More interesting dynamic derivations example

tests/functional/dyn-drv/dep-built-drv-2.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+source common.sh
+
+# Store layer needs bugfix
+requireDaemonNewerThan "2.27pre20250205"
+
+enableFeatures 'recursive-nix'
+
+export NIX_BIN_DIR=$(dirname $(type -p nix))
+
+nix build -L --file ./non-trivial.nix

tests/functional/dyn-drv/meson.build

@@ -15,6 +15,7 @@ suites += {
     'failing-outer.sh',
     'dep-built-drv.sh',
     'old-daemon-error-hack.sh',
+    'dep-built-drv-2.sh',
   ],
   'workdir': meson.current_source_dir(),
 }

tests/functional/dyn-drv/non-trivial.nix

@@ -0,0 +1,75 @@
+with import ./config.nix;
+
+builtins.outputOf (mkDerivation {
+  name = "make-derivations.drv";
+
+  requiredSystemFeatures = [ "recursive-nix" ];
+
+  buildCommand = ''
+    set -e
+    set -u
+
+    PATH=${builtins.getEnv "NIX_BIN_DIR"}:$PATH
+
+    export NIX_CONFIG='extra-experimental-features = nix-command ca-derivations dynamic-derivations'
+
+    declare -A deps=(
+      [a]=""
+      [b]="a"
+      [c]="a"
+      [d]="b c"
+      [e]="b c d"
+    )
+
+    # Cannot just literally include this, or Nix will think it is the
+    # *outer* derivation that's trying to refer to itself, and
+    # substitute the string too son.
+    placeholder=$(nix eval --raw --expr 'builtins.placeholder "out"')
+
+    declare -A drvs=()
+    for word in a b c d e; do
+      inputDrvs=""
+      for dep in ''${deps[$word]}; do
+        if [[ "$inputDrvs" != "" ]]; then
+          inputDrvs+=","
+        fi
+        read -r -d "" line <<EOF || true
+        "''${drvs[$dep]}": {
+          "outputs": ["out"],
+          "dynamicOutputs": {}
+        }
+    EOF
+        inputDrvs+="$line"
+      done
+      read -r -d "" json <<EOF || true
+      {
+        "args": ["-c", "set -xeu; echo \"word env vav $word is \$$word\" >> \"\$out\""],
+        "builder": "${shell}",
+        "env": {
+          "out": "$placeholder",
+          "$word": "hello, from $word!",
+          "PATH": ${builtins.toJSON path}
+        },
+        "inputDrvs": {
+          $inputDrvs
+        },
+        "inputSrcs": [],
+        "name": "build-$word",
+        "outputs": {
+          "out": {
+            "method": "nar",
+            "hashAlgo": "sha256"
+          }
+        },
+        "system": "${system}"
+      }
+    EOF
+      drvs[$word]="$(echo "$json" | nix derivation add)"
+    done
+    cp "''${drvs[e]}" $out
+  '';
+
+  __contentAddressed = true;
+  outputHashMode = "text";
+  outputHashAlgo = "sha256";
+}).outPath "out"