nix: Respect meta.outputsToInstall, and use all outputs by default

'nix profile install' will now install all outputs listed in the
package's meta.outputsToInstall attribute, or all outputs if that
attribute doesn't exist. This makes it behave consistently with
nix-env. Fixes #6385.

Furthermore, for consistency, all other 'nix' commands do this as
well. E.g. 'nix build' will build and symlink the outputs in
meta.outputsToInstall, defaulting to all outputs. Previously, it only
built/symlinked the first output. Note that this means that selecting
a specific output using attrpath selection (e.g. 'nix build
nixpkgs#libxml2.dev') no longer works. A subsequent PR will add a way
to specify the desired outputs explicitly.

10 files changed, 96 insertions, 27 deletions

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index e3210d18d..e2ee47dea 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -440,10 +440,8 @@ DerivedPaths InstallableValue::toDerivedPaths()
 
     // Group by derivation, helps with .all in particular
     for (auto & drv : toDerivations()) {
-        auto outputName = drv.outputName;
-        if (outputName == "")
-            throw Error("derivation '%s' lacks an 'outputName' attribute", state->store->printStorePath(drv.drvPath));
-        drvsToOutputs[drv.drvPath].insert(outputName);
+        for (auto & outputName : drv.outputsToInstall)
+            drvsToOutputs[drv.drvPath].insert(outputName);
         drvsToCopy.insert(drv.drvPath);
     }
 
@@ -497,7 +495,13 @@ std::vector<InstallableValue::DerivationInfo> InstallableAttrPath::toDerivations
         auto drvPath = drvInfo.queryDrvPath();
         if (!drvPath)
             throw Error("'%s' is not a derivation", what());
-        res.push_back({ *drvPath, drvInfo.queryOutputName() });
+        std::set<std::string> outputsToInstall;
+        for (auto & output : drvInfo.queryOutputs(false, true))
+            outputsToInstall.insert(output.first);
+        res.push_back(DerivationInfo {
+            .drvPath = *drvPath,
+            .outputsToInstall = std::move(outputsToInstall)
+        });
     }
 
     return res;
@@ -598,9 +602,24 @@ std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableF
 
     auto drvPath = attr->forceDerivation();
 
+    std::set<std::string> outputsToInstall;
+
+    if (auto aMeta = attr->maybeGetAttr(state->sMeta))
+        if (auto aOutputsToInstall = aMeta->maybeGetAttr("outputsToInstall"))
+            for (auto & s : aOutputsToInstall->getListOfStrings())
+                outputsToInstall.insert(s);
+
+    if (outputsToInstall.empty())
+        if (auto aOutputs = attr->maybeGetAttr(state->sOutputs))
+            for (auto & s : aOutputs->getListOfStrings())
+                outputsToInstall.insert(s);
+
+    if (outputsToInstall.empty())
+        outputsToInstall.insert("out");
+
     auto drvInfo = DerivationInfo {
-        std::move(drvPath),
-        attr->getAttr(state->sOutputName)->getString()
+        .drvPath = std::move(drvPath),
+        .outputsToInstall = std::move(outputsToInstall),
     };
 
     return {attrPath, getLockedFlake()->flake.lockedRef, std::move(drvInfo)};
diff --git a/src/libcmd/installables.hh b/src/libcmd/installables.hh
index de8b08525..3c2c33549 100644
--- a/src/libcmd/installables.hh
+++ b/src/libcmd/installables.hh
@@ -141,7 +141,7 @@ struct InstallableValue : Installable
     struct DerivationInfo
     {
         StorePath drvPath;
-        std::string outputName;
+        std::set<std::string> outputsToInstall;
     };
 
     virtual std::vector<DerivationInfo> toDerivations() = 0;
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index 6fb4bf266..3a92f2815 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -175,6 +175,24 @@ struct AttrDb
         });
     }
 
+    AttrId setListOfStrings(
+        AttrKey key,
+        const std::vector<std::string> & l)
+    {
+        return doSQLite([&]()
+        {
+            auto state(_state->lock());
+
+            state->insertAttribute.use()
+                (key.first)
+                (symbols[key.second])
+                (AttrType::ListOfStrings)
+                (concatStringsSep("\t", l)).exec();
+
+            return state->db.getLastInsertedRowId();
+        });
+    }
+
     AttrId setPlaceholder(AttrKey key)
     {
         return doSQLite([&]()
@@ -269,6 +287,8 @@ struct AttrDb
             }
             case AttrType::Bool:
                 return {{rowId, queryAttribute.getInt(2) != 0}};
+            case AttrType::ListOfStrings:
+                return {{rowId, tokenizeString<std::vector<std::string>>(queryAttribute.getStr(2), "\t")}};
             case AttrType::Missing:
                 return {{rowId, missing_t()}};
             case AttrType::Misc:
@@ -385,7 +405,7 @@ std::string AttrCursor::getAttrPathStr(Symbol name) const
 
 Value & AttrCursor::forceValue()
 {
-    debug("evaluating uncached attribute %s", getAttrPathStr());
+    debug("evaluating uncached attribute '%s'", getAttrPathStr());
 
     auto & v = getValue();
 
@@ -601,6 +621,38 @@ bool AttrCursor::getBool()
     return v.boolean;
 }
 
+std::vector<std::string> AttrCursor::getListOfStrings()
+{
+    if (root->db) {
+        if (!cachedValue)
+            cachedValue = root->db->getAttr(getKey());
+        if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
+            if (auto l = std::get_if<std::vector<std::string>>(&cachedValue->second)) {
+                debug("using cached list of strings attribute '%s'", getAttrPathStr());
+                return *l;
+            } else
+                throw TypeError("'%s' is not a list of strings", getAttrPathStr());
+        }
+    }
+
+    debug("evaluating uncached attribute '%s'", getAttrPathStr());
+
+    auto & v = getValue();
+    root->state.forceValue(v, noPos);
+
+    if (v.type() != nList)
+        throw TypeError("'%s' is not a list", getAttrPathStr());
+
+    std::vector<std::string> res;
+
+    for (auto & elem : v.listItems())
+        res.push_back(std::string(root->state.forceStringNoCtx(*elem)));
+
+    cachedValue = {root->db->setListOfStrings(getKey(), res), res};
+
+    return res;
+}
+
 std::vector<Symbol> AttrCursor::getAttrs()
 {
     if (root->db) {
diff --git a/src/libexpr/eval-cache.hh b/src/libexpr/eval-cache.hh
index b0709ebc2..636e293ad 100644
--- a/src/libexpr/eval-cache.hh
+++ b/src/libexpr/eval-cache.hh
@@ -44,6 +44,7 @@ enum AttrType {
     Misc = 4,
     Failed = 5,
     Bool = 6,
+    ListOfStrings = 7,
 };
 
 struct placeholder_t {};
@@ -61,7 +62,8 @@ typedef std::variant<
     missing_t,
     misc_t,
     failed_t,
-    bool
+    bool,
+    std::vector<std::string>
     > AttrValue;
 
 class AttrCursor : public std::enable_shared_from_this<AttrCursor>
@@ -114,6 +116,8 @@ public:
 
     bool getBool();
 
+    std::vector<std::string> getListOfStrings();
+
     std::vector<Symbol> getAttrs();
 
     bool isDerivation();
diff --git a/src/nix/app.cc b/src/nix/app.cc
index cce84d026..821964f86 100644
--- a/src/nix/app.cc
+++ b/src/nix/app.cc
@@ -89,7 +89,7 @@ UnresolvedApp Installable::toApp(EvalState & state)
         auto outputName = cursor->getAttr(state.sOutputName)->getString();
         auto name = cursor->getAttr(state.sName)->getString();
         auto aPname = cursor->maybeGetAttr("pname");
-        auto aMeta = cursor->maybeGetAttr("meta");
+        auto aMeta = cursor->maybeGetAttr(state.sMeta);
         auto aMainProgram = aMeta ? aMeta->maybeGetAttr("mainProgram") : nullptr;
         auto mainProgram =
             aMainProgram
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 040c1c7af..6a34ca67b 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -1015,8 +1015,8 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                     auto name = visitor.getAttr(state->sName)->getString();
                     if (json) {
                         std::optional<std::string> description;
-                        if (auto aMeta = visitor.maybeGetAttr("meta")) {
-                            if (auto aDescription = aMeta->maybeGetAttr("description"))
+                        if (auto aMeta = visitor.maybeGetAttr(state->sMeta)) {
+                            if (auto aDescription = aMeta->maybeGetAttr(state->sDescription))
                                 description = aDescription->getString();
                         }
                         j.emplace("type", "derivation");
diff --git a/src/nix/search.cc b/src/nix/search.cc
index 76451f810..87dc1c0de 100644
--- a/src/nix/search.cc
+++ b/src/nix/search.cc
@@ -93,10 +93,10 @@ struct CmdSearch : InstallableCommand, MixJSON
                 };
 
                 if (cursor.isDerivation()) {
-                    DrvName name(cursor.getAttr("name")->getString());
+                    DrvName name(cursor.getAttr(state->sName)->getString());
 
-                    auto aMeta = cursor.maybeGetAttr("meta");
-                    auto aDescription = aMeta ? aMeta->maybeGetAttr("description") : nullptr;
+                    auto aMeta = cursor.maybeGetAttr(state->sMeta);
+                    auto aDescription = aMeta ? aMeta->maybeGetAttr(state->sDescription) : nullptr;
                     auto description = aDescription ? aDescription->getString() : "";
                     std::replace(description.begin(), description.end(), '\n', ' ');
                     auto attrPath2 = concatStringsSep(".", attrPathS);
diff --git a/tests/build.sh b/tests/build.sh
index 13a0f42be..339155991 100644
--- a/tests/build.sh
+++ b/tests/build.sh
@@ -2,15 +2,8 @@ source common.sh
 
 clearStore
 
-# Make sure that 'nix build' only returns the outputs we asked for.
-nix build -f multiple-outputs.nix --json a --no-link | jq --exit-status '
-  (.[0] |
-    (.drvPath | match(".*multiple-outputs-a.drv")) and
-    (.outputs | keys | length == 1) and
-    (.outputs.first | match(".*multiple-outputs-a-first")))
-'
-
-nix build -f multiple-outputs.nix --json a.all b.all --no-link | jq --exit-status '
+# Make sure that 'nix build' returns all outputs by default.
+nix build -f multiple-outputs.nix --json a b --no-link | jq --exit-status '
   (.[0] |
     (.drvPath | match(".*multiple-outputs-a.drv")) and
     (.outputs | keys | length == 2) and
diff --git a/tests/ca/content-addressed.nix b/tests/ca/content-addressed.nix
index 1be3eeb6e..31c144ae0 100644
--- a/tests/ca/content-addressed.nix
+++ b/tests/ca/content-addressed.nix
@@ -23,7 +23,7 @@ rec {
   };
   rootCA = mkCADerivation {
     name = "rootCA";
-    outputs = [ "out" "dev" "foo"];
+    outputs = [ "out" "dev" "foo" ];
     buildCommand = ''
       echo "building a CA derivation"
       echo "The seed is ${toString seed}"
diff --git a/tests/ca/substitute.sh b/tests/ca/substitute.sh
index 3d9001bb8..819f3fd85 100644
--- a/tests/ca/substitute.sh
+++ b/tests/ca/substitute.sh
@@ -25,7 +25,8 @@ buildDrvs --substitute --substituters $REMOTE_STORE --no-require-sigs -j0 transi
 # Check that the thing we’ve just substituted has its realisation stored
 nix realisation info --file ./content-addressed.nix transitivelyDependentCA
 # Check that its dependencies have it too
-nix realisation info --file ./content-addressed.nix dependentCA rootCA
+nix realisation info --file ./content-addressed.nix dependentCA
+# nix realisation info --file ./content-addressed.nix rootCA --outputs out
 
 # Same thing, but
 # 1. With non-ca derivations