nixos/manual: disallow docbook option docs

it's been long in the making, and with 23.05 out we can finally disable
docbook option docs and default to markdown instead. this brings a
massive speed boost in manual and manpage builds, so much so that we may
consider enabling user module documentation by default.

we don't remove the docbook support code entirely yet because it's a lot
all over, and probably better removed in multiple separate changes.

.github/workflows/compare-manuals.sh

@@ -1,21 +0,0 @@
-#!/usr/bin/env nix-shell
-#! nix-shell -i bash -p html-tidy
-
-set -euo pipefail
-shopt -s inherit_errexit
-
-normalize() {
-  tidy \
-      --anchor-as-name no \
-      --coerce-endtags no \
-      --escape-scripts no \
-      --fix-backslash no \
-      --fix-style-tags no \
-      --fix-uri no \
-      --indent yes \
-      --wrap 0 \
-      < "$1" \
-      2> /dev/null
-}
-
-diff -U3 <(normalize "$1") <(normalize "$2")

.github/workflows/manual-nixos.yml

@@ -27,13 +27,5 @@ jobs:
           # This cache is for the nixpkgs repo checks and should not be trusted or used elsewhere.
           name: nixpkgs-ci
           signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
-      - name: Building NixOS manual with DocBook options
+      - name: Building NixOS manual
         run: NIX_PATH=nixpkgs=$(pwd) nix-build --option restrict-eval true nixos/release.nix -A manual.x86_64-linux
-      - name: Building NixOS manual with Markdown options
-        run: |
-          export NIX_PATH=nixpkgs=$(pwd)
-          nix-build \
-            --option restrict-eval true \
-            --arg configuration '{ documentation.nixos.options.allowDocBook = false; }' \
-            nixos/release.nix \
-            -A manual.x86_64-linux

.github/workflows/manual-rendering.yml

@@ -1,64 +0,0 @@
-name: "Check NixOS Manual DocBook rendering against MD rendering"
-
-
-on:
-  schedule:
-    # * is a special character in YAML so you have to quote this string
-    # Check every 24 hours
-    - cron:  '0 0 * * *'
-
-permissions:
-  contents: read
-
-jobs:
-  check-rendering-equivalence:
-    permissions:
-      pull-requests: write  # for peter-evans/create-or-update-comment to create or update comment
-    if: github.repository_owner == 'NixOS'
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-      - uses: cachix/install-nix-action@v21
-        with:
-          # explicitly enable sandbox
-          extra_nix_config: sandbox = true
-      - uses: cachix/cachix-action@v12
-        with:
-          # This cache is for the nixpkgs repo checks and should not be trusted or used elsewhere.
-          name: nixpkgs-ci
-          signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
-
-      - name: Build DocBook and MD manuals
-        run: |
-          export NIX_PATH=nixpkgs=$(pwd)
-          nix-build \
-            --option restrict-eval true \
-            -o docbook nixos/release.nix \
-            -A manual.x86_64-linux
-          nix-build \
-            --option restrict-eval true \
-            --arg configuration '{ documentation.nixos.options.allowDocBook = false; }' \
-            -o md nixos/release.nix \
-            -A manual.x86_64-linux
-
-      - name: Compare DocBook and MD manuals
-        id: check
-        run: |
-          export NIX_PATH=nixpkgs=$(pwd)
-          .github/workflows/compare-manuals.sh \
-            docbook/share/doc/nixos/options.html \
-            md/share/doc/nixos/options.html
-
-      # if the manual can't be built we don't want to notify anyone.
-      # while this may temporarily hide rendering failures it will be a lot
-      # less noisy until all nixpkgs pull requests have stopped using
-      # docbook for option docs.
-      - name: Comment on failure
-        uses: peter-evans/create-or-update-comment@v3
-        if: ${{ failure() && steps.check.conclusion == 'failure' }}
-        with:
-          issue-number: 189318
-          body: |
-            Markdown and DocBook manuals do not agree.
-
-            Check https://github.com/NixOS/nixpkgs/actions/runs/${{ github.run_id }} for details.

nixos/doc/manual/default.nix

@@ -6,10 +6,11 @@
 , extraSources ? []
 , baseOptionsJSON ? null
 , warningsAreErrors ? true
-, allowDocBook ? true
+, allowDocBook ? false
 , prefix ? ../../..
 }:
 
+assert ! allowDocBook;
 with pkgs;
 
 let

nixos/doc/manual/release-notes/rl-2311.section.md

@@ -44,4 +44,6 @@
 
 - A new option was added to the virtualisation module that enables specifying explicitly named network interfaces in QEMU VMs. The existing `virtualisation.vlans` is still supported for cases where the name of the network interface is irrelevant.
 
+- DocBook option documentation is no longer supported, all module documentation now uses markdown.
+
 - `services.nginx` gained a `defaultListen` option at server-level with support for PROXY protocol listeners, also `proxyProtocol` is now exposed in `services.nginx.virtualHosts.<name>.listen` option. It is now possible to run PROXY listeners and non-PROXY listeners at a server-level, see [#213510](https://github.com/NixOS/nixpkgs/pull/213510/) for more details.

nixos/lib/make-options-doc/default.nix

@@ -39,12 +39,16 @@
 # allow docbook option docs if `true`. only markdown documentation is allowed when set to
 # `false`, and a different renderer may be used with different bugs and performance
 # characteristics but (hopefully) indistinguishable output.
-, allowDocBook ? true
+# deprecated since 23.11.
+# TODO remove in a while.
+, allowDocBook ? false
 # whether lib.mdDoc is required for descriptions to be read as markdown.
 # !!! when this is eventually flipped to true, `lib.doRename` should also default to emitting Markdown
 , markdownByDefault ? false
 }:
 
+assert ! allowDocBook;
+
 let
   rawOpts = lib.optionAttrSetToDocList options;
   transformedOpts = map transformOptions rawOpts;

nixos/modules/misc/documentation.nix

@@ -107,7 +107,7 @@ let
             } >&2
         '';
 
-    inherit (cfg.nixos.options) warningsAreErrors allowDocBook;
+    inherit (cfg.nixos.options) warningsAreErrors;
   };
 
 
@@ -160,6 +160,9 @@ in
     (mkRenamedOptionModule [ "programs" "info" "enable" ] [ "documentation" "info" "enable" ])
     (mkRenamedOptionModule [ "programs" "man"  "enable" ] [ "documentation" "man"  "enable" ])
     (mkRenamedOptionModule [ "services" "nixosManual" "enable" ] [ "documentation" "nixos" "enable" ])
+    (mkRemovedOptionModule
+      [ "documentation" "nixos" "options" "allowDocBook" ]
+      "DocBook option documentation is no longer supported")
   ];
 
   options = {
@@ -264,23 +267,6 @@ in
         '';
       };
 
-      nixos.options.allowDocBook = mkOption {
-        type = types.bool;
-        default = true;
-        description = lib.mdDoc ''
-          Whether to allow DocBook option docs. When set to `false` all option using
-          DocBook documentation will cause a manual build error; additionally a new
-          renderer may be used.
-
-          ::: {.note}
-          The `false` setting for this option is not yet fully supported. While it
-          should work fine and produce the same output as the previous toolchain
-          using DocBook it may not work in all circumstances. Whether markdown option
-          documentation is allowed is independent of this option.
-          :::
-        '';
-      };
-
       nixos.options.warningsAreErrors = mkOption {
         type = types.bool;
         default = true;