From 99a2a29f0ae69c01fdeedd701fd1c6a44123ad3a Mon Sep 17 00:00:00 2001
From: Fintan Halpenny <fintan.halpenny@gmail.com>
Date: Sat, 25 Apr 2026 16:24:25 +0100
Subject: [PATCH] flake: Use lychee for link checking

Introduce [lychee] link checking in the flake.nix checks.
Since `nix flake check` is limited by sandboxing, it only checks for
internal links.

Running `lychee` from the directory will check external links.
In the future, this can be done via git hooks.

[lychee]: https://github.com/lycheeverse/lychee
---
 .gitignore  |  2 ++
 flake.nix   | 44 ++++++++++++++++++++++++++++++--------------
 lychee.toml | 12 ++++++++++++
 3 files changed, 44 insertions(+), 14 deletions(-)
 create mode 100644 lychee.toml

diff --git a/.gitignore b/.gitignore
index 8583d22..a42b609 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
 node_modules/
 result
+.lycheecache
+.direnv/
diff --git a/flake.nix b/flake.nix
index e0ff168..dbd9963 100644
--- a/flake.nix
+++ b/flake.nix
@@ -26,6 +26,7 @@
         buildInputs =
           (with pkgs; [
             asciidoctor
+            pkgs.lychee
             nodejs
             shellcheck
             yq
@@ -35,20 +36,35 @@
           ];
       };
 
-      checks.grammar =
-        pkgs.runCommand "grammar-check" {
-          nativeBuildInputs =
-            (with pkgs; [
-              nearley
-              nodejs
-              yq
-            ])
-            ++ [
-              nearley
+      checks = {
+        grammar =
+          pkgs.runCommand "grammar-check" {
+            nativeBuildInputs =
+              (with pkgs; [
+                nearley
+                nodejs
+                yq
+              ])
+              ++ [
+                nearley
+              ];
+          } ''
+            ${./0004-general-uri-scheme/data/test/uri-scheme-tester.sh} ${./0004-general-uri-scheme/data}
+            touch $out
+          '';
+
+        links = pkgs.testers.lycheeLinkCheck {
+          site = pkgs.lib.sources.sourceFilesBySuffices ./. [".md" ".adoc"];
+          extraConfig = {
+            extensions = ["md" "adoc"];
+            include_fragments = true;
+            exclude = [
+              "^rad:.*$"
+              "^web\\+rad:.*$"
+              "^vscode:.*$"
             ];
-        } ''
-          ${./0004-general-uri-scheme/data/test/uri-scheme-tester.sh} ${./0004-general-uri-scheme/data}
-          touch $out
-        '';
+          };
+        };
+      };
     });
 }
diff --git a/lychee.toml b/lychee.toml
new file mode 100644
index 0000000..14afa65
--- /dev/null
+++ b/lychee.toml
@@ -0,0 +1,12 @@
+extensions = ["md", "adoc"]
+include_fragments = true
+# Exclude custom URI schemes that lychee cannot resolve
+exclude = [
+  '^rad:',
+  '^web\+rad:',
+  '^vscode:',
+]
+include_mail = false
+timeout = 20
+max_retries = 2
+retry_wait_time = 2