From 047fe2fe23a902c777e10ba37534b8a1b7072a1e Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Sat, 12 Jun 2021 17:28:00 +0200
Subject: [PATCH 1/3] emptyFile, emptyDirectory: init

---
 pkgs/build-support/trivial-builders.nix | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/pkgs/build-support/trivial-builders.nix b/pkgs/build-support/trivial-builders.nix
index 0bf67d21b3be..219f808403cc 100644
--- a/pkgs/build-support/trivial-builders.nix
+++ b/pkgs/build-support/trivial-builders.nix
@@ -571,6 +571,22 @@ rec {
       installPhase = "cp -R ./ $out";
     };
 
+  /* An immutable file in the store with a length of 0 bytes. */
+  emptyFile = runCommand "empty-file" {
+    outputHashAlgo = "sha256";
+    outputHashMode = "recursive";
+    outputHash = "0ip26j2h11n1kgkz36rl4akv694yz65hr72q4kv4b3lxcbi65b3p";
+    preferLocalBuild = true;
+  } "touch $out";
+
+  /* An immutable empty directory in the store. */
+  emptyDirectory = runCommand "empty-directory" {
+    outputHashAlgo = "sha256";
+    outputHashMode = "recursive";
+    outputHash = "0sjjj9z1dhilhpc8pq4154czrb79z9cm044jvn75kxcjv6v5l2m5";
+    preferLocalBuild = true;
+  } "mkdir $out";
+
   /* Checks the command output contains the specified version
    *
    * Although simplistic, this test assures that the main program

From d48591123f4d5936ef6c9fd5d963ce3b1925d4c4 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Sat, 12 Jun 2021 17:28:42 +0200
Subject: [PATCH 2/3] nixos/apache-httpd: Use pkgs.emptyDirectory

---
 nixos/modules/services/web-servers/apache-httpd/default.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/nixos/modules/services/web-servers/apache-httpd/default.nix b/nixos/modules/services/web-servers/apache-httpd/default.nix
index a7b93c9c4598..df7035c03cc2 100644
--- a/nixos/modules/services/web-servers/apache-httpd/default.nix
+++ b/nixos/modules/services/web-servers/apache-httpd/default.nix
@@ -202,7 +202,7 @@ let
     let
       documentRoot = if hostOpts.documentRoot != null
         then hostOpts.documentRoot
-        else pkgs.runCommand "empty" { preferLocalBuild = true; } "mkdir -p $out"
+        else pkgs.emptyDirectory
       ;
 
       mkLocations = locations: concatStringsSep "\n" (map (config: ''

From c38c5dba10e5a239a4d297c64f4c0a5fd2d5e1b9 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Sat, 12 Jun 2021 17:29:27 +0200
Subject: [PATCH 3/3] tests.trivial: Add emptyFile, emptyDirectory to samples

---
 pkgs/build-support/trivial-builders/test/sample.nix | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pkgs/build-support/trivial-builders/test/sample.nix b/pkgs/build-support/trivial-builders/test/sample.nix
index 060be011093a..27aee6b73dbe 100644
--- a/pkgs/build-support/trivial-builders/test/sample.nix
+++ b/pkgs/build-support/trivial-builders/test/sample.nix
@@ -12,4 +12,8 @@ in
   norefs = writeText "hi" "hello";
   helloRef = writeText "hi" "hello ${hello}";
   helloFigletRef = writeText "hi" "hello ${hello} ${figlet}";
+  inherit (pkgs)
+    emptyFile
+    emptyDirectory
+  ;
 }