ec2: fix fleet launch template versioning

Author: nik-localstack

moto/ec2/models/fleets.py

@@ -86,7 +86,10 @@ def __init__(
             # Always include the template ID in response (AWS does this even when name is used)
             resolved_launch_spec["LaunchTemplateId"] = launch_template.id
 
-            launch_template_data = launch_template.latest_version().data
+            template_version = resolved_launch_spec.get(
+                "Version", launch_template.default_version_number
+            )
+            launch_template_data = launch_template.get_version(template_version).data
             overrides_list = config.get("Overrides") or [{}]
             for override in overrides_list:
                 # Merge launch template data with override

tests/test_ec2/test_fleets.py

@@ -914,7 +914,7 @@ def test_user_data():
 @pytest.mark.parametrize("version_specified", ["$Latest", "$Default"])
 def test_version_resolves_to_actual_version_number(version_specified, ec2_client=None):
     """Test that $Latest or $Default in a fleet LaunchTemplateSpecification resolves to the actual version number"""
-    with launch_template_context() as ctxt:
+    with launch_template_context(region=ec2_client.meta.region_name) as ctxt:
         fleet_response = ctxt.ec2.create_fleet(
             LaunchTemplateConfigs=[
                 {
@@ -946,6 +946,45 @@ def test_version_resolves_to_actual_version_number(version_specified, ec2_client
             ctxt.ec2.delete_fleets(FleetIds=[fleet_id], TerminateInstances=True)
 
 
+@pytest.mark.aws_verified
+@ec2_aws_verified()
+def test_fleet_uses_data_from_specified_template_version(ec2_client=None):
+    with launch_template_context(region=ec2_client.meta.region_name) as ctxt:
+        # Version 1 was created by the context manager with t2.micro;
+        # add version 2 with a different instance type
+        ctxt.ec2.create_launch_template_version(
+            LaunchTemplateId=ctxt.lt_id,
+            LaunchTemplateData={"InstanceType": "t3.medium"},
+        )
+
+        fleet = ctxt.ec2.create_fleet(
+            LaunchTemplateConfigs=[
+                {
+                    "LaunchTemplateSpecification": {
+                        "LaunchTemplateId": ctxt.lt_id,
+                        "Version": "1",
+                    },
+                }
+            ],
+            TargetCapacitySpecification={
+                "TotalTargetCapacity": 1,
+                "OnDemandTargetCapacity": 1,
+                "DefaultTargetCapacityType": "on-demand",
+            },
+            OnDemandOptions={"AllocationStrategy": "lowest-price"},
+            Type="instant",
+        )
+        fleet_id = fleet["FleetId"]
+        instance_id = fleet["Instances"][0]["InstanceIds"][0]
+        try:
+            instance = ctxt.ec2.describe_instances(InstanceIds=[instance_id])[
+                "Reservations"
+            ][0]["Instances"][0]
+            assert instance["InstanceType"] == "t2.micro"
+        finally:
+            ctxt.ec2.delete_fleets(FleetIds=[fleet_id], TerminateInstances=True)
+
+
 @pytest.mark.aws_verified
 @ec2_aws_verified()
 @pytest.mark.parametrize(