;
 
     /* Get a cursor to each value this Installable could refer to. However
@@ -37,6 +63,11 @@ 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

@@ -517,7 +517,7 @@ std::vector<std::pair<ref<Installable>, BuiltPathWithResult>> Installable::build
 
     struct Aux
     {
-        ExtraPathInfo info;
+        ref<ExtraPathInfo> info;
         ref<Installable> installable;
     };
 

src/libcmd/installables.hh

@@ -4,19 +4,14 @@
 #include "path.hh"
 #include "outputs-spec.hh"
 #include "derived-path.hh"
-#include "eval.hh"
 #include "store-api.hh"
-#include "flake/flake.hh"
 #include "build-result.hh"
 
 #include <optional>
 
 namespace nix {
 
 struct DrvInfo;
-struct SourceExprCommand;
-
-namespace eval_cache { class EvalCache; class AttrCursor; }
 
 enum class Realise {
     /* Build the derivation. Postcondition: the
@@ -39,28 +34,27 @@ enum class OperateOn {
     Derivation
 };
 
+/**
+ * Extra info about a derived class. Will be sub-classed by the
+ * subclasses of Installable to provide more info.
+ */
 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;
+    virtual ~ExtraPathInfo() = default;
 };
 
 /* A derived path with any additional info that commands might
    need from the derivation. */
 struct DerivedPathWithInfo
 {
     DerivedPath path;
-    ExtraPathInfo info;
+    ref<ExtraPathInfo> info;
 };
 
 struct BuiltPathWithResult
 {
     BuiltPath path;
-    ExtraPathInfo info;
+    ref<ExtraPathInfo> info;
     std::optional<BuildResult> result;
 };
 
@@ -86,11 +80,6 @@ struct Installable
         return {};
     }
 
-    virtual FlakeRef nixpkgsFlakeRef() const
-    {
-        return FlakeRef::fromAttrs({{"type","indirect"}, {"id", "nixpkgs"}});
-    }
-
     static std::vector<BuiltPathWithResult> build(
         ref<Store> evalStore,
         ref<Store> store,

src/nix/build.cc

@@ -1,4 +1,3 @@
-#include "eval.hh"
 #include "command.hh"
 #include "common-args.hh"
 #include "shared.hh"

src/nix/bundle.cc

@@ -5,6 +5,7 @@
 #include "store-api.hh"
 #include "local-fs-store.hh"
 #include "fs-accessor.hh"
+#include "eval-inline.hh"
 
 using namespace nix;
 

src/nix/develop.cc

@@ -1,6 +1,6 @@
 #include "eval.hh"
-#include "command.hh"
 #include "installable-flake.hh"
+#include "command-installable-value.hh"
 #include "common-args.hh"
 #include "shared.hh"
 #include "store-api.hh"
@@ -252,7 +252,7 @@ static StorePath getDerivationEnvironment(ref<Store> store, ref<Store> evalStore
     throw Error("get-env.sh failed to produce an environment");
 }
 
-struct Common : InstallableCommand, MixProfile
+struct Common : InstallableValueCommand, MixProfile
 {
     std::set<std::string> ignoreVars{
         "BASHOPTS",
@@ -374,7 +374,7 @@ struct Common : InstallableCommand, MixProfile
         return res;
     }
 
-    StorePath getShellOutPath(ref<Store> store, ref<Installable> installable)
+    StorePath getShellOutPath(ref<Store> store, ref<InstallableValue> installable)
     {
         auto path = installable->getStorePath();
         if (path && hasSuffix(path->to_string(), "-env"))
@@ -393,7 +393,7 @@ struct Common : InstallableCommand, MixProfile
     }
 
     std::pair<BuildEnvironment, std::string>
-    getBuildEnvironment(ref<Store> store, ref<Installable> installable)
+    getBuildEnvironment(ref<Store> store, ref<InstallableValue> installable)
     {
         auto shellOutPath = getShellOutPath(store, installable);
 
@@ -481,7 +481,7 @@ struct CmdDevelop : Common, MixEnvironment
           ;
     }
 
-    void run(ref<Store> store, ref<Installable> installable) override
+    void run(ref<Store> store, ref<InstallableValue> installable) override
     {
         auto [buildEnvironment, gcroot] = getBuildEnvironment(store, installable);
 
@@ -605,7 +605,7 @@ struct CmdPrintDevEnv : Common, MixJSON
 
     Category category() override { return catUtility; }
 
-    void run(ref<Store> store, ref<Installable> installable) override
+    void run(ref<Store> store, ref<InstallableValue> installable) override
     {
         auto buildEnvironment = getBuildEnvironment(store, installable).first;