From 5fb20d2f8cad7a6332baafbb2986ac0ef16c6fc7 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Sat, 10 Dec 2022 23:23:42 +0100
Subject: [PATCH 1/2] lib.modules: Add error context to rendered default and
 example attrs

---
 lib/options.nix | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/lib/options.nix b/lib/options.nix
index b13687576e81..0fd5b64a65d1 100644
--- a/lib/options.nix
+++ b/lib/options.nix
@@ -221,9 +221,10 @@ rec {
   optionAttrSetToDocList' = _: options:
     concatMap (opt:
       let
+        name = showOption opt.loc;
         docOption = rec {
           loc = opt.loc;
-          name = showOption opt.loc;
+          inherit name;
           description = opt.description or null;
           declarations = filter (x: x != unknownModule) opt.declarations;
           internal = opt.internal or false;
@@ -234,8 +235,18 @@ rec {
           readOnly = opt.readOnly or false;
           type = opt.type.description or "unspecified";
         }
-        // optionalAttrs (opt ? example) { example = renderOptionValue opt.example; }
-        // optionalAttrs (opt ? default) { default = renderOptionValue (opt.defaultText or opt.default); }
+        // optionalAttrs (opt ? example) {
+          example =
+            builtins.addErrorContext "while evaluating the example of option `${name}`" (
+              renderOptionValue opt.example
+            );
+        }
+        // optionalAttrs (opt ? default) {
+          default =
+            builtins.addErrorContext "while evaluating the default value of option `${name}`" (
+              renderOptionValue (opt.defaultText or opt.default)
+            );
+        }
         // optionalAttrs (opt ? relatedPackages && opt.relatedPackages != null) { inherit (opt) relatedPackages; };
 
         subOptions =

From 1a44080088c3a4384da7e4529928f7a0a7b1aa4e Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Sat, 10 Dec 2022 23:36:46 +0100
Subject: [PATCH 2/2] lib.generators.toPretty: Add attribute name to error
 context

---
 lib/generators.nix | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/generators.nix b/lib/generators.nix
index c0fe69389e00..4c9c2d1e9869 100644
--- a/lib/generators.nix
+++ b/lib/generators.nix
@@ -342,7 +342,10 @@ rec {
       else "{" + introSpace
           + libStr.concatStringsSep introSpace (libAttr.mapAttrsToList
               (name: value:
-                "${libStr.escapeNixIdentifier name} = ${go (indent + "  ") value};") v)
+                "${libStr.escapeNixIdentifier name} = ${
+                  builtins.addErrorContext "while evaluating an attribute `${name}`"
+                    (go (indent + "  ") value)
+                };") v)
         + outroSpace + "}"
     else abort "generators.toPretty: should never happen (v = ${v})";
   in go "";