Add support for creating backend files at runtime

Add a "reconfigure" param for working directories that force an init for each command.

Add a provider for working directories to provide paths to the actual module.

rules/terraform.bzl

@@ -3,6 +3,11 @@ load("@tf_modules//rules:module.bzl", "TerraformModuleInfo")
 load("@tf_modules//rules:provider.bzl", "TerraformProviderInfo")
 load("@tf_modules//toolchains/terraform:toolchain.bzl", "TerraformExecutableInfo")
 
+TerraformWorkingDirInfo = provider(
+    doc = "Contains information about a Terraform working directory",
+    fields = ["module_working_directory", "terraform_version", "terraform_binary_path"],
+)
+
 def terraform_working_directory_impl(ctx):
   module = ctx.attr.module[TerraformModuleInfo]
   terraform_version = ctx.attr.terraform[TerraformExecutableInfo].version
@@ -29,6 +34,10 @@ def terraform_working_directory_impl(ctx):
 
   prep_command = "tar -xvzf .terraform.tar.gz > /dev/null"
 
+  reconfigure_cmd = ""
+  if ctx.attr.reconfigure:
+    reconfigure_cmd = "$BASE_PATH/{} init -input=false -reconfigure".format(ctx.executable.terraform.short_path)
+
   # Create the script that runs Terraform
   ctx.actions.write(
     output = ctx.outputs.executable,
@@ -38,12 +47,14 @@ BASE_PATH=$(pwd)
 {2}
 cd {0}
 {3}
+{4}
 $BASE_PATH/{1} $@
 """.format(
     build_base_path + "/" + working_dir, 
     ctx.executable.terraform.short_path, 
     env_vars, 
     prep_command,
+    reconfigure_cmd,
   ),
 )
 
@@ -159,11 +170,18 @@ disable_checkpoint = true
   if terraform_version < "0.14":
     all_outputs += intermediates
 
-  return DefaultInfo(
-    executable = ctx.outputs.executable,
-    files = depset(all_outputs),
-    runfiles = ctx.runfiles(all_outputs + [ctx.executable.terraform])
-  )
+  return [
+    DefaultInfo(
+      executable = ctx.outputs.executable,
+      files = depset(all_outputs),
+      runfiles = ctx.runfiles(all_outputs + [ctx.executable.terraform])
+    ),
+    TerraformWorkingDirInfo(
+      module_working_directory = dot_terraform_tar.dirname,
+      terraform_version = terraform_version,
+      terraform_binary_path = ctx.executable.terraform.path,
+    )
+  ]
 
 terraform_working_directory = rule(
    implementation = terraform_working_directory_impl,
@@ -180,5 +198,6 @@ terraform_working_directory = rule(
         "tf_vars": attr.string_dict(),
         "providers": attr.label_list(providers = [TerraformProviderInfo]),
         "allow_provider_download": attr.bool(default=False),
+        "reconfigure": attr.bool(default=False, doc="Run `terraform init -reconfigure` before each operation to accept changes in backend configuration."),
     },
 )

tests/backend_init/BUILD

@@ -0,0 +1,23 @@
+load("@tf_modules//rules:module.bzl", "terraform_module")
+load("@tf_modules//rules:terraform.bzl", "terraform_working_directory")
+
+terraform_module(
+    name = "provider",
+    srcs = ["main.tf"],
+    visibility = ["//visibility:public"],
+)
+
+terraform_working_directory(
+    name = "terraform",
+    module = ":provider",
+    allow_provider_download = True,
+    reconfigure = True,
+)
+
+sh_test(
+    name = "terraform_test",
+    size = "small",
+    srcs = ["test.sh"],
+    data = [":terraform"],
+)
+

tests/backend_init/main.tf

@@ -0,0 +1,13 @@
+terraform {
+  required_providers {
+    local = {
+      source = "hashicorp/local"
+      version = ">= 2.4.1"
+    }
+  }
+}
+
+resource "local_file" "foo" {
+  content  = "foo!"
+  filename = "${path.module}/foo.bar"
+}

tests/backend_init/test.sh

@@ -0,0 +1,49 @@
+#!/bin/bash
+
+STATE_DIR=$(mktemp -d)
+
+MODULE_DIR=./tests/backend_init/terraform_working/tests/backend_init
+
+BACKEND_FILE="$MODULE_DIR/local_backend.tf"
+cat > "$BACKEND_FILE" <<-EOF
+terraform {
+    backend "local" {
+    path = "$STATE_DIR/terraform.tfstate"
+
+    }
+}
+EOF
+
+if [ -f $STATE_DIR/terraform.tfstate ]; then
+    echo "Temp tfstate file should not exist before apply"
+    exit 1
+fi
+
+OUT=$(./tests/backend_init/terraform apply -auto-approve -no-color)
+if [ $? -ne 0 ];
+then
+    echo 'Apply failed';
+    exit 1
+fi
+
+PASS=1
+
+function expect_output() {
+    if [[ "$OUT" != *"$1"* ]]; then
+        echo "FAIL: Expected text '$1'"
+        PASS=0
+    fi   
+}
+
+expect_output "+ resource \"local_file\" \"foo\" {"
+expect_output "1 to add"
+
+if [[ $PASS == 0 ]]; then
+    echo "$OUT"
+    exit 1
+fi
+
+if [ ! -f $STATE_DIR/terraform.tfstate ]; then
+    echo "Temp tfstate file should exist after apply"
+    exit 1
+fi