From 0ba1f47823afb316cbea0fed7bd74c9d0a8bb50a Mon Sep 17 00:00:00 2001
From: Yueh-Shun Li <shamrocklee@posteo.net>
Date: Wed, 9 Jul 2025 01:08:38 +0800
Subject: [PATCH] fetchhg: make argument hash overridable

(cherry picked from commit ef2f8315bf538f1e76ca2f2257a53f583df3989e)
---
 doc/build-helpers/fetchers.chapter.md  |  2 +-
 pkgs/build-support/fetchhg/default.nix | 10 +++---
 pkgs/test/overriding.nix               | 47 +++++++++++++++++++++++++-
 3 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/doc/build-helpers/fetchers.chapter.md b/doc/build-helpers/fetchers.chapter.md
index 997f97f81bdb..ee35b2339b0c 100644
--- a/doc/build-helpers/fetchers.chapter.md
+++ b/doc/build-helpers/fetchers.chapter.md
@@ -836,7 +836,7 @@ Used with CVS. Expects `cvsRoot`, `tag`, and `hash`.
 
 ## `fetchhg` {#fetchhg}
 
-Used with Mercurial. Expects `url`, `rev`, and `hash`.
+Used with Mercurial. Expects `url`, `rev`, `hash`, overridable with [`<pkg>.overrideAttrs`](#sec-pkg-overrideAttrs).
 
 A number of fetcher functions wrap part of `fetchurl` and `fetchzip`. They are mainly convenience functions intended for commonly used destinations of source code in Nixpkgs. These wrapper fetchers are listed below.
 
diff --git a/pkgs/build-support/fetchhg/default.nix b/pkgs/build-support/fetchhg/default.nix
index 4c8a8f312929..f22e32aca44a 100644
--- a/pkgs/build-support/fetchhg/default.nix
+++ b/pkgs/build-support/fetchhg/default.nix
@@ -28,22 +28,22 @@ lib.extendMkDerivation {
 
     subrepoClause = lib.optionalString fetchSubrepos "S";
 
-    outputHashAlgo = if hash != null && hash != "" then null else "sha256";
+    outputHashAlgo = if finalAttrs.hash != null && finalAttrs.hash != "" then null else "sha256";
     outputHashMode = "recursive";
     outputHash =
       lib.throwIf
-        (hash != null && sha256 != null)
+        (finalAttrs.hash != null && sha256 != null)
         "Only one of sha256 or hash can be set"
         (
-          if hash != null then
-            hash
+          if finalAttrs.hash != null then
+            finalAttrs.hash
           else if sha256 != null then
             sha256
           else
             ""
         );
 
-    inherit url rev;
+    inherit url rev hash;
     inherit preferLocalBuild;
   };
 
diff --git a/pkgs/test/overriding.nix b/pkgs/test/overriding.nix
index 27f57ab1ab9d..29bdbf2fd8fd 100644
--- a/pkgs/test/overriding.nix
+++ b/pkgs/test/overriding.nix
@@ -5,7 +5,7 @@
 }:
 
 let
-  tests = tests-stdenv // test-extendMkDerivation // tests-go // tests-python;
+  tests = tests-stdenv // test-extendMkDerivation // tests-fetchhg // tests-go // tests-python;
 
   tests-stdenv =
     let
@@ -131,6 +131,51 @@ let
       };
     };
 
+  tests-fetchhg =
+    let
+      ruamel_0_18_14-hash = "sha256-HDkPPp1xI3uoGYlS9mwPp1ZjG2gKvx6vog0Blj6tBuI=";
+      ruamel_0_18_14-src = pkgs.fetchhg {
+        url = "http://hg.code.sf.net/p/ruamel-yaml/code";
+        rev = "0.18.14";
+        hash = ruamel_0_18_14-hash;
+      };
+      ruamel_0_17_21-hash = "sha256-6PV0NyPQfd+4RBqoj5vJaOHShx+TJVHD2IamRinU0VU=";
+      ruamel_0_17_21-src = pkgs.fetchhg {
+        url = "http://hg.code.sf.net/p/ruamel-yaml/code";
+        rev = "0.17.21";
+        hash = ruamel_0_17_21-hash;
+      };
+      ruamel_0_17_21-src-by-overriding = ruamel_0_18_14-src.overrideAttrs {
+        rev = "0.17.21";
+        hash = ruamel_0_17_21-hash;
+      };
+    in
+    {
+      hash-outputHash-equivalence = {
+        expr = ruamel_0_17_21-src.outputHash == ruamel_0_17_21-hash;
+        expected = true;
+      };
+
+      hash-overridability-outputHash = {
+        expr = ruamel_0_17_21-src-by-overriding.outputHash == ruamel_0_17_21-hash;
+        expected = true;
+      };
+
+      hash-overridability-drvPath = {
+        expr =
+          lib.isString ruamel_0_17_21-src-by-overriding.drvPath
+          && ruamel_0_17_21-src-by-overriding.drvPath == ruamel_0_17_21-src.drvPath;
+        expected = true;
+      };
+
+      hash-overridability-outPath = {
+        expr =
+          lib.isString ruamel_0_17_21-src-by-overriding.outPath
+          && ruamel_0_17_21-src-by-overriding.outPath == ruamel_0_17_21-src.outPath;
+        expected = true;
+      };
+    };
+
   tests-go =
     let
       pet_0_3_4 = pkgs.buildGoModule rec {