From 8ba40fdd4fae1edd4d725a53c04401d1f0d8b2a5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simon=20=C5=BDlender?= <pub.git@zlender.si>
Date: Wed, 20 Nov 2024 22:51:15 +0100
Subject: [PATCH] lib: add defaultTo

---
 lib/default.nix |  2 +-
 lib/trivial.nix | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/lib/default.nix b/lib/default.nix
index aff1df150f13b..48574ab3e4a25 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -71,7 +71,7 @@ let
     # these are the only ones that are currently not
     inherit (builtins) addErrorContext isPath trace typeOf unsafeGetAttrPos;
     inherit (self.trivial) id const pipe concat or and xor bitAnd bitOr bitXor
-      bitNot boolToString mergeAttrs flip mapNullable inNixShell isFloat min max
+      bitNot boolToString mergeAttrs flip defaultTo mapNullable inNixShell isFloat min max
       importJSON importTOML warn warnIf warnIfNot throwIf throwIfNot checkListOfEnum
       info showWarnings nixpkgsVersion version isInOldestRelease oldestSupportedReleaseIsAtLeast
       mod compare splitByAndCompare seq deepSeq lessThan add sub
diff --git a/lib/trivial.nix b/lib/trivial.nix
index 04fb9ffd46180..0e196018961c5 100644
--- a/lib/trivial.nix
+++ b/lib/trivial.nix
@@ -316,6 +316,40 @@ in {
   */
   flip = f: a: b: f b a;
 
+  /**
+    Return `maybeValue` if not null, otherwise return `default`.
+
+
+    # Inputs
+
+    `default`
+
+    : 1\. Function argument
+
+    `maybeValue`
+
+    : 2\. Function argument
+
+
+    # Examples
+    :::{.example}
+    ## `lib.trivial.defaultTo` usage example
+
+    ```nix
+    defaultTo "default" null
+    => "default"
+    defaultTo "default" "foo"
+    => "foo"
+    defaultTo "default" false
+    => false
+    ```
+
+    :::
+  */
+  defaultTo = default: maybeValue:
+    if maybeValue != null then maybeValue
+    else default;
+
   /**
     Apply function if the supplied argument is non-null.