refactor some nix-env and profile code to libcmd

Notably, ProfileManifest and ProfileElement are useful generic
profile management code, and nix profile is not the only place in the
codebase where profiles are relevant.

This commit is in preparation for fixing upgrade-nix's interaction with
new-style profiles.

Change-Id: Iefc8bbd34b4bc6012175cb3d6e6a8207973bc792

4 files changed, 352 insertions, 2 deletions

diff --git a/src/libcmd/cmd-profiles.cc b/src/libcmd/cmd-profiles.cc
new file mode 100644
index 000000000..b487d2a77
--- /dev/null
+++ b/src/libcmd/cmd-profiles.cc
@@ -0,0 +1,277 @@
+#include "cmd-profiles.hh"
+#include "built-path.hh"
+#include "builtins/buildenv.hh"
+#include "names.hh"
+#include "store-api.hh"
+
+namespace nix
+{
+
+DrvInfos queryInstalled(EvalState & state, const Path & userEnv)
+{
+    DrvInfos elems;
+    if (pathExists(userEnv + "/manifest.json"))
+        throw Error("profile '%s' is incompatible with 'nix-env'; please use 'nix profile' instead", userEnv);
+    auto manifestFile = userEnv + "/manifest.nix";
+    if (pathExists(manifestFile)) {
+        Value v;
+        state.evalFile(state.rootPath(CanonPath(manifestFile)), v);
+        Bindings & bindings(*state.allocBindings(0));
+        getDerivations(state, v, "", bindings, elems, false);
+    }
+    return elems;
+}
+
+std::string showVersions(const std::set<std::string> & versions)
+{
+    if (versions.empty()) return "∅";
+    std::set<std::string> versions2;
+    for (auto & version : versions)
+        versions2.insert(version.empty() ? "ε" : version);
+    return concatStringsSep(", ", versions2);
+}
+
+bool ProfileElementSource::operator<(const ProfileElementSource & other) const
+{
+    return std::tuple(originalRef.to_string(), attrPath, outputs)
+        < std::tuple(other.originalRef.to_string(), other.attrPath, other.outputs);
+}
+
+std::string ProfileElementSource::to_string() const
+{
+    return fmt("%s#%s%s", originalRef, attrPath, outputs.to_string());
+}
+
+std::string ProfileElement::identifier() const
+{
+    if (source) {
+        return source->to_string();
+    }
+    StringSet names;
+    for (auto & path : storePaths) {
+        names.insert(DrvName(path.name()).name);
+    }
+    return concatStringsSep(", ", names);
+}
+
+std::set<std::string> ProfileElement::toInstallables(Store & store)
+{
+    if (source) {
+        return {source->to_string()};
+    }
+    StringSet rawPaths;
+    for (auto & path : storePaths) {
+        rawPaths.insert(store.printStorePath(path));
+    }
+    return rawPaths;
+}
+
+std::string ProfileElement::versions() const
+{
+    StringSet versions;
+    for (auto & path : storePaths) {
+        versions.insert(DrvName(path.name()).version);
+    }
+    return showVersions(versions);
+}
+
+bool ProfileElement::operator<(const ProfileElement & other) const
+{
+    return std::tuple(identifier(), storePaths) < std::tuple(other.identifier(), other.storePaths);
+}
+
+void ProfileElement::updateStorePaths(
+    ref<Store> evalStore, ref<Store> store, const BuiltPaths & builtPaths
+)
+{
+    storePaths.clear();
+    for (auto & buildable : builtPaths) {
+        std::visit(
+            overloaded{
+                [&](const BuiltPath::Opaque & bo) { storePaths.insert(bo.path); },
+                [&](const BuiltPath::Built & bfd) {
+                    for (auto & output : bfd.outputs) {
+                        storePaths.insert(output.second);
+                    }
+                },
+            },
+            buildable.raw()
+        );
+    }
+}
+
+ProfileManifest::ProfileManifest(EvalState & state, const Path & profile)
+{
+    auto manifestPath = profile + "/manifest.json";
+
+    if (pathExists(manifestPath)) {
+        auto json = nlohmann::json::parse(readFile(manifestPath));
+
+        auto version = json.value("version", 0);
+        std::string sUrl;
+        std::string sOriginalUrl;
+        switch (version) {
+        case 1:
+            sUrl = "uri";
+            sOriginalUrl = "originalUri";
+            break;
+        case 2:
+            sUrl = "url";
+            sOriginalUrl = "originalUrl";
+            break;
+        default:
+            throw Error("profile manifest '%s' has unsupported version %d", manifestPath, version);
+        }
+
+        for (auto & e : json["elements"]) {
+            ProfileElement element;
+            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]),
+                    parseFlakeRef(e[sUrl]),
+                    e["attrPath"],
+                    e["outputs"].get<ExtendedOutputsSpec>()};
+            }
+            elements.emplace_back(std::move(element));
+        }
+    }
+
+    else if (pathExists(profile + "/manifest.nix"))
+    {
+        // FIXME: needed because of pure mode; ugly.
+        state.allowPath(state.store->followLinksToStore(profile));
+        state.allowPath(state.store->followLinksToStore(profile + "/manifest.nix"));
+
+        auto drvInfos = queryInstalled(state, state.store->followLinksToStore(profile));
+
+        for (auto & drvInfo : drvInfos) {
+            ProfileElement element;
+            element.storePaths = {drvInfo.queryOutPath()};
+            elements.emplace_back(std::move(element));
+        }
+    }
+}
+
+nlohmann::json ProfileManifest::toJSON(Store & store) const
+{
+    auto array = nlohmann::json::array();
+    for (auto & element : elements) {
+        auto paths = nlohmann::json::array();
+        for (auto & path : element.storePaths) {
+            paths.push_back(store.printStorePath(path));
+        }
+        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->lockedRef.to_string();
+            obj["attrPath"] = element.source->attrPath;
+            obj["outputs"] = element.source->outputs;
+        }
+        array.push_back(obj);
+    }
+    nlohmann::json json;
+    json["version"] = 2;
+    json["elements"] = array;
+    return json;
+}
+
+StorePath ProfileManifest::build(ref<Store> store)
+{
+    auto tempDir = createTempDir();
+
+    StorePathSet references;
+
+    Packages pkgs;
+    for (auto & element : elements) {
+        for (auto & path : element.storePaths) {
+            if (element.active) {
+                pkgs.emplace_back(store->printStorePath(path), true, element.priority);
+            }
+            references.insert(path);
+        }
+    }
+
+    buildProfile(tempDir, std::move(pkgs));
+
+    writeFile(tempDir + "/manifest.json", toJSON(*store).dump());
+
+    /* Add the symlink tree to the store. */
+    StringSink sink;
+    dumpPath(tempDir, sink);
+
+    auto narHash = hashString(htSHA256, sink.s);
+
+    ValidPathInfo info{
+        *store,
+        "profile",
+        FixedOutputInfo{
+            .method = FileIngestionMethod::Recursive,
+            .hash = narHash,
+            .references =
+                {
+                    .others = std::move(references),
+                    // profiles never refer to themselves
+                    .self = false,
+                },
+        },
+        narHash,
+    };
+    info.narSize = sink.s.size();
+
+    StringSource source(sink.s);
+    store->addToStore(info, source);
+
+    return std::move(info.path);
+}
+
+void ProfileManifest::printDiff(
+    const ProfileManifest & prev, const ProfileManifest & cur, std::string_view indent
+)
+{
+    auto prevElems = prev.elements;
+    std::sort(prevElems.begin(), prevElems.end());
+
+    auto curElems = cur.elements;
+    std::sort(curElems.begin(), curElems.end());
+
+    auto i = prevElems.begin();
+    auto j = curElems.begin();
+
+    bool changes = false;
+
+    while (i != prevElems.end() || j != curElems.end()) {
+        if (j != curElems.end() && (i == prevElems.end() || i->identifier() > j->identifier())) {
+            logger->cout("%s%s: ∅ -> %s", indent, j->identifier(), j->versions());
+            changes = true;
+            ++j;
+        } else if (i != prevElems.end() && (j == curElems.end() || i->identifier() < j->identifier())) {
+            logger->cout("%s%s: %s -> ∅", indent, i->identifier(), i->versions());
+            changes = true;
+            ++i;
+        } else {
+            auto v1 = i->versions();
+            auto v2 = j->versions();
+            if (v1 != v2) {
+                logger->cout("%s%s: %s -> %s", indent, i->identifier(), v1, v2);
+                changes = true;
+            }
+            ++i;
+            ++j;
+        }
+    }
+
+    if (!changes) {
+        logger->cout("%sNo changes.", indent);
+    }
+}
+}
diff --git a/src/libcmd/cmd-profiles.hh b/src/libcmd/cmd-profiles.hh
new file mode 100644
index 000000000..d03f9b1c2
--- /dev/null
+++ b/src/libcmd/cmd-profiles.hh
@@ -0,0 +1,73 @@
+#pragma once
+///@file
+
+#include "built-path.hh"
+#include "eval.hh"
+#include "flake/flakeref.hh"
+#include "get-drvs.hh"
+#include "types.hh"
+
+#include <string>
+#include <set>
+
+#include <nlohmann/json.hpp>
+
+namespace nix
+{
+
+struct ProfileElementSource
+{
+    FlakeRef originalRef;
+    // FIXME: record original attrpath.
+    FlakeRef lockedRef;
+    std::string attrPath;
+    ExtendedOutputsSpec outputs;
+
+    bool operator<(const ProfileElementSource & other) const;
+
+    std::string to_string() const;
+};
+
+constexpr int DEFAULT_PRIORITY = 5;
+
+struct ProfileElement
+{
+    StorePathSet storePaths;
+    std::optional<ProfileElementSource> source;
+    bool active = true;
+    int priority = DEFAULT_PRIORITY;
+
+    std::string identifier() const;
+
+    /**
+     * Return a string representing an installable corresponding to the current
+     * element, either a flakeref or a plain store path
+     */
+    std::set<std::string> toInstallables(Store & store);
+
+    std::string versions() const;
+
+    bool operator<(const ProfileElement & other) const;
+
+    void updateStorePaths(ref<Store> evalStore, ref<Store> store, const BuiltPaths & builtPaths);
+};
+
+struct ProfileManifest
+{
+    std::vector<ProfileElement> elements;
+
+    ProfileManifest() { }
+
+    ProfileManifest(EvalState & state, const Path & profile);
+
+    nlohmann::json toJSON(Store & store) const;
+
+    StorePath build(ref<Store> store);
+
+    static void printDiff(const ProfileManifest & prev, const ProfileManifest & cur, std::string_view indent);
+};
+
+DrvInfos queryInstalled(EvalState & state, const Path & userEnv);
+std::string showVersions(const std::set<std::string> & versions);
+
+}
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 120c832ac..6c6c81718 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -342,8 +342,6 @@ void completeFlakeRefWithFragment(
     const Strings & defaultFlakeAttrPaths,
     std::string_view prefix);
 
-std::string showVersions(const std::set<std::string> & versions);
-
 void printClosureDiff(
     ref<Store> store,
     const StorePath & beforePath,
diff --git a/src/libcmd/meson.build b/src/libcmd/meson.build
index 6b1b44d84..5a0e61503 100644
--- a/src/libcmd/meson.build
+++ b/src/libcmd/meson.build
@@ -1,6 +1,7 @@
 libcmd_sources = files(
   'built-path.cc',
   'command-installable-value.cc',
+  'cmd-profiles.cc',
   'command.cc',
   'common-eval-args.cc',
   'editor-for.cc',
@@ -18,6 +19,7 @@ libcmd_sources = files(
 libcmd_headers = files(
   'built-path.hh',
   'command-installable-value.hh',
+  'cmd-profiles.hh',
   'command.hh',
   'common-eval-args.hh',
   'editor-for.hh',