writeTextFile: chmod before checkPhase

Set the executable bit before running the check phase, so that the check
phase can run the script to test its behaviour.

This aligns with what `concatTextFile` is doing.

Also use explicit `if` statements so that we don't silently ignore
`chmod` failures.

1 files changed, 14 insertions, 0 deletions

diff --git a/pkgs/build-support/trivial-builders/test/write-shell-script.nix b/pkgs/build-support/trivial-builders/test/write-shell-script.nix
new file mode 100644
index 0000000000000..a5c9f1fae42f6
--- /dev/null
+++ b/pkgs/build-support/trivial-builders/test/write-shell-script.nix
@@ -0,0 +1,14 @@
+{ lib, writeShellScript }: let
+  output = "hello";
+in (writeShellScript "test-script" ''
+  echo ${lib.escapeShellArg output}
+'').overrideAttrs (old: {
+  checkPhase = old.checkPhase or "" + ''
+    expected=${lib.escapeShellArg output}
+    got=$("$target")
+    if [[ "$got" != "$expected" ]]; then
+      echo "wrong output: expected $expected, got $got"
+      exit 1
+    fi
+  '';
+})