Add priority for nix profile install

src/libstore/builtins/buildenv.cc

@@ -93,8 +93,9 @@ static void createLinks(State & state, const Path & srcDir, const Path & dstDir,
                     auto prevPriority = state.priorities[dstFile];
                     if (prevPriority == priority)
                         throw Error(
-                                "packages '%1%' and '%2%' have the same priority %3%; "
+                                "files '%1%' and '%2%' have the same priority %3%; "
                                 "use 'nix-env --set-flag priority NUMBER INSTALLED_PKGNAME' "
+                                "or 'nix profile --priority NUMBER INSTALLED_PKGNAME' "
                                 "to change the priority of one of the conflicting packages"
                                 " (0 being the highest priority)",
                                 srcFile, readLink(dstFile), priority);

src/nix/profile.cc

@@ -37,7 +37,7 @@ struct ProfileElement
     StorePathSet storePaths;
     std::optional<ProfileElementSource> source;
     bool active = true;
-    // FIXME: priority
+    int priority = 5;
 
     std::string describe() const
     {
@@ -116,6 +116,9 @@ struct ProfileManifest
                 for (auto & p : e["storePaths"])
                     element.storePaths.insert(state.store->parseStorePath((std::string) p));
                 element.active = e["active"];
+                if(e.contains("priority")) {
+                    element.priority = e["priority"];
+                }
                 if (e.value(sUrl, "") != "") {
                     element.source = ProfileElementSource {
                         parseFlakeRef(e[sOriginalUrl]),
@@ -153,6 +156,7 @@ struct ProfileManifest
             nlohmann::json obj;
             obj["storePaths"] = paths;
             obj["active"] = element.active;
+            obj["priority"] = element.priority;
             if (element.source) {
                 obj["originalUrl"] = element.source->originalRef.to_string();
                 obj["url"] = element.source->resolvedRef.to_string();
@@ -177,7 +181,7 @@ struct ProfileManifest
         for (auto & element : elements) {
             for (auto & path : element.storePaths) {
                 if (element.active)
-                    pkgs.emplace_back(store->printStorePath(path), true, 5);
+                    pkgs.emplace_back(store->printStorePath(path), true, element.priority);
                 references.insert(path);
             }
         }
@@ -259,6 +263,23 @@ builtPathsPerInstallable(
 
 struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
 {
+    std::optional<int> priority;
+    CmdProfileInstall() {
+        addFlag({
+            .longName = "priority",
+            .description = "The priority of the package to install.",
+            .labels = {"priority"},
+            .handler = {[&](std::string s) { 
+                try{
+                    priority = std::stoi(s);
+                } catch (std::invalid_argument & e) {
+                    throw ParseError("invalid priority '%s'", s);
+                }
+            }},
+            // .completer = // no completer since number
+        });
+    };
+
     std::string description() override
     {
         return "install a package into a profile";
@@ -282,6 +303,10 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
         for (auto & installable : installables) {
             ProfileElement element;
 
+            if(priority) {
+                element.priority = *priority;
+            };
+
             if (auto installable2 = std::dynamic_pointer_cast<InstallableFlake>(installable)) {
                 // FIXME: make build() return this?
                 auto [attrPath, resolvedRef, drv] = installable2->toDerivation();

tests/nix-profile.sh

@@ -120,3 +120,19 @@ nix profile install "$flake1Dir^man"
 (! [ -e $TEST_HOME/.nix-profile/bin/hello ])
 [ -e $TEST_HOME/.nix-profile/share/man ]
 (! [ -e $TEST_HOME/.nix-profile/include ])
+
+# test priority
+nix profile remove 0
+
+# Make another flake.
+flake2Dir=$TEST_ROOT/flake2
+printf World > $flake1Dir/who
+cp -r $flake1Dir $flake2Dir
+printf World2 > $flake2Dir/who
+
+nix profile install $flake1Dir
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+nix profile install $flake2Dir --priority 100
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+nix profile install $flake2Dir --priority 0
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World2" ]]