From bd10a07d17161fb4a4e1af5aa365b23d405a5216 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 1 Apr 2020 23:03:27 +0200
Subject: [PATCH] Registry: Use a struct instead of a tuple for entries

---
 src/libfetchers/registry.cc | 37 +++++++++++++++++++++----------------
 src/libfetchers/registry.hh | 15 ++++++++-------
 src/nix/flake.cc            |  4 ++--
 3 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/src/libfetchers/registry.cc b/src/libfetchers/registry.cc
index 08dbe797e..6627d3725 100644
--- a/src/libfetchers/registry.cc
+++ b/src/libfetchers/registry.cc
@@ -44,9 +44,10 @@ std::shared_ptr<Registry> Registry::read(
                 toAttrs.erase(j);
             }
             registry->entries.push_back(
-                { inputFromAttrs(jsonToAttrs(i["from"]))
-                , inputFromAttrs(toAttrs)
-                , extraAttrs
+                Entry {
+                    .from = inputFromAttrs(jsonToAttrs(i["from"])),
+                    .to = inputFromAttrs(toAttrs),
+                    .extraAttrs = extraAttrs,
                 });
         }
     }
@@ -61,12 +62,12 @@ std::shared_ptr<Registry> Registry::read(
 void Registry::write(const Path & path)
 {
     nlohmann::json arr;
-    for (auto & elem : entries) {
+    for (auto & entry : entries) {
         nlohmann::json obj;
-        obj["from"] = attrsToJson(std::get<0>(elem)->toAttrs());
-        obj["to"] = attrsToJson(std::get<1>(elem)->toAttrs());
-        if (!std::get<2>(elem).empty())
-            obj["to"].update(attrsToJson(std::get<2>(elem)));
+        obj["from"] = attrsToJson(entry.from->toAttrs());
+        obj["to"] = attrsToJson(entry.to->toAttrs());
+        if (!entry.extraAttrs.empty())
+            obj["to"].update(attrsToJson(entry.extraAttrs));
         arr.emplace_back(std::move(obj));
     }
 
@@ -83,14 +84,19 @@ void Registry::add(
     const std::shared_ptr<const Input> & to,
     const Attrs & extraAttrs)
 {
-    entries.emplace_back(from, to, extraAttrs);
+    entries.emplace_back(
+        Entry {
+            .from = from,
+            .to = to,
+            .extraAttrs = extraAttrs
+        });
 }
 
 void Registry::remove(const std::shared_ptr<const Input> & input)
 {
     // FIXME: use C++20 std::erase.
     for (auto i = entries.begin(); i != entries.end(); )
-        if (*std::get<0>(*i) == *input)
+        if (*i->from == *input)
             i = entries.erase(i);
         else
             ++i;
@@ -179,12 +185,11 @@ std::pair<std::shared_ptr<const Input>, Attrs> lookupInRegistries(
     for (auto & registry : getRegistries(store)) {
         // FIXME: O(n)
         for (auto & entry : registry->entries) {
-            auto from = std::get<0>(entry);
-            if (from->contains(*input)) {
-                input = std::get<1>(entry)->applyOverrides(
-                    !from->getRef() && input->getRef() ? input->getRef() : std::optional<std::string>(),
-                    !from->getRev() && input->getRev() ? input->getRev() : std::optional<Hash>());
-                extraAttrs = std::get<2>(entry);
+            if (entry.from->contains(*input)) {
+                input = entry.to->applyOverrides(
+                    !entry.from->getRef() && input->getRef() ? input->getRef() : std::optional<std::string>(),
+                    !entry.from->getRev() && input->getRev() ? input->getRev() : std::optional<Hash>());
+                extraAttrs = entry.extraAttrs;
                 goto restart;
             }
         }
diff --git a/src/libfetchers/registry.hh b/src/libfetchers/registry.hh
index 5e8857850..722c41b10 100644
--- a/src/libfetchers/registry.hh
+++ b/src/libfetchers/registry.hh
@@ -18,13 +18,14 @@ struct Registry
 
     RegistryType type;
 
-    std::vector<
-        std::tuple<
-            std::shared_ptr<const Input>, // from
-            std::shared_ptr<const Input>, // to
-            Attrs // extra attributes
-            >
-        > entries;
+    struct Entry
+    {
+        std::shared_ptr<const Input> from;
+        std::shared_ptr<const Input> to;
+        Attrs extraAttrs;
+    };
+
+    std::vector<Entry> entries;
 
     Registry(RegistryType type)
         : type(type)
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 16b797de8..2b7497a84 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -71,8 +71,8 @@ struct CmdFlakeList : EvalCommand
                     registry->type == Registry::User   ? "user  " :
                     registry->type == Registry::System ? "system" :
                     "global",
-                    std::get<0>(entry)->to_string(),
-                    std::get<1>(entry)->to_string());
+                    entry.from->to_string(),
+                    entry.to->to_string());
             }
         }
     }