internal/providercache: Fix incorrect logic in Installer.SetGlobalCacheDir

Due to some incomplete rework of this function in an earlier commit, the
safety check for using the same directory as both the target and the
cache was inverted and was raising an error _unless_ they matched, rather
than _if_ they matched.

This change is verified by the e2etest TestInitProviders_pluginCache,
which is also updated to use the new-style cache directory layout as part
of this commit.

command/e2etest/init_test.go

@@ -96,16 +96,19 @@ func TestInitProviders_pluginCache(t *testing.T) {
 	// 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("cache/os_arch")
-	wantMachineDir := tf.Path("cache", fmt.Sprintf("%s_%s", runtime.GOOS, runtime.GOARCH))
-	os.Rename(fixtMachineDir, wantMachineDir)
+	fixtMachineDir := tf.Path("cache/registry.terraform.io/hashicorp/template/2.1.0/os_arch")
+	wantMachineDir := tf.Path("cache/registry.terraform.io/hashicorp/template/2.1.0/", fmt.Sprintf("%s_%s", runtime.GOOS, runtime.GOARCH))
+	err := os.Rename(fixtMachineDir, wantMachineDir)
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
 
 	cmd := tf.Cmd("init")
 	cmd.Env = append(cmd.Env, "TF_PLUGIN_CACHE_DIR=./cache")
 	cmd.Stdin = nil
 	cmd.Stderr = &bytes.Buffer{}
 
-	err := cmd.Run()
+	err = cmd.Run()
 	if err != nil {
 		t.Errorf("unexpected error: %s", err)
 	}
@@ -115,7 +118,7 @@ func TestInitProviders_pluginCache(t *testing.T) {
 		t.Errorf("unexpected stderr output:\n%s\n", stderr)
 	}
 
-	path := fmt.Sprintf(".terraform/plugins/%s_%s/terraform-provider-template_v2.1.0_x4", runtime.GOOS, runtime.GOARCH)
+	path := fmt.Sprintf(".terraform/plugins/registry.terraform.io/hashicorp/template/2.1.0/%s_%s/terraform-provider-template_v2.1.0_x4", runtime.GOOS, runtime.GOARCH)
 	content, err := tf.ReadFile(path)
 	if err != nil {
 		t.Fatalf("failed to read installed plugin from %s: %s", path, err)
@@ -124,11 +127,11 @@ func TestInitProviders_pluginCache(t *testing.T) {
 		t.Errorf("template plugin was not installed from local cache")
 	}
 
-	if !tf.FileExists(fmt.Sprintf(".terraform/plugins/%s_%s/terraform-provider-null_v2.1.0_x4", runtime.GOOS, runtime.GOARCH)) {
+	if !tf.FileExists(fmt.Sprintf(".terraform/plugins/registry.terraform.io/hashicorp/null/2.1.0/%s_%s/terraform-provider-null_v2.1.0_x4", runtime.GOOS, runtime.GOARCH)) {
 		t.Errorf("null plugin was not installed")
 	}
 
-	if !tf.FileExists(fmt.Sprintf("cache/%s_%s/terraform-provider-null_v2.1.0_x4", runtime.GOOS, runtime.GOARCH)) {
+	if !tf.FileExists(fmt.Sprintf("cache/registry.terraform.io/hashicorp/null/2.1.0/%s_%s/terraform-provider-null_v2.1.0_x4", runtime.GOOS, runtime.GOARCH)) {
 		t.Errorf("null plugin is not in cache after install")
 	}
 }

internal/providercache/installer.go

@@ -64,8 +64,8 @@ func (i *Installer) SetGlobalCacheDir(cacheDir *Dir) {
 	// A little safety check to catch straightforward mistakes where the
 	// directories overlap. Better to panic early than to do
 	// possibly-distructive actions on the cache directory downstream.
-	if same, err := copydir.SameFile(i.targetDir.baseDir, cacheDir.baseDir); err == nil && !same {
-		panic(fmt.Sprintf("global cache directory %s must not match the installation target directory", i.targetDir.baseDir))
+	if same, err := copydir.SameFile(i.targetDir.baseDir, cacheDir.baseDir); err == nil && same {
+		panic(fmt.Sprintf("global cache directory %s must not match the installation target directory %s", cacheDir.baseDir, i.targetDir.baseDir))
 	}
 	i.globalCacheDir = cacheDir
 }