From f0b6425d738288f85381488cc3e25c30a441235c Mon Sep 17 00:00:00 2001
From: networkException <git@nwex.de>
Date: Sat, 21 Sep 2024 23:53:21 +0200
Subject: [PATCH 1/2] doc/build-helpers: fix wrong invokations of writeTextFile
 with destination

This patch fixes occurances of writeTextFile invokations with
a destination set but without a leading slash. This would cause
an opaque build time error.
---
 doc/build-helpers/trivial-build-helpers.chapter.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/doc/build-helpers/trivial-build-helpers.chapter.md b/doc/build-helpers/trivial-build-helpers.chapter.md
index 31b42bd77426..ff00548e049a 100644
--- a/doc/build-helpers/trivial-build-helpers.chapter.md
+++ b/doc/build-helpers/trivial-build-helpers.chapter.md
@@ -501,7 +501,7 @@ writeTextFile {
   text = ''
     Contents of File
   '';
-  destination = "share/my-file";
+  destination = "/share/my-file";
 }
 ```
 
@@ -586,7 +586,7 @@ writeTextFile {
     echo "hi"
   '';
   executable = true;
-  destination = "bin/my-script";
+  destination = "/bin/my-script";
 }
 ```
 
@@ -674,7 +674,7 @@ writeTextFile {
     echo "hi"
   '';
   executable = true;
-  destination = "bin/my-script";
+  destination = "/bin/my-script";
 }
 ```
 

From 6215daa52004e2e36117fa204db95fce46598945 Mon Sep 17 00:00:00 2001
From: networkException <git@nwex.de>
Date: Sat, 21 Sep 2024 23:54:48 +0200
Subject: [PATCH 2/2] writeTextFile: assert destination starting with a /

This patch adds an assertion to the writeTextFile trivial
builder, asserting that a specified destination starts with
a slash.

This matches the current behavior of the function and merely
provides a helpful error message.
---
 pkgs/build-support/trivial-builders/default.nix | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pkgs/build-support/trivial-builders/default.nix b/pkgs/build-support/trivial-builders/default.nix
index 3bccc871a7dc..a02fe1fd6d0a 100644
--- a/pkgs/build-support/trivial-builders/default.nix
+++ b/pkgs/build-support/trivial-builders/default.nix
@@ -86,6 +86,13 @@ rec {
     , preferLocalBuild ? true
     , derivationArgs ? { }
     }:
+    assert lib.assertMsg (destination != "" -> (lib.hasPrefix "/" destination && destination != "/")) ''
+      destination must be an absolute path, relative to the derivation's out path,
+      got '${destination}' instead.
+
+      Ensure that the path starts with a / and specifies at least the filename.
+    '';
+
     let
       matches = builtins.match "/bin/([^/]+)" destination;
     in