backend: drop dvc-specific working-dir behavior (#17)

* backend: get rid of dvc-specific make_tf behavior

- drop make_tf contextmanager
- use single working_dir per TerraformBackend instance (instead of
  nesting by resource name)

* update tests

* make default_resource public

tests/test_terraform.py

@@ -1,5 +1,4 @@
 import json
-import os
 
 import pytest
 from mock import ANY, MagicMock
@@ -66,7 +65,7 @@ def terraform(tmp_path, mocker):
 @pytest.fixture
 def resource(tmp_path):
     name = "test-resource"
-    path = tmp_path / name / "terraform.tfstate"
+    path = tmp_path / "terraform.tfstate"
     path.parent.mkdir(parents=True, exist_ok=True)
     path.write_text(TEST_RESOURCE_STATE, encoding="utf-8")
     yield name
@@ -92,21 +91,15 @@ def test_make_pemfile():
             assert fobj.read() == content
 
 
-def test_make_tf(terraform):
-    name = "foo"
-    with terraform.make_tf(name) as tf:
-        assert tf.working_dir == os.path.join(terraform.tmp_dir, name)
-
-
 def test_create(tmp_path, terraform):
     name = "foo"
     terraform.create(name=name, cloud="aws")
     terraform.cmd_mock.assert_any_call("init", capture_output=False)
     terraform.cmd_mock.assert_any_call(
         "apply", capture_output=False, auto_approve=IsFlagged
     )
-    assert (tmp_path / name / "main.tf.json").exists()
-    with open(tmp_path / name / "main.tf.json") as fobj:
+    assert (tmp_path / "main.tf.json").exists()
+    with open(tmp_path / "main.tf.json") as fobj:
         data = json.load(fobj)
     assert data["resource"]["iterative_machine"] == {
         name: {"name": name, "cloud": "aws"},

tpi/terraform.py

@@ -1,7 +1,6 @@
 import asyncio
 import os
 import sys
-from contextlib import contextmanager
 from itertools import repeat
 from typing import TYPE_CHECKING, Iterator, Optional, Union
 
@@ -18,22 +17,14 @@ class TPIException(Exception):
 
 
 class TerraformBackend:
-    def __init__(self, tmp_dir: StrPath, **kwargs):
-        self.tmp_dir = tmp_dir
-        os.makedirs(self.tmp_dir, exist_ok=True)
+    """Class for managing a named TPI iterative-machine resource."""
 
-    @contextmanager
-    def make_tf(self, name: str):
-        from tpi import TerraformProviderIterative, TPIError
+    def __init__(self, working_dir: StrPath, **kwargs):
+        from tpi import TerraformProviderIterative
 
-        try:
-            working_dir = os.path.join(self.tmp_dir, name)
-            os.makedirs(working_dir, exist_ok=True)
-            yield TerraformProviderIterative(working_dir=working_dir)
-        except TPIError:
-            raise
-        except Exception as exc:
-            raise TPIError("terraform failed") from exc
+        self.working_dir = working_dir
+        os.makedirs(self.working_dir, exist_ok=True)
+        self.tf = TerraformProviderIterative(working_dir=self.working_dir)
 
     def create(self, name: Optional[str] = None, **config):
         """Create and start an instance of the specified machine."""
@@ -42,29 +33,26 @@ def create(self, name: Optional[str] = None, **config):
         from tpi import render_json
 
         assert name and "cloud" in config
-        with self.make_tf(name) as tf:
-            tf_file = os.path.join(tf.working_dir, "main.tf.json")
-            with open(tf_file, "w", encoding="utf-8") as fobj:
-                fobj.write(render_json(name=name, **config, indent=2))
-            tf.cmd("init")
-            tf.cmd("apply", auto_approve=IsFlagged)
+        tf_file = os.path.join(self.working_dir, "main.tf.json")
+        with open(tf_file, "w", encoding="utf-8") as fobj:
+            fobj.write(render_json(name=name, **config, indent=2))
+        self.tf.cmd("init")
+        self.tf.cmd("apply", auto_approve=IsFlagged)
 
     def destroy(self, name: Optional[str] = None, **config):
         """Stop and destroy all instances of the specified machine."""
         from python_terraform import IsFlagged
 
         assert name
 
-        with self.make_tf(name) as tf:
-            if first(tf.iter_instances(name)):
-                tf.cmd("destroy", auto_approve=IsFlagged)
+        if first(self.tf.iter_instances(name)):
+            self.tf.cmd("destroy", auto_approve=IsFlagged)
 
     def instances(self, name: Optional[str] = None, **config) -> Iterator[dict]:
         """Iterate over status of all instances of the specified machine."""
         assert name
 
-        with self.make_tf(name) as tf:
-            yield from tf.iter_instances(name)
+        yield from self.tf.iter_instances(name)
 
     def close(self):
         pass
@@ -73,7 +61,7 @@ def run_shell(self, name: Optional[str] = None, **config):
         """Spawn an interactive SSH shell for the specified machine."""
         from tpi import TerraformProviderIterative
 
-        resource = self._default_resource(name)
+        resource = self.default_resource(name)
         with TerraformProviderIterative.pemfile(resource) as pem:
             self._shell(
                 host=resource["instance_ip"],
@@ -82,7 +70,7 @@ def run_shell(self, name: Optional[str] = None, **config):
                 known_hosts=None,
             )
 
-    def _default_resource(self, name):
+    def default_resource(self, name):
         from tpi import TPIError
 
         resource = first(self.instances(name))