[0002] Add autoCall helper function to package sets

eeps/0002-autocall-import.md

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+---
+Title: Add autoCall helper function to package sets
+Author: jonringer
+Discussions-To: https://github.com/NixOS/nixpkgs/pull/274179
+Status: Provisional
+Type: Standards Track
+Topic: Packaging
+Created: 2024-10-09
+---
+
+# Summary
+
+`callPackage` has been an immensely useful tool to reduce the amount of boilerplate
+needed to pass attrs to a nix expression. However, `callPackage` also universally
+applies `mkOverridable` to the result which adds both `.override` and
+`.overrideDerivation`. This isn't always desirable behavior, especially when
+the resulting attr set should be free of these continuations; for example,
+child package scope or partially applied functions. Omitting these attrs allows
+for slight eval performance wins, but also a better user experience when functions
+aren't expected in the resulting attr set.
+
+## Detailed Implementation
+
+See https://github.com/jonringer/nix-lib/pull/2 for implementation.
+
+## Trivial example
+
+```
+nix-repl> callPackage = customisation.callPackageWith { foo = "bar"; }
+
+nix-repl> autoCall = customisation.autoCallWith { foo = "bar"; }
+
+nix-repl> myFunc = { foo }: { inherit foo; }
+
+nix-repl> callPackage myFunc { }
+{ foo = "bar"; override = { ... }; overrideDerivation = «lambda @ /home/jon/projects/lib/customisation.nix:151:32»; }
+
+nix-repl> autoCall myFunc { }
+{ foo = "bar"; }
+```
+
+## Unresolved issues
+
+- Error messages are slightly less helpful now
+  - However, they previously were labeled as "callPackageWith" even though `callPackage` was used
+```
+nix-repl> autoCall ({ doesntExist }: "hi") { }
+error:
+       … from call site
+
+         at «string»:1:1:
+
+            1| autoCall ({ doesntExist }: "hi") { }
+             | ^
+
+       … while calling 'callGenericWith'
+
+         at /home/jon/projects/lib/customisation.nix:227:59:
+
+          226|   */
+          227|   callGenericWith = funcName: continuation: autoArgs: fn: args:
+             |                                                           ^
+          228|     let
+
+       error: evaluation aborted with the following error message: 'lib.customisation.autoCallWith: Function called without required argument "doesntExist" at <unknown location>'
+```
+
+- Should the name just use the function names most likely to be used by users?
+  - E.g. `error: evaluation aborted with the following error message: 'autoCall: Function called without required argument "doesntExist" at <unknown location>'`
+  - There isn't a strict correlation to what the partially applied function's name would be, however, in practice it almost always is supplied by `makeScope`
+
+## Meta concerns
+
+- Is there a better name than `autoCall`?
+  - This name plays on the theme of `makeScope` and `newScope` being used to provide a `autoCall`
+  - `callPackage` is "something when called, returns a package", so the analagous name would be `callAttSet` which doesn't feel as descriptive.
+- Similar name to `builtins.scopedImport`
+  - This is builtin is rarely used, and not even documented in the nix manual
+
+## Changes
+
+- Changed name from `scopeImprot` to `autoCall` to avoid confusion with `builtins.scopedImport`