Merge c3bdc8d892 into c655bdaab4

rfcs/0123-flake-names.md

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+---
+feature: flake-names
+start-date: 2022-03-12
+author: Anselm Schüler
+co-authors: None
+shepherd-team: None
+shepherd-leader: None
+related-issues: None
+---
+
+# Summary
+[summary]: #summary
+
+Flakes can declare the field `name`.  
+It represents the name of the flake.  
+The store paths corresponding to a flake source are no longer called `source`, but use the flake name.
+
+# Motivation
+[motivation]: #motivation
+
+- Flakes generate store paths named “source”, and it’s difficult to navigate this when manually inspecting the store.
+- This metadata can be used to make flakes more approachable and usable, in particular, it can be output instead or with the URI, making the nix commands friendlier.
+
+# Detailed design
+[design]: #detailed-design
+
+A new supported property for flakes is introduced, `name`.  
+The derivation that contains the flake’s content is called `flake-source-${name}`  
+
+# Examples and Interactions
+[examples-and-interactions]: #examples-and-interactions
+
+Running `nix flake metadata` on a flake that declares this field displays it at the top.  
+Running `nix flake show` on a flake that declares this field shows the name instead of the URL, followed by the URL in parentheses.
+
+Examples:
+
+File `/example/flake.nix`
+```nix
+{
+  name = "example";
+  outputs = { ... }: {
+    lib.example = "example";
+  };
+}
+```
+
+Shell
+```console
+$ nix eval git+file:///example
+[…] copying flake-source-example
+"example"
+```
+
+Example of interactions:
+
+Shell (using the previous file)
+```
+$ nix flake metadata /example
+Name:          example
+Resolved URL:  git+file:///example
+Locked URL:    …
+$ nix flake show /example
+example (git+file:///home/anselmschueler/Code/example?rev=b0&rev=c714c8624f5d49a9d88e6e24550dd88515923c18)
+└───lib: unknown
+```
+
+# Drawbacks
+[drawbacks]: #drawbacks
+
+- This may cause clutter and additional maintenance.
+- Since this changes the output of nix flake metadata and nix flake show, it might cause scripts that read this output to break.
+- This requires a significant change to the way flakes are handled.
+- This treats the Nix store as a user-facing part of Nix, which is generally not intended.
+
+# Alternatives
+[alternatives]: #alternatives
+
+- Flake names could be handled entirely through outside means, with things like the global registry merely pointing to flakes under names.
+
+# Unresolved questions
+[unresolved]: #unresolved-questions
+
+- The name scheme could be changed. `flake-source-${name}` could be too long. Alternatives include `source-${name}`.
+- The interactions with nix flake metadata and nix flake show are not critical to the design, which is mostly aimed at clarifying derivation names.
+
+# Future work
+[future]: #future-work
+
+- Flake usability can be improved.
+- Issues with indicipherable derivations named “source” also exist elsewhere.