1 files changed, 69 insertions, 0 deletions
diff --git a/pkgs/build-support/testers/lychee.nix b/pkgs/build-support/testers/lychee.nix
new file mode 100644
index 0000000000000..80088dc4f9638
--- /dev/null
+++ b/pkgs/build-support/testers/lychee.nix
@@ -0,0 +1,69 @@
+deps@{ formats, lib, lychee, stdenv, writeShellApplication }:
+let
+  inherit (lib) mapAttrsToList throwIf;
+  inherit (lib.strings) hasInfix hasPrefix escapeNixString;
+
+  toURL = v:
+    let s = "${v}";
+    in if hasPrefix builtins.storeDir s
+    then # lychee requires that paths on the file system are prefixed with file://
+      "file://${s}"
+    else s;
+
+  withCheckedName = name:
+    throwIf (hasInfix " " name) ''
+      lycheeLinkCheck: remap patterns must not contain spaces.
+      A space marks the end of the regex in lychee.toml.
+
+      Please change attribute name 'remap.${escapeNixString name}'
+    '';
+
+  # See https://nixos.org/manual/nixpkgs/unstable/#tester-lycheeLinkCheck
+  # or doc/builders/testers.chapter.md
+  lycheeLinkCheck = {
+    site,
+    remap ? { },
+    lychee ? deps.lychee,
+    extraConfig ? { },
+  }:
+    stdenv.mkDerivation (finalAttrs: {
+      name = "lychee-link-check";
+      inherit site;
+      nativeBuildInputs = [ finalAttrs.passthru.lychee ];
+      configFile = (formats.toml {}).generate "lychee.toml" finalAttrs.passthru.config;
+
+      # These can be overriden with overrideAttrs if needed.
+      passthru = {
+        inherit lychee remap;
+        config = {
+          include_fragments = true;
+        } // lib.optionalAttrs (finalAttrs.passthru.remap != { }) {
+          remap =
+            mapAttrsToList
+              (name: value: withCheckedName name "${name} ${toURL value}")
+              finalAttrs.passthru.remap;
+        } // extraConfig;
+        online = writeShellApplication {
+          name = "run-lychee-online";
+          runtimeInputs = [ finalAttrs.passthru.lychee ];
+          # Comment out to run shellcheck:
+          checkPhase = "";
+          text = ''
+            site=${finalAttrs.site}
+            configFile=${finalAttrs.configFile}
+            echo Checking links on $site
+            exec lychee --config $configFile $site "$@"
+          '';
+        };
+      };
+      buildCommand = ''
+        echo Checking internal links on $site
+        lychee --offline --config $configFile $site
+        touch $out
+      '';
+    });
+
+in
+{
+  inherit lycheeLinkCheck;
+}