Add some internal documentation for flake support objects.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/libfetchers/fetchers.hh b/src/libfetchers/fetchers.hh
index 89b1e6e7d..f361edf17 100644
--- a/src/libfetchers/fetchers.hh
+++ b/src/libfetchers/fetchers.hh
@@ -21,6 +21,13 @@ struct Tree
 
 struct InputScheme;
 
+// The Input object is generated by a specific fetcher, based on the
+// user-supplied input attribute in the flake.nix file, and contians
+// the information that the specific fetcher needs to perform the
+// actual fetch.  The Input object is most commonly created via the
+// "fromURL()" or "fromAttrs()" static functions which are provided the
+// url or attrset specified in the flake file.
+
 struct Input
 {
     friend struct InputScheme;
@@ -82,6 +89,15 @@ public:
     std::optional<time_t> getLastModified() const;
 };
 
+
+// The InputScheme represents a type of fetcher.  Each fetcher
+// registers with nix at startup time.  When processing an input for a
+// flake, each scheme is given an opportunity to "recognize" that
+// input from the url or attributes in the flake file's specification
+// and return an Input object to represent the input if it is
+// recognized.  The Input object contains the information the fetcher
+// needs to actually perform the "fetch()" when called.
+
 struct InputScheme
 {
     virtual std::optional<Input> inputFromURL(const ParsedURL & url) = 0;