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.

1 files changed, 26 insertions, 7 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)};