[QT-529] Always generate a Terraform configuration files (#81)

Enos scenarios always override the CLI configuration file to ensure that
we don't accidentally inherit global configuration. Previously we relied
on simply setting the environment variable and geneating actual contents
only if they were set in the scenario. Terraform 1.4.2 changed the
behavior to warn if the environment variable was set to a non-existent
file. Now we always create the file even if it's blank.

Signed-off-by: Ryan Cragun <[email protected]>

Author: ryancragun

internal/generate/generate.go

@@ -158,7 +158,21 @@ func (g *Generator) TerraformModuleDir() string {
 // file.
 func (g *Generator) generateCLIConfig() error {
 	if g.Scenario.TerraformCLI == nil || g.Scenario.TerraformCLI.ConfigVal.IsNull() {
-		return nil
+		// Always generate a configuration file even if we have not been configured
+		// with any configuration content. Enos scenarios are always configured
+		// with a CLI file so that we don't accidentally inherit something
+		// unexpected from common Terraform configuration directories.
+		// Starting with Terraform 1.4.2 this is actually a requirement as
+		// it will warn if the file override does not exist.
+
+		// Make sure our out directory exists and is a directory
+		err := g.ensureOutDir()
+		if err != nil {
+			return err
+		}
+
+		// Write our RC file to disk
+		return g.write(g.TerraformRCPath(), nil)
 	}
 
 	rc := hclwrite.NewEmptyFile()