docs: migrate docs from drv-parts

docs/src/SUMMARY.md

@@ -1,7 +1,8 @@
 
 - [Introduction](./intro.md)
-# dream2nix concept
-- [draft for modules based API](./v1-api/summary.md)
+# concepts
+- [dream2nix modules](./modules.md)
+- [DRAFT (outdated): modules based API](./v1-api/summary.md)
   - [problems of the legacy dream2nix](./v1-api/problems.md)
   - [users of dream2nix](./v1-api/users.md)
   - [v1 packaging: project initialization](./v1-api/packaging/nodejs-init-project.md)

docs/src/modules.md

@@ -0,0 +1,111 @@
+# Why Modules?
+
+Declaring derivations as modules solves a number of issues.
+For more details on the problems, visit [DavHau/pkgs-modules](https://github.com/DavHau/pkgs-modules).
+Also I recommend watching @edolstra 's [talk about this topic](https://www.youtube.com/watch?v=dTd499Y31ig).
+
+# Benefits
+
+## Deprecate override functions
+
+Changing options of packages in nixpkgs can require chaining different override functions like this:
+
+```nix
+{
+  htop-mod = let
+    htop-overridden = pkgs.htop.overrideAttrs (old: {
+      pname = "htop-mod";
+    });
+  in
+    htop-overridden.override (old: {
+      sensorsSupport = false;
+    });
+}
+```
+
+... while doing the same using `dream2nix` looks like this:
+
+```nix
+{
+  htop-mod = {
+    imports = [./htop.nix];
+    name = lib.mkForce "htop-mod";
+    flags.sensorsSupport = false;
+  };
+}
+```
+
+See htop module definition [here](https://github.com/nix-community/dream2nix/blob/main/examples/dream2nix-packages/htop-with-flags/default.nix).
+
+## Type safety
+
+The following code in nixpkgs mkDerivation mysteriously skips the patches:
+
+```nix
+mkDerivation {
+  # ...
+  dontPatch = "false";
+}
+```
+
+... while doing the same using `dream2nix` raises an informative type error:
+
+```
+A definition for option `[...].dontPatch' is not of type `boolean' [...]
+```
+
+## Catch typos
+
+The following code in nixpkgs mkDerivation builds **without** openssl_3.
+
+```nix
+mkDerivation {
+  # ...
+  nativBuildInputs = [openssl_3];
+}
+```
+
+... while doing the same using `dream2nix` raises an informative error:
+
+```
+The option `[...].nativBuildInputs' does not exist
+```
+
+## Environment variables clearly defined
+
+`dream2nix` requires a clear distinction between known parameters and user-defined variables.
+Defining `SOME_VARIABLE` at the top-level, would raise:
+
+```
+The option `[...].SOME_VARIABLE' does not exist
+```
+
+Instead it has to be defined under `env.`:
+
+```nix
+{
+  my-package = {
+    # ...
+    env.SOME_VARIABLE = "example";
+  };
+}
+```
+
+## Documentaiton / Discoverability
+
+No more digging the source code to find possible options to override.
+
+Documentation similar to [search.nixos.org](https://search.nixos.org) can be generated for packages declared via `dream2nix`.
+
+Every package built with `dream2nix` has a `.docs` attribute that builds an html documentation describing it's options.
+
+## Package blueprints
+
+With `dream2nix`, packages don't need to be fully declared. Options can be left without defaults, requiring the consumer to complete the definition.
+
+For example, this can be useful for lang2nix tools, where `src` and `version` are dynamically provided by a lock file parser.
+
+## Flexibility
+
+The nixos module system gives maintainers more freedom over how packages are split into modules. Separation of concerns can be implemented more easily.
+For example, the dependency tree of a package set can be factored out into a separate module, allowing for simpler modification.

docs/src/v1-api/summary.md

@@ -1,5 +1,7 @@
 # dream2nix v1 API
 
+!!! This document does not resemble the current API of dream2nix. It is only a draft and the real implementation differs. More docs will follow.
+
 - [problems of the current dream2nix](../v1-api/problems.md)
 - [users of dream2nix](../v1-api/users.md)
 - v1 API examples:

flake.nix

@@ -77,6 +77,7 @@
 
           packages = [
             pkgs.alejandra
+            pkgs.mdbook
             (pkgs.python3.withPackages (ps: [
               pkgs.python3.pkgs.black
             ]))