From 7f43889ef6d2014367582d5a6de8884c1b9ab637 Mon Sep 17 00:00:00 2001
From: David <6107913+ackdav@users.noreply.github.com>
Date: Tue, 4 Jul 2023 11:36:34 +0200
Subject: [PATCH] EC2: fix DescribeLaunchTemplateVersions default response
 (#6477)

---
 moto/ec2/responses/launch_templates.py  | 8 +++++---
 tests/test_ec2/test_launch_templates.py | 8 ++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/moto/ec2/responses/launch_templates.py b/moto/ec2/responses/launch_templates.py
index 58eb05ddd..01e2c8ff8 100644
--- a/moto/ec2/responses/launch_templates.py
+++ b/moto/ec2/responses/launch_templates.py
@@ -156,8 +156,10 @@ class LaunchTemplates(EC2BaseResponse):
         template_id = self._get_param("LaunchTemplateId")
         if name:
             template = self.ec2_backend.get_launch_template_by_name(name)
-        if template_id:
+        elif template_id:
             template = self.ec2_backend.get_launch_template(template_id)
+        else:
+            template = None
 
         max_results = self._get_int_param("MaxResults", 15)
         versions = self._get_multi_param("LaunchTemplateVersion")
@@ -182,7 +184,7 @@ class LaunchTemplates(EC2BaseResponse):
         versions_node = ElementTree.SubElement(tree, "launchTemplateVersionSet")
 
         ret_versions = []
-        if versions:
+        if versions and template is not None:
             for v in versions:
                 if str(v).lower() == "$latest" or "$default":
                     tv = template.get_version(v)
@@ -200,7 +202,7 @@ class LaunchTemplates(EC2BaseResponse):
         elif max_version:
             vMax = max_version
             ret_versions = template.versions[:vMax]
-        else:
+        elif template is not None:
             ret_versions = template.versions
 
         ret_versions = ret_versions[:max_results]
diff --git a/tests/test_ec2/test_launch_templates.py b/tests/test_ec2/test_launch_templates.py
index e775a0460..85c492ddc 100644
--- a/tests/test_ec2/test_launch_templates.py
+++ b/tests/test_ec2/test_launch_templates.py
@@ -140,6 +140,14 @@ def test_describe_launch_template_versions_by_name_when_absent():
 
         cli.describe_launch_template_versions(LaunchTemplateName=template_name)
 
+    # test default response
+    resp = cli.describe_launch_template_versions()
+    assert resp["LaunchTemplateVersions"] == []
+
+    # test using $Latest version
+    resp = cli.describe_launch_template_versions(Versions=["$Latest"])
+    assert resp["LaunchTemplateVersions"] == []
+
 
 @mock_ec2
 def test_create_launch_template_version():