Pluggable fetchers

Flakes are now fetched using an extensible mechanism. Also lots of
other flake cleanups.

1 files changed, 56 insertions, 0 deletions

diff --git a/src/libstore/fetchers/fetchers.cc b/src/libstore/fetchers/fetchers.cc
new file mode 100644
index 000000000..7f82d5af0
--- /dev/null
+++ b/src/libstore/fetchers/fetchers.cc
@@ -0,0 +1,56 @@
+#include "fetchers.hh"
+#include "parse.hh"
+#include "store-api.hh"
+
+namespace nix::fetchers {
+
+std::unique_ptr<std::vector<std::unique_ptr<InputScheme>>> inputSchemes = nullptr;
+
+void registerInputScheme(std::unique_ptr<InputScheme> && inputScheme)
+{
+    if (!inputSchemes) inputSchemes = std::make_unique<std::vector<std::unique_ptr<InputScheme>>>();
+    inputSchemes->push_back(std::move(inputScheme));
+}
+
+std::unique_ptr<Input> inputFromURL(const ParsedURL & url)
+{
+    for (auto & inputScheme : *inputSchemes) {
+        auto res = inputScheme->inputFromURL(url);
+        if (res) return res;
+    }
+    throw Error("input '%s' is unsupported", url.url);
+}
+
+std::unique_ptr<Input> inputFromURL(const std::string & url)
+{
+    return inputFromURL(parseURL(url));
+}
+
+std::pair<Tree, std::shared_ptr<const Input>> Input::fetchTree(ref<Store> store) const
+{
+    auto [tree, input] = fetchTreeInternal(store);
+
+    if (tree.actualPath == "")
+        tree.actualPath = store->toRealPath(store->printStorePath(tree.storePath));
+
+    if (!tree.narHash)
+        tree.narHash = store->queryPathInfo(tree.storePath)->narHash;
+
+    if (input->narHash)
+        assert(input->narHash == tree.narHash);
+
+    return {std::move(tree), input};
+}
+
+std::shared_ptr<const Input> Input::applyOverrides(
+    std::optional<std::string> ref,
+    std::optional<Hash> rev) const
+{
+    if (ref)
+        throw Error("don't know how to apply '%s' to '%s'", *ref, to_string());
+    if (rev)
+        throw Error("don't know how to apply '%s' to '%s'", rev->to_string(Base16, false), to_string());
+    return shared_from_this();
+}
+
+}