From bb140e16a2d44bbfe96911f29f1b6c5ef4947b85 Mon Sep 17 00:00:00 2001
From: Vincent Ambo <mail@tazj.in>
Date: Wed, 2 Feb 2022 12:22:58 +0300
Subject: feat(nix/buildkite): Add parentOverride argument to extra steps

This can be used to override the parent derivation if its output is
required, for example to inject versions which are only used during
releases to avoid cache-busting.

Change-Id: I2211496efa8f9bc98ea43b23e4f3f92c61a6da73
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5184
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: ezemtsov <eugene.zemtsov@gmail.com>
---
 nix/buildkite/default.nix | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/nix/buildkite/default.nix b/nix/buildkite/default.nix
index d17b5c86c4a6..b1653e1ad5f2 100644
--- a/nix/buildkite/default.nix
+++ b/nix/buildkite/default.nix
@@ -159,6 +159,13 @@ rec {
         let
           step = mkStep headBranch parentTargetMap target;
 
+          # Same step, but with an override function applied. This is
+          # used in mkExtraStep if the extra step needs to modify the
+          # parent derivation somehow.
+          #
+          # Note that this will never affect the label.
+          overridable = f: mkStep headBranch parentTargetMap (f target);
+
           # Split build/post-build steps
           splitExtraSteps = partition ({ postStep, ... }: postStep)
             (attrValues (mapAttrs
@@ -168,7 +175,7 @@ rec {
               })
               (target.meta.ci.extraSteps or { })));
 
-          mkExtraStep' = { name, value, ... }: mkExtraStep step name value;
+          mkExtraStep' = { name, value, ... }: mkExtraStep overridable name value;
           extraBuildSteps = map mkExtraStep' splitExtraSteps.wrong; # 'wrong' -> no prompt
           extraPostSteps = map mkExtraStep' splitExtraSteps.right; # 'right' -> has prompt
         in
@@ -260,6 +267,10 @@ rec {
   #     command. Output will be available as 'result'.
   #     TODO: Figure out multiple-output derivations.
   #
+  #   parentOverride (optional): A function (drv -> drv) to override
+  #     the parent's target definition when preparing its output. Only
+  #     used in extra steps that use needsOutput.
+  #
   #   branches (optional): Git references (branches, tags ... ) on
   #     which this step should be allowed to run. List of strings.
   #
@@ -291,15 +302,18 @@ rec {
 
   # Create the Buildkite configuration for an extra step, optionally
   # wrapping it in a gate group.
-  mkExtraStep = parent: key: { command
-                             , label ? key
-                             , prompt ? false
-                             , needsOutput ? false
-                             , branches ? null
-                             , alwaysRun ? false
-                             , postBuild ? false
-                             }@cfg:
+  mkExtraStep = overridableParent: key:
+    { command
+    , label ? key
+    , prompt ? false
+    , needsOutput ? false
+    , parentOverride ? (x: x)
+    , branches ? null
+    , alwaysRun ? false
+    , postBuild ? false
+    }@cfg:
     let
+      parent = overridableParent parentOverride;
       parentLabel = parent.env.READTREE_TARGET;
 
       step = {
-- 
cgit 1.4.1