fix(provisioner/terraform/tfparse): allow empty values in coder_workspace_tag defaults (#16303)

* chore(docs): update docs re workspace tag default values
* chore(coderdenttest): use random name instead of t.Name() in newExternalProvisionerDaemon
* fix(provisioner/terraform/tfparse): allow empty values in coder_workspace_tag defaults

coderd/templateversions_test.go

@@ -429,9 +429,8 @@ func TestPostTemplateVersionsByOrganization(t *testing.T) {
 							}
 						}`,
 				},
-				reqTags: map[string]string{"a": "b"},
-				// wantTags: map[string]string{"owner": "", "scope": "organization", "a": "b"},
-				expectError: `provisioner tag "a" evaluated to an empty value`,
+				reqTags:  map[string]string{"a": "b"},
+				wantTags: map[string]string{"owner": "", "scope": "organization", "a": "b"},
 			},
 			{
 				name: "main.tf with disallowed workspace tag value",
@@ -568,6 +567,42 @@ func TestPostTemplateVersionsByOrganization(t *testing.T) {
 				},
 				wantTags: map[string]string{"owner": "", "scope": "organization"},
 			},
+			{
+				name: "main.tf with tags from parameter with default value from variable no default",
+				files: map[string]string{
+					`main.tf`: `
+						variable "provisioner" {
+						  type        = string
+						}
+						variable "default_provisioner" {
+						  type        = string
+						  default     = "" # intentionally blank, set on template creation
+						}
+						data "coder_parameter" "provisioner" {
+						  name         = "provisioner"
+						  mutable      = false
+						  default      = var.default_provisioner
+						  dynamic "option" {
+							for_each = toset(split(",", var.provisioner))
+							content {
+							  name  = option.value
+							  value = option.value
+							}
+						  }
+						}
+						data "coder_workspace_tags" "tags" {
+						  tags = {
+							"provisioner" : data.coder_parameter.provisioner.value
+						  }
+						}`,
+				},
+				reqTags: map[string]string{
+					"provisioner": "alpha",
+				},
+				wantTags: map[string]string{
+					"provisioner": "alpha", "owner": "", "scope": "organization",
+				},
+			},
 		} {
 			tt := tt
 			t.Run(tt.name, func(t *testing.T) {