Nlohmann optional

.github/workflows/ci.yml

@@ -101,6 +101,9 @@ jobs:
 
   docker_push_image:
     needs: [check_secrets, tests]
+    permissions:
+      contents: read
+      packages: write
     if: >-
       github.event_name == 'push' &&
       github.ref_name == 'master' &&
@@ -126,10 +129,30 @@ jobs:
     - run: docker load -i ./result/image.tar.gz
     - run: docker tag nix:$NIX_VERSION nixos/nix:$NIX_VERSION
     - run: docker tag nix:$NIX_VERSION nixos/nix:master
+    # We'll deploy the newly built image to both Docker Hub and Github Container Registry.
+    #
+    # Push to Docker Hub first
     - name: Login to Docker Hub
       uses: docker/login-action@v3
       with:
         username: ${{ secrets.DOCKERHUB_USERNAME }}
         password: ${{ secrets.DOCKERHUB_TOKEN }}
     - run: docker push nixos/nix:$NIX_VERSION
     - run: docker push nixos/nix:master
+    # Push to GitHub Container Registry as well
+    - name: Login to GitHub Container Registry
+      uses: docker/login-action@v3
+      with:
+        registry: ghcr.io
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+    - name: Push image
+      run: |
+        IMAGE_ID=ghcr.io/${{ github.repository_owner }}/nix
+        # Change all uppercase to lowercase
+        IMAGE_ID=$(echo $IMAGE_ID | tr '[A-Z]' '[a-z]')
+
+        docker tag nix:$NIX_VERSION $IMAGE_ID:$NIX_VERSION
+        docker tag nix:$NIX_VERSION $IMAGE_ID:master
+        docker push $IMAGE_ID:$NIX_VERSION
+        docker push $IMAGE_ID:master

CONTRIBUTING.md

@@ -27,9 +27,12 @@ Check out the [security policy](https://github.com/NixOS/nix/security/policy).
 1. Search for related issues that cover what you're going to work on.
    It could help to mention there that you will work on the issue.
 
-   Issues labeled [good first issue](https://github.com/NixOS/nix/labels/good-first-issue) should be relatively easy to fix and are likely to get merged quickly.
+   Issues labeled [good first issue](https://github.com/NixOS/nix/labels/good%20first%20issue) should be relatively easy to fix and are likely to get merged quickly.
    Pull requests addressing issues labeled [idea approved](https://github.com/NixOS/nix/labels/idea%20approved) or [RFC](https://github.com/NixOS/nix/labels/RFC) are especially welcomed by maintainers and will receive prioritised review.
 
+   If you are proficient with C++, addressing one of the [popular issues](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc) will be highly appreciated by maintainers and Nix users all over the world.
+   For far-reaching changes, please investigate possible blockers and design implications, and coordinate with maintainers before investing too much time in writing code that may not end up getting merged.
+
    If there is no relevant issue yet and you're not sure whether your change is likely to be accepted, [open an issue](https://github.com/NixOS/nix/issues/new/choose) yourself.
 
 2. Check for [pull requests](https://github.com/NixOS/nix/pulls) that might already cover the contribution you are about to make.

doc/manual/src/advanced-topics/distributed-builds.md

@@ -12,14 +12,14 @@ machine is accessible via SSH and that it has Nix installed. You can
 test whether connecting to the remote Nix instance works, e.g.
 
 ```console
-$ nix store ping --store ssh://mac
+$ nix store info --store ssh://mac
 ```
 
 will try to connect to the machine named `mac`. It is possible to
 specify an SSH identity file as part of the remote store URI, e.g.
 
 ```console
-$ nix store ping --store ssh://mac?ssh-key=/home/alice/my-key
+$ nix store info --store ssh://mac?ssh-key=/home/alice/my-key
 ```
 
 Since builds should be non-interactive, the key should not have a

doc/manual/src/glossary.md

@@ -207,6 +207,7 @@
 - [output]{#gloss-output}
 
   A [store object] produced by a [derivation].
+  See [the `outputs` argument to the `derivation` function](@docroot@/language/derivations.md#attr-outputs) for details.
 
   [output]: #gloss-output
 

doc/manual/src/installation/installing-docker.md

@@ -3,14 +3,14 @@
 To run the latest stable release of Nix with Docker run the following command:
 
 ```console
-$ docker run -ti nixos/nix
-Unable to find image 'nixos/nix:latest' locally
-latest: Pulling from nixos/nix
+$ docker run -ti ghcr.io/nixos/nix
+Unable to find image 'ghcr.io/nixos/nix:latest' locally
+latest: Pulling from ghcr.io/nixos/nix
 5843afab3874: Pull complete
 b52bf13f109c: Pull complete
 1e2415612aa3: Pull complete
 Digest: sha256:27f6e7f60227e959ee7ece361f75d4844a40e1cc6878b6868fe30140420031ff
-Status: Downloaded newer image for nixos/nix:latest
+Status: Downloaded newer image for ghcr.io/nixos/nix:latest
 35ca4ada6e96:/# nix --version
 nix (Nix) 2.3.12
 35ca4ada6e96:/# exit

doc/manual/src/language/advanced-attributes.md

@@ -270,6 +270,9 @@ Derivations can declare some infrequently used optional attributes.
     useful for very trivial derivations (such as `writeText` in Nixpkgs)
     that are cheaper to build than to substitute from a binary cache.
 
+    You may disable the effects of this attibute by enabling the
+    `always-allow-substitutes` configuration option in Nix.
+
     > **Note**
     >
     > You need to have a builder configured which satisfies the

doc/manual/src/language/derivations.md

@@ -8,98 +8,205 @@ It outputs an attribute set, and produces a [store derivation] as a side effect
 
 [store derivation]: @docroot@/glossary.md#gloss-store-derivation
 
-<!-- FIXME: add a section on output attributes -->
-
 ## Input attributes
 
 ### Required
 
 - [`name`]{#attr-name} ([String](@docroot@/language/values.md#type-string))
 
   A symbolic name for the derivation.
-  It is added to the [store derivation]'s [path](@docroot@/glossary.md#gloss-store-path) and its [output paths][output path].
-
-  Example: `name = "hello";`
+  It is added to the [store path] of the corresponding [store derivation] as well as to its [output paths](@docroot@/glossary.md#gloss-output-path).
+
+  [store path]: @docroot@/glossary.md#gloss-store-path
+
+  > **Example**
+  >
+  > ```nix
+  > derivation {
+  >   name = "hello";
+  >   # ...
+  > }
+  > ```
+  >
+  > The store derivation's path will be `/nix/store/<hash>-hello.drv`.
+  > The [output](#attr-outputs) paths will be of the form `/nix/store/<hash>-hello[-<output>]`
 
-  The store derivation's path will be `/nix/store/<hash>-hello.drv`, and the output paths will be of the form `/nix/store/<hash>-hello[-<output>]`
 - [`system`]{#attr-system} ([String](@docroot@/language/values.md#type-string))
 
   The system type on which the [`builder`](#attr-builder) executable is meant to be run.
 
   A necessary condition for Nix to build derivations locally is that the `system` attribute matches the current [`system` configuration option].
   It can automatically [build on other platforms](../advanced-topics/distributed-builds.md) by forwarding build requests to other machines.
 
-  Examples:
-
-  `system = "x86_64-linux";`
-
-  `system = builtins.currentSystem;`
-
-  [`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem) has the value of the [`system` configuration option], and defaults to the system type of the current Nix installation.
-
   [`system` configuration option]: @docroot@/command-ref/conf-file.md#conf-system
 
+  > **Example**
+  >
+  > Declare a derivation to be built on a specific system type:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   system = "x86_64-linux";
+  >   # ...
+  > }
+  > ```
+
+  > **Example**
+  >
+  > Declare a derivation to be built on the system type that evaluates the expression:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   system = builtins.currentSystem;
+  >   # ...
+  > }
+  > ```
+  >
+  > [`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem) has the value of the [`system` configuration option], and defaults to the system type of the current Nix installation.
+
 - [`builder`]{#attr-builder} ([Path](@docroot@/language/values.md#type-path) | [String](@docroot@/language/values.md#type-string))
 
   Path to an executable that will perform the build.
 
-  Examples:
-
-  `builder = "/bin/bash";`
-
-  `builder = ./builder.sh;`
-
-  `builder = "${pkgs.python}/bin/python";`
+  > **Example**
+  >
+  > Use the file located at `/bin/bash` as the builder executable:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   builder = "/bin/bash";
+  >   # ...
+  > };
+  > ```
+
+  <!-- -->
+
+  > **Example**
+  >
+  > Copy a local file to the Nix store for use as the builder executable:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   builder = ./builder.sh;
+  >   # ...
+  > };
+  > ```
+
+  <!-- -->
+
+  > **Example**
+  >
+  > Use a file from another derivation as the builder executable:
+  >
+  > ```nix
+  > let pkgs = import <nixpkgs> {}; in
+  > derivation {
+  >   # ...
+  >   builder = "${pkgs.python}/bin/python";
+  >   # ...
+  > };
+  > ```
 
 ### Optional
 
-- [`args`]{#attr-args} ([List](@docroot@/language/values.md#list) of [String](@docroot@/language/values.md#type-string)) Default: `[ ]`
+- [`args`]{#attr-args} ([List](@docroot@/language/values.md#list) of [String](@docroot@/language/values.md#type-string))
+
+  Default: `[ ]`
 
   Command-line arguments to be passed to the [`builder`](#attr-builder) executable.
 
-  Example: `args = [ "-c" "echo hello world > $out" ];`
+  > **Example**
+  >
+  > Pass arguments to Bash to interpret a shell command:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   builder = "/bin/bash";
+  >   args = [ "-c" "echo hello world > $out" ];
+  >   # ...
+  > };
+  > ```
 
-- [`outputs`]{#attr-outputs} ([List](@docroot@/language/values.md#list) of [String](@docroot@/language/values.md#type-string)) Default: `[ "out" ]`
+- [`outputs`]{#attr-outputs} ([List](@docroot@/language/values.md#list) of [String](@docroot@/language/values.md#type-string))
 
-  Symbolic outputs of the derivation.
-  Each output name is passed to the [`builder`](#attr-builder) executable as an environment variable with its value set to the corresponding [output path].
+  Default: `[ "out" ]`
 
-  [output path]: @docroot@/glossary.md#gloss-output-path
+  Symbolic outputs of the derivation.
+  Each output name is passed to the [`builder`](#attr-builder) executable as an environment variable with its value set to the corresponding [store path].
 
-  By default, a derivation produces a single output path called `out`.
-  However, derivations can produce multiple output paths.
+  By default, a derivation produces a single output called `out`.
+  However, derivations can produce multiple outputs.
   This allows the associated [store objects](@docroot@/glossary.md#gloss-store-object) and their [closures](@docroot@/glossary.md#gloss-closure) to be copied or garbage-collected separately.
 
-  Examples:
-
-  Imagine a library package that provides a dynamic library, header files, and documentation.
-  A program that links against such a library doesn’t need the header files and documentation at runtime, and it doesn’t need the documentation at build time.
-  Thus, the library package could specify:
-
-  ```nix
-  derivation {
-    # ...
-    outputs = [ "lib" "dev" "doc" ];
-    # ...
-  }
-  ```
-
-  This will cause Nix to pass environment variables `lib`, `dev`, and `doc` to the builder containing the intended store paths of each output.
-  The builder would typically do something like
-
-  ```bash
-  ./configure \
-    --libdir=$lib/lib \
-    --includedir=$dev/include \
-    --docdir=$doc/share/doc
-  ```
-
-  for an Autoconf-style package.
-
-  You can refer to each output of a derivation by selecting it as an attribute, e.g. `myPackage.lib` or `myPackage.doc`.
-
-  The first element of `outputs` determines the *default output*.
-  Therefore, in the given example, `myPackage` is equivalent to `myPackage.lib`.
+  > **Example**
+  >
+  > Imagine a library package that provides a dynamic library, header files, and documentation.
+  > A program that links against such a library doesn’t need the header files and documentation at runtime, and it doesn’t need the documentation at build time.
+  > Thus, the library package could specify:
+  >
+  > ```nix
+  > derivation {
+  >   # ...
+  >   outputs = [ "lib" "dev" "doc" ];
+  >   # ...
+  > }
+  > ```
+  >
+  > This will cause Nix to pass environment variables `lib`, `dev`, and `doc` to the builder containing the intended store paths of each output.
+  > The builder would typically do something like
+  >
+  > ```bash
+  > ./configure \
+  >   --libdir=$lib/lib \
+  >   --includedir=$dev/include \
+  >   --docdir=$doc/share/doc
+  > ```
+  >
+  > for an Autoconf-style package.
+
+  The name of an output is combined with the name of the derivation to create the name part of the output's store path, unless it is `out`, in which case just the name of the derivation is used.
+
+  > **Example**
+  >
+  >
+  > ```nix
+  > derivation {
+  >   name = "example";
+  >   outputs = [ "lib" "dev" "doc" "out" ];
+  >   # ...
+  > }
+  > ```
+  >
+  > The store derivation path will be `/nix/store/<hash>-example.drv`.
+  > The output paths will be
+  > - `/nix/store/<hash>-example-lib`
+  > - `/nix/store/<hash>-example-dev`
+  > - `/nix/store/<hash>-example-doc`
+  > - `/nix/store/<hash>-example`
+
+  You can refer to each output of a derivation by selecting it as an attribute.
+  The first element of `outputs` determines the *default output* and ends up at the top-level.
+
+  > **Example**
+  >
+  > Select an output by attribute name:
+  >
+  > ```nix
+  > let
+  >   myPackage = derivation {
+  >     name = "example";
+  >     outputs = [ "lib" "dev" "doc" "out" ];
+  >     # ...
+  >   };
+  > in myPackage.dev
+  > ```
+  >
+  > Since `lib` is the first output, `myPackage` is equivalent to `myPackage.lib`.
 
   <!-- FIXME: refer to the output attributes when we have one -->
 
@@ -123,15 +230,16 @@ It outputs an attribute set, and produces a [store derivation] as a side effect
       reside in the Nix store.
 
     - A *derivation* causes that derivation to be built prior to the
-      present derivation; its default output path is put in the
-      environment variable.
+      present derivation. The environment variable is set to the [store path] of the derivation's default [output](#attr-outputs).
 
     - Lists of the previous types are also allowed. They are simply
       concatenated, separated by spaces.
 
     - `true` is passed as the string `1`, `false` and `null` are
       passed as an empty string.
 
+<!-- FIXME: add a section on output attributes -->
+
 ## Builder execution
 
 The [`builder`](#attr-builder) is executed as follows: