tests.trivial: Avoid evaluation and ${pkgs.path} dep

> There is an issue in the test added by #123111.
> [it] introduces a dependency on the contents of nixpkgs,
> making every change evaluate with a different hash.

pkgs/build-support/trivial-builders/test.nix

@@ -1,5 +1,27 @@
-{ lib, nixosTest, path, writeText, hello, figlet, stdenvNoCC }:
+{ lib, nixosTest, pkgs, writeText, hello, figlet, stdenvNoCC }:
 
+# -------------------------------------------------------------------------- #
+#
+#                         trivial-builders test
+#
+# -------------------------------------------------------------------------- #
+#
+#  This file can be run independently (quick):
+#
+#      $ pkgs/build-support/trivial-builders/test.sh
+#
+#  or in the build sandbox with a ~20s VM overhead
+#
+#      $ nix-build -A tests.trivial-builders
+#
+# -------------------------------------------------------------------------- #
+
+let
+  invokeSamples = file:
+    lib.concatStringsSep " " (
+      lib.attrValues (import file { inherit pkgs; })
+    );
+in
 nixosTest {
   name = "nixpkgs-trivial-builders";
   nodes.machine = { ... }: {
@@ -10,11 +32,15 @@ nixosTest {
     environment.etc."pre-built-paths".source = writeText "pre-built-paths" (
       builtins.toJSON [hello figlet stdenvNoCC]
     );
+    environment.variables = {
+      SAMPLE = invokeSamples ./test/sample.nix;
+      REFERENCES = invokeSamples ./test/invoke-writeReferencesToFile.nix;
+      DIRECT_REFS = invokeSamples ./test/invoke-writeDirectReferencesToFile.nix;
+    };
   };
   testScript = ''
     machine.succeed("""
-      cd ${lib.cleanSource path}
-      ./pkgs/build-support/trivial-builders/test.sh 2>/dev/console
+      ${./test.sh} 2>/dev/console
     """)
   '';
 }

pkgs/build-support/trivial-builders/test.sh

@@ -25,33 +25,32 @@ set -euo pipefail
 
 cd "$(dirname ${BASH_SOURCE[0]})"  # nixpkgs root
 
-testDirectReferences() {
-  expr="$1"
+if [[ -z ${SAMPLE:-} ]]; then
+  sample=( `nix-build test/sample.nix` )
+  directRefs=( `nix-build test/invoke-writeDirectReferencesToFile.nix` )
+  references=( `nix-build test/invoke-writeReferencesToFile.nix` )
+else
+  # Injected by Nix (to avoid evaluating in a derivation)
+  # turn them into arrays
+  sample=($SAMPLE)
+  directRefs=($DIRECT_REFS)
+  references=($REFERENCES)
+fi
+
+echo >&2 Testing direct references...
+for i in "${!sample[@]}"; do
+  echo >&2 Checking '#'$i ${sample[$i]} ${directRefs[$i]}
   diff -U3 \
-    <(sort <$(nix-build --no-out-link --expr "with import ../../.. {}; writeDirectReferencesToFile ($expr)")) \
-    <(nix-store -q --references $(nix-build --no-out-link --expr "with import ../../.. {}; ($expr)") | sort)
-}
+    <(sort <${directRefs[$i]}) \
+    <(nix-store -q --references ${sample[$i]} | sort)
+done
 
-testDirectReferences 'hello'
-testDirectReferences 'figlet'
-testDirectReferences 'writeText "hi" "hello"'
-testDirectReferences 'writeText "hi" "hello ${hello}"'
-testDirectReferences 'writeText "hi" "hello ${hello} ${figlet}"'
-
-
-
-testClosure() {
-  expr="$1"
+echo >&2 Testing closure...
+for i in "${!sample[@]}"; do
+  echo >&2 Checking '#'$i ${sample[$i]} ${references[$i]}
   diff -U3 \
-    <(sort <$(nix-build --no-out-link --expr "with import ../../.. {}; writeReferencesToFile ($expr)")) \
-    <(nix-store -q --requisites $(nix-build --no-out-link --expr "with import ../../.. {}; ($expr)") | sort)
-}
-
-testClosure 'hello'
-testClosure 'figlet'
-testClosure 'writeText "hi" "hello"'
-testClosure 'writeText "hi" "hello ${hello}"'
-testClosure 'writeText "hi" "hello ${hello} ${figlet}"'
-
+    <(sort <${references[$i]}) \
+    <(nix-store -q --requisites ${sample[$i]} | sort)
+done
 
 echo 'OK!'

pkgs/build-support/trivial-builders/test/invoke-writeDirectReferencesToFile.nix

@@ -0,0 +1,4 @@
+{ pkgs ? import ../../../.. { config = {}; overlays = []; } }:
+pkgs.lib.mapAttrs
+  (k: v: pkgs.writeDirectReferencesToFile v)
+  (import ./sample.nix { inherit pkgs; })

pkgs/build-support/trivial-builders/test/invoke-writeReferencesToFile.nix

@@ -0,0 +1,4 @@
+{ pkgs ? import ../../../.. { config = {}; overlays = []; } }:
+pkgs.lib.mapAttrs
+  (k: v: pkgs.writeReferencesToFile v)
+  (import ./sample.nix { inherit pkgs; })

pkgs/build-support/trivial-builders/test/sample.nix

@@ -0,0 +1,15 @@
+{ pkgs ? import ../../../.. { config = {}; overlays = []; } }:
+let
+  inherit (pkgs)
+    figlet
+    hello
+    writeText
+    ;
+in
+{
+  hello = hello;
+  figlet = figlet;
+  norefs = writeText "hi" "hello";
+  helloRef = writeText "hi" "hello ${hello}";
+  helloFigletRef = writeText "hi" "hello ${hello} ${figlet}";
+}