command/e2etest: provider installation with explicit install methods

This exercises the ability to customize the installation methods used by
the provider plugin installer, in this case forcing the use of a custom
local directory with a result essentially the same as what happens when
you pass -plugin-dir to "terraform init".

command/e2etest/init_test.go

@@ -173,6 +173,56 @@ func TestInitProvidersLocalOnly(t *testing.T) {
 	}
 }
 
+func TestInitProvidersCustomMethod(t *testing.T) {
+	t.Parallel()
+
+	// This test should not reach out to the network if it is behaving as
+	// intended. If it _does_ try to access an upstream registry and encounter
+	// an error doing so then that's a legitimate test failure that should be
+	// fixed. (If it incorrectly reaches out anywhere then it's likely to be
+	// to the host "example.com", which is the placeholder domain we use in
+	// the test fixture.)
+
+	for _, configFile := range []string{"cliconfig.tfrc", "cliconfig.tfrc.json"} {
+		t.Run(configFile, func(t *testing.T) {
+			fixturePath := filepath.Join("testdata", "custom-provider-install-method")
+			tf := e2e.NewBinary(terraformBin, fixturePath)
+			defer tf.Close()
+
+			// Our fixture dir has a generic os_arch dir, which we need to customize
+			// to the actual OS/arch where this test is running in order to get the
+			// desired result.
+			fixtMachineDir := tf.Path("fs-mirror/example.com/awesomecorp/happycloud/1.2.0/os_arch")
+			wantMachineDir := tf.Path("fs-mirror/example.com/awesomecorp/happycloud/1.2.0/", fmt.Sprintf("%s_%s", runtime.GOOS, runtime.GOARCH))
+			err := os.Rename(fixtMachineDir, wantMachineDir)
+			if err != nil {
+				t.Fatalf("unexpected error: %s", err)
+			}
+
+			// We'll use a local CLI configuration file taken from our fixture
+			// directory so we can force a custom installation method config.
+			tf.AddEnv("TF_CLI_CONFIG_FILE=" + tf.Path(configFile))
+
+			stdout, stderr, err := tf.Run("init")
+			if err != nil {
+				t.Errorf("unexpected error: %s", err)
+			}
+
+			if stderr != "" {
+				t.Errorf("unexpected stderr output:\n%s", stderr)
+			}
+
+			if !strings.Contains(stdout, "Terraform has been successfully initialized!") {
+				t.Errorf("success message is missing from output:\n%s", stdout)
+			}
+
+			if !strings.Contains(stdout, "- Installing example.com/awesomecorp/happycloud v1.2.0") {
+				t.Errorf("provider download message is missing from output:\n%s", stdout)
+			}
+		})
+	}
+}
+
 func TestInitProviders_pluginCache(t *testing.T) {
 	t.Parallel()
 

command/e2etest/testdata/custom-provider-install-method/cliconfig.tfrc

@@ -0,0 +1,5 @@
+provider_installation {
+  filesystem_mirror {
+    path = "./fs-mirror"
+  }
+}

command/e2etest/testdata/custom-provider-install-method/cliconfig.tfrc.json

@@ -0,0 +1,9 @@
+{
+  "provider_installation": {
+    "filesystem_mirror": [
+      {
+        "path": "./fs-mirror"
+      }
+    ]
+  }
+}

command/e2etest/testdata/custom-provider-install-method/fs-mirror/example.com/awesomecorp/happycloud/1.2.0/os_arch/terraform-provider-happycloud_v1.2.0

@@ -0,0 +1,2 @@
+This is not a real plugin executable. It's just here to be discovered by the
+provider installation process.

command/e2etest/testdata/custom-provider-install-method/main.tf

@@ -0,0 +1,21 @@
+# The purpose of this test is to refer to a provider whose address contains
+# a hostname that is only used for namespacing purposes and doesn't actually
+# have a provider registry deployed at it.
+#
+# A user can install such a provider in one of the implied local filesystem
+# directories and Terraform should accept that as the selection for that
+# provider without producing any errors about the fact that example.com
+# does not have a provider registry.
+#
+# For this test in particular we're using the "vendor" directory that is
+# the documented way to include provider plugins directly inside a
+# configuration uploaded to Terraform Cloud, but this functionality applies
+# to all of the implicit local filesystem search directories.
+
+terraform {
+  required_providers {
+    happycloud = {
+      source = "example.com/awesomecorp/happycloud"
+    }
+  }
+}