terraform: add plugins tests (#47861)

I wasn't sure if the plugins were downloaded from the Internet or not.
This makes sure that there is no regression in the plugin detection.

pkgs/applications/networking/cluster/terraform/default.nix

@@ -4,6 +4,8 @@
 , buildGoPackage
 , fetchFromGitHub
 , makeWrapper
+, runCommand
+, writeText
 , terraform-providers
 }:
 
@@ -118,4 +120,25 @@ in rec {
   });
 
   terraform_0_11-full = terraform_0_11.withPlugins lib.attrValues;
+
+  # Tests that the plugins are being used. Terraform looks at the specific
+  # file pattern and if the plugin is not found it will try to download it
+  # from the Internet. With sandboxing enable this test will fail if that is
+  # the case.
+  terraform_plugins_test = let
+    mainTf = writeText "main.tf" ''
+      resource "random_id" "test" {}
+    '';
+    terraform = terraform_0_11.withPlugins (p: [ p.random ]);
+    test = runCommand "terraform-plugin-test" { buildInputs = [terraform]; }
+      ''
+        set -e
+        # make it fail outside of sandbox
+        export HTTP_PROXY=http://127.0.0.1:0 HTTPS_PROXY=https://127.0.0.1:0
+        cp ${mainTf} main.tf
+        terraform init
+        touch $out
+      '';
+  in test;
+
 }

pkgs/top-level/all-packages.nix

@@ -22162,6 +22162,7 @@ with pkgs;
     terraform_0_10-full
     terraform_0_11
     terraform_0_11-full
+    terraform_plugins_test
     ;
 
   terraform = terraform_0_11;