Generate flake.nix from module options. Discussions: https://oeiuwq.zulipchat.com/join/nqp26cd4kngon6mo3ncgnuap/
dendrix.oeiuwq.com/Dendritic.html
dendritic
nix
inputs
bootstrap command for traditional flakes. (#82)
authored by
GitHub
bfe0475f
f18f9bad
+106
-152
+19
-4
.github/workflows/flake-check.yaml
+19
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.github/workflows/flake-check.yaml
···
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templates=$(find templates -mindepth 2 -maxdepth 2 -name flake.nix -print0 | xargs -0 dirname | xargs -n 1 basename | jq -R | jq -sc)
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echo "$templates"
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echo "templates=$templates" >> $GITHUB_OUTPUT
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bootstrap:
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name: Bootstrap
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bootstrap-command:
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name: Bootstrap command
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runs-on: ubuntu-latest
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env:
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NIX_PATH: "nixpkgs=https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz"
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steps:
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- uses: wimpysworld/nothing-but-nix@main
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- uses: cachix/install-nix-action@v31
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- uses: DeterminateSystems/magic-nix-cache-action@main
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- uses: actions/checkout@v4
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- run: echo '{ }' > flake.nix
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- run: nix-shell "https://github.com/$GITHUB_REPOSITORY/archive/$GITHUB_SHA.zip" -A flake-file.sh --run bootstrap
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- run: cat flake.nix flake-file.nix
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- run: grep inputs.flake-file.flakeModules.flake flake.nix
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- run: grep github:vic/flake-file flake.nix
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bootstrap-tests:
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name: Bootstrap apps
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runs-on: ubuntu-latest
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env:
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NIX_PATH: "nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz"
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NIX_PATH: "nixpkgs=https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz"
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steps:
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- uses: wimpysworld/nothing-but-nix@main
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- uses: cachix/install-nix-action@v31
···
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sed -i 's/# flake-file = import/flake-file = import/' default.nix
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nix-shell . -A flake-file.sh --run write-nixlock
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dev:
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needs: [bootstrap, nix-fmt]
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needs: [bootstrap-command, bootstrap-tests, nix-fmt]
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name: Check flake dev
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runs-on: ubuntu-latest
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steps:
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README.md
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README.md
+2
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docs/src/content/docs/index.mdx
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docs/src/content/docs/index.mdx
···
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**A**: It's a subset of Nix that doesn't allow computation in the flake metadata attributes.
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</Aside>
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### [Single Step Adoption](https://flake-file.oeiuwq.com/tutorials/migrate-traditional-flake/)
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#### [Try It Now!](https://flake-file.oeiuwq.com/tutorials/migrate-traditional-flake/)
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```shell
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mv flake.nix flake-file.nix
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nix-shell https://github.com/vic/flake-file/archive/main.tar.gz \
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-A flake-file.sh --run write-flake \
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--arg modules ./flake-file.nix --argstr outputs flake-file
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nix-shell https://github.com/vic/flake-file/archive/main.tar.gz -A flake-file.sh --run bootstrap
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```
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### Features
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docs/src/content/docs/tutorials/migrate-traditional-flake.mdx
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docs/src/content/docs/tutorials/migrate-traditional-flake.mdx
···
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import { Aside } from '@astrojs/starlight/components';
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-
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Suppose you have a flake that looks like:
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```nix
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# flake.nix
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{
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inputs = { # So much inputs
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nixpkgs.url = "github:nixos/nixpkgs/unstable";
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foo.url = "github:coolguy/foo";
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bar.url = "github:coolguy/bar";
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};
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outputs = inputs: { ... }; # wow! very outputs
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}
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```
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## Boostraping flake-file
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First, move your `flake.nix` file as `flake-file.nix`.
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## The bootstrap magic step.
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```shell
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mv flake.nix flake-file.nix
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nix-shell https://github.com/vic/flake-file/archive/main.tar.gz -A flake-file.sh --run bootstrap
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```
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And now, the bootstrapping magic step:
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## The new `flake.nix` (static Nix)
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```shell
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nix-shell https://github.com/vic/flake-file/archive/main.tar.gz \
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-A flake-file.sh --run write-flake \
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--arg modules ./flake-file.nix --argstr outputs flake-file
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```
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You will notice your **new** `flake.nix` has your same meta-data: `inputs`, `description`, `nixConfig`. Only the `outputs` function was changed.
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> <small>See also: all [bootstrap command args](/reference/bootstrap)</small>
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<img src="https://i.kym-cdn.com/photos/images/newsfeed/001/449/977/aba.gif" />
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And the `outputs` function treats your `flake-file.nix` - your original flake.nix file -
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as an ordinary Nix module. No changes required on your existing Nix logic.
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## The new `flake.nix` (static Nix)
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## Your `flake-file.nix` (non-static **real** Nix)
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You will notice your new `flake.nix` looks like this:
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Your inputs and all other flake meta-data are now module options (`flake-file.inputs`, etc).
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```diff lang="nix" "(A)" "(B)" "(C)" "(D)"
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# flake.nix
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# DO-NOT-EDIT. This file was auto-generated using github:vic/flake-file. (A)
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# Use `nix run .#write-flake` to regenerate it. (D)
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{
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outputs = inputs: (import ./flake-file.nix).outputs inputs; # (B)
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inputs = {
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# (C) all your inputs (static version)
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};
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}
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```
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<strong>(A)</strong> The `--arg modules ./flake-file.nix` option indicates
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the module entry-point. Your old flake is **already** a module for flake-file.
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`flake.nix` is a generated static asset intended for code distribution.
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<strong>(B)</strong> The `--argstr outputs flake-file` generated
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an `outputs` function that just **delegates** to the one in `flake-file.nix`.
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## Output Schemas
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<strong>(C)</strong> Your `inputs` are now the **static** version (Nix subset)
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of the **real Nix** inputs at your `flake-file.nix` file.
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Your outputs are now freeform types but can also be validated by **output schemas**.
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And they work with **any** Nix implementation: Lix, CppNix, DetSys, etc.
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## Edit `flake-file.nix` (real Nix)
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Add the following `flake-file.outputs-schema` to your `flake-file.nix` and then
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run `nix flake check`, then try replacing `mundo` by `world`.
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Now that `flake-file.nix` is real Nix code, you can refactor your inputs code
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to your heart's content.
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No extra check-derivation was needed, no custom nix-implementation,
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the checks are by the Nix module system as normal.
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```nix
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# flake-file.nix
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# Now with more and **real** Nix
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let
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# for example purposes
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gh = user: repo: branch: "github:${user}/${repo}/${branch}";
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{
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outputs = inputs: { hello = "mundo"; };
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coolguy = repo: gh "coolguy" repo "main";
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channel = "unstable";
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in {
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inputs = {
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nixpkgs.url = gh "nixos" "nixpkgs" channel;
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foo.url = coolguy "foo";
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bar.url = coolguy "bar";
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flake-file.outputs-schema = { lib, ... }: {
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options.hello = lib.mkOption {
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type = lib.types.enum [ "mundo" ];
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};
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};
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outputs = inputs: { ... }; # keeps the same
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}
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```
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## Update static from dynamic Nix.
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## Update `flake.nix`
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Run the **same** command again, your input changes will be reflected into
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You can run the **bootstrap** command whenever you want.
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When your input changes, run it again to propagate your input changes into
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the **static** `flake.nix`.
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```shell
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nix-shell https://github.com/vic/flake-file/archive/main.tar.gz \
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-A flake-file.sh --run write-flake \
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--arg modules ./flake-file.nix --argstr outputs flake-file
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nix-shell https://github.com/vic/flake-file/archive/main.zip -A flake-file.sh --run bootstrap
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```
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<Aside title="You are done!">
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You can stop here and enjoy your dynamic inputs at `flake-file.nix`.
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Simply run the same bootstrap command whenever inputs change.
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</Aside>
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## Moving into a module-based flake.
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<strong>(D)</strong> You might have noticed the comment about the `.#write-flake` app.
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To include this app as part of your flake and not having use the bootstrap command
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and specify all the same options each time, you need:
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Use `flake-module` outputs instead of `flake-file` on the bootstrap command:
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```shell ins="flake-module"
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nix-shell https://github.com/vic/flake-file/archive/main.tar.gz \
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-A flake-file.sh --run write-flake \
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--arg modules ./flake-file.nix --argstr outputs flake-module
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```
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Add options to your `flake-file.nix` **module**. I told you it was a module already.
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```diff lang="nix" "resolved flake inputs" " inputs =" "flake-file.inputs option" "inputs," " outputs =" "type-checked schema" ins="flake-module"
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# flake-file.nix
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+ { inputs, lib, ... }: # resolved flake inputs as specialArgs
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let
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# same helper code as before
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in
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{
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# same inputs code as before
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inputs = { # Alias option for flake-file.inputs type-checked schema!
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# make sure you add flake-file dependency.
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+ flake-file.url = lib.mkDefault "github:vic/flake-file";
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};
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# same outputs code as before
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outputs = inputs: ...; # Now with **extensible** type-checked schema!
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# since this IS a module it can import other modules
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imports = [
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# enable inside-flake and say goodbye to bootstrap
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+ inputs.flake-file.flakeModule
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# start splitting from huge monolithic code to modular nix.
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# each input can be defined on their relevant module files.
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# maybe move outputs function to ./outputs.nix
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];
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# generate the same output function we used at bootstrap
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+ flake-file.outputs = "flake-module";
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}
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```
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## Your flake is flake-file enabled
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Commands for your daily life:
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```shell
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nix run .#write-flake # whenever you need to regen flake.nix
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nix flake check # will make sure your flake.nix is up-to-date
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```
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See Reference for integrating it as a runnable package from your flake.
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</Aside>
+34
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modules/bootstrap/default.nix
+34
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modules/bootstrap/default.nix
···
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pkgs ? import <nixpkgs> { },
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modules ? [ ],
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outdir ? ".",
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bootstrap ? [ ],
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inputs ? null,
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outputs ? null,
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do-not-edit ? null,
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import-tree ? (
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pkgs.fetchFromGitHub {
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owner = "vic";
···
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type = lib.types.submodule { freeformType = lib.types.lazyAttrsOf lib.types.unspecified; };
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};
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bootstrapInputs =
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let
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ins = import ./inputs.nix { inherit lib; };
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take = name: { flake-file.inputs.${name} = ins.flake-file.inputs.${name}; };
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names =
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if bootstrap == true then lib.attrNames ins.flake-file.inputs else lib.flatten [ bootstrap ];
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in
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map take names;
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module = {
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imports = [
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tree
···
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./../write-flake.nix
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./../write-lock.nix
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./../flake-options.nix
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{ imports = bootstrapInputs; }
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(if outputs == null then { } else { flake-file.outputs = outputs; })
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(lib.optionalAttrs (inputs != null) { flake-file.inputs = inputs; })
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(lib.optionalAttrs (outputs != null) { flake-file.outputs = strOrFile outputs; })
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(lib.optionalAttrs (do-not-edit != null) { flake-file.do-not-edit = strOrFile do-not-edit; })
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+
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bootstrap-app
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];
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config.flake-file.intoPath = outdir;
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options = {
···
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};
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};
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evaled = lib.evalModules {
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modules = [ module ];
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specialArgs.inputs.self.outPath = "";
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strOrFile = str: if builtins.isPath str then builtins.readFile str else str;
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+
56
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bootstrap-app = {
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flake-file.apps.bootstrap =
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pkgs:
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let
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inputs = ''{ flake-file.url = "github:vic/flake-file"; }'';
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notice = pkgs.writeText "notice" ''
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# DO-NOT-EDIT. Generated by github:vic/flake-file from flake-file.nix. Regen with:
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# nix-shell https://github.com/vic/flake-file/archive/main.zip -A flake-file.sh --run bootstrap
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'';
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in
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pkgs.writeShellApplication {
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name = "bootstrap";
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text = ''
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if ! test -f flake-file.nix; then
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cp flake.nix flake-file.nix
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fi
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nix-shell ${../..} -A flake-file.sh --run write-flake \
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--arg modules ./flake-file.nix \
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--arg do-not-edit ${notice} \
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--argstr outputs flake-module \
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--arg inputs '${inputs}'
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'';
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};
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};
80
+
81
+
evaled = lib.evalModules { modules = [ module ]; };
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64
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in
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evaled.config
+1
-1
modules/bootstrap/inputs.nix
+1
-1
modules/bootstrap/inputs.nix
···
4
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import-tree.url = lib.mkDefault "github:vic/import-tree";
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flake-file.url = lib.mkDefault "github:vic/flake-file";
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flake-parts.url = lib.mkDefault "github:hercules-ci/flake-parts";
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flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
7
+
flake-parts.inputs.nixpkgs-lib.follows = lib.mkDefault "nixpkgs";
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nixpkgs.url = lib.mkDefault "https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz";
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};
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}
+9
-1
modules/default.nix
+9
-1
modules/default.nix
···
1
1
let
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flakeModules = {
3
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inherit
4
-
default
4
+
flake # for non-flake-parts flakes
5
+
default # for flake-parts flakes (keep as default for compatibility)
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allfollow
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nix-auto-follow
7
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dendritic
···
12
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flake-options
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;
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};
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+
17
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# A flake without flake-parts. (traditional flake)
18
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flake.imports = [
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base
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flake-options
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./write-flake.nix
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];
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flake-options = ./flake-options.nix;
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25
+1
-1
modules/flake-options.nix
+1
-1
modules/flake-options.nix
+1
-1
modules/options/outputs.nix
+1
-1
modules/options/outputs.nix