Improve Dockerfile recipe generation (#35187)

- Update default image to Ubuntu 22.04 (previously was still Ubuntu 18.04)
- Optionally use depfiles to install the environment within the container
- Allow extending Dockerfile Jinja2 template
- Allow extending Singularity definition file Jinja2 template
- Deprecate previous options to add extra instructions

lib/spack/spack/container/__init__.py

@@ -39,10 +39,10 @@ def validate(configuration_file):
     # Ensure we have a "container" attribute with sensible defaults set
     env_dict = ev.config_dict(config)
     env_dict.setdefault(
-        "container", {"format": "docker", "images": {"os": "ubuntu:18.04", "spack": "develop"}}
+        "container", {"format": "docker", "images": {"os": "ubuntu:22.04", "spack": "develop"}}
     )
     env_dict["container"].setdefault("format", "docker")
-    env_dict["container"].setdefault("images", {"os": "ubuntu:18.04", "spack": "develop"})
+    env_dict["container"].setdefault("images", {"os": "ubuntu:22.04", "spack": "develop"})
 
     # Remove attributes that are not needed / allowed in the
     # container recipe

lib/spack/spack/container/writers/__init__.py

@@ -7,6 +7,7 @@
 """
 import collections
 import copy
+from typing import Optional
 
 import spack.environment as ev
 import spack.schema.env
@@ -131,6 +132,9 @@ class PathContext(tengine.Context):
     directly via PATH.
     """
 
+    # Must be set by derived classes
+    template_name: Optional[str] = None
+
     def __init__(self, config, last_phase):
         self.config = ev.config_dict(config)
         self.container_config = self.config["container"]
@@ -146,6 +150,10 @@ def __init__(self, config, last_phase):
         # Record the last phase
         self.last_phase = last_phase
 
+    @tengine.context_property
+    def depfile(self):
+        return self.container_config.get("depfile", False)
+
     @tengine.context_property
     def run(self):
         """Information related to the run image."""
@@ -280,7 +288,8 @@ def render_phase(self):
     def __call__(self):
         """Returns the recipe as a string"""
         env = tengine.make_environment()
-        t = env.get_template(self.template_name)
+        template_name = self.container_config.get("template", self.template_name)
+        t = env.get_template(template_name)
         return t.render(**self.to_dict())
 
 

lib/spack/spack/schema/container.py

@@ -63,6 +63,8 @@
         },
         # Add labels to the image
         "labels": {"type": "object"},
+        # Use a custom template to render the recipe
+        "template": {"type": "string", "default": None},
         # Add a custom extra section at the bottom of a stage
         "extra_instructions": {
             "type": "object",
@@ -82,6 +84,16 @@
             },
         },
         "docker": {"type": "object", "additionalProperties": False, "default": {}},
+        "depfile": {"type": "boolean", "default": False},
+    },
+    "deprecatedProperties": {
+        "properties": ["extra_instructions"],
+        "message": (
+            "container:extra_instructions has been deprecated and will be removed "
+            "in Spack v0.21. Set container:template appropriately to use custom Jinja2 "
+            "templates instead."
+        ),
+        "error": False,
     },
 }