Terraform init: Error: failed to open temporary file with direnv

Question

I used direnv to install programs from a nix flake like this:

.envrc:

use flake ~/Documents/nixdesktop/shells/myshell#terraformAndOthers

myshell/flake.nix:

{
  description = "Shells with terraform, jdk, etc ";
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils/master";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let pkgs = nixpkgs.legacyPackages.${system};
      in {
        devShells.terraformAndOthers = pkgs.mkShell {
          buildInputs = [
            pkgs.openjdk17
            pkgs.bashInteractive
            pkgs.terraform
          ];
        }
      }
    );
}

Then I ran terraform init , which failed with the following error:

Initializing the backend...

Initializing provider plugins...
- terraform.io/builtin/terraform is built in to Terraform
- Reusing previous version of hashicorp/google from the dependency lock file
- Installing hashicorp/google v4.44.1...
╷
│ Error: Failed to install provider
│ 
│ Error while installing hashicorp/google v4.44.1: failed to open temporary file to download from
│ https://releases.hashicorp.com/terraform-provider-google/4.44.1/terraform-provider-google_4.44.1_darwin_arm64.zip
╵

Alternately, sometimes terraform is working for a while and then suddenly terraform apply stops working with error “failed to instantiate provider PROVIDER to obtain schema: Unrecognized remote plugin message:”:

│ Error: Failed to load plugin schemas
│ 
│ Error while loading schemas for plugin components: Failed to obtain provider schema: Could not load the schema for provider registry.terraform.io/hashicorp/google: failed to
│ instantiate provider "registry.terraform.io/hashicorp/google" to obtain schema: Unrecognized remote plugin message: 
│ 
│ This usually means that the plugin is either invalid or simply
│ needs to be recompiled to support the latest protocol...

How to fix this error?

Answer 1

Solution: call direnv allow again to have direnv create a new temporary directory.

Explanation:

Terraform (and any go program that calls os.TempDir("", …) or os.MkdirTemp("", …) , or ioutil.TempFile("", …) , or ioutil.TempDir("", …) ) creates files in the directory returned by os.TempDir() , which is the value of the environment variable $TMPDIR . $TMPDIR must exist first, or else those functions give an error.

Meanwhile, direnv's use flake calls nix print-dev-env , and nix print-dev-env --profile.direnv/flake-profile ~/Documents/nixdesktop/shells/myshell#terraformAndOthers prints a shell script which ends with

export NIX_BUILD_TOP="$(mktemp -d -t nix-shell.XXXXXX)"
export TMP="$NIX_BUILD_TOP"
export TMPDIR="$NIX_BUILD_TOP"
export TEMP="$NIX_BUILD_TOP"
export TEMPDIR="$NIX_BUILD_TOP"
…

Each time the flake is executed, mktemp should create a directory. But if $TMPDIR no longer exists, then you need to recreate it. I think $TMPDIR stopped existing because direnv cached the environmnet vars, but the temporary directory was deleted after a few hours or after a reboot. To fix this, re-run direnv allow .