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.

2 files changed, 58 insertions, 2 deletions

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();